fix(ci): downgrade contents permission to read in claude.yml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/CLAUDE.md

@@ -0,0 +1,86 @@
+# LeRobot — Claude Code Instructions
+
+You are a senior robotics ML engineer reviewing code for **LeRobot**, a PyTorch framework for real-world robot learning.
+Apply these principles to every PR review, fix, or task.
+
+---
+
+## Core Abstractions
+
+These are the load-bearing types. Handle them with care — breaking changes here affect every user.
+
+| Type             | Location                     | Role                                                         |
+| ---------------- | ---------------------------- | ------------------------------------------------------------ |
+| `LeRobotDataset` | `src/lerobot/datasets/`      | Streaming replay buffer; HF Hub integration                  |
+| `Policy`         | `src/lerobot/policies/`      | Base class for all learning agents (ACT, Diffusion, SARM, …) |
+| `Robot`          | `src/lerobot/robots/`        | Hardware abstraction; carries `_output_pipeline`             |
+| `Teleoperator`   | `src/lerobot/teleoperators/` | Leader-side hardware abstraction; carries `_output_pipeline` |
+| `Env`            | `src/lerobot/envs/`          | Gym-like robotics environments                               |
+| `Processor`      | `src/lerobot/processor/`     | Data transformation pipelines attached to robots/teleops     |
+
+**Never break their public APIs without a migration note and explicit user approval.**
+
+---
+
+## Engineering Principles
+
+### Code quality
+
+- Explicit over magic — no hidden control flow, no implicit state.
+- No deep inheritance trees. Prefer composition.
+- No decorative comment separators (`===`, `---`, etc.).
+- Add comments only where the logic is non-obvious.
+- No over-engineering. YAGNI applies strictly.
+
+### Type safety
+
+- All new and modified Python code must be fully typed (PEP 484).
+- `mypy --strict` must pass on changed files.
+- Do not widen or weaken existing type signatures.
+
+### Backwards compatibility
+
+- Public API changes require migration notes.
+- Additive changes are preferred over modifications.
+- `so100_follower` / `so101_follower` are aliases — never bleed changes there unintentionally.
+
+### HF ecosystem
+
+- Use `push_to_hub()`, HF Hub dataset streaming, and `evaluate` scripts.
+- Dataset changes must preserve streaming compatibility.
+- Prefer reusing HF primitives over rolling custom solutions.
+
+---
+
+## PR Review Checklist
+
+Before approving or marking P1 issues resolved, verify:
+
+- [ ] `pre-commit run -a` would pass (ruff, mypy, typos, zizmor, bandit)
+- [ ] All new/modified code is typed and passes `mypy --strict`
+- [ ] New features have unit tests; no silent behavioral changes
+- [ ] Public APIs of `LeRobotDataset`, `Policy`, `Robot`, `Teleoperator`, `Env` are unchanged (or migration note present)
+- [ ] HF Hub streaming still works for dataset changes
+- [ ] No unnecessary abstractions introduced
+- [ ] No breaking changes to training scripts (`lerobot-train`, `lerobot-eval`, `lerobot-record`)
+
+---
+
+## ML-Specific Checks
+
+Flag these as **P1** if found:
+
+- **Data leakage**: train and val/test splits must be constructed before any normalization or augmentation that uses train statistics.
+- **Loss function errors**: verify reduction mode (`mean` vs `sum`), correct masking, correct shape alignment.
+- **Gradient flow**: new modules must have gradients flowing (check `requires_grad`, no detached tensors in the loss path by accident).
+- **Distributed training**: operations on tensors must be DDP-safe; no in-place ops on parameters; batch norm needs `SyncBatchNorm` if used.
+- **Memory leaks**: no accumulation of tensors outside the training loop; `optimizer.zero_grad()` called correctly.
+
+---
+
+## What to Skip
+
+- Don't flag style nitpicks on unchanged surrounding code.
+- Don't propose refactors outside the PR's scope.
+- Don't add docstrings or comments to code the PR didn't touch.
+- Don't suggest speculative future features (YAGNI).

.github/workflows/claude-code-review.yml

@@ -0,0 +1,49 @@
+name: Claude Code Review
+
+on:
+  pull_request:
+    types: [opened, synchronize, ready_for_review, reopened]
+
+jobs:
+  claude-review:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+      issues: read
+      id-token: write
+      actions: read
+    env:
+      FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+          persist-credentials: false
+
+      - name: Run Claude Code Review
+        id: claude-review
+        uses: anthropics/claude-code-action@26ddc358fe3befff50c5ec2f80304c90c763f6f8 # v1
+        with:
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          use_sticky_comment: true
+          prompt: |
+            Read `.github/CLAUDE.md` for lerobot-specific conventions, then review this PR.
+            Provide structured, actionable feedback.
+
+            Focus areas (in priority order):
+            1. **Correctness**: Logic errors, off-by-ones, wrong tensor shapes, incorrect loss functions
+            2. **Type safety**: All new/modified Python code must pass `mypy --strict`; check for missing annotations
+            3. **Backwards compatibility**: Does this break `LeRobotDataset`, `Policy`, `Robot`, `Teleoperator`, `Env`, or `Processor` public APIs?
+            4. **Tests**: New features must have tests; no silent behavioral changes
+            5. **Code style**: Explicit over magic, no unnecessary abstractions, no decorative comments
+            6. **HF integration**: Dataset streaming, `push_to_hub`, HF Hub compatibility preserved?
+            7. **pre-commit**: Would `pre-commit run -a` pass? (ruff, mypy, typos, zizmor)
+
+            Format findings as P1 (must fix) / P2 (should fix) / P3 (nice to have).
+            Skip P3 if the PR is already high quality.
+          claude_args: '--model claude-opus-4-6'
+          # See https://github.com/anthropics/claude-code-action/blob/main/docs/usage.md
+          # or https://code.claude.com/docs/en/cli-reference for available options

.github/workflows/claude.yml

@@ -0,0 +1,58 @@
+name: Claude Code
+
+on:
+  issue_comment:
+    types: [created]
+  pull_request_review_comment:
+    types: [created]
+  issues:
+    types: [opened, assigned]
+  pull_request_review:
+    types: [submitted]
+
+jobs:
+  claude:
+    if: |
+      (github.event_name == 'issue_comment' &&
+       contains(github.event.comment.body, '@claude') &&
+       (github.event.comment.author_association == 'OWNER' || github.event.comment.author_association == 'MEMBER' || github.event.comment.author_association == 'COLLABORATOR')) ||
+      (github.event_name == 'pull_request_review_comment' &&
+       contains(github.event.comment.body, '@claude') &&
+       (github.event.comment.author_association == 'OWNER' || github.event.comment.author_association == 'MEMBER' || github.event.comment.author_association == 'COLLABORATOR')) ||
+      (github.event_name == 'pull_request_review' &&
+       contains(github.event.review.body, '@claude') &&
+       (github.event.review.author_association == 'OWNER' || github.event.review.author_association == 'MEMBER' || github.event.review.author_association == 'COLLABORATOR')) ||
+      (github.event_name == 'issues' &&
+       (contains(github.event.issue.body, '@claude') || contains(github.event.issue.title, '@claude')) &&
+       (github.event.issue.author_association == 'OWNER' || github.event.issue.author_association == 'MEMBER' || github.event.issue.author_association == 'COLLABORATOR'))
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+      issues: write
+      id-token: write
+      actions: read
+    env:
+      FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+          persist-credentials: false
+
+      - name: Run Claude Code
+        id: claude
+        uses: anthropics/claude-code-action@26ddc358fe3befff50c5ec2f80304c90c763f6f8 # v1
+        with:
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          use_sticky_comment: true
+
+          # This is an optional setting that allows Claude to read CI results on PRs
+          additional_permissions: |
+            actions: read
+
+          claude_args: '--system-prompt "Read .github/CLAUDE.md for lerobot-specific conventions before responding."'
+          # See https://github.com/anthropics/claude-code-action/blob/main/docs/usage.md
+          # or https://code.claude.com/docs/en/cli-reference for available options

.github/workflows/docker_publish.yml

@@ -12,8 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# This workflow handles nightly testing & docker images publishing.
-name: Nightly
+# This workflow handles Docker image publishing & testing.
+name: Docker Publish & Test
 permissions:
   contents: read
 
@@ -39,8 +39,8 @@ concurrency:
 
 jobs:
   # This job builds a CPU image for testing & distribution
-  build-docker-cpu-nightly:
-    name: Build CPU Docker for Nightly
+  build-docker-cpu:
+    name: Build CPU Docker
     runs-on:
       group: aws-general-8-plus
     if: github.repository == 'huggingface/lerobot'
@@ -74,8 +74,8 @@ jobs:
           tags: ${{ env.DOCKER_IMAGE_NAME_CPU }}
 
   # This job builds a GPU image for testing & distribution
-  build-docker-gpu-nightly:
-    name: Build GPU Docker for Nightly
+  build-docker-gpu:
+    name: Build GPU Docker
     runs-on:
       group: aws-general-8-plus
     if: github.repository == 'huggingface/lerobot'
@@ -109,9 +109,9 @@ jobs:
           tags: ${{ env.DOCKER_IMAGE_NAME_GPU }}
 
   # This job runs the E2E tests + pytest with all extras in the CPU image
-  nightly-cpu-tests:
-    name: Nightly CPU Tests
-    needs: [build-docker-cpu-nightly]
+  cpu-tests:
+    name: CPU Tests
+    needs: [build-docker-cpu]
     runs-on:
       group: aws-g6-4xlarge-plus
     env:
@@ -121,7 +121,7 @@ jobs:
       TRITON_CACHE_DIR: /home/user_lerobot/.cache/triton
       HF_USER_TOKEN: ${{ secrets.LEROBOT_HF_USER }}
     container:
-      image: ${{ needs.build-docker-cpu-nightly.outputs.image_tag }} # zizmor: ignore[unpinned-images]
+      image: ${{ needs.build-docker-cpu.outputs.image_tag }} # zizmor: ignore[unpinned-images]
       options: --shm-size "16gb"
       credentials:
         username: ${{ secrets.DOCKERHUB_LEROBOT_USERNAME }}
@@ -142,9 +142,9 @@ jobs:
         run: make test-end-to-end
 
   # This job runs the E2E tests + pytest with all extras in the GPU image
-  nightly-gpu-tests:
-    name: Nightly GPU Tests
-    needs: [build-docker-gpu-nightly]
+  gpu-tests:
+    name: GPU Tests
+    needs: [build-docker-gpu]
     runs-on:
       group: aws-g6-4xlarge-plus
     env:
@@ -154,7 +154,7 @@ jobs:
       TRITON_CACHE_DIR: /home/user_lerobot/.cache/triton
       HF_USER_TOKEN: ${{ secrets.LEROBOT_HF_USER }}
     container:
-      image: ${{ needs.build-docker-gpu-nightly.outputs.image_tag }} # zizmor: ignore[unpinned-images]
+      image: ${{ needs.build-docker-gpu.outputs.image_tag }} # zizmor: ignore[unpinned-images]
       options: --gpus all --shm-size "16gb"
       credentials:
         username: ${{ secrets.DOCKERHUB_LEROBOT_USERNAME }}
@@ -175,9 +175,9 @@ jobs:
         run: make test-end-to-end
 
   # This job runs multi-GPU training tests with 4 GPUs
-  nightly-multi-gpu-tests:
-    name: Nightly Multi-GPU Tests
-    needs: [build-docker-gpu-nightly]
+  multi-gpu-tests:
+    name: Multi-GPU Tests
+    needs: [build-docker-gpu]
     runs-on:
       group: aws-g4dn-12xlarge  # Instance with 4 GPUs
     env:
@@ -188,7 +188,7 @@ jobs:
       CUDA_VISIBLE_DEVICES: "0,1,2,3"
       HF_USER_TOKEN: ${{ secrets.LEROBOT_HF_USER }}
     container:
-      image: ${{ needs.build-docker-gpu-nightly.outputs.image_tag }} # zizmor: ignore[unpinned-images]
+      image: ${{ needs.build-docker-gpu.outputs.image_tag }} # zizmor: ignore[unpinned-images]
       options: --gpus all --shm-size "16gb"
       credentials:
         username: ${{ secrets.DOCKERHUB_LEROBOT_USERNAME }}

.github/workflows/documentation-upload-pr.yml

@@ -33,7 +33,7 @@ jobs:
       github.event.workflow_run.event == 'pull_request' &&
       github.event.workflow_run.conclusion == 'success' &&
       github.repository == 'huggingface/lerobot'
-    uses: huggingface/doc-builder/.github/workflows/upload_pr_documentation.yml@main
+    uses: huggingface/doc-builder/.github/workflows/upload_pr_documentation.yml@90b4ee2c10b81b5c1a6367c4e6fc9e2fb510a7e3  # main
     with:
       package_name: lerobot
     secrets:

.github/workflows/documentation.yml

@@ -55,7 +55,7 @@ jobs:
       github.repository == 'huggingface/lerobot'
     permissions:
       contents: read
-    uses: huggingface/doc-builder/.github/workflows/build_main_documentation.yml@main
+    uses: huggingface/doc-builder/.github/workflows/build_main_documentation.yml@90b4ee2c10b81b5c1a6367c4e6fc9e2fb510a7e3  # main
     with:
       commit_sha: ${{ github.sha }}
       package: lerobot
@@ -78,7 +78,7 @@ jobs:
     permissions:
       contents: read
       pull-requests: write
-    uses: huggingface/doc-builder/.github/workflows/build_pr_documentation.yml@main
+    uses: huggingface/doc-builder/.github/workflows/build_pr_documentation.yml@90b4ee2c10b81b5c1a6367c4e6fc9e2fb510a7e3  # main
     with:
       commit_sha: ${{ github.event.pull_request.head.sha }}
       pr_number: ${{ github.event.number }}

.github/workflows/fast_tests.yml

@@ -27,6 +27,7 @@ on:
       - "tests/**"
       - ".github/workflows/**"
       - "pyproject.toml"
+      - "uv.lock"
       - "Makefile"
   push:
     branches:
@@ -36,6 +37,7 @@ on:
       - "tests/**"
       - ".github/workflows/**"
       - "pyproject.toml"
+      - "uv.lock"
       - "Makefile"
 
 permissions:
@@ -63,7 +65,7 @@ jobs:
       HF_LEROBOT_HOME: /mnt/cache/.cache/huggingface/lerobot
       HF_USER_TOKEN: ${{ secrets.LEROBOT_HF_USER }}
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           persist-credentials: false
           lfs: true
@@ -81,14 +83,14 @@ jobs:
           libusb-1.0-0-dev speech-dispatcher libgeos-dev portaudio19-dev
 
       - name: Setup uv and Python
-        uses: astral-sh/setup-uv@v6 # zizmor: ignore[unpinned-uses]
+        uses: astral-sh/setup-uv@d0cc045d04ccac9d8b7881df0226f9e82c39688e  # v6
         with:
           enable-cache: true
           version: ${{ env.UV_VERSION }}
           python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install lerobot with test extras
-        run: uv sync --extra "test"
+        run: uv sync --locked --extra "test"
 
       - name: Login to Hugging Face
         if: env.HF_USER_TOKEN != ''

.github/workflows/full_tests.yml

@@ -29,6 +29,7 @@ on:
       - "tests/**"
       - ".github/workflows/**"
       - "pyproject.toml"
+      - "uv.lock"
       - "Makefile"
 
 permissions:
@@ -62,7 +63,7 @@ jobs:
       HF_LEROBOT_HOME: /mnt/cache/.cache/huggingface/lerobot
       HF_USER_TOKEN: ${{ secrets.LEROBOT_HF_USER }}
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           lfs: true
           persist-credentials: false
@@ -79,14 +80,14 @@ jobs:
           speech-dispatcher libgeos-dev portaudio19-dev
 
       - name: Setup uv and Python
-        uses: astral-sh/setup-uv@v6 # zizmor: ignore[unpinned-uses]
+        uses: astral-sh/setup-uv@d0cc045d04ccac9d8b7881df0226f9e82c39688e  # v6
         with:
           enable-cache: true
           version: ${{ env.UV_VERSION }}
           python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install lerobot with all extras
-        run: uv sync --extra all # TODO(Steven): Make flash-attn optional
+        run: uv sync --locked --extra all # TODO(Steven): Make flash-attn optional
 
       - name: Login to Hugging Face
         if: env.HF_USER_TOKEN != ''
@@ -136,21 +137,21 @@ jobs:
           sudo apt-get update
           sudo apt-get install git-lfs
           git lfs install
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           lfs: true
           persist-credentials: false
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3 # zizmor: ignore[unpinned-uses]
+        uses: docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f  # v3
         with:
           cache-binary: false
       - name: Login to Docker Hub
-        uses: docker/login-action@v3 # zizmor: ignore[unpinned-uses]
+        uses: docker/login-action@c94ce9fb468520275223c153574b00df6fe4bcc9  # v3
         with:
           username: ${{ secrets.DOCKERHUB_LEROBOT_USERNAME }}
           password: ${{ secrets.DOCKERHUB_LEROBOT_PASSWORD }}
       - name: Build and push Docker image
-        uses: docker/build-push-action@v6 # zizmor: ignore[unpinned-uses]
+        uses: docker/build-push-action@10e90e3645eae34f1e60eeb005ba3a3d33f178e8  # v6
         with:
           context: .
           file: ./docker/Dockerfile.internal

.github/workflows/latest_deps_tests.yml

@@ -12,38 +12,81 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# This workflow handles full testing with unboud dependencies versions.
-name: Unbound Dependency Tests
+# This workflow tests the project against the latest upstream dependencies
+# (within pyproject.toml constraints) and opens a PR to update uv.lock
+# if the tests pass and the lockfile has changed.
+name: Latest Dependency Tests
 
 on:
   # Allows running this workflow manually from the Actions tab
   workflow_dispatch:
 
-  # Run on the 1st and 15th of every month at 09:00 UTC
-  # schedule:
-  #  - cron: '0 2 1,15 * *'
-
-permissions:
-  contents: read
+  # Runs at 03:00 UTC
+  schedule:
+    - cron: "0 3 * * *"
 
 # Sets up the environment variables
 env:
   UV_VERSION: "0.8.0"
   PYTHON_VERSION: "3.12"
-  DOCKER_IMAGE_NAME: huggingface/lerobot-gpu:unbound
+  DOCKER_IMAGE_NAME: huggingface/lerobot-gpu:latest-deps
 
-# Ensures that only the latest action is built, canceling older runs.
+# Ensures that only the latest run is active, canceling older runs.
 concurrency:
-  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  group: ${{ github.workflow }}
   cancel-in-progress: true
 
 jobs:
 
-  # This job runs the E2E tests + pytest with all unbound extras
-  full-tests:
-    name: Full Unbound Tests
+  # This job upgrades the lockfile and checks if dependencies have changed
+  upgrade-lock:
+    name: Upgrade Lockfile
     runs-on: ubuntu-latest
     if: github.repository == 'huggingface/lerobot'
+    permissions:
+      contents: read
+    outputs:
+      changed: ${{ steps.diff.outputs.changed }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - name: Setup uv and Python
+        uses: astral-sh/setup-uv@v6 # zizmor: ignore[unpinned-uses]
+        with:
+          version: ${{ env.UV_VERSION }}
+          python-version: ${{ env.PYTHON_VERSION }}
+
+      - name: Upgrade uv.lock
+        run: uv lock --upgrade
+
+      - name: Check for changes
+        id: diff
+        run: |
+          if git diff --quiet uv.lock; then
+            echo "changed=false" >> "$GITHUB_OUTPUT"
+            echo "uv.lock is up to date — no dependency changes."
+          else
+            echo "changed=true" >> "$GITHUB_OUTPUT"
+            echo "uv.lock has changed — running tests."
+          fi
+
+      - name: Upload updated lockfile
+        if: steps.diff.outputs.changed == 'true'
+        uses: actions/upload-artifact@v4 # zizmor: ignore[unpinned-uses]
+        with:
+          name: uv-lock
+          path: uv.lock
+
+  # This job runs the full test suite with the upgraded dependencies
+  cpu-tests:
+    name: CPU Tests (Latest Deps)
+    needs: [upgrade-lock]
+    if: needs.upgrade-lock.outputs.changed == 'true'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
     env:
       MUJOCO_GL: egl
       HF_HOME: /mnt/cache/.cache/huggingface
@@ -55,6 +98,11 @@ jobs:
           lfs: true
           persist-credentials: false
 
+      - name: Download updated lockfile
+        uses: actions/download-artifact@v4 # zizmor: ignore[unpinned-uses]
+        with:
+          name: uv-lock
+
       # NOTE(Steven): Mount to `/mnt` to avoid the limited storage on `/home`. Consider cleaning default SDKs or using self-hosted runners for more space.
       # (As of 2024-06-10, the runner's `/home` has only 6.2 GB free—8% of its 72 GB total.)
       - name: Setup /mnt storage
@@ -73,34 +121,32 @@ jobs:
           version: ${{ env.UV_VERSION }}
           python-version: ${{ env.PYTHON_VERSION }}
 
-      - name: Unbound dependencies
-        run: |
-          sed -i 's/,[[:space:]]*<[0-9\.]*//g' pyproject.toml
-          echo "Dependencies unbound:" && cat pyproject.toml
-
       - name: Install lerobot with all extras
-        run: uv sync --extra all # TODO(Steven): Make flash-attn optional
+        run: uv sync --locked --extra all # TODO(Steven): Make flash-attn optional
+
       - name: Login to Hugging Face
         if: env.HF_USER_TOKEN != ''
         run: |
           uv run hf auth login --token "$HF_USER_TOKEN" --add-to-git-credential
           uv run hf auth whoami
+
       - name: Run pytest (all extras)
-        run: uv run pytest tests -vv
+        run: uv run pytest tests -vv --maxfail=10
 
       - name: Run end-to-end tests
         run: uv run make test-end-to-end
 
-  # This job builds a GPU enabled image for testing
+  # This job builds a GPU-enabled Docker image with the upgraded dependencies
   build-and-push-docker:
     name: Build and Push Docker
+    needs: [upgrade-lock]
+    if: needs.upgrade-lock.outputs.changed == 'true'
+    permissions:
+      contents: read
     runs-on:
       group: aws-general-8-plus
-    if: github.repository == 'huggingface/lerobot'
     outputs:
       image_tag: ${{ env.DOCKER_IMAGE_NAME }}
-    env:
-      GITHUB_REF: ${{ github.ref }}
     steps:
       - name: Install Git LFS
         run: |
@@ -111,6 +157,12 @@ jobs:
         with:
           lfs: true
           persist-credentials: false
+
+      - name: Download updated lockfile
+        uses: actions/download-artifact@v4 # zizmor: ignore[unpinned-uses]
+        with:
+          name: uv-lock
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3 # zizmor: ignore[unpinned-uses]
         with:
@@ -127,14 +179,13 @@ jobs:
           file: ./docker/Dockerfile.internal
           push: true
           tags: ${{ env.DOCKER_IMAGE_NAME }}
-          build-args: |
-            UNBOUND_DEPS=true
 
-  # This job runs pytest with all unbound extras in a GPU enabled host
-  # It runs everytime a test image is created
+  # This job runs pytest with all extras on a GPU-enabled host
   gpu-tests:
-    name: GPU Unbound Tests
+    name: GPU Tests (Latest Deps)
     needs: [build-and-push-docker]
+    permissions:
+      contents: read
     runs-on:
       group: aws-g6-4xlarge-plus
     env:
@@ -159,17 +210,69 @@ jobs:
         run: |
           hf auth login --token "$HF_USER_TOKEN" --add-to-git-credential
           hf auth whoami
+      - name: Fix ptxas permissions
+        run: chmod +x /lerobot/.venv/lib/python3.12/site-packages/triton/backends/nvidia/bin/ptxas
       - name: Run pytest on GPU
-        run: pytest tests -vv
+        run: pytest tests -vv --maxfail=10
       - name: Run end-to-end tests
         run: make test-end-to-end
 
-  # This job deletes the test image recently created
-  # It runs everytime after the gpu-tests have finished
-  delete-unbound-image:
-    name: Delete Unbound Image
+  # This job creates or updates a PR with the upgraded lockfile
+  open-pr:
+    name: Open PR
+    needs: [cpu-tests, gpu-tests, upgrade-lock]
+    if: success() && needs.upgrade-lock.outputs.changed == 'true'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    env:
+      GH_TOKEN: ${{ secrets.UPDATE_LOCK_TOKEN }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - name: Download updated lockfile
+        uses: actions/download-artifact@v4 # zizmor: ignore[unpinned-uses]
+        with:
+          name: uv-lock
+
+      - name: Create or update PR
+        run: |
+          set -euo pipefail
+          BRANCH="auto/update-uv-lock"
+
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git remote set-url origin "https://x-access-token:${GH_TOKEN}@github.com/${{ github.repository }}.git"
+
+          git checkout -B "$BRANCH"
+          git add uv.lock
+          git commit -m "chore(dependencies): update uv.lock"
+          git push --force origin "$BRANCH"
+
+          # Create PR only if one doesn't already exist for this branch
+          EXISTING_PR=$(gh pr list --head "$BRANCH" --state open --json number --jq '.[0].number')
+          if [ -z "$EXISTING_PR" ]; then
+            gh pr create \
+              --title "chore(dependencies): update uv.lock" \
+              --body "Automated update of \`uv.lock\` after successful latest dependency tests (CPU + GPU).
+
+          This PR upgrades all dependencies to their latest versions within the ranges specified in \`pyproject.toml\`." \
+              --head "$BRANCH" \
+              --base main
+          else
+            echo "PR #$EXISTING_PR already exists, branch has been updated."
+          fi
+
+  # This job deletes the temporary Docker image after tests complete
+  cleanup-docker:
+    name: Cleanup Docker Image
     needs: [gpu-tests, build-and-push-docker]
     if: always() && needs.build-and-push-docker.result == 'success'
+    permissions:
+      contents: read
     runs-on: ubuntu-latest
     steps:
       - name: Get Docker Hub Token and Delete Image
@@ -180,8 +283,7 @@ jobs:
           IMAGE_FULL: ${{ needs.build-and-push-docker.outputs.image_tag }}
         run: |
           IMAGE_NAME=$(echo "$IMAGE_FULL" | cut -d':' -f1)
-          IMAGE_TAG=$(echo "$IMAGE_FULL" | cut -d':' -f2)
-
+          IMAGE_TAG=$(echo "$IMAGE_FULL" | cut -d':' -f2-)
           echo "Attempting to delete image: $IMAGE_NAME:$IMAGE_TAG"
 
           TOKEN=$(curl -s -H "Content-Type: application/json" \

.github/workflows/quality.yml

@@ -43,16 +43,16 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           persist-credentials: false
 
       - name: Set up Python
-        uses: actions/setup-python@v6
+        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405  # v6
         with:
           python-version: '3.12'
 
       - name: Run pre-commit hooks
-        uses: pre-commit/action@v3.0.1 # zizmor: ignore[unpinned-uses]
+        uses: pre-commit/action@2c7b3805fd2a0fd8c1884dcaebf91fc102a13ecd  # v3.0.1
         with:
           extra_args: --all-files --show-diff-on-failure --color=always

.github/workflows/release.yml

@@ -38,12 +38,12 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           persist-credentials: false
 
       - name: Set up Python
-        uses: actions/setup-python@v6
+        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405  # v6
         with:
           python-version: '3.12'
 
@@ -104,7 +104,7 @@ jobs:
       - name: Publish to TestPyPI for pre-releases
         # True for tags like 'v0.2.0-rc1'
         if: startsWith(github.ref, 'refs/tags/v') && contains(github.ref, '-')
-        uses: pypa/gh-action-pypi-publish@v1.13.0 # zizmor: ignore[unpinned-uses, use-trusted-publishing]
+        uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e  # v1.13.0
         with:
           repository-url: https://test.pypi.org/legacy/
           verbose: true
@@ -112,7 +112,7 @@ jobs:
 
       - name: Publish to PyPI
         if: startsWith(github.ref, 'refs/tags/v') && !contains(github.ref, '-')
-        uses: pypa/gh-action-pypi-publish@v1.13.0 # zizmor: ignore[unpinned-uses, use-trusted-publishing]
+        uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e  # v1.13.0
         with:
           verbose: true
           print-hash: true
@@ -127,7 +127,7 @@ jobs:
     env:
       MUJOCO_GL: egl
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           lfs: true
           persist-credentials: false
@@ -137,7 +137,7 @@ jobs:
           git curl libglib2.0-0 libegl1-mesa-dev ffmpeg libusb-1.0-0-dev \
           speech-dispatcher libgeos-dev portaudio19-dev
       - name: Setup uv and Python
-        uses: astral-sh/setup-uv@v6 # zizmor: ignore[unpinned-uses]
+        uses: astral-sh/setup-uv@d0cc045d04ccac9d8b7881df0226f9e82c39688e  # v6
         with:
           enable-cache: true # zizmor: ignore[cache-poisoning]
           version: ${{ env.UV_VERSION }}

.github/workflows/security.yml

@@ -43,12 +43,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v6 # zizmor: ignore[unpinned-uses]
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
           fetch-depth: 0
           persist-credentials: false
 
       - name: Secret Scanning
-        uses: trufflesecurity/trufflehog@v3.90.0  # zizmor: ignore[unpinned-uses]
+        uses: trufflesecurity/trufflehog@eafb8c5f6a06175141c27f17bcc17941853d0047  # v3.90.0
         with:
           extra_args: --only-verified

.gitignore

@@ -25,7 +25,6 @@ node_modules/
 
 # Lock files
 poetry.lock
-uv.lock
 Pipfile.lock
 
 ### Build & Distribution ###

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 Everyone is welcome to contribute, and we value everybody's contribution. Code is not the only way to help the community. Answering questions, helping others, reaching out, and improving the documentation are immensely valuable.
 
-Whichever way you choose to contribute, please be mindful to respect our [code of conduct](./CODE_OF_CONDUCT.md) and our [AI policy](./AI_POLICY.md).
+Whichever way you choose to contribute, please be mindful to respect our [code of conduct](https://github.com/huggingface/lerobot/blob/main/CODE_OF_CONDUCT.md) and our [AI policy](https://github.com/huggingface/lerobot/blob/main/AI_POLICY.md).
 
 ## Ways to Contribute
 
@@ -32,7 +32,7 @@ git remote add upstream https://github.com/huggingface/lerobot.git
 
 ### 2. Environment Installation
 
-Please follow our [Installation Guide](./docs/source/installation.mdx) for the environment setup & installation from source.
+Please follow our [Installation Guide](https://huggingface.co/docs/lerobot/installation) for the environment setup & installation from source.
 
 ## Running Tests & Quality Checks
 
@@ -75,8 +75,8 @@ pytest -sv tests/test_specific_feature.py
 
 Use the templates for required fields and examples.
 
-- **Issues:** Follow the [ticket template](./.github/ISSUE_TEMPLATE/bug-report.yml).
-- **Pull requests:** Rebase on `upstream/main`, use a descriptive branch (don't work on `main`), run `pre-commit` and tests locally, and follow the [PR template](./.github/PULL_REQUEST_TEMPLATE.md).
+- **Issues:** Follow the [ticket template](https://github.com/huggingface/lerobot/blob/main/.github/ISSUE_TEMPLATE/bug-report.yml).
+- **Pull requests:** Rebase on `upstream/main`, use a descriptive branch (don't work on `main`), run `pre-commit` and tests locally, and follow the [PR template](https://github.com/huggingface/lerobot/blob/main/.github/PULL_REQUEST_TEMPLATE.md).
 
 One member of the LeRobot team will then review your contribution.
 

README.md

@@ -4,7 +4,8 @@
 
 <div align="center">
 
-[![Tests](https://github.com/huggingface/lerobot/actions/workflows/nightly.yml/badge.svg?branch=main)](https://github.com/huggingface/lerobot/actions/workflows/nightly.yml?query=branch%3Amain)
+[![Tests](https://github.com/huggingface/lerobot/actions/workflows/latest_deps_tests.yml/badge.svg?branch=main)](https://github.com/huggingface/lerobot/actions/workflows/latest_deps_tests.yml?query=branch%3Amain)
+[![Tests](https://github.com/huggingface/lerobot/actions/workflows/docker_publish.yml/badge.svg?branch=main)](https://github.com/huggingface/lerobot/actions/workflows/docker_publish.yml?query=branch%3Amain)
 [![Python versions](https://img.shields.io/pypi/pyversions/lerobot)](https://www.python.org/downloads/)
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/huggingface/lerobot/blob/main/LICENSE)
 [![Status](https://img.shields.io/pypi/status/lerobot)](https://pypi.org/project/lerobot/)
@@ -100,11 +101,11 @@ lerobot-train \
   --dataset.repo_id=lerobot/aloha_mobile_cabinet
 ```
 
-| Category                   | Models                                                                                                                                                                                                       |
-| -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
-| **Imitation Learning**     | [ACT](./docs/source/policy_act_README.md), [Diffusion](./docs/source/policy_diffusion_README.md), [VQ-BeT](./docs/source/policy_vqbet_README.md)                                                             |
-| **Reinforcement Learning** | [HIL-SERL](./docs/source/hilserl.mdx), [TDMPC](./docs/source/policy_tdmpc_README.md) & QC-FQL (coming soon)                                                                                                  |
-| **VLAs Models**            | [Pi0Fast](./docs/source/pi0fast.mdx), [Pi0.5](./docs/source/pi05.mdx), [GR00T N1.5](./docs/source/policy_groot_README.md), [SmolVLA](./docs/source/policy_smolvla_README.md), [XVLA](./docs/source/xvla.mdx) |
+| Category                   | Models                                                                                                                                                                                                                  |
+| -------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| **Imitation Learning**     | [ACT](./docs/source/policy_act_README.md), [Diffusion](./docs/source/policy_diffusion_README.md), [VQ-BeT](./docs/source/policy_vqbet_README.md), [Multitask DiT Policy](./docs/source/policy_multi_task_dit_README.md) |
+| **Reinforcement Learning** | [HIL-SERL](./docs/source/hilserl.mdx), [TDMPC](./docs/source/policy_tdmpc_README.md) & QC-FQL (coming soon)                                                                                                             |
+| **VLAs Models**            | [Pi0Fast](./docs/source/pi0fast.mdx), [Pi0.5](./docs/source/pi05.mdx), [GR00T N1.5](./docs/source/policy_groot_README.md), [SmolVLA](./docs/source/policy_smolvla_README.md), [XVLA](./docs/source/xvla.mdx)            |
 
 Similarly to the hardware, you can easily implement your own policy & leverage LeRobot's data collection, training, and visualization tools, and share your model to the HF Hub
 
@@ -165,7 +166,7 @@ If you are referencing our research or the academic paper, please also cite our
 
 ## Contribute
 
-We welcome contributions from everyone in the community! To get started, please read our [CONTRIBUTING.md](./CONTRIBUTING.md) guide. Whether you're adding a new feature, improving documentation, or fixing a bug, your help and feedback are invaluable. We're incredibly excited about the future of open-source robotics and can't wait to work with you on what's next—thank you for your support!
+We welcome contributions from everyone in the community! To get started, please read our [CONTRIBUTING.md](https://github.com/huggingface/lerobot/blob/main/CONTRIBUTING.md) guide. Whether you're adding a new feature, improving documentation, or fixing a bug, your help and feedback are invaluable. We're incredibly excited about the future of open-source robotics and can't wait to work with you on what's next—thank you for your support!
 
 <p align="center">
   <img alt="SO101 Video" src="./media/readme/so100_video.webp" width="640px">

docker/Dockerfile.internal

@@ -73,17 +73,10 @@ ENV HOME=/home/user_lerobot \
 RUN uv venv --python python${PYTHON_VERSION}
 
 # Install Python dependencies for caching
-COPY --chown=user_lerobot:user_lerobot setup.py pyproject.toml README.md MANIFEST.in ./
+COPY --chown=user_lerobot:user_lerobot setup.py pyproject.toml uv.lock README.md MANIFEST.in ./
 COPY --chown=user_lerobot:user_lerobot src/ src/
 
-ARG UNBOUND_DEPS=false
-
-RUN if [ "$UNBOUND_DEPS" = "true" ]; then \
-    sed -i 's/,[[:space:]]*<[0-9\.]*//g' pyproject.toml; \
-    echo "Dependencies unbound:" && cat pyproject.toml; \
-    fi
-
-RUN uv pip install --no-cache ".[all]"
+RUN uv sync --locked --extra all --no-cache
 
 RUN chmod +x /lerobot/.venv/lib/python${PYTHON_VERSION}/site-packages/triton/backends/nvidia/bin/ptxas
 

docker/Dockerfile.user

@@ -18,6 +18,8 @@
 # docker build -f docker/Dockerfile.user -t lerobot-user .
 # docker run -it --rm lerobot-user
 
+# With USB physical access : docker run -it --device=/dev/ -v /dev/:/dev/ --rm lerobot-user
+
 # Configure the base image
 ARG PYTHON_VERSION=3.12
 FROM python:${PYTHON_VERSION}-slim
@@ -59,17 +61,10 @@ ENV HOME=/home/user_lerobot \
 RUN uv venv
 
 # Install Python dependencies for caching
-COPY --chown=user_lerobot:user_lerobot setup.py pyproject.toml README.md MANIFEST.in ./
+COPY --chown=user_lerobot:user_lerobot setup.py pyproject.toml uv.lock README.md MANIFEST.in ./
 COPY --chown=user_lerobot:user_lerobot src/ src/
 
-ARG UNBOUND_DEPS=false
-
-RUN if [ "$UNBOUND_DEPS" = "true" ]; then \
-    sed -i 's/,[[:space:]]*<[0-9\.]*//g' pyproject.toml; \
-    echo "Dependencies unbound:" && cat pyproject.toml; \
-    fi
-
-RUN uv pip install --no-cache ".[all]"
+RUN uv sync --locked --extra all --no-cache
 
 # Copy the rest of the application code
 # Make sure to have the git-LFS files for testing

docker/README.md

@@ -0,0 +1,77 @@
+# Docker
+
+This directory contains Dockerfiles for running LeRobot in containerized environments. Both images are **built nightly from `main`** and published to Docker Hub with the full environment pre-baked — no dependency setup required.
+
+## Pre-built Images
+
+```bash
+# CPU-only image (based on Dockerfile.user)
+docker pull huggingface/lerobot-cpu:latest
+
+# GPU image with CUDA support (based on Dockerfile.internal)
+docker pull huggingface/lerobot-gpu:latest
+```
+
+## Quick Start
+
+The fastest way to start training is to pull the GPU image and run `lerobot-train` directly. This is the same environment used for all of our CI, so it is a well-tested, batteries-included setup.
+
+```bash
+docker run -it --rm --gpus all --shm-size 16gb huggingface/lerobot-gpu:latest
+
+# inside the container:
+lerobot-train --policy.type=act --dataset.repo_id=lerobot/aloha_sim_transfer_cube_human
+```
+
+## Dockerfiles
+
+### `Dockerfile.user` (CPU)
+
+A lightweight image based on `python:3.12-slim`. Includes all Python dependencies and system libraries but does not include CUDA — there is no GPU support. Useful for exploring the codebase, running scripts, or working with robots, but not practical for training.
+
+### `Dockerfile.internal` (GPU)
+
+A CUDA-enabled image based on `nvidia/cuda`. This is the image for training — mostly used for internal interactions with the GPU cluster.
+
+## Usage
+
+### Running a pre-built image
+
+```bash
+# CPU
+docker run -it --rm huggingface/lerobot-cpu:latest
+
+# GPU
+docker run -it --rm --gpus all --shm-size 16gb huggingface/lerobot-gpu:latest
+```
+
+### Building locally
+
+From the repo root:
+
+```bash
+# CPU
+docker build -f docker/Dockerfile.user -t lerobot-user .
+docker run -it --rm lerobot-user
+
+# GPU
+docker build -f docker/Dockerfile.internal -t lerobot-internal .
+docker run -it --rm --gpus all --shm-size 16gb lerobot-internal
+```
+
+### Multi-GPU training
+
+To select specific GPUs, set `CUDA_VISIBLE_DEVICES` when launching the container:
+
+```bash
+# Use 4 GPUs
+docker run -it --rm --gpus all --shm-size 16gb \
+  -e CUDA_VISIBLE_DEVICES=0,1,2,3 \
+  huggingface/lerobot-gpu:latest
+```
+
+### USB device access (e.g. robots, cameras)
+
+```bash
+docker run -it --device=/dev/ -v /dev/:/dev/ --rm huggingface/lerobot-cpu:latest
+```

docs/source/_toctree.yml

@@ -17,8 +17,12 @@
     title: Train RL in Simulation
   - local: multi_gpu_training
     title: Multi GPU training
+  - local: hil_data_collection
+    title: Human In the Loop Data Collection
   - local: peft_training
     title: Training with PEFT (e.g., LoRA)
+  - local: rename_map
+    title: Using Rename Map and Empty Cameras
   title: "Tutorials"
 - sections:
   - local: lerobot-dataset-v3
@@ -47,6 +51,8 @@
     title: NVIDIA GR00T N1.5
   - local: xvla
     title: X-VLA
+  - local: multi_task_dit
+    title: Multitask DiT Policy
   - local: walloss
     title: WALL-OSS
   title: "Policies"
@@ -65,13 +71,17 @@
     title: Environments from the Hub
   - local: envhub_leisaac
     title: Control & Train Robots in Sim (LeIsaac)
+  title: "Simulation"
+- sections:
+  - local: adding_benchmarks
+    title: Adding a New Benchmark
+  - local: libero
+    title: LIBERO
+  - local: metaworld
+    title: Meta-World
   - local: envhub_isaaclab_arena
     title: NVIDIA IsaacLab Arena Environments
-  - local: libero
-    title: Using Libero
-  - local: metaworld
-    title: Using MetaWorld
-  title: "Simulation"
+  title: "Benchmarks"
 - sections:
   - local: introduction_processors
     title: Introduction to Robot Processors
@@ -83,6 +93,8 @@
     title: Processors for Robots and Teleoperators
   - local: env_processor
     title: Environment Processors
+  - local: action_representations
+    title: Action Representations
   title: "Robot Processors"
 - sections:
   - local: so101

docs/source/action_representations.mdx

@@ -0,0 +1,223 @@
+# Action Representations
+
+This guide explains the different ways robot actions can be represented in LeRobot, how they relate to each other, and when to use each one.
+
+## Joint Space vs End-Effector Space
+
+Before discussing action representations, it helps to understand the two coordinate spaces actions can live in.
+
+### Joint Space
+
+Joint-space actions directly specify target positions for each motor. For a 6-DOF arm with a gripper, a joint-space action might look like:
+
+```
+action = [shoulder_pan: 45.0, shoulder_lift: -20.0, elbow: -30.0, wrist_pitch: 10.0, wrist_roll: 0.0, wrist_yaw: 5.0, gripper: 0.8]
+```
+
+Joint space is the default in LeRobot. It is simple, requires no kinematics model, and maps directly to motor commands. Most beginner setups (SO-100, Koch) use joint-space actions.
+
+### End-Effector (EE) Space
+
+End-effector-space actions specify the desired position and orientation of the robot's tool tip (gripper) in Cartesian coordinates:
+
+```
+action = [x: 0.25, y: -0.10, z: 0.15, wx: 0.0, wy: 0.0, wz: 0.1, gripper: 0.8]
+```
+
+EE space is more intuitive for tasks like pick-and-place because it directly describes where the gripper should go, but it requires a kinematics model (URDF) to convert between EE poses and joint angles.
+
+### Converting Between Spaces
+
+LeRobot provides processor steps for converting between joint and EE spaces using forward and inverse kinematics. These are built on top of `RobotKinematics`, which loads a URDF model of your robot.
+
+```python
+from lerobot.model.kinematics import RobotKinematics
+from lerobot.robots.so_follower.robot_kinematic_processor import (
+    ForwardKinematicsJointsToEE,
+    InverseKinematicsEEToJoints,
+)
+
+kinematics = RobotKinematics(
+    urdf_path="./SO101/so101_new_calib.urdf",
+    target_frame_name="gripper_frame_link",
+    joint_names=["shoulder", "elbow", "wrist_pitch", "wrist_roll", "wrist_yaw"],
+)
+
+# Joints → EE (for observations: "where is my gripper?")
+fk_step = ForwardKinematicsJointsToEE(kinematics=kinematics, motor_names=[...])
+
+# EE → Joints (for actions: "move my gripper here")
+ik_step = InverseKinematicsEEToJoints(kinematics=kinematics, motor_names=[...])
+```
+
+See [`examples/so100_to_so100_EE/`](https://github.com/huggingface/lerobot/tree/main/examples/so100_to_so100_EE) for a complete working example of recording, replaying, and evaluating with EE-space actions on an SO-100 arm.
+
+## Absolute, Relative, and Delta Actions
+
+Regardless of whether you work in joint space or EE space, the action values can be expressed in three different ways. The terminology follows [UMI (Chi et al., 2024)](https://arxiv.org/abs/2402.10329).
+
+### Absolute Actions (LeRobot default)
+
+Each action specifies the target position directly.
+
+**Example** (joint space, chunk of 4):
+
+```
+current_state = [45.0, -30.0, 10.0]
+
+action_chunk = [
+    [46.0, -29.0, 11.0],   # go to 46, -29, 11
+    [47.5, -27.0, 12.0],   # go to 47.5, -27, 12
+    [49.0, -25.0, 13.5],   # go to 49, -25, 13.5
+    [50.0, -24.0, 15.0],   # go to 50, -24, 15
+]
+```
+
+Each value is a target position in the robot's coordinate frame. Simple and direct, but requires a consistent global coordinate frame. This is the default in LeRobot.
+
+### Relative Actions (used by OpenPI / pi0)
+
+Each action in the chunk is an offset from the **current state at the moment of prediction**. All actions in the chunk share the same reference point:
+
+```
+current_state = [45.0, -30.0, 10.0]
+
+relative_chunk = [
+    [1.0,  1.0, 1.0],   # +1 from current → target 46, -29, 11
+    [2.5,  3.0, 2.0],   # +2.5 from current → target 47.5, -27, 12
+    [4.0,  5.0, 3.5],   # +4 from current → target 49, -25, 13.5
+    [5.0,  6.0, 5.0],   # +5 from current → target 50, -24, 15
+]
+```
+
+The conversion is straightforward: `relative = absolute - current_state`. To recover absolute: `absolute = relative + current_state`.
+
+**Why use relative actions?** The model learns to predict offsets centered around zero, which is easier to normalize and leads to more stable training. Because every chunk references the same current state, there is no error accumulation across chunks.
+
+### Delta Actions (sequential differences)
+
+Each action is an offset from the **previous action** (or from the current state for the first step):
+
+```
+current_state = [45.0, -30.0, 10.0]
+
+delta_chunk = [
+    [1.0,  1.0, 1.0],   # current → 46, -29, 11
+    [1.5,  2.0, 1.0],   # previous action → 47.5, -27, 12
+    [1.5,  2.0, 1.5],   # previous action → 49, -25, 13.5
+    [1.0,  1.0, 1.5],   # previous action → 50, -24, 15
+]
+```
+
+Here each step is relative to the one before it. To recover absolute positions you must sum all previous deltas, which means errors accumulate over time. UMI explicitly argues against this representation for this reason.
+
+### Visual Comparison
+
+The figure below (based on a figure from [UMI, Chi et al., 2024](https://arxiv.org/abs/2402.10329)) illustrates the key difference. With **relative trajectory**, every action in the chunk points back to the same origin (current state), so a new inference step cleanly resets the reference. With **delta**, each action depends on the previous one, so errors accumulate. **Absolute** actions require a consistent global coordinate frame.
+
+<img
+  src="https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/lerobot/action_representations_umi.png"
+  alt="Relative Trajectory as Action Representation (UMI, Chi et al., 2024)"
+  width="85%"
+/>
+
+## Using Relative Actions in LeRobot
+
+LeRobot provides `RelativeActionsProcessorStep` to convert between absolute and relative actions inside the processor pipeline. This is how pi0, pi0.5, and pi0_fast support relative actions.
+
+> **Note:** All pi models (pi0, pi0.5, pi0*fast) apply relative conversion \_before* normalization (`relative → normalize`), so the normalizer always sees delta (relative) values. This means **relative action stats are required** for all of them when training with `use_relative_actions=true`. In pi0_fast the `RelativeActionsProcessorStep` only modifies the action — the state observation is unchanged — so `NormalizerProcessorStep` still runs before the state tokenizer and the tokenizer continues to receive normalized state as expected.
+
+### How it works
+
+During **training** (preprocessing), actions are converted from absolute to relative before the model sees them:
+
+```
+raw absolute action → RelativeActionsProcessorStep → normalize → model
+```
+
+During **inference** (postprocessing), model predictions are converted back to absolute before being sent to the robot:
+
+```
+model output → unnormalize → AbsoluteActionsProcessorStep → robot
+```
+
+The `AbsoluteActionsProcessorStep` reads the cached current state from its paired `RelativeActionsProcessorStep`, so the two must be wired together (handled automatically by the policy factory).
+
+### Enabling relative actions for the pi family (pi0, pi0.5, pi0_fast)
+
+**Step 1**: Precompute relative action statistics for your dataset:
+
+```bash
+lerobot-edit-dataset \
+    --repo_id your_dataset \
+    --operation.type recompute_stats \
+    --operation.relative_action true \
+    --operation.chunk_size 50 \
+    --operation.relative_exclude_joints "['gripper']"
+```
+
+**Step 2**: Train with relative actions enabled:
+
+```bash
+lerobot-train \
+    --dataset.repo_id=your_dataset \
+    --policy.type=pi0 \
+    --policy.use_relative_actions=true \
+    --policy.relative_exclude_joints='["gripper"]'
+```
+
+The `relative_exclude_joints` parameter specifies joints that should remain in absolute space. For example, gripper commands are typically binary (open/close) and don't benefit from relative encoding.
+
+### Combining relative actions with RTC
+
+[RTC](https://arxiv.org/abs/2506.07339) runs policy inference at high frequency and sends actions to the robot as they are predicted rather than waiting for a full chunk. Relative actions and RTC are fully compatible: because every chunk in relative mode references the **same** current state (captured at the start of inference), each predicted action in the chunk remains a valid offset even if the robot has already moved. No special handling is needed — `RelativeActionsProcessorStep` caches the state once per inference call and `AbsoluteActionsProcessorStep` applies it to every action in the streamed output.
+
+### Combining relative actions with EE space
+
+Relative actions work in both joint space and EE space. For example, if your dataset stores EE actions, relative encoding converts them to offsets from the current EE pose:
+
+```
+current_ee_state = [x: 0.25, y: -0.10, z: 0.15, gripper: 0.8]
+
+absolute_ee_chunk = [
+    [0.26, -0.09, 0.16, 0.8],
+    [0.28, -0.07, 0.18, 0.8],
+]
+
+relative_ee_chunk = [
+    [0.01,  0.01, 0.01, 0.0],   # offset from current EE pose
+    [0.03,  0.03, 0.03, 0.0],   # offset from current EE pose
+]
+```
+
+## Processing Pipeline Summary
+
+Here is how the different processors compose. Each arrow is a processor step, and they can be chained in a `RobotProcessorPipeline` or `PolicyProcessorPipeline`:
+
+```
+                    ┌─────────────────────────────────────────┐
+   Action Space     │   Joint Space  ←──IK──→  EE Space      │
+                    │   ForwardKinematicsJointsToEE           │
+                    │   InverseKinematicsEEToJoints           │
+                    └─────────────────────────────────────────┘
+
+                    ┌─────────────────────────────────────────┐
+   Representation   │   Absolute  ←────→  Relative            │
+                    │   RelativeActionsProcessorStep (pre)    │
+                    │   AbsoluteActionsProcessorStep (post)   │
+                    └─────────────────────────────────────────┘
+
+                    ┌─────────────────────────────────────────┐
+   Normalization    │   Raw  ←────→  Normalized               │
+                    │   NormalizerProcessorStep (pre)         │
+                    │   UnnormalizerProcessorStep (post)      │
+                    └─────────────────────────────────────────┘
+```
+
+A typical training preprocessor might chain: `raw absolute joint actions → relative → normalize`. A typical inference postprocessor: `unnormalize → absolute → (optionally IK to joints)`.
+
+## References
+
+- [Universal Manipulation Interface (UMI)](https://arxiv.org/abs/2402.10329) - Chi et al., 2024. Defines the relative trajectory action representation and compares it with absolute and delta actions.
+- [Introduction to Processors](./introduction_processors) - How processor pipelines work in LeRobot.
+- [`examples/so100_to_so100_EE/`](https://github.com/huggingface/lerobot/tree/main/examples/so100_to_so100_EE) - Complete example of recording and evaluating with EE-space actions.

docs/source/adding_benchmarks.mdx

@@ -0,0 +1,320 @@
+# Adding a New Benchmark
+
+This guide walks you through adding a new simulation benchmark to LeRobot. Follow the steps in order and use the existing benchmarks as templates.
+
+A benchmark in LeRobot is a set of [Gymnasium](https://gymnasium.farama.org/) environments that wrap a third-party simulator (like LIBERO or Meta-World) behind a standard `gym.Env` interface. The `lerobot-eval` CLI then runs evaluation uniformly across all benchmarks.
+
+## Existing benchmarks at a glance
+
+Before diving in, here is what is already integrated:
+
+| Benchmark      | Env file            | Config class       | Tasks               | Action dim   | Processor                    |
+| -------------- | ------------------- | ------------------ | ------------------- | ------------ | ---------------------------- |
+| LIBERO         | `envs/libero.py`    | `LiberoEnv`        | 130 across 5 suites | 7            | `LiberoProcessorStep`        |
+| Meta-World     | `envs/metaworld.py` | `MetaworldEnv`     | 50 (MT50)           | 4            | None                         |
+| IsaacLab Arena | Hub-hosted          | `IsaaclabArenaEnv` | Configurable        | Configurable | `IsaaclabArenaProcessorStep` |
+
+Use `src/lerobot/envs/libero.py` and `src/lerobot/envs/metaworld.py` as reference implementations.
+
+## How it all fits together
+
+### Data flow
+
+During evaluation, data moves through four stages:
+
+```
+1. gym.Env  ──→  raw observations (numpy dicts)
+
+2. Preprocessing  ──→  standard LeRobot keys + task description
+   (preprocess_observation, add_envs_task in envs/utils.py)
+
+3. Processors  ──→  env-specific then policy-specific transforms
+   (env_preprocessor, policy_preprocessor)
+
+4. Policy  ──→  select_action()  ──→  action tensor
+   then reverse: policy_postprocessor → env_postprocessor → numpy action → env.step()
+```
+
+Most benchmarks only need to care about stage 1 (producing observations in the right format) and optionally stage 3 (if env-specific transforms are needed).
+
+### Environment structure
+
+`make_env()` returns a nested dict of vectorized environments:
+
+```python
+dict[str, dict[int, gym.vector.VectorEnv]]
+#    ^suite       ^task_id
+```
+
+A single-task env (e.g. PushT) looks like `{"pusht": {0: vec_env}}`.
+A multi-task benchmark (e.g. LIBERO) looks like `{"libero_spatial": {0: vec0, 1: vec1, ...}, ...}`.
+
+### How evaluation runs
+
+All benchmarks are evaluated the same way by `lerobot-eval`:
+
+1. `make_env()` builds the nested `{suite: {task_id: VectorEnv}}` dict.
+2. `eval_policy_all()` iterates over every suite and task.
+3. For each task, it runs `n_episodes` rollouts via `rollout()`.
+4. Results are aggregated hierarchically: episode, task, suite, overall.
+5. Metrics include `pc_success` (success rate), `avg_sum_reward`, and `avg_max_reward`.
+
+The critical piece: your env must return `info["is_success"]` on every `step()` call. This is how the eval loop knows whether a task was completed.
+
+## What your environment must provide
+
+LeRobot does not enforce a strict observation schema. Instead it relies on a set of conventions that all benchmarks follow.
+
+### Env attributes
+
+Your `gym.Env` must set these attributes:
+
+| Attribute            | Type  | Why                                                  |
+| -------------------- | ----- | ---------------------------------------------------- |
+| `_max_episode_steps` | `int` | `rollout()` uses this to cap episode length          |
+| `task_description`   | `str` | Passed to VLA policies as a language instruction     |
+| `task`               | `str` | Fallback identifier if `task_description` is not set |
+
+### Success reporting
+
+Your `step()` and `reset()` must include `"is_success"` in the `info` dict:
+
+```python
+info = {"is_success": True}   # or False
+return observation, reward, terminated, truncated, info
+```
+
+### Observations
+
+The simplest approach is to map your simulator's outputs to the standard keys that `preprocess_observation()` already understands. Do this inside your `gym.Env` (e.g. in a `_format_raw_obs()` helper):
+
+| Your env should output    | LeRobot maps it to         | What it is                            |
+| ------------------------- | -------------------------- | ------------------------------------- |
+| `"pixels"` (single array) | `observation.image`        | Single camera image, HWC uint8        |
+| `"pixels"` (dict)         | `observation.images.<cam>` | Multiple cameras, each HWC uint8      |
+| `"agent_pos"`             | `observation.state`        | Proprioceptive state vector           |
+| `"environment_state"`     | `observation.env_state`    | Full environment state (e.g. PushT)   |
+| `"robot_state"`           | `observation.robot_state`  | Nested robot state dict (e.g. LIBERO) |
+
+If your simulator uses different key names, you have two options:
+
+1. **Recommended:** Rename them to the standard keys inside your `gym.Env` wrapper.
+2. **Alternative:** Write an env processor to transform observations after `preprocess_observation()` runs (see step 4 below).
+
+### Actions
+
+Actions are continuous numpy arrays in a `gym.spaces.Box`. The dimensionality depends on your benchmark (7 for LIBERO, 4 for Meta-World, etc.). Policies adapt to different action dimensions through their `input_features` / `output_features` config.
+
+### Feature declaration
+
+Each `EnvConfig` subclass declares two dicts that tell the policy what to expect:
+
+- `features` — maps feature names to `PolicyFeature(type, shape)` (e.g. action dim, image shape).
+- `features_map` — maps raw observation keys to LeRobot convention keys (e.g. `"agent_pos"` to `"observation.state"`).
+
+## Step by step
+
+<Tip>
+  At minimum, you need two files: a **gym.Env wrapper** and an **EnvConfig
+  subclass** with a `create_envs()` override. Everything else is optional or
+  documentation. No changes to `factory.py` are needed.
+</Tip>
+
+### Checklist
+
+| File                                     | Required | Why                                                          |
+| ---------------------------------------- | -------- | ------------------------------------------------------------ |
+| `src/lerobot/envs/<benchmark>.py`        | Yes      | Wraps the simulator as a standard gym.Env                    |
+| `src/lerobot/envs/configs.py`            | Yes      | Registers your benchmark and its `create_envs()` for the CLI |
+| `src/lerobot/processor/env_processor.py` | Optional | Custom observation/action transforms                         |
+| `src/lerobot/envs/utils.py`              | Optional | Only if you need new raw observation keys                    |
+| `pyproject.toml`                         | Yes      | Declares benchmark-specific dependencies                     |
+| `docs/source/<benchmark>.mdx`            | Yes      | User-facing documentation page                               |
+| `docs/source/_toctree.yml`               | Yes      | Adds your page to the docs sidebar                           |
+
+### 1. The gym.Env wrapper (`src/lerobot/envs/<benchmark>.py`)
+
+Create a `gym.Env` subclass that wraps the third-party simulator:
+
+```python
+class MyBenchmarkEnv(gym.Env):
+    metadata = {"render_modes": ["rgb_array"], "render_fps": <fps>}
+
+    def __init__(self, task_suite, task_id, ...):
+        super().__init__()
+        self.task = <task_name_string>
+        self.task_description = <natural_language_instruction>
+        self._max_episode_steps = <max_steps>
+        self.observation_space = spaces.Dict({...})
+        self.action_space = spaces.Box(low=..., high=..., shape=(...,), dtype=np.float32)
+
+    def reset(self, seed=None, **kwargs):
+        ...  # return (observation, info) — info must contain {"is_success": False}
+
+    def step(self, action: np.ndarray):
+        ...  # return (obs, reward, terminated, truncated, info) — info must contain {"is_success": <bool>}
+
+    def render(self):
+        ...  # return RGB image as numpy array
+
+    def close(self):
+        ...
+```
+
+Also provide a factory function that returns the nested dict structure:
+
+```python
+def create_mybenchmark_envs(
+    task: str,
+    n_envs: int,
+    gym_kwargs: dict | None = None,
+    env_cls: type | None = None,
+) -> dict[str, dict[int, Any]]:
+    """Create {suite_name: {task_id: VectorEnv}} for MyBenchmark."""
+    ...
+```
+
+See `create_libero_envs()` (multi-suite, multi-task) and `create_metaworld_envs()` (difficulty-grouped tasks) for reference.
+
+### 2. The config (`src/lerobot/envs/configs.py`)
+
+Register a config dataclass so users can select your benchmark with `--env.type=<name>`. Each config owns its environment creation and processor logic via two methods:
+
+- **`create_envs(n_envs, use_async_envs)`** — Returns `{suite: {task_id: VectorEnv}}`. The base class default uses `gym.make()` for single-task envs. Multi-task benchmarks override this.
+- **`get_env_processors()`** — Returns `(preprocessor, postprocessor)`. The base class default returns identity (no-op) pipelines. Override if your benchmark needs observation/action transforms.
+
+```python
+@EnvConfig.register_subclass("<benchmark_name>")
+@dataclass
+class MyBenchmarkEnvConfig(EnvConfig):
+    task: str = "<default_task>"
+    fps: int = <fps>
+    obs_type: str = "pixels_agent_pos"
+
+    features: dict[str, PolicyFeature] = field(default_factory=lambda: {
+        ACTION: PolicyFeature(type=FeatureType.ACTION, shape=(<action_dim>,)),
+    })
+    features_map: dict[str, str] = field(default_factory=lambda: {
+        ACTION: ACTION,
+        "agent_pos": OBS_STATE,
+        "pixels": OBS_IMAGE,
+    })
+
+    def __post_init__(self):
+        ...  # populate features based on obs_type
+
+    @property
+    def gym_kwargs(self) -> dict:
+        return {"obs_type": self.obs_type, "render_mode": self.render_mode}
+
+    def create_envs(self, n_envs: int, use_async_envs: bool = False):
+        """Override for multi-task benchmarks or custom env creation."""
+        from lerobot.envs.<benchmark> import create_<benchmark>_envs
+        return create_<benchmark>_envs(task=self.task, n_envs=n_envs, ...)
+
+    def get_env_processors(self):
+        """Override if your benchmark needs observation/action transforms."""
+        from lerobot.processor.pipeline import PolicyProcessorPipeline
+        from lerobot.processor.env_processor import MyBenchmarkProcessorStep
+        return (
+            PolicyProcessorPipeline(steps=[MyBenchmarkProcessorStep()]),
+            PolicyProcessorPipeline(steps=[]),
+        )
+```
+
+Key points:
+
+- The `register_subclass` name is what users pass on the CLI (`--env.type=<name>`).
+- `features` tells the policy what the environment produces.
+- `features_map` maps raw observation keys to LeRobot convention keys.
+- **No changes to `factory.py` needed** — the factory delegates to `cfg.create_envs()` and `cfg.get_env_processors()` automatically.
+
+### 3. Env processor (optional — `src/lerobot/processor/env_processor.py`)
+
+Only needed if your benchmark requires observation transforms beyond what `preprocess_observation()` handles (e.g. image flipping, coordinate conversion). Define the processor step here and return it from `get_env_processors()` in your config (see step 2):
+
+```python
+@dataclass
+@ProcessorStepRegistry.register(name="<benchmark>_processor")
+class MyBenchmarkProcessorStep(ObservationProcessorStep):
+    def _process_observation(self, observation):
+        processed = observation.copy()
+        # your transforms here
+        return processed
+
+    def transform_features(self, features):
+        return features  # update if shapes change
+
+    def observation(self, observation):
+        return self._process_observation(observation)
+```
+
+See `LiberoProcessorStep` for a full example (image rotation, quaternion-to-axis-angle conversion).
+
+### 4. Dependencies (`pyproject.toml`)
+
+Add a new optional-dependency group:
+
+```toml
+mybenchmark = ["my-benchmark-pkg==1.2.3", "lerobot[scipy-dep]"]
+```
+
+Pinning rules:
+
+- **Always pin** benchmark packages to exact versions for reproducibility (e.g. `metaworld==3.0.0`).
+- **Add platform markers** when needed (e.g. `; sys_platform == 'linux'`).
+- **Pin fragile transitive deps** if known (e.g. `gymnasium==1.1.0` for Meta-World).
+- **Document constraints** in your benchmark doc page.
+
+Users install with:
+
+```bash
+pip install -e ".[mybenchmark]"
+```
+
+### 5. Documentation (`docs/source/<benchmark>.mdx`)
+
+Write a user-facing page following the template in the next section. See `docs/source/libero.mdx` and `docs/source/metaworld.mdx` for full examples.
+
+### 6. Table of contents (`docs/source/_toctree.yml`)
+
+Add your benchmark to the "Benchmarks" section:
+
+```yaml
+- sections:
+    - local: libero
+      title: LIBERO
+    - local: metaworld
+      title: Meta-World
+    - local: envhub_isaaclab_arena
+      title: NVIDIA IsaacLab Arena Environments
+    - local: <your_benchmark>
+      title: <Your Benchmark Name>
+  title: "Benchmarks"
+```
+
+## Verifying your integration
+
+After completing the steps above, confirm that everything works:
+
+1. **Install** — `pip install -e ".[mybenchmark]"` and verify the dependency group installs cleanly.
+2. **Smoke test env creation** — call `make_env()` with your config in Python, check that the returned dict has the expected `{suite: {task_id: VectorEnv}}` shape, and that `reset()` returns observations with the right keys.
+3. **Run a full eval** — `lerobot-eval --env.type=<name> --env.task=<task> --eval.n_episodes=1 --eval.batch_size=1 --policy.path=<any_compatible_policy>` to exercise the full pipeline end-to-end.
+4. **Check success detection** — verify that `info["is_success"]` flips to `True` when the task is actually completed. This is what the eval loop uses to compute success rates.
+
+## Writing a benchmark doc page
+
+Each benchmark `.mdx` page should include:
+
+- **Title and description** — 1-2 paragraphs on what the benchmark tests and why it matters.
+- **Links** — paper, GitHub repo, project website (if available).
+- **Overview image or GIF.**
+- **Available tasks** — table of task suites with counts and brief descriptions.
+- **Installation** — `pip install -e ".[<benchmark>]"` plus any extra steps (env vars, system packages).
+- **Evaluation** — recommended `lerobot-eval` command with `n_episodes` and `batch_size` for reproducible results. Include single-task and multi-task examples if applicable.
+- **Policy inputs and outputs** — observation keys with shapes, action space description.
+- **Recommended evaluation episodes** — how many episodes per task is standard.
+- **Training** — example `lerobot-train` command.
+- **Reproducing published results** — link to pretrained model, eval command, results table (if available).
+
+See `docs/source/libero.mdx` and `docs/source/metaworld.mdx` for complete examples.

docs/source/async.mdx

@@ -310,4 +310,4 @@ Asynchronous inference represents a significant advancement in real-time robotic
 - **Universal Compatibility**: Works with all LeRobot-supported policies, from lightweight ACT models to vision-language models like SmolVLA
 
 Start experimenting with the default parameters, monitor your action queue sizes, and iteratively refine your setup to achieve optimal performance for your specific use case.
-If you want to discuss this further, hop into our [Discord community](https://discord.gg/s3KuuzsPFb), or open an issue on our [GitHub repository](https://github.com/lerobot/lerobot/issues).
+If you want to discuss this further, hop into our [Discord community](https://discord.gg/s3KuuzsPFb), or open an issue on our [GitHub repository](https://github.com/huggingface/lerobot/issues).

docs/source/bring_your_own_policies.mdx

@@ -41,13 +41,15 @@ requires = # your-build-system
 
 ## Step 2: Define the Policy Configuration
 
-Create a configuration class that inherits from `PreTrainedConfig` and registers your policy type:
+Create a configuration class that inherits from [`PreTrainedConfig`](https://github.com/huggingface/lerobot/blob/main/src/lerobot/configs/policies.py) and registers your policy type:
+Here is a template to get you started, customize the parameters and methods as needed for your policy's architecture and training requirements.
 
 ```python
 # configuration_my_custom_policy.py
 from dataclasses import dataclass, field
 from lerobot.configs.policies import PreTrainedConfig
-from lerobot.configs.types import NormalizationMode
+from lerobot.optim.optimizers import AdamWConfig
+from lerobot.optim.schedulers import CosineDecayWithWarmupSchedulerConfig
 
 @PreTrainedConfig.register_subclass("my_custom_policy")
 @dataclass
@@ -61,22 +63,56 @@ class MyCustomPolicyConfig(PreTrainedConfig):
         hidden_dim: Hidden dimension for the policy network
         # Add your policy-specific parameters here
     """
-    # ...PreTrainedConfig fields...
-    pass
+
+    horizon: int = 50
+    n_action_steps: int = 50
+    hidden_dim: int = 256
+
+    optimizer_lr: float = 1e-4
+    optimizer_weight_decay: float = 1e-4
 
     def __post_init__(self):
         super().__post_init__()
-        # Add any validation logic here
+        if self.n_action_steps > self.horizon:
+            raise ValueError("n_action_steps cannot exceed horizon")
 
     def validate_features(self) -> None:
         """Validate input/output feature compatibility."""
-        # Implement validation logic for your policy's requirements
-        pass
+        if not self.image_features:
+            raise ValueError("MyCustomPolicy requires at least one image feature.")
+        if self.action_feature is None:
+            raise ValueError("MyCustomPolicy requires 'action' in output_features.")
+
+    def get_optimizer_preset(self) -> AdamWConfig:
+        return AdamWConfig(lr=self.optimizer_lr, weight_decay=self.optimizer_weight_decay)
+
+    def get_scheduler_preset(self):
+        return None
+
+    @property
+    def observation_delta_indices(self) -> list[int] | None:
+        """Relative timestep offsets the dataset loader provides per observation.
+
+        Return `None` for single-frame policies. For temporal policies that consume
+        multiple past or future frames, return a list of offsets, e.g. `[-20, -10, 0, 10]` for
+        3 past frames at stride 10 and 1 future frame at stride 10.
+        """
+        return None
+
+    @property
+    def action_delta_indices(self) -> list[int]:
+        """Relative timestep offsets for the action chunk the dataset loader returns.
+        """
+        return list(range(self.horizon))
+
+    @property
+    def reward_delta_indices(self) -> None:
+        return None
 ```
 
 ## Step 3: Implement the Policy Class
 
-Create your policy implementation by inheriting from LeRobot's base `PreTrainedPolicy` class:
+Create your policy implementation by inheriting from [`PreTrainedPolicy`](https://github.com/huggingface/lerobot/blob/main/src/lerobot/policies/pretrained.py):
 
 ```python
 # modeling_my_custom_policy.py
@@ -85,38 +121,74 @@ import torch.nn as nn
 from typing import Any
 
 from lerobot.policies.pretrained import PreTrainedPolicy
+from lerobot.utils.constants import ACTION
 from .configuration_my_custom_policy import MyCustomPolicyConfig
 
 class MyCustomPolicy(PreTrainedPolicy):
-    config_class = MyCustomPolicyConfig
+    config_class = MyCustomPolicyConfig  # must match the string in @register_subclass
     name = "my_custom_policy"
 
     def __init__(self, config: MyCustomPolicyConfig, dataset_stats: dict[str, Any] = None):
         super().__init__(config, dataset_stats)
+        config.validate_features()  # not called automatically by the base class
+        self.config = config
+        self.model = ...  # your nn.Module here
+
+    def reset(self):
+        """Reset episode state."""
         ...
+
+    def get_optim_params(self) -> dict:
+        """Return parameters to pass to the optimizer (e.g. with per-group lr/wd)."""
+        return {"params": self.parameters()}
+
+    def predict_action_chunk(self, batch: dict[str, torch.Tensor], **kwargs) -> torch.Tensor:
+        """Return the full action chunk (B, chunk_size, action_dim) for the current observation."""
+        ...
+
+    def select_action(self, batch: dict[str, torch.Tensor], **kwargs) -> torch.Tensor:
+        """Return a single action for the current timestep (called at inference)."""
+        ...
+
+    def forward(self, batch: dict[str, torch.Tensor]) -> dict[str, torch.Tensor]:
+        """Compute the training loss.
+
+        `batch["action_is_pad"]` is a bool mask of shape (B, horizon) that marks
+        timesteps padded because the episode ended before `horizon` steps, you
+        can exclude those from your loss.
+        """
+        actions = batch[ACTION]
+        action_is_pad = batch.get("action_is_pad")
+        ...
+        return {"loss": ...}
 ```
 
 ## Step 4: Add Data Processors
 
-Create processor functions:
+Create processor functions. For a concrete reference, see [processor_act.py](https://github.com/huggingface/lerobot/blob/main/src/lerobot/policies/act/processor_act.py) or [processor_diffusion.py](https://github.com/huggingface/lerobot/blob/main/src/lerobot/policies/diffusion/processor_diffusion.py).
 
 ```python
 # processor_my_custom_policy.py
 from typing import Any
 import torch
 
+from lerobot.processor import PolicyAction, PolicyProcessorPipeline
+
 
 def make_my_custom_policy_pre_post_processors(
     config,
+    dataset_stats: dict[str, dict[str, torch.Tensor]] | None = None,
 ) -> tuple[
     PolicyProcessorPipeline[dict[str, Any], dict[str, Any]],
     PolicyProcessorPipeline[PolicyAction, PolicyAction],
 ]:
-    """Create preprocessing and postprocessing functions for your policy."""
-    pass  # Define your preprocessing and postprocessing logic here
-
+    preprocessor = ...   # build your PolicyProcessorPipeline for inputs
+    postprocessor = ...  # build your PolicyProcessorPipeline for outputs
+    return preprocessor, postprocessor
 ```
 
+**Important - function naming:** LeRobot discovers your processor by name. The function **must** be called `make_{policy_name}_pre_post_processors` (matching the string you passed to `@PreTrainedConfig.register_subclass`).
+
 ## Step 5: Package Initialization
 
 Expose your classes in the package's `__init__.py`:

docs/source/earthrover_mini_plus.mdx

@@ -204,22 +204,26 @@ Replace `your_username/dataset_name` with your Hugging Face username and a name
 
 Your dataset includes:
 
-**Your Actions (2 things)**:
+**Your Actions (2 features)**:
 
-- How much you moved forward/backward
-- How much you turned left/right
+- `linear_velocity`: How much you moved forward/backward
+- `angular_velocity`: How much you turned left/right
 
-**Robot Observations (12 things)**:
+**Robot Observations (24 features)**:
 
 - Front camera video
 - Rear camera video
 - Current speed
 - Battery level
-- Which way the robot is facing
-- GPS location (latitude, longitude, signal strength)
+- Orientation
+- GPS (latitude, longitude, signal strength)
 - Network signal strength
 - Vibration level
-- Lamp status (on/off)
+- Lamp state (on/off)
+- Accelerometer (x, y, z)
+- Gyroscope (x, y, z)
+- Magnetometer (x, y, z)
+- Wheel RPMs (4 wheels)
 
 ### Where Your Data Goes
 

docs/source/env_processor.mdx

@@ -90,11 +90,17 @@ The same policy can work with different environment processors, and the same env
 
 ```python
 # Use SmolVLA policy with LIBERO environment
-libero_preprocessor, libero_postprocessor = make_env_pre_post_processors(libero_cfg)
+# Use SmolVLA policy with LIBERO environment
+libero_preprocessor, libero_postprocessor = make_env_pre_post_processors(
+    env_cfg=libero_cfg,
+    policy_cfg=smolvla_cfg,
+)
 smolvla_preprocessor, smolvla_postprocessor = make_pre_post_processors(smolvla_cfg)
-
 # Or use ACT policy with the same LIBERO environment
-libero_preprocessor, libero_postprocessor = make_env_pre_post_processors(libero_cfg)
+libero_preprocessor, libero_postprocessor = make_env_pre_post_processors(
+    env_cfg=libero_cfg,
+    policy_cfg=act_cfg,
+)
 act_preprocessor, act_postprocessor = make_pre_post_processors(act_cfg)
 ```
 
@@ -151,7 +157,7 @@ observation = {
 
 ### Factory Function
 
-The `make_env_pre_post_processors` function follows the same pattern as `make_pre_post_processors` for policies:
+The `make_env_pre_post_processors` function delegates to `env_cfg.get_env_processors()`:
 
 ```python
 from lerobot.envs.factory import make_env_pre_post_processors
@@ -159,47 +165,31 @@ from lerobot.envs.configs import LiberoEnv, PushtEnv
 
 # For LIBERO: Returns LiberoProcessorStep in preprocessor
 libero_cfg = LiberoEnv(task="libero_spatial", camera_name=["agentview"])
-env_preprocessor, env_postprocessor = make_env_pre_post_processors(libero_cfg)
+env_preprocessor, env_postprocessor = make_env_pre_post_processors(libero_cfg, policy_cfg)
 
 # For other environments: Returns identity processors (no-op)
 pusht_cfg = PushtEnv()
-env_preprocessor, env_postprocessor = make_env_pre_post_processors(pusht_cfg)
+env_preprocessor, env_postprocessor = make_env_pre_post_processors(pusht_cfg, policy_cfg)
 ```
 
-### Implementation in `envs/factory.py`
+### How It Works
+
+Each `EnvConfig` subclass can override `get_env_processors()` to return benchmark-specific
+processor pipelines. The base class returns identity (no-op) processors by default.
 
 ```python
-def make_env_pre_post_processors(
-    env_cfg: EnvConfig,
-) -> tuple[
-    PolicyProcessorPipeline[dict[str, Any], dict[str, Any]],
-    PolicyProcessorPipeline[dict[str, Any], dict[str, Any]],
-]:
-    """
-    Create preprocessor and postprocessor pipelines for environment observations.
-
-    Args:
-        env_cfg: The configuration of the environment.
-
-    Returns:
-        A tuple containing:
-            - preprocessor: Pipeline that processes environment observations
-            - postprocessor: Pipeline that processes environment outputs
-    """
-    # For LIBERO environments, add the LiberoProcessorStep to preprocessor
-    if isinstance(env_cfg, LiberoEnv) or "libero" in env_cfg.type:
-        preprocessor = PolicyProcessorPipeline(steps=[LiberoProcessorStep()])
-    else:
-        # For all other environments, return an identity preprocessor
-        preprocessor = PolicyProcessorPipeline(steps=[])
-
-    # Postprocessor is currently identity for all environments
-    # Future: Could add environment-specific action transformations
-    postprocessor = PolicyProcessorPipeline(steps=[])
-
-    return preprocessor, postprocessor
+# In your EnvConfig subclass:
+def get_env_processors(self):
+    from lerobot.processor.pipeline import PolicyProcessorPipeline
+    return (
+        PolicyProcessorPipeline(steps=[MyProcessorStep()]),
+        PolicyProcessorPipeline(steps=[]),
+    )
 ```
 
+The factory function `make_env_pre_post_processors` simply delegates to this method,
+with a special case for `XVLAConfig` policies which override the env processors entirely.
+
 ### Integration in Evaluation
 
 In `lerobot_eval.py`, the environment processors are created once and used throughout:
@@ -219,7 +209,10 @@ def eval_main(cfg: EvalPipelineConfig):
     )
 
     # Create environment processors (NEW!)
-    env_preprocessor, env_postprocessor = make_env_pre_post_processors(env_cfg=cfg.env)
+    env_preprocessor, env_postprocessor = make_env_pre_post_processors(
+        env_cfg=cfg.env,
+        policy_cfg=cfg.policy,
+    )
 
     # Run evaluation with both processor types
     eval_policy_all(
@@ -323,21 +316,22 @@ class MyEnvProcessorStep(ObservationProcessorStep):
         return processed
 ```
 
-### 2. Update the Factory
+### 2. Update Your `EnvConfig` Subclass
 
 ```python
-# In src/lerobot/envs/factory.py
+# In src/lerobot/envs/configs.py
+@EnvConfig.register_subclass("myenv")
+@dataclass
+class MyEnvConfig(EnvConfig):
+    # ... task/features/gym kwargs ...
 
-def make_env_pre_post_processors(env_cfg: EnvConfig):
-    if isinstance(env_cfg, LiberoEnv) or "libero" in env_cfg.type:
-        preprocessor = PolicyProcessorPipeline(steps=[LiberoProcessorStep()])
-    elif isinstance(env_cfg, MyEnvConfig) or "myenv" in env_cfg.type:
-        preprocessor = PolicyProcessorPipeline(steps=[MyEnvProcessorStep()])
-    else:
-        preprocessor = PolicyProcessorPipeline(steps=[])
+    def get_env_processors(self):
+        from lerobot.processor.pipeline import PolicyProcessorPipeline
 
-    postprocessor = PolicyProcessorPipeline(steps=[])
-    return preprocessor, postprocessor
+        return (
+            PolicyProcessorPipeline(steps=[MyEnvProcessorStep()]),
+            PolicyProcessorPipeline(steps=[]),
+        )
 ```
 
 ### 3. Use in Evaluation

docs/source/groot.mdx

@@ -131,4 +131,4 @@ lerobot-record \
 
 ## License
 
-This model follows the **Apache 2.0 License**, consistent with the original [GR00T repository](https://github.com/NVIDIA/Isaac-GR00T).
+This model follows NVIDIA's proprietary license, consistent with the original [GR00T repository](https://github.com/NVIDIA/Isaac-GR00T). Future versions (starting from N1.7) will follow **Apache 2.0 License**.

docs/source/hil_data_collection.mdx

@@ -0,0 +1,269 @@
+# Human-In-the-Loop Data Collection
+
+Human-In-the-Loop (HIL) data collection lets you improve a trained policy by deploying it on a real robot while a human operator monitors and intervenes when needed. The intervention data (recovery movements and corrections) is recorded alongside autonomous segments, producing a richer training dataset that teaches the policy how to handle failures.
+
+---
+
+## Why Human-In-the-Loop?
+
+Standard behavioral cloning trains policies on successful demonstrations only. During deployment, small errors can compound and push the robot into states never seen during training (distribution shift). HIL data collection addresses this by:
+
+- Running the trained policy on the real robot
+- Having a human intervene when the robot is about to fail
+- Recording the human's recovery and correction as training data
+- Fine-tuning the policy on the combined dataset
+
+This produces a policy that not only knows how to perform the task, but also how to recover when things go wrong.
+
+---
+
+## How It Works
+
+During a HIL session, the human operator follows this loop within each episode:
+
+1. **Watch** the policy run autonomously
+2. **Pause** when failure is imminent, the robot holds its position
+3. **Take control** and teleoperate the robot back to a good state (recovery), then correct the behavior
+4. **Return control to the policy**, the policy resumes autonomous execution
+5. Repeat steps 2–4 as many times as needed during the episode
+6. **End the episode** when the task is complete, save and move on to the next rollout
+
+Both autonomous and human-controlled segments are recorded. The policy and human can alternate control multiple times within a single episode, and the episode continues from the current state after each handoff (no reset required just because intervention happened). This captures autonomous execution, recovery, and correction in one continuous trajectory. After collection, the combined dataset (original demonstrations + HIL data) is used to fine-tune the policy.
+
+This process can be repeated iteratively: deploy, collect, fine-tune, repeat. Each round targets the current policy's failure modes.
+
+```
+┌─────────────────────────────────────────────────────────────────────────┐
+│  Policy v0 (trained on demos)                                           │
+│       ↓                                                                 │
+│  HIL Collection (target current failure modes) → Fine-tune → Policy v1  │
+│       ↓                                                                 │
+│  HIL Collection (target new failure modes) → Fine-tune → Policy v2      │
+│       ↓                                                                 │
+│  ... (repeat until satisfactory performance)                            │
+└─────────────────────────────────────────────────────────────────────────┘
+```
+
+---
+
+## Hardware Requirements
+
+### Teleoperator Requirements
+
+The `examples/hil` HIL scripts require **teleoperators with active motors** that can:
+
+- Enable/disable torque programmatically
+- Move to target positions (to mirror the robot state when pausing)
+
+**Compatible teleoperators in the current `examples/hil` scripts:**
+
+- `openarm_mini` - OpenArm Mini
+- `so_leader` - SO100 / SO101 leader arm
+
+> [!IMPORTANT]
+> The provided `examples/hil` commands default to `bi_openarm_follower` + `openarm_mini`.
+> `so_follower` + `so_leader` configs are also registered and can be used via CLI flags.
+
+---
+
+## Script
+
+A single script handles both synchronous and RTC-based inference. Toggle RTC with `--rtc.enabled=true`:
+
+| Mode                     | Flag                 | Models                |
+| ------------------------ | -------------------- | --------------------- |
+| Standard (default)       | _(no flag needed)_   | ACT, Diffusion Policy |
+| Real-Time Chunking (RTC) | `--rtc.enabled=true` | Pi0, Pi0.5, SmolVLA   |
+
+---
+
+## Step-by-Step Guide
+
+### Step 1: Pre-train a Base Policy
+
+First, train a policy on your demonstration dataset:
+
+```bash
+python src/lerobot/scripts/lerobot_train.py \
+    --dataset.repo_id=your-username/demo-dataset \
+    --policy.type=pi0 \
+    --output_dir=outputs/pretrain \
+    --batch_size=32 \
+    --steps=50000
+```
+
+### Step 2: Collect HIL Data
+
+**Standard inference (ACT, Diffusion Policy):**
+
+```bash
+python examples/hil/hil_data_collection.py \
+    --robot.type=bi_openarm_follower \
+    --robot.left_arm_config.port=can1 \
+    --robot.left_arm_config.side=left \
+    --robot.right_arm_config.port=can0 \
+    --robot.right_arm_config.side=right \
+    --robot.cameras='{left_wrist: {type: opencv, index_or_path: "/dev/video0", width: 1280, height: 720, fps: 30}, right_wrist: {type: opencv, index_or_path: "/dev/video4", width: 1280, height: 720, fps: 30}, base: {type: opencv, index_or_path: "/dev/video2", width: 640, height: 480, fps: 30}}' \
+    --teleop.type=openarm_mini \
+    --teleop.port_left=/dev/ttyACM0 \
+    --teleop.port_right=/dev/ttyACM1 \
+    --policy.path=outputs/pretrain/checkpoints/last/pretrained_model \
+    --dataset.repo_id=your-username/hil-dataset \
+    --dataset.single_task="Fold the T-shirt properly" \
+    --dataset.fps=30 \
+    --dataset.episode_time_s=1000 \
+    --dataset.num_episodes=50 \
+    --interpolation_multiplier=2
+```
+
+**With RTC for large models (Pi0, Pi0.5, SmolVLA):**
+
+For models with high inference latency, enable RTC for smooth execution:
+
+```bash
+python examples/hil/hil_data_collection.py \
+    --rtc.enabled=true \
+    --rtc.execution_horizon=20 \
+    --rtc.max_guidance_weight=5.0 \
+    --rtc.prefix_attention_schedule=LINEAR \
+    --robot.type=bi_openarm_follower \
+    --robot.left_arm_config.port=can1 \
+    --robot.left_arm_config.side=left \
+    --robot.right_arm_config.port=can0 \
+    --robot.right_arm_config.side=right \
+    --robot.cameras='{left_wrist: {type: opencv, index_or_path: "/dev/video0", width: 1280, height: 720, fps: 30}, right_wrist: {type: opencv, index_or_path: "/dev/video4", width: 1280, height: 720, fps: 30}, base: {type: opencv, index_or_path: "/dev/video2", width: 640, height: 480, fps: 30}}' \
+    --teleop.type=openarm_mini \
+    --teleop.port_left=/dev/ttyACM0 \
+    --teleop.port_right=/dev/ttyACM1 \
+    --policy.path=outputs/pretrain/checkpoints/last/pretrained_model \
+    --dataset.repo_id=your-username/hil-rtc-dataset \
+    --dataset.single_task="Fold the T-shirt properly" \
+    --dataset.fps=30 \
+    --dataset.episode_time_s=1000 \
+    --dataset.num_episodes=50 \
+    --interpolation_multiplier=3
+```
+
+**Controls (Conceptual):**
+
+The interaction model is:
+
+- **Pause input**: pause autonomous policy execution
+- **Takeover input**: transfer control to the human operator and record intervention data
+- **Return-to-policy input**: hand control back to the policy and continue the same episode
+- **Episode control inputs**: save/re-record/stop/reset as needed
+
+Exact key/pedal bindings can differ across scripts and hardware integrations. Use each script's printed controls as the source of truth for the concrete mapping on your setup.
+
+**The HIL Protocol:**
+
+1. Watch the policy run autonomously (teleop is idle/free)
+2. When you see imminent failure, trigger the **pause input**
+   - Policy stops
+   - Teleoperator moves to match robot position (torque enabled)
+   - No frames recorded during pause
+3. Trigger the **takeover input** to take control
+   - Teleoperator torque disabled, free to move
+   - **Recovery**: Teleoperate the robot back to a good state
+   - **Correction**: Correct the behavior
+   - All movements are recorded
+4. Trigger the **return-to-policy input**
+   - Policy resumes autonomous execution from the current state
+   - You can intervene again at any time (repeat steps 2–4)
+5. End and save the episode when the task is complete (or episode time limit is reached)
+6. **Reset**: Teleop moves to robot position, you can move the robot to the starting position
+7. Start the next episode
+
+**Foot Pedal Setup (Linux):**
+
+If using a USB foot pedal (PCsensor FootSwitch), ensure access:
+
+```bash
+sudo setfacl -m u:$USER:rw /dev/input/by-id/usb-PCsensor_FootSwitch-event-kbd
+```
+
+### Step 3: Fine-tune the Policy
+
+Fine-tune on the **combined** dataset (`demo-dataset` + `hil-dataset` merged together):
+
+```bash
+python src/lerobot/scripts/lerobot_train.py \
+    --dataset.repo_id=your-username/hil-dataset \
+    --policy.type=pi0 \
+    --policy.pretrained_path=outputs/pretrain/checkpoints/last/pretrained_model \
+    --output_dir=outputs/hil_finetune \
+    --steps=20000
+```
+
+Then deploy the fine-tuned policy and repeat from Step 2 to target its remaining failure modes.
+
+---
+
+## Tips for Effective HIL Collection
+
+### When to Intervene
+
+Intervene when you see:
+
+- Robot about to make an irreversible mistake
+- Robot hesitating or showing uncertain behavior
+- Robot deviating from the expected trajectory
+
+### Recovery: Teleoperating Back to a Good State
+
+During recovery, teleoperate the robot back to a state where:
+
+- The robot is in a familiar, in-distribution configuration
+- The current subtask can still be completed
+- The recovery trajectory itself is informative training data
+
+### Quality of Corrections
+
+During correction:
+
+- Provide **confident, clean** trajectories
+- Complete the current subtask fully
+- Don't overcorrect or add unnecessary movements
+
+---
+
+## Related Work
+
+This HIL data collection approach builds on ideas from interactive imitation learning:
+
+- **DAgger** (Ross et al., 2011) introduced the core idea: instead of only training on expert demonstrations, query the expert for corrections on states the _learner_ visits. This breaks the compounding-error cycle of standard behavioral cloning by iteratively collecting on-policy data.
+
+- **HG-DAgger** (Kelly et al., 2019) made this practical for robotics: a human expert monitors the robot and only intervenes when needed, rather than labeling every state. The gating between autonomous and human control is exactly the pause → takeover → return-to-policy loop used in the scripts here.
+
+- **RaC** (Hu et al., 2025) scales this loop to long-horizon tasks by explicitly decomposing interventions into **recovery** (teleoperating back to a good state) and **correction** (demonstrating the right behavior from there). This decomposition is the protocol followed by the HIL scripts in `examples/hil`.
+
+- **π0.6/RECAP** (Physical Intelligence, 2025) applies the same iterative collect-and-finetune loop at scale with VLA models, showing that even large pretrained policies benefit substantially from targeted human corrections on their own failure modes. π0.6 is trained using RECAP.
+
+```bibtex
+@article{ross2011dagger,
+  title={A Reduction of Imitation Learning and Structured Prediction to No-Regret Online Learning},
+  author={Ross, Stéphane and Gordon, Geoffrey and Bagnell, Drew},
+  journal={Proceedings of the Fourteenth International Conference on Artificial Intelligence and Statistics},
+  year={2011}
+}
+
+@article{kelly2019hgdagger,
+  title={HG-DAgger: Interactive Imitation Learning with Human Experts},
+  author={Kelly, Michael and Sidrane, Chelsea and Driggs-Campbell, Katherine and Kochenderfer, Mykel J},
+  journal={arXiv preprint arXiv:1810.02890},
+  year={2019}
+}
+
+@article{hu2025rac,
+  title={RaC: Robot Learning for Long-Horizon Tasks by Scaling Recovery and Correction},
+  author={Hu, Zheyuan and Wu, Robyn and Enock, Naveen and Li, Jasmine and Kadakia, Riya and Erickson, Zackory and Kumar, Aviral},
+  journal={arXiv preprint arXiv:2509.07953},
+  year={2025}
+}
+
+@article{pi2025recap,
+  title={π0.6: a VLA That Learns From Experience},
+  author={Physical Intelligence},
+  year={2025}
+}
+```

docs/source/il_robots.mdx

@@ -165,7 +165,7 @@ hf auth login --token ${HUGGINGFACE_TOKEN} --add-to-git-credential
 Then store your Hugging Face repository name in a variable:
 
 ```bash
-HF_USER=$(hf auth whoami | awk -F': *' 'NR==1 {print $2}')
+HF_USER=$(NO_COLOR=1 hf auth whoami | awk -F': *' 'NR==1 {print $2}')
 echo $HF_USER
 ```
 
@@ -424,7 +424,7 @@ robot = SO100Follower(robot_config)
 robot.connect()
 
 dataset = LeRobotDataset("<hf_username>/<dataset_repo_id>", episodes=[episode_idx])
-actions = dataset.hf_dataset.select_columns("action")
+actions = dataset.select_columns("action")
 
 log_say(f"Replaying episode {episode_idx}")
 for idx in range(dataset.num_frames):

docs/source/installation.mdx

@@ -1,6 +1,6 @@
 # Installation
 
-This guide uses `conda` (via miniforge) to manage environments (recommended). If you prefer another environment manager (e.g. `uv`, `venv`), ensure you have Python >=3.12 and `ffmpeg` installed with the `libsvtav1` encoder, then skip ahead to [Environment Setup](#step-2-environment-setup).
+This guide uses `conda` (via miniforge) to manage environments (recommended). If you prefer another environment manager (e.g. `uv`, `venv`), ensure you have Python >=3.12 and support PyTorch >= 2.10, then skip ahead to [Environment Setup](#step-2-environment-setup).
 
 ## Step 1 (`conda` only): Install [`miniforge`](https://conda-forge.org/download/)
 
@@ -20,7 +20,7 @@ Create a virtual environment with Python 3.12:
 conda create -y -n lerobot python=3.12
 ```
 </hfoption>
-<hfoption id="uv">
+<hfoption id="uv (PyTorch >= 2.10 only)">
 ```bash
 uv python install 3.12
 uv venv --python 3.12
@@ -32,48 +32,87 @@ uv venv --python 3.12
 Then activate your virtual environment, you have to do this each time you open a shell to use lerobot:
 
 <!-- prettier-ignore-start -->
+
 <hfoptions id="activate_venv">
-<hfoption id="conda">```bash
+<hfoption id="conda">
+```bash
 conda activate lerobot
-```</hfoption>
-<hfoption id="uv">
-```bash
-# Linux/macOSsource
-source .venv/bin/activate
-# Windows PowerShell
-source .venv\Scripts\Activate.ps1
 ```
-</hfoption>
-</hfoptions>
-<!-- prettier-ignore-end -->
-
-When using `conda`, install `ffmpeg` in your environment:
-
-```bash
-conda install ffmpeg -c conda-forge
-ffmpeg -version  # ffmpeg 8.X is not yet supported !
-```
-
-> [!TIP]
-> This usually installs `ffmpeg 7.X` for your platform compiled with the `libsvtav1` encoder. If `libsvtav1` is not supported (check supported encoders with `ffmpeg -encoders`), you can:
->
-> - _[On any platform]_ Explicitly install `ffmpeg 7.X` using:
->
-> ```bash
-> conda install ffmpeg=7.1.1 -c conda-forge
-> ```
->
-> - _[On Linux only]_ If you want to bring your own ffmpeg: Install [ffmpeg build dependencies](https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu#GettheDependencies) and [compile ffmpeg from source with libsvtav1](https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu#libsvtav1), and make sure you use the corresponding ffmpeg binary to your install with `which ffmpeg`.
 
 > [!NOTE]
-> When installing LeRobot inside WSL (Windows Subsystem for Linux), make sure to install `evdev` with the following command:
+> When installing LeRobot inside WSL (Windows Subsystem for Linux), make sure to also install `evdev`:
 >
 > ```bash
 > conda install evdev -c conda-forge
 > ```
 
+</hfoption>
+<hfoption id="uv (PyTorch >= 2.10 only)">
+```bash
+# Linux/macOS
+source .venv/bin/activate
+# Windows PowerShell
+.venv\Scripts\activate
+```
+
+> [!NOTE]
+> When installing LeRobot inside WSL (Windows Subsystem for Linux), make sure to also install `evdev`:
+>
+> ```bash
+> sudo apt install libevdev-dev
+> uv pip install evdev
+> ```
+
+</hfoption>
+</hfoptions>
+<!-- prettier-ignore-end -->
+
+### Install `ffmpeg` (for video decoding)
+
+LeRobot uses [TorchCodec](https://github.com/meta-pytorch/torchcodec) for video decoding by default, which requires `ffmpeg`.
+
+> [!NOTE]
+> **Platform support:** TorchCodec is **not available** on macOS Intel (x86_64), Linux ARM (aarch64, arm64, armv7l), or Windows with PyTorch < 2.8. On these platforms, LeRobot automatically falls back to `pyav` — so you do not need to install `ffmpeg` and can skip to Step 3.
+
+If your platform supports TorchCodec, install `ffmpeg` using one of the methods below:
+
+<!-- prettier-ignore-start -->
+
+<hfoptions id="install_ffmpeg">
+<hfoption id="conda (any PyTorch version)">
+
+Install `ffmpeg` in your conda environment. This works with **all PyTorch versions** and is **required for PyTorch < 2.10**:
+
+```bash
+conda install ffmpeg -c conda-forge
+```
+
+> [!TIP]
+> This usually installs `ffmpeg 8.X` with the `libsvtav1` encoder. If you run into issues (e.g. `libsvtav1` missing — check with `ffmpeg -encoders` — or a version mismatch with `torchcodec`), you can explicitly install `ffmpeg 7.1.1` using:
+>
+> ```bash
+> conda install ffmpeg=7.1.1 -c conda-forge
+> ```
+
+</hfoption>
+<hfoption id="uv (PyTorch >= 2.10 only)">
+
+Starting with **PyTorch >= 2.10** (TorchCodec ≥ 0.10), TorchCodec can dynamically link to a system-wide `ffmpeg` installation. This is useful when using `uv` or other non-`conda` environment managers:
+
+```bash
+# Ubuntu/Debian
+sudo apt install ffmpeg
+
+# macOS (Apple Silicon)
+brew install ffmpeg
+```
+
 > [!IMPORTANT]
-> If you are using `uv` you will have to install `ffmpeg` system-wide (outside of the virtual environment). You rely on `uv` and `torchcodec` ability to dynamically link to the system `ffmpeg`.
+> System-wide `ffmpeg` is **only supported with PyTorch >= 2.10** (TorchCodec ≥ 0.10). For older PyTorch versions, you **must** use `conda install ffmpeg -c conda-forge` instead.
+
+</hfoption>
+</hfoptions>
+<!-- prettier-ignore-end -->
 
 ## Step 3: Install LeRobot 🤗
 

docs/source/libero.mdx

@@ -1,36 +1,61 @@
 # LIBERO
 
-**LIBERO** is a benchmark designed to study **lifelong robot learning**. The idea is that robots won’t just be pretrained once in a factory, they’ll need to keep learning and adapting with their human users over time. This ongoing adaptation is called **lifelong learning in decision making (LLDM)**, and it’s a key step toward building robots that become truly personalized helpers.
+LIBERO is a benchmark designed to study **lifelong robot learning** — the idea that robots need to keep learning and adapting with their users over time, not just be pretrained once. It provides a set of standardized manipulation tasks that focus on **knowledge transfer**: how well a robot can apply what it has already learned to new situations. By evaluating on LIBERO, different algorithms can be compared fairly and researchers can build on each other's work.
 
-- 📄 [LIBERO paper](https://arxiv.org/abs/2306.03310)
-- 💻 [Original LIBERO repo](https://github.com/Lifelong-Robot-Learning/LIBERO)
-
-To make progress on this challenge, LIBERO provides a set of standardized tasks that focus on **knowledge transfer**: how well a robot can apply what it has already learned to new situations. By evaluating on LIBERO, different algorithms can be compared fairly and researchers can build on each other’s work.
-
-LIBERO includes **five task suites**:
-
-- **LIBERO-Spatial (`libero_spatial`)** – tasks that require reasoning about spatial relations.
-- **LIBERO-Object (`libero_object`)** – tasks centered on manipulating different objects.
-- **LIBERO-Goal (`libero_goal`)** – goal-conditioned tasks where the robot must adapt to changing targets.
-- **LIBERO-90 (`libero_90`)** – 90 short-horizon tasks from the LIBERO-100 collection.
-- **LIBERO-Long (`libero_10`)** – 10 long-horizon tasks from the LIBERO-100 collection.
-
-Together, these suites cover **130 tasks**, ranging from simple object manipulations to complex multi-step scenarios. LIBERO is meant to grow over time, and to serve as a shared benchmark where the community can test and improve lifelong learning algorithms.
+- Paper: [Benchmarking Knowledge Transfer for Lifelong Robot Learning](https://arxiv.org/abs/2306.03310)
+- GitHub: [Lifelong-Robot-Learning/LIBERO](https://github.com/Lifelong-Robot-Learning/LIBERO)
+- Project website: [libero-project.github.io](https://libero-project.github.io)
 
 ![An overview of the LIBERO benchmark](https://libero-project.github.io/assets/img/libero/fig1.png)
 
-## Evaluating with LIBERO
+## Available tasks
 
-At **LeRobot**, we ported [LIBERO](https://github.com/Lifelong-Robot-Learning/LIBERO) into our framework and used it mainly to **evaluate [SmolVLA](https://huggingface.co/docs/lerobot/en/smolvla)**, our lightweight Vision-Language-Action model.
+LIBERO includes **five task suites** covering **130 tasks**, ranging from simple object manipulations to complex multi-step scenarios:
 
-LIBERO is now part of our **multi-eval supported simulation**, meaning you can benchmark your policies either on a **single suite of tasks** or across **multiple suites at once** with just a flag.
+| Suite          | CLI name         | Tasks | Description                                        |
+| -------------- | ---------------- | ----- | -------------------------------------------------- |
+| LIBERO-Spatial | `libero_spatial` | 10    | Tasks requiring reasoning about spatial relations  |
+| LIBERO-Object  | `libero_object`  | 10    | Tasks centered on manipulating different objects   |
+| LIBERO-Goal    | `libero_goal`    | 10    | Goal-conditioned tasks with changing targets       |
+| LIBERO-90      | `libero_90`      | 90    | Short-horizon tasks from the LIBERO-100 collection |
+| LIBERO-Long    | `libero_10`      | 10    | Long-horizon tasks from the LIBERO-100 collection  |
 
-To Install LIBERO, after following LeRobot official instructions, just do:
-`pip install -e ".[libero]"`
+## Installation
+
+After following the LeRobot installation instructions:
+
+```bash
+pip install -e ".[libero]"
+```
+
+<Tip>
+LIBERO requires Linux (`sys_platform == 'linux'`). LeRobot uses MuJoCo for simulation — set the rendering backend before training or evaluation:
+
+```bash
+export MUJOCO_GL=egl  # for headless servers (HPC, cloud)
+```
+
+</Tip>
+
+## Evaluation
+
+### Default evaluation (recommended)
+
+Evaluate across the four standard suites (10 episodes per task):
+
+```bash
+lerobot-eval \
+  --policy.path="your-policy-id" \
+  --env.type=libero \
+  --env.task=libero_spatial,libero_object,libero_goal,libero_10 \
+  --eval.batch_size=1 \
+  --eval.n_episodes=10 \
+  --env.max_parallel_tasks=1
+```
 
 ### Single-suite evaluation
 
-Evaluate a policy on one LIBERO suite:
+Evaluate on one LIBERO suite:
 
 ```bash
 lerobot-eval \
@@ -42,15 +67,13 @@ lerobot-eval \
 ```
 
 - `--env.task` picks the suite (`libero_object`, `libero_spatial`, etc.).
-- `--env.task_ids` picks task ids to run (`[0]`, `[1,2,3]`, etc.). Omit this flag (or set it to `null`) to run all tasks in the suite.
+- `--env.task_ids` restricts to specific task indices (`[0]`, `[1,2,3]`, etc.). Omit to run all tasks in the suite.
 - `--eval.batch_size` controls how many environments run in parallel.
-- `--eval.n_episodes` sets how many episodes to run in total.
-
----
+- `--eval.n_episodes` sets how many episodes to run per task.
 
 ### Multi-suite evaluation
 
-Benchmark a policy across multiple suites at once:
+Benchmark a policy across multiple suites at once by passing a comma-separated list:
 
 ```bash
 lerobot-eval \
@@ -61,50 +84,49 @@ lerobot-eval \
   --eval.n_episodes=2
 ```
 
-- Pass a comma-separated list to `--env.task` for multi-suite evaluation.
+### Control mode
 
-### Control Mode
+LIBERO supports two control modes — `relative` (default) and `absolute`. Different VLA checkpoints are trained with different action parameterizations, so make sure the mode matches your policy:
 
-LIBERO now supports two control modes: relative and absolute. This matters because different VLA checkpoints are trained with different mode of action to output hence control parameterizations.
-You can switch them with: `env.control_mode = "relative"` and `env.control_mode = "absolute"`
+```bash
+--env.control_mode=relative   # or "absolute"
+```
 
 ### Policy inputs and outputs
 
-When using LIBERO through LeRobot, policies interact with the environment via **observations** and **actions**:
+**Observations:**
 
-- **Observations**
-  - `observation.state` – proprioceptive features (agent state).
-  - `observation.images.image` – main camera view (`agentview_image`).
-  - `observation.images.image2` – wrist camera view (`robot0_eye_in_hand_image`).
+- `observation.state` — 8-dim proprioceptive features (eef position, axis-angle orientation, gripper qpos)
+- `observation.images.image` — main camera view (`agentview_image`), HWC uint8
+- `observation.images.image2` — wrist camera view (`robot0_eye_in_hand_image`), HWC uint8
 
-  ⚠️ **Note:** LeRobot enforces the `.images.*` prefix for any multi-modal visual features. Always ensure that your policy config `input_features` use the same naming keys, and that your dataset metadata keys follow this convention during evaluation.
-  If your data contains different keys, you must rename the observations to match what the policy expects, since naming keys are encoded inside the normalization statistics layer.
-  This will be fixed with the upcoming Pipeline PR.
+<Tip warning={true}>
+  LeRobot enforces the `.images.*` prefix for visual features. Ensure your
+  policy config `input_features` use the same naming keys, and that your dataset
+  metadata keys follow this convention. If your data contains different keys,
+  you must rename the observations to match what the policy expects, since
+  naming keys are encoded inside the normalization statistics layer.
+</Tip>
 
-- **Actions**
-  - Continuous control values in a `Box(-1, 1, shape=(7,))` space.
+**Actions:**
 
-We also provide a notebook for quick testing:
-Training with LIBERO
+- Continuous control in `Box(-1, 1, shape=(7,))` — 6D end-effector delta + 1D gripper
 
-## Training with LIBERO
+### Recommended evaluation episodes
 
-When training on LIBERO tasks, make sure your dataset parquet and metadata keys follow the LeRobot convention.
+For reproducible benchmarking, use **10 episodes per task** across all four standard suites (Spatial, Object, Goal, Long). This gives 400 total episodes and matches the protocol used for published results.
 
-The environment expects:
+## Training
 
-- `observation.state` → 8-dim agent state
-- `observation.images.image` → main camera (`agentview_image`)
-- `observation.images.image2` → wrist camera (`robot0_eye_in_hand_image`)
+### Dataset
 
-⚠️ Cleaning the dataset upfront is **cleaner and more efficient** than remapping keys inside the code.
-To avoid potential mismatches and key errors, we provide a **preprocessed LIBERO dataset** that is fully compatible with the current LeRobot codebase and requires no additional manipulation:
-👉 [HuggingFaceVLA/libero](https://huggingface.co/datasets/HuggingFaceVLA/libero)
+We provide a preprocessed LIBERO dataset fully compatible with LeRobot:
 
-For reference, here is the **original dataset** published by Physical Intelligence:
-👉 [physical-intelligence/libero](https://huggingface.co/datasets/physical-intelligence/libero)
+- [HuggingFaceVLA/libero](https://huggingface.co/datasets/HuggingFaceVLA/libero)
 
----
+For reference, the original dataset published by Physical Intelligence:
+
+- [physical-intelligence/libero](https://huggingface.co/datasets/physical-intelligence/libero)
 
 ### Example training command
 
@@ -121,52 +143,39 @@ lerobot-train \
   --batch_size=4 \
   --eval.batch_size=1 \
   --eval.n_episodes=1 \
-  --eval_freq=1000 \
+  --eval_freq=1000
 ```
 
----
+## Reproducing published results
 
-### Note on rendering
+We reproduce the results of Pi0.5 on the LIBERO benchmark. We take the Physical Intelligence LIBERO base model (`pi05_libero`) and finetune for an additional 6k steps in bfloat16, with batch size of 256 on 8 H100 GPUs using the [HuggingFace LIBERO dataset](https://huggingface.co/datasets/HuggingFaceVLA/libero).
 
-LeRobot uses MuJoCo for simulation. You need to set the rendering backend before training or evaluation:
+The finetuned model: [lerobot/pi05_libero_finetuned](https://huggingface.co/lerobot/pi05_libero_finetuned)
 
-- `export MUJOCO_GL=egl` → for headless servers (e.g. HPC, cloud)
-
-## Reproducing π₀.₅ results
-
-We reproduce the results of π₀.₅ on the LIBERO benchmark using the LeRobot implementation. We take the Physical Intelligence LIBERO base model (`pi05_libero`) and finetune for an additional 6k steps in bfloat16, with batch size of 256 on 8 H100 GPUs using the [HuggingFace LIBERO dataset](https://huggingface.co/datasets/HuggingFaceVLA/libero).
-
-The finetuned model can be found here:
-
-- **π₀.₅ LIBERO**: [lerobot/pi05_libero_finetuned](https://huggingface.co/lerobot/pi05_libero_finetuned)
-
-We then evaluate the finetuned model using the LeRobot LIBERO implementation, by running the following command:
+### Evaluation command
 
 ```bash
 lerobot-eval \
-  --output_dir=/logs/ \
+  --output_dir=./eval_logs/ \
   --env.type=libero \
   --env.task=libero_spatial,libero_object,libero_goal,libero_10 \
   --eval.batch_size=1 \
   --eval.n_episodes=10 \
   --policy.path=pi05_libero_finetuned \
   --policy.n_action_steps=10 \
-  --output_dir=./eval_logs/ \
   --env.max_parallel_tasks=1
 ```
 
-**Note:** We set `n_action_steps=10`, similar to the original OpenPI implementation.
+We set `n_action_steps=10`, matching the original OpenPI implementation.
 
 ### Results
 
-We obtain the following results on the LIBERO benchmark:
+| Model               | LIBERO Spatial | LIBERO Object | LIBERO Goal | LIBERO 10 | Average  |
+| ------------------- | -------------- | ------------- | ----------- | --------- | -------- |
+| **Pi0.5 (LeRobot)** | 97.0           | 99.0          | 98.0        | 96.0      | **97.5** |
 
-| Model    | LIBERO Spatial | LIBERO Object | LIBERO Goal | LIBERO 10 | Average  |
-| -------- | -------------- | ------------- | ----------- | --------- | -------- |
-| **π₀.₅** | 97.0           | 99.0          | 98.0        | 96.0      | **97.5** |
+These results are consistent with the [original results](https://github.com/Physical-Intelligence/openpi/tree/main/examples/libero#results) reported by Physical Intelligence:
 
-These results are consistent with the original [results](https://github.com/Physical-Intelligence/openpi/tree/main/examples/libero#results) reported by Physical Intelligence:
-
-| Model    | LIBERO Spatial | LIBERO Object | LIBERO Goal | LIBERO 10 | Average   |
-| -------- | -------------- | ------------- | ----------- | --------- | --------- |
-| **π₀.₅** | 98.8           | 98.2          | 98.0        | 92.4      | **96.85** |
+| Model              | LIBERO Spatial | LIBERO Object | LIBERO Goal | LIBERO 10 | Average   |
+| ------------------ | -------------- | ------------- | ----------- | --------- | --------- |
+| **Pi0.5 (OpenPI)** | 98.8           | 98.2          | 98.0        | 92.4      | **96.85** |

docs/source/metaworld.mdx

@@ -1,32 +1,111 @@
 # Meta-World
 
-Meta-World is a well-designed, open-source simulation benchmark for multi-task and meta reinforcement learning in continuous-control robotic manipulation. It gives researchers a shared, realistic playground to test whether algorithms can _learn many different tasks_ and _generalize quickly to new ones_ — two central challenges for real-world robotics.
+Meta-World is an open-source simulation benchmark for **multi-task and meta reinforcement learning** in continuous-control robotic manipulation. It bundles 50 diverse manipulation tasks using everyday objects and a common tabletop Sawyer arm, providing a standardized playground to test whether algorithms can learn many different tasks and generalize quickly to new ones.
 
-- 📄 [MetaWorld paper](https://arxiv.org/pdf/1910.10897)
-- 💻 [Original MetaWorld repo](https://github.com/Farama-Foundation/Metaworld)
+- Paper: [Meta-World: A Benchmark and Evaluation for Multi-Task and Meta Reinforcement Learning](https://arxiv.org/abs/1910.10897)
+- GitHub: [Farama-Foundation/Metaworld](https://github.com/Farama-Foundation/Metaworld)
+- Project website: [metaworld.farama.org](https://metaworld.farama.org)
 
 ![MetaWorld MT10 demo](https://meta-world.github.io/figures/ml45.gif)
 
-## Why Meta-World matters
+## Available tasks
 
-- **Diverse, realistic tasks.** Meta-World bundles a large suite of simulated manipulation tasks (50 in the MT50 suite) using everyday objects and a common tabletop Sawyer arm. This diversity exposes algorithms to a wide variety of dynamics, contacts and goal specifications while keeping a consistent control and observation structure.
-- **Focus on generalization and multi-task learning.** By evaluating across task distributions that share structure but differ in goals and objects, Meta-World reveals whether an agent truly learns transferable skills rather than overfitting to a narrow task.
-- **Standardized evaluation protocol.** It provides clear evaluation modes and difficulty splits, so different methods can be compared fairly across easy, medium, hard and very-hard regimes.
-- **Empirical insight.** Past evaluations on Meta-World show impressive progress on some fronts, but also highlight that current multi-task and meta-RL methods still struggle with large, diverse task sets. That gap points to important research directions.
+Meta-World provides 50 tasks organized into difficulty groups. In LeRobot, you can evaluate on individual tasks, difficulty groups, or the full MT50 suite:
 
-## What it enables in LeRobot
+| Group      | CLI name             | Tasks | Description                                            |
+| ---------- | -------------------- | ----- | ------------------------------------------------------ |
+| Easy       | `easy`               | 28    | Tasks with simple dynamics and single-step goals       |
+| Medium     | `medium`             | 11    | Tasks requiring multi-step reasoning                   |
+| Hard       | `hard`               | 6     | Tasks with complex contacts and precise manipulation   |
+| Very Hard  | `very_hard`          | 5     | The most challenging tasks in the suite                |
+| MT50 (all) | Comma-separated list | 50    | All 50 tasks — the most challenging multi-task setting |
 
-In LeRobot, you can evaluate any policy or vision-language-action (VLA) model on Meta-World tasks and get a clear success-rate measure. The integration is designed to be straightforward:
+You can also pass individual task names directly (e.g., `assembly-v3`, `dial-turn-v3`).
 
-- We provide a LeRobot-ready dataset for Meta-World (MT50) on the HF Hub: `https://huggingface.co/datasets/lerobot/metaworld_mt50`.
-  - This dataset is formatted for the MT50 evaluation that uses all 50 tasks (the most challenging multi-task setting).
-  - MT50 gives the policy a one-hot task vector and uses fixed object/goal positions for consistency.
+We provide a LeRobot-ready dataset for Meta-World MT50 on the HF Hub: [lerobot/metaworld_mt50](https://huggingface.co/datasets/lerobot/metaworld_mt50). This dataset is formatted for the MT50 evaluation that uses all 50 tasks with fixed object/goal positions and one-hot task vectors for consistency.
 
-- Task descriptions and the exact keys required for evaluation are available in the repo/dataset — use these to ensure your policy outputs the right success signals.
+## Installation
 
-## Quick start, train a SmolVLA policy on Meta-World
+After following the LeRobot installation instructions:
 
-Example command to train a SmolVLA policy on a subset of tasks:
+```bash
+pip install -e ".[metaworld]"
+```
+
+<Tip warning={true}>
+If you encounter an `AssertionError: ['human', 'rgb_array', 'depth_array']` when running Meta-World environments, this is a mismatch between Meta-World and your Gymnasium version. Fix it with:
+
+```bash
+pip install "gymnasium==1.1.0"
+```
+
+</Tip>
+
+## Evaluation
+
+### Default evaluation (recommended)
+
+Evaluate on the medium difficulty split (a good balance of coverage and compute):
+
+```bash
+lerobot-eval \
+  --policy.path="your-policy-id" \
+  --env.type=metaworld \
+  --env.task=medium \
+  --eval.batch_size=1 \
+  --eval.n_episodes=10
+```
+
+### Single-task evaluation
+
+Evaluate on a specific task:
+
+```bash
+lerobot-eval \
+  --policy.path="your-policy-id" \
+  --env.type=metaworld \
+  --env.task=assembly-v3 \
+  --eval.batch_size=1 \
+  --eval.n_episodes=10
+```
+
+### Multi-task evaluation
+
+Evaluate across multiple tasks or difficulty groups:
+
+```bash
+lerobot-eval \
+  --policy.path="your-policy-id" \
+  --env.type=metaworld \
+  --env.task=assembly-v3,dial-turn-v3,handle-press-side-v3 \
+  --eval.batch_size=1 \
+  --eval.n_episodes=10
+```
+
+- `--env.task` accepts explicit task lists (comma-separated) or difficulty groups (e.g., `easy`, `medium`, `hard`, `very_hard`).
+- `--eval.batch_size` controls how many environments run in parallel.
+- `--eval.n_episodes` sets how many episodes to run per task.
+
+### Policy inputs and outputs
+
+**Observations:**
+
+- `observation.image` — single camera view (`corner2`), 480x480 HWC uint8
+- `observation.state` — 4-dim proprioceptive state (end-effector position + gripper)
+
+**Actions:**
+
+- Continuous control in `Box(-1, 1, shape=(4,))` — 3D end-effector delta + 1D gripper
+
+### Recommended evaluation episodes
+
+For reproducible benchmarking, use **10 episodes per task**. For the full MT50 suite this gives 500 total episodes. If you care about generalization, run on the full MT50 — it is intentionally challenging and reveals strengths/weaknesses better than a few narrow tasks.
+
+## Training
+
+### Example training command
+
+Train a SmolVLA policy on a subset of Meta-World tasks:
 
 ```bash
 lerobot-train \
@@ -44,37 +123,8 @@ lerobot-train \
   --eval_freq=1000
 ```
 
-Notes:
-
-- `--env.task` accepts explicit task lists (comma separated) or difficulty groups (e.g., `env.task="hard"`).
-- Adjust `batch_size`, `steps`, and `eval_freq` to match your compute budget.
-- **Gymnasium Assertion Error**: if you encounter an error like
-  `AssertionError: ['human', 'rgb_array', 'depth_array']` when running MetaWorld environments, this comes from a mismatch between MetaWorld and your Gymnasium version.
-  We recommend using:
-
-```bash
-  pip install "gymnasium==1.1.0"
-```
-
-to ensure proper compatibility.
-
-## Quick start — evaluate a trained policy
-
-To evaluate a trained policy on the Meta-World medium difficulty split:
-
-```bash
-lerobot-eval \
-  --policy.path="your-policy-id" \
-  --env.type=metaworld \
-  --env.task=medium \
-  --eval.batch_size=1 \
-  --eval.n_episodes=2
-```
-
-This will run episodes and return per-task success rates using the standard Meta-World evaluation keys.
-
 ## Practical tips
 
-- If you care about generalization, run on the full MT50 suite — it’s intentionally challenging and reveals strengths/weaknesses better than a few narrow tasks.
-- Use the one-hot task conditioning for multi-task training (MT10 / MT50 conventions) so policies have explicit task context.
+- Use the one-hot task conditioning for multi-task training (MT10/MT50 conventions) so policies have explicit task context.
 - Inspect the dataset task descriptions and the `info["is_success"]` keys when writing post-processing or logging so your success metrics line up with the benchmark.
+- Adjust `batch_size`, `steps`, and `eval_freq` to match your compute budget.

docs/source/multi_task_dit.mdx

@@ -0,0 +1,388 @@
+# Multitask DiT Policy
+
+Multitask Diffusion Transformer (DiT) Policy is an evolution of the original Diffusion Policy architecture, which leverages a large DiT with text and vision conditioning for multitask robot learning. This implementation supports both diffusion and flow matching objectives for action generation, enabling robots to perform diverse manipulation tasks conditioned on language instructions.
+
+## Model Overview
+
+The model uses:
+
+- **CLIP Vision Encoder**: Processes RGB images from multiple camera views
+- **CLIP Text Encoder**: Encodes language task instructions (frozen weights with learnable projection)
+- **Diffusion Transformer**: Predicts action sequences conditioned on observations and language
+- **Two Objectives**: Supports both diffusion (DDPM/DDIM) and flow matching for action generation
+
+This model is exciting because you can achieve extremely high dexterity, competitive with multi-billion parameter
+VLAs, with only ~450M parameters and significantly less training.
+
+## Installation Requirements
+
+Multitask DiT Policy has additional dependencies. Install it with:
+
+```bash
+pip install lerobot[multi_task_dit]
+```
+
+This will install all necessary dependencies including the HuggingFace Transformers library for CLIP models.
+
+## Usage
+
+To use Multitask DiT in your LeRobot configuration, specify the policy type as:
+
+```python
+policy.type=multi_task_dit
+```
+
+## Training
+
+### Basic Training Command
+
+Here's a complete training command for training Multitask DiT on your dataset:
+
+```bash
+lerobot-train \
+  --dataset.repo_id=YOUR_DATASET \
+  --output_dir=./outputs/multitask_dit_training \
+  --batch_size=32 \
+  --steps=5000 \
+  --save_freq=500 \
+  --log_freq=100 \
+  --policy.type=multi_task_dit \
+  --policy.device=cuda \
+  --policy.repo_id="HF_USER/multitask-dit-your-robot" \
+  --wandb.enable=true
+```
+
+### Recommended Hyperparameters and Dataset Details (30Hz Control Frequency)
+
+For reliable performance, start with these suggested default hyperparameters:
+
+```bash
+lerobot-train \
+  --dataset.repo_id=YOUR_DATASET \
+  --output_dir=./outputs/mutitask_dit_training \
+  --batch_size=320 \
+  --steps=30000 \
+  --policy.type=multi_task_dit \
+  --policy.device=cuda \
+  --policy.horizon=32 \
+  --policy.n_action_steps=24 \
+  --policy.objective=diffusion \
+  --policy.noise_scheduler_type=DDPM \
+  --policy.num_train_timesteps=100 \
+  --policy.repo_id="HF_USER/multitask-dit-your-robot" \
+  --wandb.enable=true
+```
+
+**Key Parameters:**
+
+- **Batch Size**: 192-320 - If you have access to a GPU that can support this, you will get the best training dynamics
+- **Horizon**: 32 - number of action steps to predict, ~1.0 sec at 30Hz
+- **n_action_steps**: 24 - ~0.8 seconds at 30Hz
+- **Objective**: `diffusion` - start with diffusion and experiment with flow matching if generation quality is poor
+- **Training Steps**: >30k steps recommended for a single task
+
+### Training Configuration Parameters
+
+#### Objective Selection
+
+Choose between diffusion and flow matching:
+
+```bash
+# Diffusion objective (default)
+--policy.objective=diffusion \
+--policy.noise_scheduler_type=DDPM \  # or "DDIM"
+--policy.num_train_timesteps=100 \
+--policy.num_inference_steps=10 \  # For faster inference
+--policy.beta_schedule=squaredcos_cap_v2 \  # Noise schedule type
+--policy.prediction_type=epsilon \  # "epsilon" (predict noise) or "sample" (predict clean)
+--policy.clip_sample=true \  # Clip samples during denoising
+--policy.clip_sample_range=1.0  # Clipping range [-x, x]
+
+# Flow matching objective
+--policy.objective=flow_matching \
+--policy.timestep_sampling_strategy=beta \  # or "uniform" | the beta sampling strategy performance appears much better in practice
+--policy.num_integration_steps=100 \
+--policy.integration_method=euler \  # or "rk4"
+--policy.sigma_min=0.0  # Minimum noise in flow interpolation path
+```
+
+#### Transformer Architecture
+
+Adjust model capacity based on dataset size:
+
+```bash
+# Small datasets (< 100 examples)
+--policy.num_layers=4 \
+--policy.hidden_dim=512 \
+--policy.num_heads=8  # should ideally be hidden_dim // 64
+
+# Medium datasets (100-5k examples) - default
+--policy.num_layers=6 \
+--policy.hidden_dim=512 \
+--policy.num_heads=8  # should ideally be hidden_dim // 64
+
+# Large datasets (> 5k examples)
+--policy.num_layers=8 \
+--policy.hidden_dim=512 \
+--policy.num_heads=8   # should ideally be hidden_dim // 64
+```
+
+**Positional Encoding Options:**
+
+The model supports two positional encoding methods for action sequences:
+
+```bash
+# Rotary Position Embedding (RoPE) - default, recommended
+--policy.use_rope=true \
+--policy.rope_base=10000.0  # Base frequency for RoPE
+
+# Absolute positional encoding
+--policy.use_positional_encoding=true  # Disables RoPE when true
+```
+
+**Other Transformer Parameters:**
+
+```bash
+--policy.dropout=0.1  # Dropout rate for DiT blocks (0.0-1.0)
+--policy.timestep_embed_dim=256  # Timestep embedding dimension
+```
+
+#### Vision Encoder Configuration
+
+```bash
+# Use different CLIP model for more expressivity at the cost of inference time
+# experiment with larger or smaller models depending on the complexity of your tasks and size of dataset
+--policy.vision_encoder_name=openai/clip-vit-large-patch14
+
+# Use separate vision encoder per camera
+# This may be useful when cameras have significantly different characteristics, but
+# be wary of increased VRAM footprint.
+--policy.use_separate_rgb_encoder_per_camera=true
+
+# Image preprocessing
+--policy.image_resize_shape=[XXX,YYY] \ # you may need to resize your images for inference speed ups
+--policy.image_crop_shape=[224,224] \
+--policy.image_crop_is_random=true  # Random during training, center at inference
+```
+
+#### Text Encoder Configuration
+
+```bash
+# Use different CLIP text encoder model
+# same as vision: experiment with larger or smaller models depending on the
+# complexity of your tasks and size of dataset
+--policy.text_encoder_name=openai/clip-vit-large-patch14
+```
+
+#### Learning Rate Configuration
+
+The vision encoder uses a separate learning rate multiplier, where 1/10th is suggested to be the ideal staritng point:
+
+```bash
+--policy.optimizer_lr=2e-5 \
+--policy.vision_encoder_lr_multiplier=0.1  # Vision encoder LR = 0.1 * optimizer_lr
+```
+
+### Training Tuning Guidelines
+
+#### 1. Flow Matching with Beta Sampling
+
+The original diffusion implementation here is based on the work described in [TRI's LBM paper](https://arxiv.org/abs/2507.05331)
+
+Additionally, we have implemented a flow-matching objective, which is described at a high-level in [Boston Dynamics blog post](https://bostondynamics.com/blog/large-behavior-models-atlas-find-new-footing/).
+
+Consider testing the flow-matching objective and evaluating performance differences for your task:
+
+```bash
+--policy.objective=flow_matching \
+--policy.timestep_sampling_strategy=beta \
+--policy.timestep_sampling_alpha=1.5 \
+--policy.timestep_sampling_beta=1.0 \
+--policy.timestep_sampling_s=0.999
+```
+
+This hasn't been shown to be a silver bullet across every user case, but it occasionally results in smoother and more consistent actions.
+
+#### 2. Number of Transformer Layers
+
+Match model capacity to your dataset size:
+
+- **Small datasets** (< 100 examples): Reduce to 4 layers
+- **Large datasets** (> 5k examples): Increase to 8 layers
+
+#### 3. `horizon` Tuning
+
+The model can be sensitive to the horizon you choose. Start with around a 1 second horizon based on your control frequency:
+
+- **30 Hz frequency**: `horizon=30`
+- **10 Hz frequency**: `horizon=10`
+
+Then experiment with increasing from there. The horizon determines how far into the future the model predicts actions.
+
+#### 4. `n_action_steps` Sensitivity
+
+The model can also be very sensitive to `n_action_steps`. Start with it being around 0.8 seconds based on your control frequency and tune from there:
+
+- **Lower values**: More reactive but potentially less stable for long-horizon tasks
+- **Higher values**: Better for long-horizon execution but open-loop failures are limited in their recovery
+
+### Inference Tuning
+
+For faster inference, use DDIM with fewer sampling steps:
+
+```bash
+--policy.noise_scheduler_type=DDIM \
+--policy.num_inference_steps=10
+```
+
+### Resuming Training
+
+To resume training from a checkpoint:
+
+```bash
+lerobot-train \
+  --config_path=./outputs/mutitask_dit_training/checkpoints/last/pretrained_model/train_config.json \
+  --resume=true
+```
+
+The checkpoint directory should contain `model.safetensors` and `config.json` files (saved automatically during training). When resuming, the configuration is loaded from the checkpoint, so you don't need to specify other parameters.
+
+## Common Failure Modes and Debugging
+
+Training these models can be finicky. Here are common failure modes and debugging approaches:
+
+### Idling / No Motion
+
+The model may "collapse" during inference, resulting in static or no motion. This can occur when:
+
+1. **Insufficient training data**: If you only have 20-50 examples, try to roughly double your dataset size. Once you have above 300 examples, if you're still seeing this, the task may be too complex.
+
+2. **Multiple similar tasks**: When your dataset contains multiple similar tasks (e.g., picking up 2 different objects), the model may rely too heavily on language conditioning which might not be rich enough.
+
+**Debugging tips:**
+
+- Increase dataset size (double until you get to over 300 examples)
+- Train for longer, up to 100k steps, even when the loss flatlines
+- Check if the model is receiving proper language instructions or increase diversity of instruction
+
+### Executing the Wrong Task
+
+Sometimes the robot will completely ignore your instruction and perform some other task. This generally only happens if you have trained on multiple tasks.
+
+**Potential causes:**
+
+- Language instruction ambiguity
+- Insufficient task-specific training data
+- Model confusion between similar tasks in the multitask dataset
+
+**Debugging tips:**
+
+- Verify language instruction specificity, especially if descriptions are similar between multiple tasks
+- Check task distribution in your training dataset and add weighting to the failing/ignored task
+- Consider task-specific fine-tuning
+
+### Training Instability
+
+If training loss is unstable or diverging:
+
+- Try adjusting learning rate between `1e-5` and `3e-4`
+- Increase batch size if possible
+- Check that your dataset normalization is correct
+- Verify image preprocessing is working correctly
+
+## Performance Considerations
+
+### GPU Requirements
+
+- **Inference**: At least an RTX 5070 Ti (or equivalent GPU) is recommended for reasonable speed performance
+- **Training**: A GPU with enough VRAM to load batch sizes of >64 is ideal, which will vary depending on the number of image observations, etc
+
+### Batch Size Recommendations
+
+- **Minimum**: 64 (less than this may result in unstable training)
+- **Recommended**: 256-320 (best performance, requires larger GPU)
+
+## Example: Training on Custom Dataset
+
+Here's a complete example training on a custom dataset:
+
+```bash
+lerobot-train \
+  --dataset.repo_id=YOUR_DATASET \
+  --output_dir=./outputs/mutitask_dit_training \
+  --batch_size=320 \
+  --steps=30000 \
+  --save_freq=1000 \
+  --log_freq=100 \
+  --eval_freq=1000 \
+  --policy.type=multi_task_dit \
+  --policy.device=cuda \
+  --policy.horizon=32 \
+  --policy.n_action_steps=24 \
+  --policy.objective=diffusion \
+  --policy.noise_scheduler_type=DDPM \
+  --policy.num_layers=6 \
+  --policy.hidden_dim=512 \
+  --policy.vision_encoder_name=openai/clip-vit-base-patch16 \
+  --policy.image_resize_shape=[320,240] \
+  --policy.image_crop_shape=[224,224] \
+  --policy.repo_id="HF_USER/multitask-dit-your-robot" \
+  --wandb.enable=true \
+  --wandb.project=multitask_dit
+```
+
+## Libero Results
+
+```
+python -m lerobot.scripts.lerobot_train \
+  --dataset.repo_id=HuggingFaceVLA/libero \
+  --policy.type=multi_task_dit \
+  --policy.push_to_hub=false \
+  --output_dir="./outputs/multitask_dit_libero" \
+  --job_name="multitask-dit-libero" \
+  --wandb.enable=true \
+  --wandb.project=multitask_dit_libero \
+  --dataset.image_transforms.enable=true \
+  --dataset.image_transforms.max_num_transforms=4 \
+  --dataset.image_transforms.tfs='{"brightness":{"type":"ColorJitter","kwargs":{"brightness":[0.75,1.25]}},"contrast":{"type":"ColorJitter","kwargs":{"contrast":[0.6,1.4]}},"saturation":{"type":"ColorJitter","kwargs":{"saturation":[0.8,1.2]}},"hue":{"type":"ColorJitter","kwargs":{"hue":[-0.05,0.05]}},"sharpness":{"type":"SharpnessJitter","kwargs":{"sharpness":[0.6,1.4]}},"rotation":{"type":"RandomRotation","kwargs":{"degrees":[-5,5]}},"translation":{"type":"RandomAffine","kwargs":{"degrees":0,"translate":[0.1,0.1]}}}' \
+  --dataset.video_backend=torchcodec \
+  --policy.use_amp=true \
+  --policy.horizon=48 \
+  --policy.n_obs_steps=2 \
+  --policy.use_rope=true \
+  --policy.use_positional_encoding=false \
+  --policy.hidden_dim=768 \
+  --policy.num_layers=8 \
+  --policy.num_heads=12 \
+  --policy.dropout=0.1 \
+  --policy.timestep_embed_dim=256 \
+  --policy.objective=diffusion \
+  --policy.optimizer_lr=3e-4 \
+  --policy.optimizer_weight_decay=0 \
+  --policy.scheduler_warmup_steps=0 \
+  --policy.vision_encoder_name=openai/clip-vit-base-patch16 \
+  --policy.image_resize_shape=[256,256] \
+  --policy.image_crop_is_random=true \
+  --policy.text_encoder_name=openai/clip-vit-base-patch16 \
+  --policy.vision_encoder_lr_multiplier=0.1 \
+  --policy.device=cuda \
+  --num_workers=8 \
+  --save_freq=4000 \
+  --log_freq=100 \
+  --steps=100000 \
+  --batch_size=320
+```
+
+Results:
+
+| LIBERO Spatial | LIBERO Object | LIBERO Goal | LIBERO 10 | Average |
+| -------------- | ------------- | ----------- | --------- | ------- |
+| 87.0           | 98.2          | 93.8        | 83.2      | 90.6    |
+
+## References
+
+For more details on the technical implementation and architecture, see:
+
+- [A Careful Examination of Large Behavior Models for Multitask Dexterous Manipulation](https://arxiv.org/abs/2507.05331)
+- [Large Behavior Models and Atlas Find New Footing](https://bostondynamics.com/blog/large-behavior-models-atlas-find-new-footing/)
+- [Dissecting and Open-Sourcing Multitask Diffusion Transformer Policy](https://brysonkjones.substack.com/p/dissecting-and-open-sourcing-multitask-diffusion-transformer-policy)

docs/source/pi0.mdx

@@ -91,6 +91,46 @@ lerobot-train \
 
 **💡 Tip**: Setting `train_expert_only=true` freezes the VLM and trains only the action expert and projections, allowing finetuning with reduced memory usage.
 
+## Relative Actions
+
+By default, π₀ predicts absolute actions. You can enable **relative actions** so the model predicts offsets relative to the current robot state. This can improve training stability for certain setups.
+
+To use relative actions, first recompute your dataset stats in relative space via the CLI:
+
+```bash
+lerobot-edit-dataset \
+    --repo_id your_dataset \
+    --operation.type recompute_stats \
+    --operation.relative_action true \
+    --operation.chunk_size 50 \
+    --operation.relative_exclude_joints "['gripper']" \
+    --push_to_hub true
+```
+
+Or equivalently in Python:
+
+```python
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+from lerobot.datasets.dataset_tools import recompute_stats
+
+dataset = LeRobotDataset("your_dataset")
+recompute_stats(dataset, relative_action=True, chunk_size=50, relative_exclude_joints=["gripper"])
+dataset.push_to_hub()
+```
+
+The `chunk_size` should match your policy's `chunk_size` (default 50 for π₀). `relative_exclude_joints` lists joint names that should remain in absolute space (e.g. gripper commands). Use `--push_to_hub true` to upload the updated stats to the Hub.
+
+Then train with relative actions enabled:
+
+```bash
+lerobot-train \
+    --dataset.repo_id=your_dataset \
+    --policy.type=pi0 \
+    --policy.use_relative_actions=true \
+    --policy.relative_exclude_joints='["gripper"]' \
+    ...
+```
+
 ## License
 
 This model follows the **Apache 2.0 License**, consistent with the original [OpenPI repository](https://github.com/Physical-Intelligence/openpi).

docs/source/pi05.mdx

@@ -97,6 +97,46 @@ python src/lerobot/datasets/v30/augment_dataset_quantile_stats.py \
 
 Or train pi05 with this normalization mapping: `--policy.normalization_mapping='{"ACTION": "MEAN_STD", "STATE": "MEAN_STD", "VISUAL": "IDENTITY"}'`
 
+## Relative Actions
+
+By default, π₀.₅ predicts absolute actions. You can enable **relative actions** so the model predicts offsets relative to the current robot state. This can improve training stability for certain setups.
+
+To use relative actions, first recompute your dataset stats in relative space via the CLI:
+
+```bash
+lerobot-edit-dataset \
+    --repo_id your_dataset \
+    --operation.type recompute_stats \
+    --operation.relative_action true \
+    --operation.chunk_size 50 \
+    --operation.relative_exclude_joints "['gripper']" \
+    --push_to_hub true
+```
+
+Or equivalently in Python:
+
+```python
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+from lerobot.datasets.dataset_tools import recompute_stats
+
+dataset = LeRobotDataset("your_dataset")
+recompute_stats(dataset, relative_action=True, chunk_size=50, relative_exclude_joints=["gripper"])
+dataset.push_to_hub()
+```
+
+The `chunk_size` should match your policy's `chunk_size` (default 50 for π₀.₅). `relative_exclude_joints` lists joint names that should remain in absolute space (e.g. gripper commands). Use `--push_to_hub true` to upload the updated stats to the Hub.
+
+Then train with relative actions enabled:
+
+```bash
+lerobot-train \
+    --dataset.repo_id=your_dataset \
+    --policy.type=pi05 \
+    --policy.use_relative_actions=true \
+    --policy.relative_exclude_joints='["gripper"]' \
+    ...
+```
+
 ## Performance Results
 
 ### Libero Benchmark Results

docs/source/policy_multi_task_dit_README.md

@@ -0,0 +1,37 @@
+# Multitask DiT Policy
+
+## Citation
+
+If you use this work, please cite the following works:
+
+```bibtex
+@misc{jones2025multitaskditpolicy,
+  author = {Bryson Jones},
+  title = {Dissecting and Open-Sourcing Multitask Diffusion Transformer Policy},
+  year = {2025},
+  url = {https://brysonkjones.substack.com/p/dissecting-and-open-sourcing-multitask-diffusion-transformer-policy},
+  note = {Blog post}
+}
+```
+
+```bibtex
+@misc{trilbmteam2025carefulexaminationlargebehaviormodels,
+  author       = {TRI LBM Team},
+  title        = {A Careful Examination of Large Behavior Models for Multitask Dexterous Manipulation},
+  year         = {2025},
+  eprint       = {arXiv:2507.05331},
+  archivePrefix = {arXiv},
+  primaryClass = {cs.RO},
+  url          = {https://arxiv.org/abs/2507.05331}
+}
+```
+
+```bibtex
+@misc{bostondynamics2025largebehaviormodelsatlas,
+  author       = {Boston Dynamics and TRI Research Team},
+  title        = {Large Behavior Models and Atlas Find New Footing},
+  year         = {2025},
+  url          = {https://bostondynamics.com/blog/large-behavior-models-atlas-find-new-footing/},
+  note         = {Blog post}
+}
+```

docs/source/policy_pi05_README.md

@@ -0,0 +1,91 @@
+# π₀.₅ (pi05)
+
+This repository contains the Hugging Face port of **π₀.₅**, adapted from [OpenPI](https://github.com/Physical-Intelligence/openpi) by the Physical Intelligence.
+It is designed as a **Vision-Language-Action model with open-world generalization**.
+
+---
+
+## Model Overview
+
+| Feature              | π₀                                                     | π₀.₅                                      |
+| -------------------- | ------------------------------------------------------ | ----------------------------------------- |
+| Time Conditioning    | Concatenates time with actions via `action_time_mlp_*` | Uses `time_mlp_*` for AdaRMS conditioning |
+| AdaRMS               | Not used                                               | Used in action expert                     |
+| Tokenizer Length     | 48 tokens                                              | 200 tokens                                |
+| Discrete State Input | False (Uses `state_proj` layer)                        | True                                      |
+| Parameter Count      | Higher (includes state embedding)                      | Lower (no state embedding)                |
+
+---
+
+## Relative Actions
+
+π₀.₅ supports training with **relative actions**, where the model learns relative offsets
+from the current robot state instead of absolute joint positions. This mirrors the
+relative-action transform in OpenPI (`DeltaActions`) and can improve performance.
+
+### How it works
+
+1. **During preprocessing**, absolute actions are converted to relative offsets:
+   `relative = action - state` (for selected joints).
+2. The relative actions are normalized using statistics computed from the relative distribution.
+3. **During postprocessing**, predicted relative actions are converted back to absolute:
+   `absolute = relative + state`.
+
+Joints listed in `relative_exclude_joints` (e.g., gripper) are kept absolute.
+
+### Configuration
+
+| Parameter                 | Type        | Default       | Description                                                      |
+| ------------------------- | ----------- | ------------- | ---------------------------------------------------------------- |
+| `use_relative_actions`    | `bool`      | `False`       | Enable relative-action training                                  |
+| `relative_exclude_joints` | `list[str]` | `["gripper"]` | Joint names to keep absolute (matched by substring)              |
+| `action_feature_names`    | `list[str]` | `None`        | Auto-populated from dataset metadata at runtime by `make_policy` |
+
+### Training example
+
+```bash
+python -m lerobot.scripts.lerobot_train \
+  --policy.type=pi05 \
+  --dataset.repo_id=your_org/your_dataset \
+  --policy.use_relative_actions=true \
+  --policy.relative_exclude_joints='["gripper"]'
+```
+
+When `use_relative_actions=true`, the training script automatically:
+
+- Computes relative action statistics from the dataset (sampled chunk-level relative actions)
+- Replaces the standard action stats with relative stats for normalization
+- Broadcasts these stats across all ranks in distributed training
+
+---
+
+## Citation
+
+If you use this work, please cite both **OpenPI** and the π₀.₅ paper:
+
+```bibtex
+@misc{openpi2024,
+  author       = {Physical Intelligence Lab},
+  title        = {OpenPI: PyTorch Implementation of π0 and π0.5 Policies},
+  year         = {2024},
+  publisher    = {GitHub},
+  howpublished = {\url{https://github.com/Physical-Intelligence/openpi}},
+  license      = {Apache-2.0}
+}
+
+@misc{intelligence2025pi05visionlanguageactionmodelopenworld,
+  title        = {π₀.₅: a Vision-Language-Action Model with Open-World Generalization},
+  author       = {Physical Intelligence and Kevin Black and Noah Brown and James Darpinian and Karan Dhabalia and Danny Driess and Adnan Esmail and Michael Equi and Chelsea Finn and Niccolo Fusai and Manuel Y. Galliker and Dibya Ghosh and Lachy Groom and Karol Hausman and Brian Ichter and Szymon Jakubczak and Tim Jones and Liyiming Ke and Devin LeBlanc and Sergey Levine and Adrian Li-Bell and Mohith Mothukuri and Suraj Nair and Karl Pertsch and Allen Z. Ren and Lucy Xiaoyang Shi and Laura Smith and Jost Tobias Springenberg and Kyle Stachowicz and James Tanner and Quan Vuong and Homer Walke and Anna Walling and Haohuan Wang and Lili Yu and Ury Zhilinsky},
+  year         = {2025},
+  eprint       = {2504.16054},
+  archivePrefix= {arXiv},
+  primaryClass = {cs.LG},
+  url          = {https://arxiv.org/abs/2504.16054},
+}
+```
+
+---
+
+## License
+
+This port follows the **Apache 2.0 License**, consistent with the original [OpenPI repository](https://github.com/Physical-Intelligence/openpi).

docs/source/policy_pi0_README.md

@@ -0,0 +1,108 @@
+# π₀ (pi0)
+
+This repository contains the Hugging Face port of **π₀**, adapted from [OpenPI](https://github.com/Physical-Intelligence/openpi) by the Physical Intelligence.
+It is designed as a **Vision-Language-Action model for general robot control**.
+
+---
+
+## Model Overview
+
+| Feature              | π₀                                                     | π₀.₅                                      |
+| -------------------- | ------------------------------------------------------ | ----------------------------------------- |
+| Time Conditioning    | Concatenates time with actions via `action_time_mlp_*` | Uses `time_mlp_*` for AdaRMS conditioning |
+| AdaRMS               | Not used                                               | Used in action expert                     |
+| Tokenizer Length     | 48 tokens                                              | 200 tokens                                |
+| Discrete State Input | False (Uses `state_proj` layer)                        | True                                      |
+| Parameter Count      | Higher (includes state embedding)                      | Lower (no state embedding)                |
+
+---
+
+## Relative Actions
+
+π₀ supports training with **relative actions**, where the model learns relative offsets
+from the current robot state instead of absolute joint positions. This mirrors the
+relative-action transform in OpenPI (`DeltaActions`) and can improve performance.
+
+### How it works
+
+1. **During preprocessing**, absolute actions are converted to relative offsets:
+   `relative = action - state` (for selected joints).
+2. The relative actions are normalized using statistics computed from the relative distribution.
+3. **During postprocessing**, predicted relative actions are converted back to absolute:
+   `absolute = relative + state`.
+
+Joints listed in `relative_exclude_joints` (e.g., gripper) are kept absolute.
+
+### Configuration
+
+| Parameter                 | Type        | Default       | Description                                                      |
+| ------------------------- | ----------- | ------------- | ---------------------------------------------------------------- |
+| `use_relative_actions`    | `bool`      | `False`       | Enable relative-action training                                  |
+| `relative_exclude_joints` | `list[str]` | `["gripper"]` | Joint names to keep absolute (matched by substring)              |
+| `action_feature_names`    | `list[str]` | `None`        | Auto-populated from dataset metadata at runtime by `make_policy` |
+
+### Training example
+
+```bash
+python -m lerobot.scripts.lerobot_train \
+  --policy.type=pi0 \
+  --dataset.repo_id=your_org/your_dataset \
+  --policy.use_relative_actions=true \
+  --policy.relative_exclude_joints='["gripper"]'
+```
+
+When `use_relative_actions=true`, the training script automatically:
+
+- Computes relative action statistics from the dataset (sampled chunk-level relative actions)
+- Replaces the standard action stats with relative stats for normalization
+- Broadcasts these stats across all ranks in distributed training
+
+### Recomputing stats for an existing dataset
+
+If you want to precompute relative action stats offline, use `recompute_stats` from
+`lerobot.datasets.dataset_tools`:
+
+```python
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+from lerobot.datasets.dataset_tools import recompute_stats
+
+dataset = LeRobotDataset("your_org/your_dataset")
+dataset = recompute_stats(
+    dataset,
+    relative_action=True,
+    relative_exclude_joints=["gripper"],
+)
+```
+
+---
+
+## Citation
+
+If you use this work, please cite both **OpenPI** and the π₀ paper:
+
+```bibtex
+@misc{openpi2024,
+  author       = {Physical Intelligence Lab},
+  title        = {OpenPI: PyTorch Implementation of π0 and π0.5 Policies},
+  year         = {2024},
+  publisher    = {GitHub},
+  howpublished = {\url{https://github.com/Physical-Intelligence/openpi}},
+  license      = {Apache-2.0}
+}
+
+@misc{black2024pi0visionlanguageactionflowmodel,
+  title        = {π₀: A Vision-Language-Action Flow Model for General Robot Control},
+  author       = {Kevin Black and Noah Brown and Danny Driess and Adnan Esmail and Michael Equi and Chelsea Finn and Niccolo Fusai and Lachy Groom and Karol Hausman and Brian Ichter and Szymon Jakubczak and Tim Jones and Liyiming Ke and Sergey Levine and Adrian Li-Bell and Mohith Mothukuri and Suraj Nair and Karl Pertsch and Lucy Xiaoyang Shi and James Tanner and Quan Vuong and Anna Walling and Haohuan Wang and Ury Zhilinsky},
+  year         = {2024},
+  eprint       = {2410.24164},
+  archivePrefix= {arXiv},
+  primaryClass = {cs.LG},
+  url          = {https://arxiv.org/abs/2410.24164},
+}
+```
+
+---
+
+## License
+
+This port follows the **Apache 2.0 License**, consistent with the original [OpenPI repository](https://github.com/Physical-Intelligence/openpi).

docs/source/policy_rtc_README.md

@@ -0,0 +1,38 @@
+# Real-Time Chunking (RTC)
+
+This module contains the LeRobot implementation of **Real-Time Chunking (RTC)**, an inference-time technique for flow-matching based policies.
+
+**Note**: RTC is not a policy itself, but rather an inference enhancement that works with flow-matching based policies including [π₀](../pi0/), [π₀.₅](../pi05/), and [SmolVLA](../smolvla/).
+
+---
+
+## Citation
+
+If you use Real-Time Chunking in your work, please cite:
+
+```bibtex
+@misc{openpi2024,
+  author       = {Physical Intelligence Lab},
+  title        = {OpenPI: PyTorch Implementation of π0 and π0.5 Policies},
+  year         = {2024},
+  publisher    = {GitHub},
+  howpublished = {\url{https://github.com/Physical-Intelligence/openpi}},
+  license      = {Apache-2.0}
+}
+
+@misc{black2025realtimeexecutionactionchunking,
+      title={Real-Time Execution of Action Chunking Flow Policies},
+      author={Kevin Black and Manuel Y. Galliker and Sergey Levine},
+      year={2025},
+      eprint={2506.07339},
+      archivePrefix={arXiv},
+      primaryClass={cs.RO},
+      url={https://arxiv.org/abs/2506.07339},
+}
+```
+
+---
+
+## License
+
+This implementation follows the **Apache 2.0 License**, consistent with the LeRobot project.

docs/source/policy_sarm_README.md

@@ -0,0 +1,14 @@
+## Paper
+
+https://arxiv.org/abs/2509.25358
+
+## Citation
+
+```bibtex
+@article{chen2025sarm,
+  title={SARM: Stage-Aware Reward Modeling for Long Horizon Robot Manipulation},
+  author={Chen, Qianzhong and Yu, Justin and Schwager, Mac and Abbeel, Pieter and Shentu, Yide and Wu, Philipp},
+  journal={arXiv preprint arXiv:2509.25358},
+  year={2025}
+}
+```

docs/source/rename_map.mdx

@@ -0,0 +1,114 @@
+# Rename Map and Empty Cameras
+
+When you train, evaluate, or record with a robot policy, your **dataset** or **environment** provides observations under one set of keys (e.g. `observation.images.front`, `observation.images.eagle`), while your **policy** expects another (e.g. `observation.images.image`, `observation.images.image2`). The **rename map** bridges that gap without changing the policy or data source.
+
+> **Scope:** The rename map only renames **observation** keys (images and state). Action keys are not affected.
+
+## Why observation keys don't always match
+
+Policies have a fixed set of **input feature names** baked into their pretrained config. For example:
+
+- [pi0fast-libero](https://huggingface.co/lerobot/pi0fast-libero) expects `observation.images.base_0_rgb` and `observation.images.left_wrist_0_rgb`.
+- [xvla-base](https://huggingface.co/lerobot/xvla-base) expects `observation.images.image`, `observation.images.image2`, and `observation.images.image3`.
+
+Your dataset might use different names entirely (e.g. `observation.images.front`, `observation.images.eagle`, `observation.images.glove`), and your eval environment might use yet another set. Rather than editing the policy config or renaming columns in the dataset, you pass a **rename map**: a JSON dictionary that maps source keys to the keys the policy expects. Renaming happens inside the preprocessor pipeline, so the policy always sees its expected keys.
+
+## Using the rename map
+
+Pass the mapping as a JSON string on the command line. The convention is always:
+
+```
+--rename_map='{"source_key": "policy_key", ...}'
+```
+
+where **source_key** is what the dataset or environment provides, and **policy_key** is what the policy expects.
+
+Only listed keys are renamed; everything else passes through unchanged. Order of entries doesn't matter.
+
+Supported policies: **PI0**, **PI05**, **PI0Fast**, **SmolVLA**, and **XVLA**.
+
+### Training
+
+Suppose you fine-tune [lerobot/xvla-base](https://huggingface.co/lerobot/xvla-base) on a dataset with images under `observation.images.front`, `observation.images.eagle`, and `observation.images.glove`. XVLA expects `observation.images.image`, `observation.images.image2`, and `observation.images.image3`:
+
+```bash
+lerobot-train \
+  --dataset.repo_id=YOUR_DATASET \
+  --output_dir=./outputs/xvla_training \
+  --job_name=xvla_training \
+  --policy.path="lerobot/xvla-base" \
+  --policy.repo_id="HF_USER/xvla-your-robot" \
+  --policy.dtype=bfloat16 \
+  --policy.action_mode=auto \
+  --steps=20000 \
+  --policy.device=cuda \
+  --policy.freeze_vision_encoder=false \
+  --policy.freeze_language_encoder=false \
+  --policy.train_policy_transformer=true \
+  --policy.train_soft_prompts=true \
+  --rename_map='{"observation.images.front": "observation.images.image", "observation.images.eagle": "observation.images.image2", "observation.images.glove": "observation.images.image3"}'
+```
+
+### Evaluation
+
+A policy that expects `observation.images.base_0_rgb` and `observation.images.left_wrist_0_rgb` (e.g. [pi0fast-libero](https://huggingface.co/lerobot/pi0fast-libero)), but the LIBERO environment returns `observation.images.image` and `observation.images.image2`:
+
+```bash
+lerobot-eval \
+  --policy.path=lerobot/pi0fast-libero \
+  --env.type=libero \
+  ... \
+  --rename_map='{"observation.images.image": "observation.images.base_0_rgb", "observation.images.image2": "observation.images.left_wrist_0_rgb"}'
+```
+
+### Recording
+
+`lerobot-record` also supports rename maps, nested under the dataset config:
+
+```bash
+lerobot-record \ # When running inference
+  --policy.path="<user>/smolVLA_finetuned" \
+  ... \
+  --dataset.rename_map='{"observation.images.glove2": "observation.images.image"}'
+```
+
+## Alternative: edit the policy config directly
+
+If you always use the same dataset or environment, you can **edit the policy's `config.json`** so its observation keys match your data source. Then no rename map is needed.
+
+The tradeoff: modifying the policy config ties it to one data source. A rename map keeps one policy usable across many datasets and environments.
+
+## Empty cameras: fewer views than the policy expects
+
+Some policies are built for a fixed number of image inputs. If your dataset has fewer cameras, you can set **`empty_cameras`** in the policy config instead of modifying the model architecture.
+
+### How it works
+
+Setting `empty_cameras=N` adds N placeholder image features to the policy config, named:
+
+```
+observation.images.empty_camera_0
+observation.images.empty_camera_1
+...
+```
+
+At runtime, these keys have no corresponding data in the batch. The policy fills them with masked dummy tensors (padded with `-1` for SigLIP-based vision encoders, with a zero attention mask), so the extra image slots are effectively ignored during training and inference.
+
+### Example
+
+XVLA-base has three visual inputs and `empty_cameras=0` by default. Your dataset only has two cameras:
+
+1. Set `--policy.empty_cameras=1`.
+2. The config adds a third key: `observation.images.empty_camera_0`.
+3. Use the rename map for your two real cameras as usual.
+4. The third slot is masked out — no fake images needed in your dataset.
+
+## Quick reference
+
+| Goal                                      | What to do                                                                  |
+| ----------------------------------------- | --------------------------------------------------------------------------- |
+| Dataset keys ≠ policy keys                | `--rename_map='{"dataset_key": "policy_key", ...}'`                         |
+| Env keys ≠ policy keys (eval)             | `--rename_map='{"env_key": "policy_key", ...}'`                             |
+| Recording with different keys (inference) | `--dataset.rename_map='{"source_key": "policy_key", ...}'`.                 |
+| Fewer cameras than policy expects         | `--policy.empty_cameras=N` (supported by PI0, PI05, PI0Fast, SmolVLA, XVLA) |
+| Avoid passing a rename map                | Edit the policy's `config.json` so its keys match your data source          |

docs/source/so101.mdx

@@ -236,10 +236,10 @@ It is advisable to install one 3-pin cable in the motor after placing them befor
 
 ### Joint 1
 
+- Install both motor horns. Secure the top horn with a M3x6mm screw. No screws are required for the bottom horn.
 - Place the first motor into the base.
 - Fasten the motor with 4 M2x6mm screws (smallest screws). Two from the top and two from the bottom.
 - Slide over the first motor holder and fasten it using two M2x6mm screws (one on each side).
-- Install both motor horns, securing the top horn with a M3x6mm screw.
 - Attach the shoulder part.
 - Tighten the shoulder part with 4 M3x6mm screws on top and 4 M3x6mm screws on the bottom
 - Add the shoulder motor holder.
@@ -255,9 +255,9 @@ It is advisable to install one 3-pin cable in the motor after placing them befor
 
 ### Joint 2
 
+- Install both motor horns. Secure the top horn with a M3x6mm screw. No screws are required for the bottom horn.
 - Slide the second motor in from the top.
 - Fasten the second motor with 4 M2x6mm screws.
-- Attach both motor horns to motor 2, again use the M3x6mm horn screw.
 - Attach the upper arm with 4 M3x6mm screws on each side.
 
 <div class="video-container">
@@ -271,8 +271,8 @@ It is advisable to install one 3-pin cable in the motor after placing them befor
 
 ### Joint 3
 
-- Insert motor 3 and fasten using 4 M2x6mm screws
-- Attach both motor horns to motor 3 and secure one again with a M3x6mm horn screw.
+- Install both motor horns. Secure the top horn with a M3x6mm screw. No screws are required for the bottom horn.
+- Insert motor 3 and fasten using 4 M2x6mm screws.
 - Connect the forearm to motor 3 using 4 M3x6mm screws on each side.
 
 <div class="video-container">
@@ -286,9 +286,10 @@ It is advisable to install one 3-pin cable in the motor after placing them befor
 
 ### Joint 4
 
+- Install both motor horns. Secure the top horn with a M3x6mm screw. No screws are required for the bottom horn.
 - Slide over motor holder 4.
 - Slide in motor 4.
-- Fasten motor 4 with 4 M2x6mm screws and attach its motor horns, use a M3x6mm horn screw.
+- Fasten motor 4 with 4 M2x6mm screws.
 
 <div class="video-container">
   <video controls width="600">
@@ -321,7 +322,7 @@ It is advisable to install one 3-pin cable in the motor after placing them befor
 
 - Attach the gripper to motor 5, attach it to the motor horn on the wrist using 4 M3x6mm screws.
 - Insert the gripper motor and secure it with 2 M2x6mm screws on each side.
-- Attach the motor horns and again use a M3x6mm horn screw.
+- Install both motor horns on the gripper motor. Secure the top horn with a M3x6mm screw; no screws are required for the bottom horn.
 - Install the gripper claw and secure it with 4 M3x6mm screws on both sides.
 
 <div class="video-container">

docs/source/unitree_g1.mdx

@@ -12,36 +12,59 @@ The Unitree G1 humanoid is now supported in LeRobot! You can teleoperate, train
 
 ## Part 1: Getting Started
 
-### Install LeRobot on Your Machine
+### Install the Unitree SDK
+
+Follow the [unitree_sdk2_python installation guide](https://github.com/unitreerobotics/unitree_sdk2_python#installation). Tested with `unitree_sdk2py==1.0.1` and `cyclonedds==0.10.2`:
 
 ```bash
 conda create -y -n lerobot python=3.12
 conda activate lerobot
 git clone https://github.com/unitreerobotics/unitree_sdk2_python.git
-cd unitree_sdk2_python && pip install -e .
+cd unitree_sdk2_python
+pip install -e .
+cd ..
+```
+
+### Install LeRobot
+
+```bash
+conda install ffmpeg -c conda-forge
+conda install -c conda-forge "pinocchio>=3.0.0,<4.0.0"
 git clone https://github.com/huggingface/lerobot.git
 cd lerobot
 pip install -e '.[unitree_g1]'
 ```
 
+<Tip>
+  For now, pinocchio must be installed from conda-forge (not pip) to include the
+  CasADi bindings needed for arm IK.
+</Tip>
+
 ### Test the Installation (Simulation)
 
+The simulation environment has its own dependencies. Check the Simulation environment dependencies: [Unitree G1 Mujoco EnvHub](https://huggingface.co/lerobot/unitree-g1-mujoco/tree/main).
+
+```bash
+pip install mujoco loguru msgpack msgpack-numpy
+```
+
 ```bash
 lerobot-teleoperate \
   --robot.type=unitree_g1 \
   --robot.is_simulation=true \
   --teleop.type=unitree_g1 \
   --teleop.id=wbc_unitree \
-  --robot.cameras='{"global_view": {"type": "zmq", "server_address": "localhost", "port": 5555, "camera_name": "head_camera", "width": 640, "height": 480, "fps": 30}}' \
-  --display_data=true
+  --robot.cameras='{"global_view": {"type": "zmq", "server_address": "localhost", "port": 5555, "camera_name": "head_camera", "width": 640, "height": 480, "fps": 30, "warmup_s": 5}}' \
+  --display_data=true \
+  --robot.controller=GrootLocomotionController
 ```
 
-This will launch a [MuJoCo sim instance](https://huggingface.co/lerobot/unitree-g1-mujoco/tree/main) for the G1.
+This will launch a [MuJoCo sim instance](https://huggingface.co/lerobot/unitree-g1-mujoco/tree/main) for the G1. You can connect a gamepad to your machine before launching in order to control the robot's locomotion in sim. We support both [HolosomaLocomotionController](https://github.com/amazon-far/holosoma) and [GrootLocomotionController](https://github.com/NVlabs/GR00T-WholeBodyControl) via `--robot.controller`.
 
 - Press `9` to release the robot
 - Press `7` / `8` to increase / decrease waist height
 
-### Connect to the Robot
+### Connect to the Physical Robot
 
 The G1's Ethernet IP is fixed at `192.168.123.164`. Your machine must have a static IP on the same subnet: `192.168.123.x` where `x ≠ 164`.
 
@@ -59,37 +82,11 @@ ssh unitree@192.168.123.164
 # Password: 123
 ```
 
-### Install LeRobot on the G1
+### Share Internet via Ethernet
 
-From the robot:
+The G1 needs internet access to clone repos and install packages. Share your laptop's connection over Ethernet:
 
-```bash
-conda create -y -n lerobot python=3.12
-conda activate lerobot
-git clone https://github.com/unitreerobotics/unitree_sdk2_python.git
-cd unitree_sdk2_python && pip install -e .
-git clone https://github.com/huggingface/lerobot.git
-cd lerobot
-pip install -e '.[unitree_g1]'
-```
-
-> **Note:** The Unitree SDK requires CycloneDDS v0.10.2. See the [Unitree SDK docs](https://github.com/unitreerobotics/unitree_sdk2_python) for details.
-
----
-
-## Part 2: Enable WiFi on the Robot
-
-Wi-Fi connectivity is blocked by default on the G1. To activate:
-
-```bash
-sudo rfkill unblock all
-sudo ip link set wlan0 up
-sudo nmcli radio wifi on
-sudo nmcli device set wlan0 managed yes
-sudo systemctl restart NetworkManager
-```
-
-**On your laptop** (share internet via Ethernet):
+**On your laptop:**
 
 ```bash
 sudo sysctl -w net.ipv4.ip_forward=1
@@ -100,7 +97,7 @@ sudo iptables -A FORWARD -i wlp132s0f0 -o enp131s0 -m state --state RELATED,ESTA
 sudo iptables -A FORWARD -i enp131s0 -o wlp132s0f0 -j ACCEPT
 ```
 
-**On the G1** (set default route through your laptop):
+**On the G1:**
 
 ```bash
 sudo ip route del default 2>/dev/null || true
@@ -111,6 +108,45 @@ echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf
 ping -c 3 8.8.8.8
 ```
 
+### Install the Unitree SDK on the G1
+
+Follow the [unitree_sdk2_python installation guide](https://github.com/unitreerobotics/unitree_sdk2_python#installation):
+
+```bash
+conda create -y -n lerobot python=3.12
+conda activate lerobot
+git clone https://github.com/unitreerobotics/unitree_sdk2_python.git
+cd unitree_sdk2_python
+python -m pip install -e .
+cd ..
+```
+
+### Install LeRobot on the G1
+
+```bash
+git clone https://github.com/huggingface/lerobot.git
+cd lerobot
+conda install -c conda-forge "pinocchio>=3.0.0,<4.0.0"
+python -m pip install -e '.[unitree_g1]'
+```
+
+<Tip>
+  For now, pinocchio must be installed from conda-forge (not pip) to include the
+  CasADi bindings needed for arm IK.
+</Tip>
+
+### (Optional) Enable WiFi on the Robot
+
+For wireless SSH access, you can enable WiFi on the G1 (it's blocked by default):
+
+```bash
+sudo rfkill unblock all
+sudo ip link set wlan0 up
+sudo nmcli radio wifi on
+sudo nmcli device set wlan0 managed yes
+sudo systemctl restart NetworkManager
+```
+
 **Connect to a WiFi network:**
 
 ```bash
@@ -125,7 +161,7 @@ sudo nmcli connection up "YourNetwork"
 ip a show wlan0
 ```
 
-You can now SSH over WiFi:
+You can then SSH over WiFi instead of Ethernet:
 
 ```bash
 ssh unitree@<ROBOT_WIFI_IP>
@@ -134,18 +170,23 @@ ssh unitree@<ROBOT_WIFI_IP>
 
 ---
 
-## Part 3: Teleoperation & Locomotion
+## Part 2: Teleoperation & Locomotion
 
 ### Run the Robot Server
 
-On the robot:
+On the robot (from `~/lerobot`):
 
 ```bash
+cd ~/lerobot
 python src/lerobot/robots/unitree_g1/run_g1_server.py --camera
 ```
 
 ### Run the Locomotion Policy
 
+You can run the teleoperation client from your laptop over Ethernet, over WiFi (experimental), or directly on the robot itself. Mind potential latency introduced by your network.
+
+**From your laptop:**
+
 ```bash
 lerobot-teleoperate \
   --robot.type=unitree_g1 \
@@ -158,13 +199,13 @@ lerobot-teleoperate \
   --robot.controller=HolosomaLocomotionController
 ```
 
-We support both [HolosomaLocomotionController](https://github.com/amazon-far/holosoma) and [GrootLocomotionController](https://github.com/NVlabs/GR00T-WholeBodyControl).
+We support both [GrootLocomotionController](https://github.com/NVlabs/GR00T-WholeBodyControl) and [HolosomaLocomotionController](https://github.com/amazon-far/holosoma) via `--robot.controller`.
 
 ---
 
-## Part 4: Loco-Manipulation with the Homunculus Exoskeleton
+## Part 3: Loco-Manipulation with the Homunculus Exoskeleton
 
-We provide a loco-manipulation solution via the Homunculus Exoskeleton — an open-source 7 DoF exoskeleton for whole-body control. Assembly instructions [here](https://github.com/nepyope/hmc_exo).
+We provide a loco-manipulation solution via the Homunculus Exoskeleton — an open-source 7 DoF exoskeleton for whole-body control. Check it out [here](https://github.com/nepyope/hmc_exo).
 
 ### Calibrate
 
@@ -205,7 +246,7 @@ Example dataset: [nepyope/unitree_box_move_blue_full](https://huggingface.co/dat
 
 ---
 
-## Part 5: Training & Inference
+## Part 4: Training & Inference
 
 ### Train
 

examples/backward_compatibility/replay.py

@@ -78,7 +78,7 @@ def replay(cfg: ReplayConfig):
 
     robot = make_robot_from_config(cfg.robot)
     dataset = LeRobotDataset(cfg.dataset.repo_id, root=cfg.dataset.root, episodes=[cfg.dataset.episode])
-    actions = dataset.hf_dataset.select_columns(ACTION)
+    actions = dataset.select_columns(ACTION)
     robot.connect()
 
     try:

examples/dataset/create_progress_videos.py

@@ -0,0 +1,680 @@
+#!/usr/bin/env python
+
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Create MP4 (or GIF) videos with sarm_progress overlay for specified episodes.
+
+Downloads datasets from HuggingFace, seeks directly into the episode segment
+of the source video, draws a progress line on each frame, and writes the result.
+
+Usage:
+    python examples/dataset/create_progress_videos.py \
+        --repo-id lerobot-data-collection/level2_final_quality3 \
+        --episode 1100
+
+    python examples/dataset/create_progress_videos.py \
+        --repo-id lerobot-data-collection/level2_final_quality3 \
+        --episode 1100 \
+        --camera-key observation.images.top \
+        --output-dir ./my_videos \
+        --gif
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import logging
+import subprocess
+from pathlib import Path
+
+import cv2
+import numpy as np
+import pandas as pd
+from huggingface_hub import snapshot_download
+
+GRAPH_Y_TOP_FRAC = 0.01
+GRAPH_Y_BOT_FRAC = 0.99
+LINE_THICKNESS = 3
+SHADOW_THICKNESS = 6
+REF_ALPHA = 0.45
+FILL_ALPHA = 0.55
+SCORE_FONT_SCALE = 0.8
+TASK_FONT_SCALE = 0.55
+
+
+def download_episode_metadata(repo_id: str, episode: int) -> Path:
+    """Download only the metadata and sarm_progress files for a dataset.
+
+    Args:
+        repo_id: HuggingFace dataset repository ID.
+        episode: Episode index (used for logging only; all meta is fetched).
+
+    Returns:
+        Local cache path for the downloaded snapshot.
+    """
+    logging.info("[1/4] Downloading metadata for %s (episode %d) ...", repo_id, episode)
+    local_path = Path(
+        snapshot_download(
+            repo_id=repo_id,
+            repo_type="dataset",
+            allow_patterns=["meta/**", "sarm_progress.parquet"],
+            ignore_patterns=["*.mp4"],
+        )
+    )
+    return local_path
+
+
+def load_episode_meta(local_path: Path, episode: int, camera_key: str | None) -> dict:
+    """Read info.json and episode parquet to resolve fps, video path, and timestamps.
+
+    Args:
+        local_path: Local cache directory containing meta/.
+        episode: Episode index to look up.
+        camera_key: Camera observation key (e.g. "observation.images.base").
+            If None, the first available video key is used.
+
+    Returns:
+        Dict with keys: fps, camera, video_rel, chunk_index, file_index,
+        from_ts, to_ts, task_name.
+    """
+    info = json.loads((local_path / "meta" / "info.json").read_text())
+    fps = info["fps"]
+    features = info["features"]
+
+    video_keys = [k for k, v in features.items() if v.get("dtype") == "video"]
+    if not video_keys:
+        raise RuntimeError("No video keys found in dataset features")
+
+    if camera_key is not None:
+        if camera_key not in video_keys:
+            raise RuntimeError(f"camera_key='{camera_key}' not found. Available: {video_keys}")
+        selected_camera = camera_key
+    else:
+        selected_camera = video_keys[0]
+    logging.info("   fps=%d  camera='%s'  all_cams=%s", fps, selected_camera, video_keys)
+
+    episode_rows = []
+    for parquet_file in sorted((local_path / "meta" / "episodes").glob("**/*.parquet")):
+        episode_rows.append(pd.read_parquet(parquet_file))
+    episode_df = pd.concat(episode_rows, ignore_index=True)
+    row = episode_df[episode_df["episode_index"] == episode]
+    if row.empty:
+        raise RuntimeError(f"Episode {episode} not found in episode metadata")
+    row = row.iloc[0]
+
+    chunk_col = f"videos/{selected_camera}/chunk_index"
+    file_col = f"videos/{selected_camera}/file_index"
+    ts_from_col = f"videos/{selected_camera}/from_timestamp"
+    ts_to_col = f"videos/{selected_camera}/to_timestamp"
+
+    if chunk_col not in row.index:
+        chunk_col = f"{selected_camera}/chunk_index"
+        file_col = f"{selected_camera}/file_index"
+        ts_from_col = f"{selected_camera}/from_timestamp"
+        ts_to_col = f"{selected_camera}/to_timestamp"
+    if chunk_col not in row.index:
+        raise RuntimeError(
+            f"Cannot find video metadata columns for {selected_camera}.\nAvailable: {list(row.index)}"
+        )
+
+    chunk_index = int(row[chunk_col])
+    file_index = int(row[file_col])
+    from_timestamp = float(row[ts_from_col])
+    to_timestamp = float(row[ts_to_col])
+
+    video_template = info.get(
+        "video_path", "videos/{video_key}/chunk-{chunk_index:03d}/file-{file_index:03d}.mp4"
+    )
+    video_rel = video_template.format(
+        video_key=selected_camera,
+        chunk_index=chunk_index,
+        file_index=file_index,
+    )
+
+    task_name = _resolve_task_name(row, local_path)
+
+    return {
+        "fps": fps,
+        "camera": selected_camera,
+        "video_rel": video_rel,
+        "chunk_index": chunk_index,
+        "file_index": file_index,
+        "from_ts": from_timestamp,
+        "to_ts": to_timestamp,
+        "task_name": task_name,
+    }
+
+
+def _resolve_task_name(row: pd.Series, local_path: Path) -> str:
+    """Best-effort extraction of the task name for an episode row.
+
+    Args:
+        row: Single-episode row from the episodes parquet.
+        local_path: Dataset cache root.
+
+    Returns:
+        Task name string, or empty string if unavailable.
+    """
+    try:
+        if "tasks" in row.index and row["tasks"] is not None:
+            tasks_val = row["tasks"]
+            if isinstance(tasks_val, (list, tuple, np.ndarray)) and len(tasks_val) > 0:
+                return str(tasks_val[0])
+            return str(tasks_val).strip("[]'")
+
+        tasks_parquet = local_path / "meta" / "tasks.parquet"
+        if tasks_parquet.exists():
+            tasks_df = pd.read_parquet(tasks_parquet)
+            task_idx = int(row.get("task_index", 0)) if "task_index" in row.index else 0
+            match = tasks_df[tasks_df["task_index"] == task_idx]
+            if not match.empty:
+                return str(match.index[0])
+    except Exception as exc:
+        logging.warning("Could not load task name: %s", exc)
+    return ""
+
+
+def download_video_file(repo_id: str, local_path: Path, video_rel: str) -> Path:
+    """Download the specific video file if not already cached.
+
+    Args:
+        repo_id: HuggingFace dataset repository ID.
+        local_path: Local cache directory.
+        video_rel: Relative path to the video file within the dataset.
+
+    Returns:
+        Absolute path to the downloaded video file.
+    """
+    video_path = local_path / video_rel
+    if video_path.exists():
+        logging.info("   Video already cached: %s", video_path)
+        return video_path
+    logging.info("[2/4] Downloading video file %s ...", video_rel)
+    snapshot_download(
+        repo_id=repo_id,
+        repo_type="dataset",
+        local_dir=str(local_path),
+        allow_patterns=[video_rel],
+    )
+    if not video_path.exists():
+        raise RuntimeError(f"Video not found after download: {video_path}")
+    return video_path
+
+
+def load_progress_data(local_path: Path, episode: int) -> np.ndarray | None:
+    """Load sarm_progress values for an episode.
+
+    Args:
+        local_path: Dataset cache root.
+        episode: Episode index.
+
+    Returns:
+        Sorted (N, 2) array of (frame_index, progress), or None if unavailable.
+    """
+    parquet_path = local_path / "sarm_progress.parquet"
+    if not parquet_path.exists():
+        logging.warning("sarm_progress.parquet not found")
+        return None
+    df = pd.read_parquet(parquet_path)
+    logging.info("   sarm_progress.parquet columns: %s", list(df.columns))
+    episode_df = df[df["episode_index"] == episode].copy()
+    if episode_df.empty:
+        logging.warning("No sarm_progress rows for episode %d", episode)
+        return None
+    episode_df = episode_df.sort_values("frame_index")
+
+    if "progress_dense" in episode_df.columns and episode_df["progress_dense"].notna().any():
+        progress_column = "progress_dense"
+    elif "progress_sparse" in episode_df.columns:
+        progress_column = "progress_sparse"
+    else:
+        progress_columns = [c for c in episode_df.columns if "progress" in c.lower()]
+        if not progress_columns:
+            return None
+        progress_column = progress_columns[0]
+
+    logging.info("   Using progress column: '%s'", progress_column)
+    return episode_df[["frame_index", progress_column]].rename(columns={progress_column: "progress"}).values
+
+
+def _precompute_pixel_coords(
+    progress_data: np.ndarray,
+    num_frames: int,
+    frame_width: int,
+    frame_height: int,
+) -> np.ndarray:
+    """Map progress samples to pixel coordinates for overlay drawing.
+
+    Args:
+        progress_data: (N, 2) array of (frame_index, progress).
+        num_frames: Total number of video frames.
+        frame_width: Video width in pixels.
+        frame_height: Video height in pixels.
+
+    Returns:
+        (N, 2) array of (x, y) pixel coordinates.
+    """
+    frame_indices = progress_data[:, 0].astype(float)
+    progress_values = np.clip(progress_data[:, 1].astype(float), 0.0, 1.0)
+
+    y_top = int(frame_height * GRAPH_Y_TOP_FRAC)
+    y_bot = int(frame_height * GRAPH_Y_BOT_FRAC)
+    graph_height = y_bot - y_top
+
+    x_coords = (frame_indices / (num_frames - 1) * (frame_width - 1)).astype(int)
+    y_coords = (y_bot - progress_values * graph_height).astype(int)
+
+    return np.stack([x_coords, y_coords], axis=1)
+
+
+def _progress_color(normalized_position: float) -> tuple[int, int, int]:
+    """Interpolate BGR color from red to green based on position in [0, 1].
+
+    Args:
+        normalized_position: Value in [0, 1] indicating how far along the episode.
+
+    Returns:
+        BGR color tuple.
+    """
+    red = int(255 * (1.0 - normalized_position))
+    green = int(255 * normalized_position)
+    return (0, green, red)
+
+
+def _prerender_fill_polygon(
+    pixel_coords: np.ndarray,
+    frame_width: int,
+    frame_height: int,
+) -> np.ndarray:
+    """Pre-render the grey fill polygon under the progress curve as a BGRA image.
+
+    Args:
+        pixel_coords: (N, 2) array of (x, y) pixel coordinates.
+        frame_width: Video width in pixels.
+        frame_height: Video height in pixels.
+
+    Returns:
+        BGRA image array of shape (frame_height, frame_width, 4).
+    """
+    y_bot = int(frame_height * GRAPH_Y_BOT_FRAC)
+    fill_image = np.zeros((frame_height, frame_width, 4), dtype=np.uint8)
+    polygon = np.concatenate(
+        [
+            pixel_coords,
+            [[pixel_coords[-1][0], y_bot], [pixel_coords[0][0], y_bot]],
+        ],
+        axis=0,
+    ).astype(np.int32)
+    cv2.fillPoly(fill_image, [polygon], color=(128, 128, 128, int(255 * FILL_ALPHA)))
+    return fill_image
+
+
+def _alpha_composite_region(base: np.ndarray, overlay_bgra: np.ndarray, x_limit: int) -> None:
+    """Blend BGRA overlay onto BGR base in-place, up to x_limit columns.
+
+    Args:
+        base: BGR frame to draw on (modified in-place).
+        overlay_bgra: BGRA overlay image.
+        x_limit: Only blend columns [0, x_limit).
+    """
+    if x_limit <= 0:
+        return
+    region_base = base[:, :x_limit]
+    region_overlay = overlay_bgra[:, :x_limit]
+    alpha = region_overlay[:, :, 3:4].astype(np.float32) / 255.0
+    region_base[:] = np.clip(
+        region_overlay[:, :, :3].astype(np.float32) * alpha + region_base.astype(np.float32) * (1.0 - alpha),
+        0,
+        255,
+    ).astype(np.uint8)
+
+
+def _draw_text_outlined(
+    frame: np.ndarray,
+    text: str,
+    position: tuple[int, int],
+    font_scale: float,
+    thickness: int = 1,
+) -> None:
+    """Draw white text with a dark outline for readability on any background.
+
+    Args:
+        frame: BGR image to draw on (modified in-place).
+        text: String to render.
+        position: (x, y) bottom-left corner of the text.
+        font_scale: OpenCV font scale.
+        thickness: Text stroke thickness.
+    """
+    font = cv2.FONT_HERSHEY_SIMPLEX
+    cv2.putText(frame, text, position, font, font_scale, (0, 0, 0), thickness + 2, cv2.LINE_AA)
+    cv2.putText(frame, text, position, font, font_scale, (255, 255, 255), thickness, cv2.LINE_AA)
+
+
+def composite_progress_video(
+    video_path: Path,
+    from_timestamp: float,
+    to_timestamp: float,
+    progress_data: np.ndarray,
+    output_path: Path,
+    fps: float,
+    task_name: str = "",
+) -> Path:
+    """Read episode frames by seeking into the source video, draw progress overlay, write output.
+
+    Uses cv2.CAP_PROP_POS_MSEC to seek directly into the source video,
+    eliminating the need for an intermediate clip file.
+
+    Args:
+        video_path: Path to the full source video file.
+        from_timestamp: Start timestamp of the episode in seconds.
+        to_timestamp: End timestamp of the episode in seconds.
+        progress_data: (N, 2) array of (frame_index, progress).
+        output_path: Path to write the output MP4.
+        fps: Frames per second for the output video.
+        task_name: Optional task name to display at the top of the video.
+
+    Returns:
+        Path to the written output file (MP4).
+    """
+    capture = cv2.VideoCapture(str(video_path))
+    try:
+        capture.set(cv2.CAP_PROP_POS_MSEC, from_timestamp * 1000)
+
+        frame_width = int(capture.get(cv2.CAP_PROP_FRAME_WIDTH))
+        frame_height = int(capture.get(cv2.CAP_PROP_FRAME_HEIGHT))
+        duration_seconds = to_timestamp - from_timestamp
+        num_frames = int(round(duration_seconds * fps))
+
+        logging.info(
+            "   Video: %dx%d, %d frames @ %.1f fps (%.2fs)",
+            frame_width,
+            frame_height,
+            num_frames,
+            fps,
+            duration_seconds,
+        )
+
+        pixel_coords = _precompute_pixel_coords(progress_data, num_frames, frame_width, frame_height)
+        y_ref = int(frame_height * GRAPH_Y_TOP_FRAC)
+
+        fill_image = _prerender_fill_polygon(pixel_coords, frame_width, frame_height)
+
+        ref_line_image = np.zeros((frame_height, frame_width, 4), dtype=np.uint8)
+        cv2.line(
+            ref_line_image,
+            (0, y_ref),
+            (frame_width - 1, y_ref),
+            (200, 200, 200, int(255 * REF_ALPHA)),
+            1,
+            cv2.LINE_AA,
+        )
+
+        frame_indices = progress_data[:, 0].astype(int)
+        progress_values = progress_data[:, 1].astype(float)
+
+        logging.info("[3/4] Compositing %d frames ...", num_frames)
+        fourcc = cv2.VideoWriter_fourcc(*"mp4v")
+        writer = cv2.VideoWriter(str(output_path), fourcc, fps, (frame_width, frame_height))
+
+        for frame_idx in range(num_frames):
+            ret, frame = capture.read()
+            if not ret:
+                break
+
+            drawn_count = int(np.searchsorted(frame_indices, frame_idx, side="right"))
+            x_current = (
+                int(pixel_coords[min(drawn_count, len(pixel_coords)) - 1][0]) + 1 if drawn_count > 0 else 0
+            )
+
+            _alpha_composite_region(frame, ref_line_image, frame_width)
+            _alpha_composite_region(frame, fill_image, x_current)
+
+            if drawn_count >= 2:
+                time_position = (drawn_count - 1) / max(len(progress_values) - 1, 1)
+                line_color = _progress_color(time_position)
+                points = pixel_coords[:drawn_count].reshape(-1, 1, 2).astype(np.int32)
+                cv2.polylines(
+                    frame,
+                    [points],
+                    isClosed=False,
+                    color=(255, 255, 255),
+                    thickness=SHADOW_THICKNESS,
+                    lineType=cv2.LINE_AA,
+                )
+                cv2.polylines(
+                    frame,
+                    [points],
+                    isClosed=False,
+                    color=line_color,
+                    thickness=LINE_THICKNESS,
+                    lineType=cv2.LINE_AA,
+                )
+
+            if drawn_count > 0:
+                score = float(progress_values[min(drawn_count, len(progress_values)) - 1])
+                score_text = f"{score:.2f}"
+                (text_width, _), _ = cv2.getTextSize(
+                    score_text, cv2.FONT_HERSHEY_SIMPLEX, SCORE_FONT_SCALE, 2
+                )
+                score_x = frame_width - text_width - 12
+                score_y = frame_height - 12
+                time_position = (drawn_count - 1) / max(len(progress_values) - 1, 1)
+                score_color = _progress_color(time_position)
+                cv2.putText(
+                    frame,
+                    score_text,
+                    (score_x, score_y),
+                    cv2.FONT_HERSHEY_SIMPLEX,
+                    SCORE_FONT_SCALE,
+                    (0, 0, 0),
+                    4,
+                    cv2.LINE_AA,
+                )
+                cv2.putText(
+                    frame,
+                    score_text,
+                    (score_x, score_y),
+                    cv2.FONT_HERSHEY_SIMPLEX,
+                    SCORE_FONT_SCALE,
+                    score_color,
+                    2,
+                    cv2.LINE_AA,
+                )
+
+            if task_name:
+                (text_width, _), _ = cv2.getTextSize(task_name, cv2.FONT_HERSHEY_SIMPLEX, TASK_FONT_SCALE, 1)
+                task_x = max((frame_width - text_width) // 2, 4)
+                _draw_text_outlined(frame, task_name, (task_x, 22), TASK_FONT_SCALE)
+
+            writer.write(frame)
+            if frame_idx % 100 == 0:
+                logging.info("   Frame %d/%d ...", frame_idx, num_frames)
+
+        writer.release()
+    finally:
+        capture.release()
+
+    logging.info("   MP4 written: %s", output_path)
+    return output_path
+
+
+def convert_mp4_to_gif(mp4_path: Path) -> Path:
+    """Convert an MP4 to an optimized GIF using ffmpeg palette generation.
+
+    Args:
+        mp4_path: Path to the source MP4 file.
+
+    Returns:
+        Path to the generated GIF file.
+    """
+    capture = cv2.VideoCapture(str(mp4_path))
+    frame_width = int(capture.get(cv2.CAP_PROP_FRAME_WIDTH))
+    capture.release()
+
+    gif_path = mp4_path.with_suffix(".gif")
+    palette_path = mp4_path.parent / "_palette.png"
+
+    logging.info("[4/4] Converting to GIF ...")
+    result_palette = subprocess.run(  # nosec B607
+        [
+            "ffmpeg",
+            "-y",
+            "-i",
+            str(mp4_path),
+            "-vf",
+            f"fps=10,scale={frame_width}:-1:flags=lanczos,palettegen=max_colors=128:stats_mode=diff",
+            "-update",
+            "1",
+            str(palette_path),
+        ],
+        capture_output=True,
+        text=True,
+    )
+    if result_palette.returncode != 0:
+        logging.warning("palettegen failed:\n%s", result_palette.stderr[-500:])
+
+    result_gif = subprocess.run(  # nosec B607
+        [
+            "ffmpeg",
+            "-y",
+            "-i",
+            str(mp4_path),
+            "-i",
+            str(palette_path),
+            "-filter_complex",
+            f"fps=10,scale={frame_width}:-1:flags=lanczos[v];[v][1:v]paletteuse=dither=bayer:bayer_scale=3",
+            str(gif_path),
+        ],
+        capture_output=True,
+        text=True,
+    )
+    if result_gif.returncode != 0:
+        logging.warning("GIF encode failed:\n%s", result_gif.stderr[-500:])
+
+    palette_path.unlink(missing_ok=True)
+    logging.info("   GIF written: %s", gif_path)
+    return gif_path
+
+
+def process_dataset(
+    repo_id: str,
+    episode: int,
+    camera_key: str | None,
+    output_dir: Path,
+    create_gif: bool = False,
+) -> Path | None:
+    """Full pipeline: download, extract metadata, composite progress, write output.
+
+    Args:
+        repo_id: HuggingFace dataset repository ID.
+        episode: Episode index.
+        camera_key: Camera key to use, or None for auto-selection.
+        output_dir: Directory to write output files.
+        create_gif: If True, also generate a GIF from the MP4.
+
+    Returns:
+        Path to the final output file, or None on failure.
+    """
+    safe_name = repo_id.replace("/", "_")
+    logging.info("Processing: %s  |  episode %d", repo_id, episode)
+
+    local_path = download_episode_metadata(repo_id, episode)
+    logging.info("   Local cache: %s", local_path)
+
+    episode_meta = load_episode_meta(local_path, episode, camera_key)
+    logging.info("   Episode meta: %s", episode_meta)
+
+    video_path = download_video_file(repo_id, local_path, episode_meta["video_rel"])
+
+    progress_data = load_progress_data(local_path, episode)
+    if progress_data is None:
+        logging.error("Could not load sarm_progress data. Skipping overlay.")
+        return None
+
+    logging.info("   Progress frames: %d", len(progress_data))
+
+    output_path = output_dir / f"{safe_name}_ep{episode}_progress.mp4"
+    final_path = composite_progress_video(
+        video_path=video_path,
+        from_timestamp=episode_meta["from_ts"],
+        to_timestamp=episode_meta["to_ts"],
+        progress_data=progress_data,
+        output_path=output_path,
+        fps=episode_meta["fps"],
+        task_name=episode_meta.get("task_name", ""),
+    )
+
+    if create_gif:
+        final_path = convert_mp4_to_gif(final_path)
+
+    logging.info("Done: %s", final_path)
+    return final_path
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Create MP4/GIF videos with sarm_progress overlay for dataset episodes."
+    )
+    parser.add_argument(
+        "--repo-id",
+        type=str,
+        required=True,
+        help="HuggingFace dataset repository ID (e.g. 'lerobot-data-collection/level2_final_quality3').",
+    )
+    parser.add_argument(
+        "--episode",
+        type=int,
+        required=True,
+        help="Episode index to visualize.",
+    )
+    parser.add_argument(
+        "--camera-key",
+        type=str,
+        default=None,
+        help="Camera observation key (e.g. 'observation.images.base'). Auto-selects first camera if omitted.",
+    )
+    parser.add_argument(
+        "--output-dir",
+        type=Path,
+        default=Path("progress_videos"),
+        help="Directory to write output files (default: ./progress_videos).",
+    )
+    parser.add_argument(
+        "--gif",
+        action="store_true",
+        help="Also generate a GIF from the MP4 output.",
+    )
+    args = parser.parse_args()
+
+    logging.basicConfig(level=logging.INFO, format="%(levelname)s: %(message)s")
+
+    args.output_dir.mkdir(parents=True, exist_ok=True)
+
+    result = process_dataset(
+        repo_id=args.repo_id,
+        episode=args.episode,
+        camera_key=args.camera_key,
+        output_dir=args.output_dir,
+        create_gif=args.gif,
+    )
+
+    if result:
+        logging.info("Output: %s", result)
+
+
+if __name__ == "__main__":
+    main()

examples/dataset/load_lerobot_dataset.py

@@ -32,7 +32,8 @@ import torch
 from huggingface_hub import HfApi
 
 import lerobot
-from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 
 
 def main():
@@ -87,9 +88,8 @@ def main():
     # The previous metadata class is contained in the 'meta' attribute of the dataset:
     print(dataset.meta)
 
-    # LeRobotDataset actually wraps an underlying Hugging Face dataset
-    # (see https://huggingface.co/docs/datasets for more information).
-    print(dataset.hf_dataset)
+    # You can inspect the dataset using its repr:
+    print(dataset)
 
     # LeRobot datasets also subclasses PyTorch datasets so you can do everything you know and love from working
     # with the latter, like iterating through the dataset.

examples/hil/hil_utils.py

@@ -0,0 +1,228 @@
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Shared utilities for Human-in-the-Loop data collection scripts."""
+
+import logging
+import time
+from dataclasses import dataclass, field
+from pathlib import Path
+
+from lerobot.processor import (
+    IdentityProcessorStep,
+    RobotAction,
+    RobotObservation,
+    RobotProcessorPipeline,
+)
+from lerobot.processor.converters import (
+    observation_to_transition,
+    robot_action_observation_to_transition,
+    transition_to_observation,
+    transition_to_robot_action,
+)
+from lerobot.robots import Robot
+from lerobot.teleoperators import Teleoperator
+from lerobot.utils.control_utils import is_headless
+from lerobot.utils.robot_utils import precise_sleep
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class HILDatasetConfig:
+    repo_id: str
+    single_task: str
+    root: str | Path | None = None
+    fps: int = 30
+    episode_time_s: float = 120
+    num_episodes: int = 50
+    video: bool = True
+    push_to_hub: bool = True
+    private: bool = False
+    tags: list[str] | None = None
+    num_image_writer_processes: int = 0
+    num_image_writer_threads_per_camera: int = 4
+    video_encoding_batch_size: int = 1
+    vcodec: str = "auto"
+    streaming_encoding: bool = True
+    encoder_queue_maxsize: int = 30
+    encoder_threads: int | None = None
+    rename_map: dict[str, str] = field(default_factory=dict)
+
+
+def teleop_has_motor_control(teleop: Teleoperator) -> bool:
+    """Check if teleoperator has motor control capabilities."""
+    return all(hasattr(teleop, attr) for attr in ("enable_torque", "disable_torque", "write_goal_positions"))
+
+
+def teleop_disable_torque(teleop: Teleoperator) -> None:
+    """Disable teleop torque if supported."""
+    if hasattr(teleop, "disable_torque"):
+        teleop.disable_torque()
+
+
+def teleop_enable_torque(teleop: Teleoperator) -> None:
+    """Enable teleop torque if supported."""
+    if hasattr(teleop, "enable_torque"):
+        teleop.enable_torque()
+
+
+def teleop_smooth_move_to(teleop: Teleoperator, target_pos: dict, duration_s: float = 2.0, fps: int = 50):
+    """Smoothly move teleop to target position if motor control is available."""
+    if not teleop_has_motor_control(teleop):
+        logger.warning("Teleop does not support motor control - cannot mirror robot position")
+        return
+
+    teleop_enable_torque(teleop)
+    current = teleop.get_action()
+    steps = max(int(duration_s * fps), 1)
+
+    for step in range(steps + 1):
+        t = step / steps
+        interp = {}
+        for k in current:
+            if k in target_pos:
+                interp[k] = current[k] * (1 - t) + target_pos[k] * t
+            else:
+                interp[k] = current[k]
+        teleop.write_goal_positions(interp)
+        time.sleep(1 / fps)
+
+
+def init_keyboard_listener():
+    """Initialize keyboard listener with HIL controls."""
+    events = {
+        "exit_early": False,
+        "rerecord_episode": False,
+        "stop_recording": False,
+        "policy_paused": False,
+        "correction_active": False,
+        "resume_policy": False,
+        "in_reset": False,
+        "start_next_episode": False,
+    }
+
+    if is_headless():
+        logger.warning("Headless environment - keyboard controls unavailable")
+        return None, events
+
+    from pynput import keyboard
+
+    def on_press(key):
+        try:
+            if events["in_reset"]:
+                if key in [keyboard.Key.space, keyboard.Key.right]:
+                    logger.info("[HIL] Starting next episode...")
+                    events["start_next_episode"] = True
+                elif hasattr(key, "char") and key.char == "c":
+                    events["start_next_episode"] = True
+                elif key == keyboard.Key.esc:
+                    logger.info("[HIL] ESC - Stop recording, pushing to hub...")
+                    events["stop_recording"] = True
+                    events["start_next_episode"] = True
+            else:
+                if key == keyboard.Key.space:
+                    if not events["policy_paused"] and not events["correction_active"]:
+                        logger.info("[HIL] PAUSED - Press 'c' to take control or 'p' to resume policy")
+                        events["policy_paused"] = True
+                elif hasattr(key, "char") and key.char == "c":
+                    if events["policy_paused"] and not events["correction_active"]:
+                        logger.info("[HIL] Taking control...")
+                        events["start_next_episode"] = True
+                elif hasattr(key, "char") and key.char == "p":
+                    if events["policy_paused"] or events["correction_active"]:
+                        logger.info("[HIL] Resuming policy...")
+                        events["resume_policy"] = True
+                elif key == keyboard.Key.right:
+                    logger.info("[HIL] End episode")
+                    events["exit_early"] = True
+                elif key == keyboard.Key.left:
+                    logger.info("[HIL] Re-record episode")
+                    events["rerecord_episode"] = True
+                    events["exit_early"] = True
+                elif key == keyboard.Key.esc:
+                    logger.info("[HIL] ESC - Stop recording...")
+                    events["stop_recording"] = True
+                    events["exit_early"] = True
+        except Exception as e:
+            logger.info(f"Key error: {e}")
+
+    listener = keyboard.Listener(on_press=on_press)
+    listener.start()
+    return listener, events
+
+
+def make_identity_processors():
+    """Create identity processors for recording."""
+    teleop_proc = RobotProcessorPipeline[tuple[RobotAction, RobotObservation], RobotAction](
+        steps=[IdentityProcessorStep()],
+        to_transition=robot_action_observation_to_transition,
+        to_output=transition_to_robot_action,
+    )
+    obs_proc = RobotProcessorPipeline[RobotObservation, RobotObservation](
+        steps=[IdentityProcessorStep()],
+        to_transition=observation_to_transition,
+        to_output=transition_to_observation,
+    )
+    return teleop_proc, obs_proc
+
+
+def reset_loop(robot: Robot, teleop: Teleoperator, events: dict, fps: int):
+    """Reset period where human repositions environment."""
+    logger.info("[HIL] RESET")
+
+    events["in_reset"] = True
+    events["start_next_episode"] = False
+
+    obs = robot.get_observation()
+    robot_pos = {k: v for k, v in obs.items() if k.endswith(".pos") and k in robot.observation_features}
+    teleop_smooth_move_to(teleop, robot_pos, duration_s=2.0, fps=50)
+
+    logger.info("Press any key to enable teleoperation")
+    while not events["start_next_episode"] and not events["stop_recording"]:
+        precise_sleep(0.05)
+
+    if events["stop_recording"]:
+        return
+
+    events["start_next_episode"] = False
+    teleop_disable_torque(teleop)
+    logger.info("Teleop enabled - press any key to start episode")
+
+    while not events["start_next_episode"] and not events["stop_recording"]:
+        loop_start = time.perf_counter()
+        action = teleop.get_action()
+        robot.send_action(action)
+        precise_sleep(1 / fps - (time.perf_counter() - loop_start))
+
+    events["in_reset"] = False
+    events["start_next_episode"] = False
+    events["exit_early"] = False
+    events["policy_paused"] = False
+    events["correction_active"] = False
+    events["resume_policy"] = False
+
+
+def print_controls(rtc: bool = False):
+    """Print control instructions."""
+    mode = "Human-in-the-Loop Data Collection" + (" (RTC)" if rtc else "")
+    logger.info(
+        "%s\n  Controls:\n"
+        "    SPACE  - Pause policy\n"
+        "    c      - Take control\n"
+        "    p      - Resume policy after pause/correction\n"
+        "    →      - End episode\n"
+        "    ESC    - Stop and push to hub",
+        mode,
+    )

examples/lekiwi/evaluate.py

@@ -14,8 +14,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from lerobot.datasets.feature_utils import hw_to_dataset_features
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
-from lerobot.datasets.utils import hw_to_dataset_features
 from lerobot.policies.act.modeling_act import ACTPolicy
 from lerobot.policies.factory import make_pre_post_processors
 from lerobot.processor import make_default_processors

examples/lekiwi/record.py

@@ -14,8 +14,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from lerobot.datasets.feature_utils import hw_to_dataset_features
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
-from lerobot.datasets.utils import hw_to_dataset_features
 from lerobot.processor import make_default_processors
 from lerobot.robots.lekiwi.config_lekiwi import LeKiwiClientConfig
 from lerobot.robots.lekiwi.lekiwi_client import LeKiwiClient

examples/lekiwi/replay.py

@@ -35,9 +35,7 @@ def main():
 
     # Fetch the dataset to replay
     dataset = LeRobotDataset("<hf_username>/<dataset_repo_id>", episodes=[EPISODE_IDX])
-    # Filter dataset to only include frames from the specified episode since episodes are chunked in dataset V3.0
-    episode_frames = dataset.hf_dataset.filter(lambda x: x["episode_index"] == EPISODE_IDX)
-    actions = episode_frames.select_columns(ACTION)
+    actions = dataset.select_columns(ACTION)
 
     # Connect to the robot
     robot.connect()
@@ -48,7 +46,7 @@ def main():
 
         print("Starting replay loop...")
         log_say(f"Replaying episode {EPISODE_IDX}")
-        for idx in range(len(episode_frames)):
+        for idx in range(dataset.num_frames):
             t0 = time.perf_counter()
 
             # Get recorded action from dataset

examples/phone_to_so100/evaluate.py

@@ -16,15 +16,13 @@
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
 from lerobot.configs.types import FeatureType, PolicyFeature
+from lerobot.datasets.feature_utils import combine_feature_dicts
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.datasets.pipeline_features import aggregate_pipeline_dataset_features, create_initial_features
-from lerobot.datasets.utils import combine_feature_dicts
 from lerobot.model.kinematics import RobotKinematics
 from lerobot.policies.act.modeling_act import ACTPolicy
 from lerobot.policies.factory import make_pre_post_processors
 from lerobot.processor import (
-    RobotAction,
-    RobotObservation,
     RobotProcessorPipeline,
     make_default_teleop_action_processor,
 )
@@ -40,6 +38,7 @@ from lerobot.robots.so_follower.robot_kinematic_processor import (
     InverseKinematicsEEToJoints,
 )
 from lerobot.scripts.lerobot_record import record_loop
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.control_utils import init_keyboard_listener
 from lerobot.utils.utils import log_say
 from lerobot.utils.visualization_utils import init_rerun

examples/phone_to_so100/record.py

@@ -15,11 +15,11 @@
 # limitations under the License.
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
+from lerobot.datasets.feature_utils import combine_feature_dicts
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.datasets.pipeline_features import aggregate_pipeline_dataset_features, create_initial_features
-from lerobot.datasets.utils import combine_feature_dicts
 from lerobot.model.kinematics import RobotKinematics
-from lerobot.processor import RobotAction, RobotObservation, RobotProcessorPipeline
+from lerobot.processor import RobotProcessorPipeline
 from lerobot.processor.converters import (
     observation_to_transition,
     robot_action_observation_to_transition,
@@ -38,6 +38,7 @@ from lerobot.scripts.lerobot_record import record_loop
 from lerobot.teleoperators.phone.config_phone import PhoneConfig, PhoneOS
 from lerobot.teleoperators.phone.phone_processor import MapPhoneActionToRobotAction
 from lerobot.teleoperators.phone.teleop_phone import Phone
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.control_utils import init_keyboard_listener
 from lerobot.utils.utils import log_say
 from lerobot.utils.visualization_utils import init_rerun

examples/phone_to_so100/replay.py

@@ -18,7 +18,7 @@ import time
 
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.model.kinematics import RobotKinematics
-from lerobot.processor import RobotAction, RobotObservation, RobotProcessorPipeline
+from lerobot.processor import RobotProcessorPipeline
 from lerobot.processor.converters import (
     robot_action_observation_to_transition,
     transition_to_robot_action,
@@ -27,6 +27,7 @@ from lerobot.robots.so_follower import SO100Follower, SO100FollowerConfig
 from lerobot.robots.so_follower.robot_kinematic_processor import (
     InverseKinematicsEEToJoints,
 )
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.constants import ACTION
 from lerobot.utils.robot_utils import precise_sleep
 from lerobot.utils.utils import log_say
@@ -66,9 +67,7 @@ def main():
 
     # Fetch the dataset to replay
     dataset = LeRobotDataset(HF_REPO_ID, episodes=[EPISODE_IDX])
-    # Filter dataset to only include frames from the specified episode since episodes are chunked in dataset V3.0
-    episode_frames = dataset.hf_dataset.filter(lambda x: x["episode_index"] == EPISODE_IDX)
-    actions = episode_frames.select_columns(ACTION)
+    actions = dataset.select_columns(ACTION)
 
     # Connect to the robot
     robot.connect()
@@ -79,7 +78,7 @@ def main():
 
         print("Starting replay loop...")
         log_say(f"Replaying episode {EPISODE_IDX}")
-        for idx in range(len(episode_frames)):
+        for idx in range(dataset.num_frames):
             t0 = time.perf_counter()
 
             # Get recorded action from dataset

examples/phone_to_so100/teleoperate.py

@@ -16,7 +16,7 @@
 import time
 
 from lerobot.model.kinematics import RobotKinematics
-from lerobot.processor import RobotAction, RobotObservation, RobotProcessorPipeline
+from lerobot.processor import RobotProcessorPipeline
 from lerobot.processor.converters import (
     robot_action_observation_to_transition,
     transition_to_robot_action,
@@ -31,6 +31,7 @@ from lerobot.robots.so_follower.robot_kinematic_processor import (
 from lerobot.teleoperators.phone.config_phone import PhoneConfig, PhoneOS
 from lerobot.teleoperators.phone.phone_processor import MapPhoneActionToRobotAction
 from lerobot.teleoperators.phone.teleop_phone import Phone
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.robot_utils import precise_sleep
 from lerobot.utils.visualization_utils import init_rerun, log_rerun_data
 

examples/port_datasets/port_droid.py

@@ -22,7 +22,8 @@ from pathlib import Path
 import numpy as np
 import tensorflow_datasets as tfds
 
-from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.utils.utils import get_elapsed_time_in_days_hours_minutes_seconds
 
 DROID_SHARDS = 2048

examples/port_datasets/slurm_upload.py

@@ -26,7 +26,7 @@ from huggingface_hub import HfApi
 from huggingface_hub.constants import REPOCARD_NAME
 from port_droid import DROID_SHARDS
 
-from lerobot.datasets.lerobot_dataset import CODEBASE_VERSION, LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import CODEBASE_VERSION, LeRobotDatasetMetadata
 from lerobot.datasets.utils import create_lerobot_dataset_card
 from lerobot.utils.utils import init_logging
 
@@ -155,7 +155,7 @@ class UploadDataset(PipelineStep):
         from datasets.utils.tqdm import disable_progress_bars
         from huggingface_hub import CommitOperationAdd, preupload_lfs_files
 
-        from lerobot.datasets.lerobot_dataset import LeRobotDatasetMetadata
+        from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
         from lerobot.utils.utils import init_logging
 
         init_logging()

examples/rtc/eval_dataset.py

@@ -113,8 +113,9 @@ from lerobot.configs import parser
 from lerobot.configs.default import DatasetConfig
 from lerobot.configs.policies import PreTrainedConfig
 from lerobot.configs.types import RTCAttentionSchedule
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
 from lerobot.datasets.factory import resolve_delta_timestamps
-from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.policies.factory import get_policy_class, make_pre_post_processors
 from lerobot.policies.rtc.configuration_rtc import RTCConfig
 from lerobot.policies.rtc.debug_visualizer import RTCDebugVisualizer

examples/rtc/eval_with_real_robot.py

@@ -63,6 +63,31 @@ Usage:
         --robot.cameras="{ gripper: {type: opencv, index_or_path: 0, width: 640, height: 480, fps: 30}, front: {type: opencv, index_or_path: 1, width: 640, height: 480, fps: 30}}" \
         --task="Move green small object into the purple platform" \
         --duration=120
+
+    # Run RTC with bi_openarm_follower (dual-arm OpenArms) and pi0.5 policy
+    python examples/rtc/eval_with_real_robot.py \
+        --policy.path=lerobot-data-collection/folding_final \
+        --robot.type=bi_openarm_follower \
+        --robot.cameras='{left_wrist: {type: opencv, index_or_path: "/dev/video4", width: 1280, height: 720, fps: 30}, base: {type: opencv, index_or_path: "/dev/video2", width: 640, height: 480, fps: 30}, right_wrist: {type: opencv, index_or_path: "/dev/video0", width: 1280, height: 720, fps: 30}}' \
+        --robot.left_arm_config.port=can0 \
+        --robot.left_arm_config.side=left \
+        --robot.left_arm_config.can_interface=socketcan \
+        --robot.left_arm_config.disable_torque_on_disconnect=true \
+        --robot.left_arm_config.max_relative_target=8.0 \
+        --robot.right_arm_config.port=can1 \
+        --robot.right_arm_config.side=right \
+        --robot.right_arm_config.can_interface=socketcan \
+        --robot.right_arm_config.disable_torque_on_disconnect=true \
+        --robot.right_arm_config.max_relative_target=8.0 \
+        --task="Fold the T-shirt properly" \
+        --fps=30 \
+        --duration=2000 \
+        --interpolation_multiplier=3 \
+        --rtc.enabled=true \
+        --rtc.execution_horizon=20 \
+        --rtc.max_guidance_weight=5.0 \
+        --rtc.prefix_attention_schedule=LINEAR \
+        --device=cuda
 """
 
 import logging
@@ -82,26 +107,32 @@ from lerobot.cameras.zmq.configuration_zmq import ZMQCameraConfig  # noqa: F401
 from lerobot.configs import parser
 from lerobot.configs.policies import PreTrainedConfig
 from lerobot.configs.types import RTCAttentionSchedule
-from lerobot.datasets.utils import build_dataset_frame, hw_to_dataset_features
+from lerobot.datasets.feature_utils import build_dataset_frame, hw_to_dataset_features
 from lerobot.policies.factory import get_policy_class, make_pre_post_processors
-from lerobot.policies.rtc.action_queue import ActionQueue
-from lerobot.policies.rtc.configuration_rtc import RTCConfig
-from lerobot.policies.rtc.latency_tracker import LatencyTracker
+from lerobot.policies.rtc import ActionInterpolator, ActionQueue, LatencyTracker, RTCConfig
+from lerobot.processor import (
+    NormalizerProcessorStep,
+    RelativeActionsProcessorStep,
+    TransitionKey,
+    create_transition,
+)
 from lerobot.processor.factory import (
     make_default_robot_action_processor,
     make_default_robot_observation_processor,
 )
+from lerobot.processor.relative_action_processor import to_relative_actions
 from lerobot.rl.process import ProcessSignalHandler
 from lerobot.robots import (  # noqa: F401
     Robot,
     RobotConfig,
+    bi_openarm_follower,
     bi_so_follower,
     koch_follower,
     so_follower,
     unitree_g1,
 )
 from lerobot.robots.utils import make_robot_from_config
-from lerobot.utils.constants import OBS_IMAGES
+from lerobot.utils.constants import OBS_IMAGES, OBS_STATE
 from lerobot.utils.hub import HubMixin
 from lerobot.utils.utils import init_logging
 
@@ -153,6 +184,7 @@ class RTCDemoConfig(HubMixin):
     # Demo parameters
     duration: float = 30.0  # Duration to run the demo (seconds)
     fps: float = 10.0  # Action execution frequency (Hz)
+    interpolation_multiplier: int = 1  # Control rate multiplier (1=off, 2=2x, 3=3x)
 
     # Compute device
     device: str | None = None  # Device to run on (cuda, cpu, auto)
@@ -212,6 +244,35 @@ def is_image_key(k: str) -> bool:
     return k.startswith(OBS_IMAGES)
 
 
+def _reanchor_relative_rtc_prefix(
+    prev_actions_absolute: Tensor,
+    current_state: Tensor,
+    relative_step: RelativeActionsProcessorStep,
+    normalizer_step: NormalizerProcessorStep | None,
+    policy_device: torch.device | str,
+) -> Tensor:
+    """Convert absolute leftovers into model-space for relative-action RTC policies.
+
+    When a policy uses relative actions, the RTC prefix (leftover actions from
+    the previous chunk) is stored in absolute space. Before feeding it back to
+    the policy we need to re-express it relative to the *current* robot state
+    and then re-normalize.
+    """
+    state = current_state.detach().cpu()
+    if state.dim() == 1:
+        state = state.unsqueeze(0)
+
+    action_cpu = prev_actions_absolute.detach().cpu()
+    mask = relative_step._build_mask(action_cpu.shape[-1])
+    relative_actions = to_relative_actions(action_cpu, state, mask)
+
+    transition = create_transition(action=relative_actions)
+    if normalizer_step is not None:
+        transition = normalizer_step(transition)
+
+    return transition[TransitionKey.ACTION].to(policy_device)
+
+
 def get_actions(
     policy,
     robot: RobotWrapper,
@@ -237,7 +298,15 @@ def get_actions(
         fps = cfg.fps
         time_per_chunk = 1.0 / fps
 
-        dataset_features = hw_to_dataset_features(robot.observation_features(), "observation")
+        # Only keep .pos joints + camera streams if the policy was trained on positions,
+        # not the full pos/vel/torque state the robot exposes.
+        observation_features_hw = {
+            key: value
+            for key, value in robot.observation_features().items()
+            if key.endswith(".pos") or isinstance(value, tuple)
+        }
+
+        dataset_features = hw_to_dataset_features(observation_features_hw, "observation")
         policy_device = policy.config.device
 
         # Load preprocessor and postprocessor from pretrained files
@@ -255,6 +324,25 @@ def get_actions(
 
         logger.info("[GET_ACTIONS] Preprocessor/postprocessor loaded successfully with embedded stats")
 
+        relative_step = next(
+            (s for s in preprocessor.steps if isinstance(s, RelativeActionsProcessorStep) and s.enabled),
+            None,
+        )
+        normalizer_step = next(
+            (s for s in preprocessor.steps if isinstance(s, NormalizerProcessorStep)),
+            None,
+        )
+        if relative_step is not None:
+            if relative_step.action_names is None:
+                cfg_names = getattr(cfg.policy, "action_feature_names", None)
+                if cfg_names:
+                    relative_step.action_names = list(cfg_names)
+                else:
+                    relative_step.action_names = [
+                        k for k in robot.robot.action_features if k.endswith(".pos")
+                    ]
+            logger.info("[GET_ACTIONS] Relative actions enabled: will re-anchor RTC prefix")
+
         get_actions_threshold = cfg.action_queue_size_to_get_new_actions
 
         if not cfg.rtc.enabled:
@@ -297,6 +385,28 @@ def get_actions(
 
                 preproceseded_obs = preprocessor(obs_with_policy_features)
 
+                # Re-anchor leftover actions for relative-action policies.
+                # We need the *postprocessed* (absolute) leftover, not the original
+                # (normalized/relative) one that get_left_over() returns.
+                if (
+                    prev_actions is not None
+                    and relative_step is not None
+                    and OBS_STATE in obs_with_policy_features
+                ):
+                    with action_queue.lock:
+                        if action_queue.queue is not None:
+                            prev_actions_abs = action_queue.queue[action_queue.last_index :].clone()
+                        else:
+                            prev_actions_abs = None
+                    if prev_actions_abs is not None and prev_actions_abs.numel() > 0:
+                        prev_actions = _reanchor_relative_rtc_prefix(
+                            prev_actions_absolute=prev_actions_abs,
+                            current_state=obs_with_policy_features[OBS_STATE],
+                            relative_step=relative_step,
+                            normalizer_step=normalizer_step,
+                            policy_device=policy_device,
+                        )
+
                 # Generate actions WITH RTC
                 actions = policy.predict_action_chunk(
                     preproceseded_obs,
@@ -352,21 +462,26 @@ def actor_control(
     try:
         logger.info("[ACTOR] Starting actor thread")
 
+        action_keys = [k for k in robot.action_features() if k.endswith(".pos")]
+
         action_count = 0
-        action_interval = 1.0 / cfg.fps
+        interpolator = ActionInterpolator(multiplier=cfg.interpolation_multiplier)
+        action_interval = interpolator.get_control_interval(cfg.fps)
 
         while not shutdown_event.is_set():
             start_time = time.perf_counter()
 
-            # Try to get an action from the queue with timeout
-            action = action_queue.get()
+            if interpolator.needs_new_action():
+                new_action = action_queue.get()
+                if new_action is not None:
+                    interpolator.add(new_action.cpu())
 
+            action = interpolator.get()
             if action is not None:
                 action = action.cpu()
-                action_dict = {key: action[i].item() for i, key in enumerate(robot.action_features())}
+                action_dict = {key: action[i].item() for i, key in enumerate(action_keys)}
                 action_processed = robot_action_processor((action_dict, None))
                 robot.send_action(action_processed)
-
                 action_count += 1
 
             dt_s = time.perf_counter() - start_time

examples/so100_to_so100_EE/evaluate.py

@@ -16,15 +16,13 @@
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
 from lerobot.configs.types import FeatureType, PolicyFeature
+from lerobot.datasets.feature_utils import combine_feature_dicts
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.datasets.pipeline_features import aggregate_pipeline_dataset_features, create_initial_features
-from lerobot.datasets.utils import combine_feature_dicts
 from lerobot.model.kinematics import RobotKinematics
 from lerobot.policies.act.modeling_act import ACTPolicy
 from lerobot.policies.factory import make_pre_post_processors
 from lerobot.processor import (
-    RobotAction,
-    RobotObservation,
     RobotProcessorPipeline,
     make_default_teleop_action_processor,
 )
@@ -40,6 +38,7 @@ from lerobot.robots.so_follower.robot_kinematic_processor import (
     InverseKinematicsEEToJoints,
 )
 from lerobot.scripts.lerobot_record import record_loop
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.control_utils import init_keyboard_listener
 from lerobot.utils.utils import log_say
 from lerobot.utils.visualization_utils import init_rerun

examples/so100_to_so100_EE/record.py

@@ -16,11 +16,11 @@
 
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
+from lerobot.datasets.feature_utils import combine_feature_dicts
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.datasets.pipeline_features import aggregate_pipeline_dataset_features, create_initial_features
-from lerobot.datasets.utils import combine_feature_dicts
 from lerobot.model.kinematics import RobotKinematics
-from lerobot.processor import RobotAction, RobotObservation, RobotProcessorPipeline
+from lerobot.processor import RobotProcessorPipeline
 from lerobot.processor.converters import (
     observation_to_transition,
     robot_action_observation_to_transition,
@@ -35,6 +35,7 @@ from lerobot.robots.so_follower.robot_kinematic_processor import (
 )
 from lerobot.scripts.lerobot_record import record_loop
 from lerobot.teleoperators.so_leader import SO100Leader, SO100LeaderConfig
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.control_utils import init_keyboard_listener
 from lerobot.utils.utils import log_say
 from lerobot.utils.visualization_utils import init_rerun

examples/so100_to_so100_EE/replay.py

@@ -19,7 +19,7 @@ import time
 
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.model.kinematics import RobotKinematics
-from lerobot.processor import RobotAction, RobotObservation, RobotProcessorPipeline
+from lerobot.processor import RobotProcessorPipeline
 from lerobot.processor.converters import (
     robot_action_observation_to_transition,
     transition_to_robot_action,
@@ -28,6 +28,7 @@ from lerobot.robots.so_follower import SO100Follower, SO100FollowerConfig
 from lerobot.robots.so_follower.robot_kinematic_processor import (
     InverseKinematicsEEToJoints,
 )
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.constants import ACTION
 from lerobot.utils.robot_utils import precise_sleep
 from lerobot.utils.utils import log_say
@@ -67,9 +68,7 @@ def main():
 
     # Fetch the dataset to replay
     dataset = LeRobotDataset(HF_REPO_ID, episodes=[EPISODE_IDX])
-    # Filter dataset to only include frames from the specified episode since episodes are chunked in dataset V3.0
-    episode_frames = dataset.hf_dataset.filter(lambda x: x["episode_index"] == EPISODE_IDX)
-    actions = episode_frames.select_columns(ACTION)
+    actions = dataset.select_columns(ACTION)
 
     # Connect to the robot
     robot.connect()
@@ -80,7 +79,7 @@ def main():
 
         print("Starting replay loop...")
         log_say(f"Replaying episode {EPISODE_IDX}")
-        for idx in range(len(episode_frames)):
+        for idx in range(dataset.num_frames):
             t0 = time.perf_counter()
 
             # Get recorded action from dataset

examples/so100_to_so100_EE/teleoperate.py

@@ -17,7 +17,7 @@
 import time
 
 from lerobot.model.kinematics import RobotKinematics
-from lerobot.processor import RobotAction, RobotObservation, RobotProcessorPipeline
+from lerobot.processor import RobotProcessorPipeline
 from lerobot.processor.converters import (
     robot_action_observation_to_transition,
     robot_action_to_transition,
@@ -30,6 +30,7 @@ from lerobot.robots.so_follower.robot_kinematic_processor import (
     InverseKinematicsEEToJoints,
 )
 from lerobot.teleoperators.so_leader import SO100Leader, SO100LeaderConfig
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.robot_utils import precise_sleep
 from lerobot.utils.visualization_utils import init_rerun, log_rerun_data
 

examples/training/train_policy.py

@@ -19,8 +19,9 @@ from pathlib import Path
 import torch
 
 from lerobot.configs.types import FeatureType
-from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
-from lerobot.datasets.utils import dataset_to_policy_features
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import dataset_to_policy_features
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.policies.diffusion.configuration_diffusion import DiffusionConfig
 from lerobot.policies.diffusion.modeling_diffusion import DiffusionPolicy
 from lerobot.policies.factory import make_pre_post_processors

examples/training/train_with_streaming.py

@@ -20,9 +20,9 @@ from pathlib import Path
 import torch
 
 from lerobot.configs.types import FeatureType
-from lerobot.datasets.lerobot_dataset import LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import dataset_to_policy_features
 from lerobot.datasets.streaming_dataset import StreamingLeRobotDataset
-from lerobot.datasets.utils import dataset_to_policy_features
 from lerobot.policies.act.configuration_act import ACTConfig
 from lerobot.policies.act.modeling_act import ACTPolicy
 from lerobot.policies.factory import make_pre_post_processors

examples/tutorial/act/act_training_example.py

@@ -5,8 +5,9 @@ from pathlib import Path
 import torch
 
 from lerobot.configs.types import FeatureType
-from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
-from lerobot.datasets.utils import dataset_to_policy_features
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import dataset_to_policy_features
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.policies.act.configuration_act import ACTConfig
 from lerobot.policies.act.modeling_act import ACTPolicy
 from lerobot.policies.factory import make_pre_post_processors

examples/tutorial/act/act_using_example.py

@@ -1,7 +1,7 @@
 import torch
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
-from lerobot.datasets.lerobot_dataset import LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
 from lerobot.policies.act.modeling_act import ACTPolicy
 from lerobot.policies.factory import make_pre_post_processors
 from lerobot.policies.utils import build_inference_frame, make_robot_action

examples/tutorial/diffusion/diffusion_training_example.py

@@ -5,8 +5,9 @@ from pathlib import Path
 import torch
 
 from lerobot.configs.types import FeatureType
-from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
-from lerobot.datasets.utils import dataset_to_policy_features
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import dataset_to_policy_features
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.policies.diffusion.configuration_diffusion import DiffusionConfig
 from lerobot.policies.diffusion.modeling_diffusion import DiffusionPolicy
 from lerobot.policies.factory import make_pre_post_processors

examples/tutorial/diffusion/diffusion_using_example.py

@@ -1,7 +1,7 @@
 import torch
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
-from lerobot.datasets.lerobot_dataset import LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
 from lerobot.policies.diffusion.modeling_diffusion import DiffusionPolicy
 from lerobot.policies.factory import make_pre_post_processors
 from lerobot.policies.utils import build_inference_frame, make_robot_action

examples/tutorial/pi0/using_pi0_example.py

@@ -1,7 +1,7 @@
 import torch
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
-from lerobot.datasets.utils import hw_to_dataset_features
+from lerobot.datasets.feature_utils import hw_to_dataset_features
 from lerobot.policies.factory import make_pre_post_processors
 from lerobot.policies.pi0.modeling_pi0 import PI0Policy
 from lerobot.policies.utils import build_inference_frame, make_robot_action

examples/tutorial/rl/hilserl_example.py

@@ -6,8 +6,8 @@ from queue import Empty, Full
 import torch
 import torch.optim as optim
 
+from lerobot.datasets.feature_utils import hw_to_dataset_features
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
-from lerobot.datasets.utils import hw_to_dataset_features
 from lerobot.envs.configs import HILSerlProcessorConfig, HILSerlRobotEnvConfig
 from lerobot.policies.sac.configuration_sac import SACConfig
 from lerobot.policies.sac.modeling_sac import SACPolicy

examples/tutorial/smolvla/using_smolvla_example.py

@@ -1,7 +1,7 @@
 import torch
 
 from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
-from lerobot.datasets.utils import hw_to_dataset_features
+from lerobot.datasets.feature_utils import hw_to_dataset_features
 from lerobot.policies.factory import make_pre_post_processors
 from lerobot.policies.smolvla.modeling_smolvla import SmolVLAPolicy
 from lerobot.policies.utils import build_inference_frame, make_robot_action

pyproject.toml

@@ -25,7 +25,7 @@ discord = "https://discord.gg/s3KuuzsPFb"
 
 [project]
 name = "lerobot"
-version = "0.5.1"
+version = "0.5.2"
 description = "🤗 LeRobot: State-of-the-art Machine Learning for Real-World Robotics in Pytorch"
 dynamic = ["readme"]
 license = { text = "Apache-2.0" }
@@ -71,12 +71,12 @@ dependencies = [
     "cmake>=3.29.0.1,<4.2.0",
     "packaging>=24.2,<26.0",
 
-    "torch>=2.2.1,<2.11.0",
-    "torchcodec>=0.2.1,<0.11.0; sys_platform != 'win32' and (sys_platform != 'linux' or (platform_machine != 'aarch64' and platform_machine != 'arm64' and platform_machine != 'armv7l')) and (sys_platform != 'darwin' or platform_machine != 'x86_64')",
-    "torchvision>=0.21.0,<0.26.0",
+    "torch>=2.7,<2.11.0",
+    "torchcodec>=0.3.0,<0.11.0; sys_platform != 'win32' and (sys_platform != 'linux' or (platform_machine != 'aarch64' and platform_machine != 'arm64' and platform_machine != 'armv7l')) and (sys_platform != 'darwin' or platform_machine != 'x86_64')", # NOTE: Windows support starts at version 0.7 (needs torch==2.8), ffmpeg>=8 support starts at version 0.8.1 (needs torch==2.9), system-wide ffmpeg support starts at version 0.10 (needs torch==2.10).
+    "torchvision>=0.22.0,<0.26.0",
 
     "einops>=0.8.0,<0.9.0",
-    "opencv-python-headless>=4.9.0,<4.13.0",
+    "opencv-python-headless>=4.9.0,<4.14.0",
     "av>=15.0.0,<16.0.0",
     "jsonlines>=4.0.0,<5.0.0",
     "pynput>=1.7.8,<1.9.0",
@@ -99,7 +99,7 @@ dependencies = [
 # Common
 pygame-dep = ["pygame>=2.5.1,<2.7.0"]
 placo-dep = ["placo>=0.9.6,<0.9.17"]
-transformers-dep = ["transformers>=5.3.0,<6.0.0"]
+transformers-dep = ["transformers==5.3.0"] # TODO(Steven): https://github.com/huggingface/lerobot/pull/3249
 grpcio-dep = ["grpcio==1.73.1", "protobuf>=6.31.1,<6.32.0"]
 can-dep = ["python-can>=4.2.0,<5.0.0"]
 peft-dep = ["peft>=0.18.0,<1.0.0"]
@@ -119,14 +119,13 @@ gamepad = ["lerobot[pygame-dep]", "hidapi>=0.14.0,<0.15.0"]
 hopejr = ["lerobot[feetech]", "lerobot[pygame-dep]"]
 lekiwi = ["lerobot[feetech]", "pyzmq>=26.2.1,<28.0.0"]
 unitree_g1 = [
-    "unitree-sdk2==1.0.1",
+    # "unitree-sdk2==1.0.1",
     "pyzmq>=26.2.1,<28.0.0",
     "onnxruntime>=1.16.0,<2.0.0",
-    "pin>=3.0.0,<4.0.0",
+    "onnx>=1.16.0,<2.0.0",
     "meshcat>=0.3.0,<0.4.0",
     "lerobot[matplotlib-dep]",
     "lerobot[pygame-dep]",
-    "casadi>=3.6.0,<4.0.0",
 ]
 reachy2 = ["reachy2_sdk>=1.0.15,<1.1.0"]
 kinematics = ["lerobot[placo-dep]"]
@@ -146,6 +145,7 @@ wallx = [
 ]
 pi = ["lerobot[transformers-dep]", "lerobot[scipy-dep]"]
 smolvla = ["lerobot[transformers-dep]", "num2words>=0.5.14,<0.6.0", "accelerate>=1.7.0,<2.0.0", "safetensors>=0.4.3,<1.0.0"]
+multi_task_dit = ["lerobot[transformers-dep]"]
 groot = [
     "lerobot[transformers-dep]",
     "lerobot[peft]",

src/lerobot/async_inference/helpers.py

@@ -23,7 +23,7 @@ from typing import Any
 import torch
 
 from lerobot.configs.types import PolicyFeature
-from lerobot.datasets.utils import build_dataset_frame, hw_to_dataset_features
+from lerobot.datasets.feature_utils import build_dataset_frame, hw_to_dataset_features
 
 # NOTE: Configs need to be loaded for the client to be able to instantiate the policy config
 from lerobot.policies import (  # noqa: F401

src/lerobot/async_inference/policy_server.py

@@ -39,15 +39,13 @@ import grpc
 import torch
 
 from lerobot.policies.factory import get_policy_class, make_pre_post_processors
-from lerobot.processor import (
-    PolicyAction,
-    PolicyProcessorPipeline,
-)
+from lerobot.processor import PolicyProcessorPipeline
 from lerobot.transport import (
     services_pb2,  # type: ignore
     services_pb2_grpc,  # type: ignore
 )
 from lerobot.transport.utils import receive_bytes_in_chunks
+from lerobot.types import PolicyAction
 
 from .configs import PolicyServerConfig
 from .constants import SUPPORTED_POLICIES

src/lerobot/configs/default.py

@@ -27,7 +27,8 @@ class DatasetConfig:
     # "dataset_index" into the returned item. The index mapping is made according to the order in which the
     # datasets are provided.
     repo_id: str
-    # Root directory where the dataset will be stored (e.g. 'dataset/path'). If None, defaults to $HF_LEROBOT_HOME/repo_id.
+    # Root directory for a concrete local dataset tree (e.g. 'dataset/path'). If None, local datasets are
+    # looked up under $HF_LEROBOT_HOME/repo_id and Hub downloads use a revision-safe cache under $HF_LEROBOT_HOME/hub.
     root: str | None = None
     episodes: list[int] | None = None
     image_transforms: ImageTransformsConfig = field(default_factory=ImageTransformsConfig)
@@ -36,6 +37,16 @@ class DatasetConfig:
     video_backend: str = field(default_factory=get_safe_default_codec)
     streaming: bool = False
 
+    def __post_init__(self) -> None:
+        if self.episodes is not None:
+            if any(ep < 0 for ep in self.episodes):
+                raise ValueError(
+                    f"Episode indices must be non-negative, got: {[ep for ep in self.episodes if ep < 0]}"
+                )
+            if len(self.episodes) != len(set(self.episodes)):
+                duplicates = sorted({ep for ep in self.episodes if self.episodes.count(ep) > 1})
+                raise ValueError(f"Episode indices contain duplicates: {duplicates}")
+
 
 @dataclass
 class WandBConfig:
@@ -47,6 +58,7 @@ class WandBConfig:
     notes: str | None = None
     run_id: str | None = None
     mode: str | None = None  # Allowed values: 'online', 'offline' 'disabled'. Defaults to 'online'
+    add_tags: bool = True  # If True, save configuration as tags in the WandB run.
 
 
 @dataclass

src/lerobot/configs/policies.py

@@ -30,8 +30,8 @@ from lerobot.configs.types import FeatureType, PolicyFeature
 from lerobot.optim.optimizers import OptimizerConfig
 from lerobot.optim.schedulers import LRSchedulerConfig
 from lerobot.utils.constants import ACTION, OBS_STATE
+from lerobot.utils.device_utils import auto_select_torch_device, is_amp_available, is_torch_device_available
 from lerobot.utils.hub import HubMixin
-from lerobot.utils.utils import auto_select_torch_device, is_amp_available, is_torch_device_available
 
 T = TypeVar("T", bound="PreTrainedConfig")
 logger = getLogger(__name__)

src/lerobot/configs/train.py

@@ -51,7 +51,7 @@ class TrainPipelineConfig(HubMixin):
     # AND for the evaluation environments.
     seed: int | None = 1000
     # Set to True to use deterministic cuDNN algorithms for reproducibility.
-    # This disables cudnn.benchmark and may reduce training speed by ~10-20%.
+    # This disables cudnn.benchmark and may reduce training speed by ~10-20 percent.
     cudnn_deterministic: bool = False
     # Number of workers for the dataloader.
     num_workers: int = 4

src/lerobot/data_processing/sarm_annotations/subtask_annotation.py

@@ -746,7 +746,8 @@ def save_annotations_to_dataset(
     dataset_path: Path, annotations: dict[int, SubtaskAnnotation], fps: int, prefix: str = "sparse"
 ):
     """Save annotations to LeRobot dataset parquet format."""
-    from lerobot.datasets.utils import DEFAULT_EPISODES_PATH, load_episodes
+    from lerobot.datasets.io_utils import load_episodes
+    from lerobot.datasets.utils import DEFAULT_EPISODES_PATH
 
     episodes_dataset = load_episodes(dataset_path)
     if not episodes_dataset or len(episodes_dataset) == 0:
@@ -840,7 +841,7 @@ def generate_auto_sparse_annotations(
 
 def load_annotations_from_dataset(dataset_path: Path, prefix: str = "sparse") -> dict[int, SubtaskAnnotation]:
     """Load annotations from LeRobot dataset parquet files."""
-    from lerobot.datasets.utils import load_episodes
+    from lerobot.datasets.io_utils import load_episodes
 
     episodes_dataset = load_episodes(dataset_path)
     if not episodes_dataset or len(episodes_dataset) == 0:

src/lerobot/datasets/__init__.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+
+# Copyright 2026 The HuggingFace Inc. team.
+# All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+from lerobot.datasets.multi_dataset import MultiLeRobotDataset
+from lerobot.datasets.sampler import EpisodeAwareSampler
+from lerobot.datasets.streaming_dataset import StreamingLeRobotDataset
+from lerobot.datasets.transforms import ImageTransforms, ImageTransformsConfig
+
+__all__ = [
+    "EpisodeAwareSampler",
+    "ImageTransforms",
+    "ImageTransformsConfig",
+    "LeRobotDataset",
+    "LeRobotDatasetMetadata",
+    "MultiLeRobotDataset",
+    "StreamingLeRobotDataset",
+]

src/lerobot/datasets/aggregate.py

@@ -24,7 +24,16 @@ import pandas as pd
 import tqdm
 
 from lerobot.datasets.compute_stats import aggregate_stats
-from lerobot.datasets.lerobot_dataset import LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import get_hf_features_from_features
+from lerobot.datasets.io_utils import (
+    get_file_size_in_mb,
+    get_parquet_file_size_in_mb,
+    to_parquet_with_hf_images,
+    write_info,
+    write_stats,
+    write_tasks,
+)
 from lerobot.datasets.utils import (
     DEFAULT_CHUNK_SIZE,
     DEFAULT_DATA_FILE_SIZE_IN_MB,
@@ -32,14 +41,7 @@ from lerobot.datasets.utils import (
     DEFAULT_EPISODES_PATH,
     DEFAULT_VIDEO_FILE_SIZE_IN_MB,
     DEFAULT_VIDEO_PATH,
-    get_file_size_in_mb,
-    get_hf_features_from_features,
-    get_parquet_file_size_in_mb,
-    to_parquet_with_hf_images,
     update_chunk_file_indices,
-    write_info,
-    write_stats,
-    write_tasks,
 )
 from lerobot.datasets.video_utils import concatenate_video_files, get_video_duration_in_s
 

src/lerobot/datasets/backward_compatibility.py

@@ -1,56 +0,0 @@
-# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import packaging.version
-
-V30_MESSAGE = """
-The dataset you requested ({repo_id}) is in {version} format.
-
-We introduced a new format since v3.0 which is not backward compatible with v2.1.
-Please, update your dataset to the new format using this command:
-```
-python -m lerobot.datasets.v30.convert_dataset_v21_to_v30 --repo-id={repo_id}
-```
-
-If you already have a converted version uploaded to the hub, then this error might be because of
-an older version in your local cache. Consider deleting the cached version and retrying.
-
-If you encounter a problem, contact LeRobot maintainers on [Discord](https://discord.com/invite/s3KuuzsPFb)
-or open an [issue on GitHub](https://github.com/huggingface/lerobot/issues/new/choose).
-"""
-
-FUTURE_MESSAGE = """
-The dataset you requested ({repo_id}) is only available in {version} format.
-As we cannot ensure forward compatibility with it, please update your current version of lerobot.
-"""
-
-
-class CompatibilityError(Exception): ...
-
-
-class BackwardCompatibilityError(CompatibilityError):
-    def __init__(self, repo_id: str, version: packaging.version.Version):
-        if version.major == 2 and version.minor == 1:
-            message = V30_MESSAGE.format(repo_id=repo_id, version=version)
-        else:
-            raise NotImplementedError(
-                "Contact the maintainer on [Discord](https://discord.com/invite/s3KuuzsPFb)."
-            )
-        super().__init__(message)
-
-
-class ForwardCompatibilityError(CompatibilityError):
-    def __init__(self, repo_id: str, version: packaging.version.Version):
-        message = FUTURE_MESSAGE.format(repo_id=repo_id, version=version)
-        super().__init__(message)

src/lerobot/datasets/compute_stats.py

@@ -13,9 +13,14 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
+
+import logging
+
 import numpy as np
 
-from lerobot.datasets.utils import load_image_as_numpy
+from lerobot.datasets.io_utils import load_image_as_numpy
+from lerobot.utils.constants import ACTION, OBS_STATE
 
 DEFAULT_QUANTILES = [0.01, 0.10, 0.50, 0.90, 0.99]
 
@@ -624,3 +629,141 @@ def aggregate_stats(stats_list: list[dict[str, dict]]) -> dict[str, dict[str, np
         aggregated_stats[key] = aggregate_feature_stats(stats_with_key)
 
     return aggregated_stats
+
+
+def _get_valid_chunk_starts(episode_indices: np.ndarray, chunk_size: int) -> np.ndarray:
+    """Return all start indices where a chunk of ``chunk_size`` stays within one episode."""
+    total = len(episode_indices)
+    if total < chunk_size:
+        return np.array([], dtype=np.int64)
+    max_start = total - chunk_size
+    starts = np.arange(max_start + 1)
+    valid = episode_indices[starts] == episode_indices[starts + chunk_size - 1]
+    return starts[valid]
+
+
+def _compute_relative_chunk_batch(
+    start_indices: np.ndarray,
+    all_actions: np.ndarray,
+    all_states: np.ndarray,
+    chunk_size: int,
+    relative_mask: np.ndarray,
+) -> np.ndarray:
+    """Vectorised relative-action computation for a batch of start indices.
+
+    Returns an ``(N * chunk_size, action_dim)`` float32 array.
+    """
+    if len(start_indices) == 0:
+        return np.empty((0, all_actions.shape[1]), dtype=np.float32)
+    offsets = np.arange(chunk_size)
+    frame_idx = start_indices[:, None] + offsets[None, :]
+    chunks = all_actions[frame_idx].copy()
+    states = all_states[start_indices]
+    mask_dim = len(relative_mask)
+    chunks[:, :, :mask_dim] -= states[:, None, :mask_dim] * relative_mask[None, None, :]
+    return chunks.reshape(-1, all_actions.shape[1])
+
+
+def compute_relative_action_stats(
+    hf_dataset,
+    features: dict,
+    chunk_size: int,
+    exclude_joints: list[str] | None = None,
+    num_workers: int = 0,
+) -> dict[str, np.ndarray]:
+    """Compute normalization statistics for relative actions over the full dataset.
+
+    Iterates *all* valid action chunks (within single episodes), converts them to
+    relative actions (action − current_state), and computes per-dimension
+    statistics suitable for normalization.
+
+    Args:
+        hf_dataset: The underlying HuggingFace dataset with "action",
+            "observation.state", and "episode_index" columns.
+        features: Dataset feature metadata (must contain "action" with "shape"
+            and optionally "names").
+        chunk_size: Number of consecutive frames per action chunk.
+        exclude_joints: Joint names whose dimensions should remain absolute
+            (not converted to relative actions).
+        num_workers: Number of parallel threads for computation. Values ≤1
+            mean single-threaded. Numpy releases the GIL so threads give
+            real parallelism here.
+
+    Returns:
+        Statistics dict with keys "mean", "std", "min", "max", "q01", …, "q99".
+
+    Raises:
+        ValueError: If the dataset has fewer frames than ``chunk_size``.
+        RuntimeError: If no valid (single-episode) chunks are found.
+    """
+    from lerobot.processor.relative_action_processor import RelativeActionsProcessorStep
+
+    if exclude_joints is None:
+        exclude_joints = []
+
+    action_dim = features[ACTION]["shape"][0]
+    action_names = features.get(ACTION, {}).get("names")
+    mask_step = RelativeActionsProcessorStep(
+        enabled=True,
+        exclude_joints=exclude_joints,
+        action_names=action_names,
+    )
+    relative_mask = np.array(mask_step._build_mask(action_dim), dtype=np.float32)
+
+    logging.info("Loading action/state data for relative action stats...")
+    all_actions = np.array(hf_dataset[ACTION], dtype=np.float32)
+    all_states = np.array(hf_dataset[OBS_STATE], dtype=np.float32)
+    episode_indices = np.array(hf_dataset["episode_index"])
+
+    valid_starts = _get_valid_chunk_starts(episode_indices, chunk_size)
+    if len(valid_starts) == 0:
+        raise RuntimeError(
+            f"No valid chunks found (total_frames={len(episode_indices)}, chunk_size={chunk_size})"
+        )
+
+    effective_workers = max(num_workers, 1)
+    logging.info(
+        f"Computing relative action stats from {len(valid_starts)} chunks "
+        f"(chunk_size={chunk_size}, workers={effective_workers})"
+    )
+
+    batch_size = 50_000
+    batches = [valid_starts[i : i + batch_size] for i in range(0, len(valid_starts), batch_size)]
+
+    running_stats = RunningQuantileStats()
+
+    if num_workers > 1:
+        from concurrent.futures import ThreadPoolExecutor, as_completed
+
+        with ThreadPoolExecutor(max_workers=num_workers) as pool:
+            futures = [
+                pool.submit(
+                    _compute_relative_chunk_batch,
+                    batch,
+                    all_actions,
+                    all_states,
+                    chunk_size,
+                    relative_mask,
+                )
+                for batch in batches
+            ]
+            for future in as_completed(futures):
+                running_stats.update(future.result())
+    else:
+        for batch in batches:
+            running_stats.update(
+                _compute_relative_chunk_batch(batch, all_actions, all_states, chunk_size, relative_mask)
+            )
+
+    stats = running_stats.get_statistics()
+
+    excluded_dims = int(len(relative_mask) - relative_mask.sum())
+    total_frames = len(valid_starts) * chunk_size
+    logging.info(
+        f"Relative action stats ({len(valid_starts)} chunks, {total_frames} frames): "
+        f"relative_dims={int(relative_mask.sum())}/{len(relative_mask)} (excluded={excluded_dims}), "
+        f"mean={np.abs(stats['mean']).mean():.4f}, std={stats['std'].mean():.4f}, "
+        f"q01={stats['q01'].mean():.4f}, q99={stats['q99'].mean():.4f}"
+    )
+
+    return stats

src/lerobot/datasets/dataset_metadata.py

@@ -0,0 +1,652 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import contextlib
+from pathlib import Path
+
+import numpy as np
+import packaging.version
+import pandas as pd
+import pyarrow as pa
+import pyarrow.parquet as pq
+from huggingface_hub import snapshot_download
+
+from lerobot.datasets.compute_stats import aggregate_stats
+from lerobot.datasets.feature_utils import _validate_feature_names, create_empty_dataset_info
+from lerobot.datasets.io_utils import (
+    get_file_size_in_mb,
+    load_episodes,
+    load_info,
+    load_stats,
+    load_subtasks,
+    load_tasks,
+    write_info,
+    write_json,
+    write_stats,
+    write_tasks,
+)
+from lerobot.datasets.utils import (
+    DEFAULT_EPISODES_PATH,
+    DEFAULT_FEATURES,
+    INFO_PATH,
+    check_version_compatibility,
+    flatten_dict,
+    get_safe_version,
+    has_legacy_hub_download_metadata,
+    is_valid_version,
+    update_chunk_file_indices,
+)
+from lerobot.datasets.video_utils import get_video_info
+from lerobot.utils.constants import HF_LEROBOT_HOME, HF_LEROBOT_HUB_CACHE
+
+CODEBASE_VERSION = "v3.0"
+
+
+class LeRobotDatasetMetadata:
+    """Metadata container for a LeRobot dataset.
+
+    Manages the ``info.json``, ``stats.json``, ``tasks.parquet``, and
+    ``episodes/`` parquet files that describe a dataset's structure, content,
+    and statistics.
+    """
+
+    def __init__(
+        self,
+        repo_id: str,
+        root: str | Path | None = None,
+        revision: str | None = None,
+        force_cache_sync: bool = False,
+        metadata_buffer_size: int = 10,
+    ):
+        """Load or download metadata for an existing LeRobot dataset.
+
+        Attempts to load metadata from local disk. If files are missing or
+        ``force_cache_sync`` is ``True``, downloads the ``meta/`` directory from
+        the Hub.
+
+        Args:
+            repo_id: Repository identifier (e.g. ``'lerobot/aloha_sim'``).
+            root: Local directory for the dataset. When provided, Hub downloads
+                are materialized directly into this directory. When omitted,
+                existing local datasets are still looked up under
+                ``$HF_LEROBOT_HOME/{repo_id}``, but Hub downloads use a
+                revision-safe snapshot cache under
+                ``$HF_LEROBOT_HOME/hub``.
+            revision: Git revision (branch, tag, or commit hash). Defaults to
+                the current codebase version.
+            force_cache_sync: If ``True``, re-download metadata from the Hub
+                even when local files exist.
+            metadata_buffer_size: Number of episode metadata records to buffer
+                in memory before flushing to parquet.
+        """
+        self.repo_id = repo_id
+        self.revision = revision if revision else CODEBASE_VERSION
+        self._requested_root = Path(root) if root is not None else None
+        self.root = self._requested_root if self._requested_root is not None else HF_LEROBOT_HOME / repo_id
+        self._pq_writer = None
+        self.latest_episode = None
+        self._metadata_buffer: list[dict] = []
+        self._metadata_buffer_size = metadata_buffer_size
+        self._finalized = False
+
+        try:
+            if force_cache_sync or (
+                self._requested_root is None and has_legacy_hub_download_metadata(self.root)
+            ):
+                raise FileNotFoundError
+            self._load_metadata()
+        except (FileNotFoundError, NotADirectoryError):
+            if is_valid_version(self.revision):
+                self.revision = get_safe_version(self.repo_id, self.revision)
+
+            self._pull_from_repo(allow_patterns="meta/")
+            self._load_metadata()
+
+    def _flush_metadata_buffer(self) -> None:
+        """Write all buffered episode metadata to parquet file."""
+        if not hasattr(self, "_metadata_buffer") or len(self._metadata_buffer) == 0:
+            return
+
+        combined_dict = {}
+        for episode_dict in self._metadata_buffer:
+            for key, value in episode_dict.items():
+                if key not in combined_dict:
+                    combined_dict[key] = []
+                # Extract value and serialize numpy arrays
+                # because PyArrow's from_pydict function doesn't support numpy arrays
+                val = value[0] if isinstance(value, list) else value
+                combined_dict[key].append(val.tolist() if isinstance(val, np.ndarray) else val)
+
+        first_ep = self._metadata_buffer[0]
+        chunk_idx = first_ep["meta/episodes/chunk_index"][0]
+        file_idx = first_ep["meta/episodes/file_index"][0]
+
+        table = pa.Table.from_pydict(combined_dict)
+
+        if not self._pq_writer:
+            path = Path(self.root / DEFAULT_EPISODES_PATH.format(chunk_index=chunk_idx, file_index=file_idx))
+            path.parent.mkdir(parents=True, exist_ok=True)
+            self._pq_writer = pq.ParquetWriter(
+                path, schema=table.schema, compression="snappy", use_dictionary=True
+            )
+
+        self._pq_writer.write_table(table)
+
+        self.latest_episode = self._metadata_buffer[-1]
+        self._metadata_buffer.clear()
+
+    def _close_writer(self) -> None:
+        """Close and cleanup the parquet writer if it exists."""
+        self._flush_metadata_buffer()
+
+        writer = getattr(self, "_pq_writer", None)
+        if writer is not None:
+            writer.close()
+            self._pq_writer = None
+
+    def finalize(self) -> None:
+        """Flush metadata buffer and close the parquet writer.
+
+        Idempotent — safe to call multiple times.
+        """
+        if getattr(self, "_finalized", False):
+            return
+        self._close_writer()
+        self._finalized = True
+
+    def __del__(self):
+        """Safety net: flush and close parquet writer on garbage collection."""
+        # During interpreter shutdown, referenced objects may already be collected.
+        with contextlib.suppress(Exception):
+            self.finalize()
+
+    def _load_metadata(self):
+        self.info = load_info(self.root)
+        check_version_compatibility(self.repo_id, self._version, CODEBASE_VERSION)
+        self.tasks = load_tasks(self.root)
+        self.subtasks = load_subtasks(self.root)
+        self.episodes = load_episodes(self.root)
+        self.stats = load_stats(self.root)
+
+    def _pull_from_repo(
+        self,
+        allow_patterns: list[str] | str | None = None,
+        ignore_patterns: list[str] | str | None = None,
+    ) -> None:
+        if self._requested_root is None:
+            self.root = Path(
+                snapshot_download(
+                    self.repo_id,
+                    repo_type="dataset",
+                    revision=self.revision,
+                    cache_dir=HF_LEROBOT_HUB_CACHE,
+                    allow_patterns=allow_patterns,
+                    ignore_patterns=ignore_patterns,
+                )
+            )
+            return
+
+        self._requested_root.mkdir(exist_ok=True, parents=True)
+        snapshot_download(
+            self.repo_id,
+            repo_type="dataset",
+            revision=self.revision,
+            local_dir=self._requested_root,
+            allow_patterns=allow_patterns,
+            ignore_patterns=ignore_patterns,
+        )
+        self.root = self._requested_root
+
+    @property
+    def url_root(self) -> str:
+        """Hugging Face Hub URL root for this dataset."""
+        return f"hf://datasets/{self.repo_id}"
+
+    @property
+    def _version(self) -> packaging.version.Version:
+        """Codebase version used to create this dataset."""
+        return packaging.version.parse(self.info["codebase_version"])
+
+    def get_data_file_path(self, ep_index: int) -> Path:
+        """Return the relative parquet file path for the given episode index.
+
+        Args:
+            ep_index: Zero-based episode index.
+
+        Returns:
+            Path to the parquet file containing this episode's data.
+
+        Raises:
+            IndexError: If ``ep_index`` is out of range.
+        """
+        if self.episodes is None:
+            self.episodes = load_episodes(self.root)
+        if ep_index >= len(self.episodes):
+            raise IndexError(
+                f"Episode index {ep_index} out of range. Episodes: {len(self.episodes) if self.episodes else 0}"
+            )
+        ep = self.episodes[ep_index]
+        chunk_idx = ep["data/chunk_index"]
+        file_idx = ep["data/file_index"]
+        fpath = self.data_path.format(chunk_index=chunk_idx, file_index=file_idx)
+        return Path(fpath)
+
+    def get_video_file_path(self, ep_index: int, vid_key: str) -> Path:
+        """Return the relative video file path for the given episode and video key.
+
+        Args:
+            ep_index: Zero-based episode index.
+            vid_key: Feature key identifying the video stream
+                (e.g. ``'observation.images.laptop'``).
+
+        Returns:
+            Path to the video file containing this episode's frames.
+
+        Raises:
+            IndexError: If ``ep_index`` is out of range.
+        """
+        if self.episodes is None:
+            self.episodes = load_episodes(self.root)
+        if ep_index >= len(self.episodes):
+            raise IndexError(
+                f"Episode index {ep_index} out of range. Episodes: {len(self.episodes) if self.episodes else 0}"
+            )
+        ep = self.episodes[ep_index]
+        chunk_idx = ep[f"videos/{vid_key}/chunk_index"]
+        file_idx = ep[f"videos/{vid_key}/file_index"]
+        fpath = self.video_path.format(video_key=vid_key, chunk_index=chunk_idx, file_index=file_idx)
+        return Path(fpath)
+
+    @property
+    def data_path(self) -> str:
+        """Formattable string for the parquet files."""
+        return self.info["data_path"]
+
+    @property
+    def video_path(self) -> str | None:
+        """Formattable string for the video files."""
+        return self.info["video_path"]
+
+    @property
+    def robot_type(self) -> str | None:
+        """Robot type used in recording this dataset."""
+        return self.info["robot_type"]
+
+    @property
+    def fps(self) -> int:
+        """Frames per second used during data collection."""
+        return self.info["fps"]
+
+    @property
+    def features(self) -> dict[str, dict]:
+        """All features contained in the dataset."""
+        return self.info["features"]
+
+    @property
+    def image_keys(self) -> list[str]:
+        """Keys to access visual modalities stored as images."""
+        return [key for key, ft in self.features.items() if ft["dtype"] == "image"]
+
+    @property
+    def video_keys(self) -> list[str]:
+        """Keys to access visual modalities stored as videos."""
+        return [key for key, ft in self.features.items() if ft["dtype"] == "video"]
+
+    @property
+    def camera_keys(self) -> list[str]:
+        """Keys to access visual modalities (regardless of their storage method)."""
+        return [key for key, ft in self.features.items() if ft["dtype"] in ["video", "image"]]
+
+    @property
+    def names(self) -> dict[str, list | dict]:
+        """Names of the various dimensions of vector modalities."""
+        return {key: ft["names"] for key, ft in self.features.items()}
+
+    @property
+    def shapes(self) -> dict:
+        """Shapes for the different features."""
+        return {key: tuple(ft["shape"]) for key, ft in self.features.items()}
+
+    @property
+    def total_episodes(self) -> int:
+        """Total number of episodes available."""
+        return self.info["total_episodes"]
+
+    @property
+    def total_frames(self) -> int:
+        """Total number of frames saved in this dataset."""
+        return self.info["total_frames"]
+
+    @property
+    def total_tasks(self) -> int:
+        """Total number of different tasks performed in this dataset."""
+        return self.info["total_tasks"]
+
+    @property
+    def chunks_size(self) -> int:
+        """Max number of files per chunk."""
+        return self.info["chunks_size"]
+
+    @property
+    def data_files_size_in_mb(self) -> int:
+        """Max size of data file in mega bytes."""
+        return self.info["data_files_size_in_mb"]
+
+    @property
+    def video_files_size_in_mb(self) -> int:
+        """Max size of video file in mega bytes."""
+        return self.info["video_files_size_in_mb"]
+
+    def get_task_index(self, task: str) -> int | None:
+        """
+        Given a task in natural language, returns its task_index if the task already exists in the dataset,
+        otherwise return None.
+        """
+        if task in self.tasks.index:
+            return int(self.tasks.loc[task].task_index)
+        else:
+            return None
+
+    def save_episode_tasks(self, tasks: list[str]):
+        """Register tasks for the current episode and persist to disk.
+
+        New tasks that do not already exist in the dataset are assigned
+        sequential task indices and appended to the tasks parquet file.
+
+        Args:
+            tasks: List of unique task descriptions in natural language.
+
+        Raises:
+            ValueError: If ``tasks`` contains duplicates.
+        """
+        if len(set(tasks)) != len(tasks):
+            raise ValueError(f"Tasks are not unique: {tasks}")
+
+        if self.tasks is None:
+            new_tasks = tasks
+            task_indices = range(len(tasks))
+            self.tasks = pd.DataFrame({"task_index": task_indices}, index=pd.Index(tasks, name="task"))
+        else:
+            new_tasks = [task for task in tasks if task not in self.tasks.index]
+            new_task_indices = range(len(self.tasks), len(self.tasks) + len(new_tasks))
+            for task_idx, task in zip(new_task_indices, new_tasks, strict=False):
+                self.tasks.loc[task] = task_idx
+
+        if len(new_tasks) > 0:
+            # Update on disk
+            write_tasks(self.tasks, self.root)
+
+    def _save_episode_metadata(self, episode_dict: dict) -> None:
+        """Buffer episode metadata and write to parquet in batches for efficiency.
+
+        This function accumulates episode metadata in a buffer and flushes it when the buffer
+        reaches the configured size. This reduces I/O overhead by writing multiple episodes
+        at once instead of one row at a time.
+
+        Notes: We both need to update parquet files and HF dataset:
+        - `pandas` loads parquet file in RAM
+        - `datasets` relies on a memory mapping from pyarrow (no RAM). It either converts parquet files to a pyarrow cache on disk,
+          or loads directly from pyarrow cache.
+        """
+        # Convert to list format for each value
+        episode_dict = {key: [value] for key, value in episode_dict.items()}
+        num_frames = episode_dict["length"][0]
+
+        if self.latest_episode is None:
+            # Initialize indices and frame count for a new dataset made of the first episode data
+            chunk_idx, file_idx = 0, 0
+            if self.episodes is not None and len(self.episodes) > 0:
+                # It means we are resuming recording, so we need to load the latest episode
+                # Update the indices to avoid overwriting the latest episode
+                chunk_idx = self.episodes[-1]["meta/episodes/chunk_index"]
+                file_idx = self.episodes[-1]["meta/episodes/file_index"]
+                latest_num_frames = self.episodes[-1]["dataset_to_index"]
+                episode_dict["dataset_from_index"] = [latest_num_frames]
+                episode_dict["dataset_to_index"] = [latest_num_frames + num_frames]
+
+                # When resuming, move to the next file
+                chunk_idx, file_idx = update_chunk_file_indices(chunk_idx, file_idx, self.chunks_size)
+            else:
+                episode_dict["dataset_from_index"] = [0]
+                episode_dict["dataset_to_index"] = [num_frames]
+
+            episode_dict["meta/episodes/chunk_index"] = [chunk_idx]
+            episode_dict["meta/episodes/file_index"] = [file_idx]
+        else:
+            chunk_idx = self.latest_episode["meta/episodes/chunk_index"][0]
+            file_idx = self.latest_episode["meta/episodes/file_index"][0]
+
+            latest_path = (
+                self.root / DEFAULT_EPISODES_PATH.format(chunk_index=chunk_idx, file_index=file_idx)
+                if self._pq_writer is None
+                else self._pq_writer.where
+            )
+
+            if Path(latest_path).exists():
+                latest_size_in_mb = get_file_size_in_mb(Path(latest_path))
+                latest_num_frames = self.latest_episode["episode_index"][0]
+
+                av_size_per_frame = latest_size_in_mb / latest_num_frames if latest_num_frames > 0 else 0.0
+
+                if latest_size_in_mb + av_size_per_frame * num_frames >= self.data_files_size_in_mb:
+                    # Size limit is reached, flush buffer and prepare new parquet file
+                    self._flush_metadata_buffer()
+                    chunk_idx, file_idx = update_chunk_file_indices(chunk_idx, file_idx, self.chunks_size)
+                    self._close_writer()
+
+            # Update the existing pandas dataframe with new row
+            episode_dict["meta/episodes/chunk_index"] = [chunk_idx]
+            episode_dict["meta/episodes/file_index"] = [file_idx]
+            episode_dict["dataset_from_index"] = [self.latest_episode["dataset_to_index"][0]]
+            episode_dict["dataset_to_index"] = [self.latest_episode["dataset_to_index"][0] + num_frames]
+
+        # Add to buffer
+        self._metadata_buffer.append(episode_dict)
+        self.latest_episode = episode_dict
+
+        if len(self._metadata_buffer) >= self._metadata_buffer_size:
+            self._flush_metadata_buffer()
+
+    def save_episode(
+        self,
+        episode_index: int,
+        episode_length: int,
+        episode_tasks: list[str],
+        episode_stats: dict[str, dict],
+        episode_metadata: dict,
+    ) -> None:
+        """Persist episode metadata, update dataset info, and aggregate stats.
+
+        Writes the episode's metadata to the buffered parquet writer, increments
+        the total episode/frame counters in ``info.json``, and merges the
+        episode's statistics into the running dataset statistics.
+
+        Args:
+            episode_index: Zero-based index of the episode being saved.
+            episode_length: Number of frames in this episode.
+            episode_tasks: List of task descriptions for this episode.
+            episode_stats: Per-feature statistics for this episode.
+            episode_metadata: Additional metadata (chunk/file indices, frame
+                ranges, video timestamps, etc.).
+        """
+        episode_dict = {
+            "episode_index": episode_index,
+            "tasks": episode_tasks,
+            "length": episode_length,
+        }
+        episode_dict.update(episode_metadata)
+        episode_dict.update(flatten_dict({"stats": episode_stats}))
+        self._save_episode_metadata(episode_dict)
+
+        # Update info
+        self.info["total_episodes"] += 1
+        self.info["total_frames"] += episode_length
+        self.info["total_tasks"] = len(self.tasks)
+        self.info["splits"] = {"train": f"0:{self.info['total_episodes']}"}
+
+        write_info(self.info, self.root)
+
+        self.stats = aggregate_stats([self.stats, episode_stats]) if self.stats is not None else episode_stats
+        write_stats(self.stats, self.root)
+
+    def update_video_info(self, video_key: str | None = None) -> None:
+        """
+        Warning: this function writes info from first episode videos, implicitly assuming that all videos have
+        been encoded the same way. Also, this means it assumes the first episode exists.
+        """
+        if video_key is not None and video_key not in self.video_keys:
+            raise ValueError(f"Video key {video_key} not found in dataset")
+
+        video_keys = [video_key] if video_key is not None else self.video_keys
+        for key in video_keys:
+            if not self.features[key].get("info", None):
+                video_path = self.root / self.video_path.format(video_key=key, chunk_index=0, file_index=0)
+                self.info["features"][key]["info"] = get_video_info(video_path)
+
+    def update_chunk_settings(
+        self,
+        chunks_size: int | None = None,
+        data_files_size_in_mb: int | None = None,
+        video_files_size_in_mb: int | None = None,
+    ) -> None:
+        """Update chunk and file size settings after dataset creation.
+
+        This allows users to customize storage organization without modifying the constructor.
+        These settings control how episodes are chunked and how large files can grow before
+        creating new ones.
+
+        Args:
+            chunks_size: Maximum number of files per chunk directory. If None, keeps current value.
+            data_files_size_in_mb: Maximum size for data parquet files in MB. If None, keeps current value.
+            video_files_size_in_mb: Maximum size for video files in MB. If None, keeps current value.
+        """
+        if chunks_size is not None:
+            if chunks_size <= 0:
+                raise ValueError(f"chunks_size must be positive, got {chunks_size}")
+            self.info["chunks_size"] = chunks_size
+
+        if data_files_size_in_mb is not None:
+            if data_files_size_in_mb <= 0:
+                raise ValueError(f"data_files_size_in_mb must be positive, got {data_files_size_in_mb}")
+            self.info["data_files_size_in_mb"] = data_files_size_in_mb
+
+        if video_files_size_in_mb is not None:
+            if video_files_size_in_mb <= 0:
+                raise ValueError(f"video_files_size_in_mb must be positive, got {video_files_size_in_mb}")
+            self.info["video_files_size_in_mb"] = video_files_size_in_mb
+
+        # Update the info file on disk
+        write_info(self.info, self.root)
+
+    def get_chunk_settings(self) -> dict[str, int]:
+        """Get current chunk and file size settings.
+
+        Returns:
+            Dict containing chunks_size, data_files_size_in_mb, and video_files_size_in_mb.
+        """
+        return {
+            "chunks_size": self.chunks_size,
+            "data_files_size_in_mb": self.data_files_size_in_mb,
+            "video_files_size_in_mb": self.video_files_size_in_mb,
+        }
+
+    def __repr__(self):
+        feature_keys = list(self.features)
+        return (
+            f"{self.__class__.__name__}({{\n"
+            f"    Repository ID: '{self.repo_id}',\n"
+            f"    Total episodes: '{self.total_episodes}',\n"
+            f"    Total frames: '{self.total_frames}',\n"
+            f"    Features: '{feature_keys}',\n"
+            "})',\n"
+        )
+
+    @classmethod
+    def create(
+        cls,
+        repo_id: str,
+        fps: int,
+        features: dict,
+        robot_type: str | None = None,
+        root: str | Path | None = None,
+        use_videos: bool = True,
+        metadata_buffer_size: int = 10,
+        chunks_size: int | None = None,
+        data_files_size_in_mb: int | None = None,
+        video_files_size_in_mb: int | None = None,
+    ) -> "LeRobotDatasetMetadata":
+        """Create metadata for a new LeRobot dataset from scratch.
+
+        Initializes the ``info.json`` file on disk with the provided feature
+        schema and dataset settings. No episode data is written yet.
+
+        Args:
+            repo_id: Repository identifier (e.g. ``'user/my_dataset'``).
+            fps: Frames per second used during data collection.
+            features: Feature specification dict mapping feature names to their
+                type/shape metadata.
+            robot_type: Optional robot type string stored in metadata.
+            root: Local directory for the dataset. Defaults to
+                ``$HF_LEROBOT_HOME/{repo_id}``. Must not already exist.
+            use_videos: If ``True``, visual modalities are encoded as MP4 videos.
+            metadata_buffer_size: Number of episode metadata records to buffer
+                before flushing to parquet.
+            chunks_size: Max number of files per chunk directory. ``None`` uses
+                the default.
+            data_files_size_in_mb: Max parquet file size in MB. ``None`` uses the
+                default.
+            video_files_size_in_mb: Max video file size in MB. ``None`` uses the
+                default.
+
+        Returns:
+            A new :class:`LeRobotDatasetMetadata` instance.
+        """
+        obj = cls.__new__(cls)
+        obj.repo_id = repo_id
+        obj._requested_root = Path(root) if root is not None else None
+        obj.root = obj._requested_root if obj._requested_root is not None else HF_LEROBOT_HOME / repo_id
+
+        obj.root.mkdir(parents=True, exist_ok=False)
+
+        features = {**features, **DEFAULT_FEATURES}
+        _validate_feature_names(features)
+
+        obj.tasks = None
+        obj.subtasks = None
+        obj.episodes = None
+        obj.stats = None
+        obj.info = create_empty_dataset_info(
+            CODEBASE_VERSION,
+            fps,
+            features,
+            use_videos,
+            robot_type,
+            chunks_size,
+            data_files_size_in_mb,
+            video_files_size_in_mb,
+        )
+        if len(obj.video_keys) > 0 and not use_videos:
+            raise ValueError(
+                f"Features contain video keys {obj.video_keys}, but 'use_videos' is set to False. "
+                "Either remove video features from the features dict, or set 'use_videos=True'."
+            )
+        write_json(obj.info, obj.root / INFO_PATH)
+        obj.revision = None
+        obj._pq_writer = None
+        obj.latest_episode = None
+        obj._metadata_buffer = []
+        obj._metadata_buffer_size = metadata_buffer_size
+        obj._finalized = False
+        return obj

src/lerobot/datasets/dataset_reader.py

@@ -0,0 +1,288 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Private reader component for LeRobotDataset. Handles random-access reading (HF dataset, delta indices, video decoding)."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+import datasets
+import torch
+
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import (
+    check_delta_timestamps,
+    get_delta_indices,
+    get_hf_features_from_features,
+)
+from lerobot.datasets.io_utils import (
+    hf_transform_to_torch,
+    load_nested_dataset,
+)
+from lerobot.datasets.video_utils import decode_video_frames
+
+
+class DatasetReader:
+    """Encapsulates read-side state and methods for LeRobotDataset.
+
+    Owns: hf_dataset, _absolute_to_relative_idx, delta_indices.
+    """
+
+    def __init__(
+        self,
+        meta: LeRobotDatasetMetadata,
+        root: Path,
+        episodes: list[int] | None,
+        tolerance_s: float,
+        video_backend: str,
+        delta_timestamps: dict[str, list[float]] | None,
+        image_transforms: Callable | None,
+    ):
+        """Initialize the reader with metadata, filtering, and transform config.
+
+        The HF dataset is not loaded here — call :meth:`try_load` or
+        :meth:`load_and_activate` afterward.
+
+        Args:
+            meta: Dataset metadata instance.
+            root: Local dataset root directory.
+            episodes: Optional list of episode indices to select. ``None``
+                means all episodes.
+            tolerance_s: Timestamp synchronization tolerance in seconds.
+            video_backend: Video decoding backend identifier.
+            delta_timestamps: Optional dict mapping feature keys to lists of
+                relative timestamp offsets for temporal context windows.
+            image_transforms: Optional torchvision v2 transform applied to
+                visual features.
+        """
+        self._meta = meta
+        self.root = root
+        self.episodes = episodes
+        self._tolerance_s = tolerance_s
+        self._video_backend = video_backend
+        self._image_transforms = image_transforms
+
+        self.hf_dataset: datasets.Dataset | None = None
+        self._absolute_to_relative_idx: dict[int, int] | None = None
+
+        # Setup delta_indices (doesn't depend on hf_dataset)
+        self.delta_indices = None
+        if delta_timestamps is not None:
+            check_delta_timestamps(delta_timestamps, meta.fps, tolerance_s)
+            self.delta_indices = get_delta_indices(delta_timestamps, meta.fps)
+
+    def try_load(self) -> bool:
+        """Attempt to load from local cache. Returns True if data is sufficient."""
+        try:
+            self.hf_dataset = self._load_hf_dataset()
+        except (FileNotFoundError, NotADirectoryError):
+            self.hf_dataset = None
+            return False
+        if not self._check_cached_episodes_sufficient():
+            self.hf_dataset = None
+            return False
+        self._build_index_mapping()
+        return True
+
+    def load_and_activate(self) -> None:
+        """Load HF dataset from disk and build index mapping. Call after data is on disk."""
+        self.hf_dataset = self._load_hf_dataset()
+        self._build_index_mapping()
+
+    def _build_index_mapping(self) -> None:
+        """Build absolute-to-relative index mapping from loaded hf_dataset."""
+        self._absolute_to_relative_idx = None
+        if self.episodes is not None and self.hf_dataset is not None:
+            self._absolute_to_relative_idx = {
+                abs_idx.item() if isinstance(abs_idx, torch.Tensor) else abs_idx: rel_idx
+                for rel_idx, abs_idx in enumerate(self.hf_dataset["index"])
+            }
+
+    @property
+    def num_frames(self) -> int:
+        """Number of frames in selected episodes."""
+        if self.episodes is not None and self.hf_dataset is not None:
+            return len(self.hf_dataset)
+        return self._meta.total_frames
+
+    @property
+    def num_episodes(self) -> int:
+        """Number of episodes selected."""
+        return len(self.episodes) if self.episodes is not None else self._meta.total_episodes
+
+    def _load_hf_dataset(self) -> datasets.Dataset:
+        """hf_dataset contains all the observations, states, actions, rewards, etc."""
+        features = get_hf_features_from_features(self._meta.features)
+        hf_dataset = load_nested_dataset(self.root / "data", features=features, episodes=self.episodes)
+        hf_dataset.set_transform(hf_transform_to_torch)
+        return hf_dataset
+
+    def _check_cached_episodes_sufficient(self) -> bool:
+        """Check if the cached dataset contains all requested episodes and their video files."""
+        if self.hf_dataset is None or len(self.hf_dataset) == 0:
+            return False
+
+        available_episodes = {
+            ep_idx.item() if isinstance(ep_idx, torch.Tensor) else ep_idx
+            for ep_idx in self.hf_dataset.unique("episode_index")
+        }
+
+        if self.episodes is None:
+            requested_episodes = set(range(self._meta.total_episodes))
+        else:
+            requested_episodes = set(self.episodes)
+
+        if not requested_episodes.issubset(available_episodes):
+            return False
+
+        if len(self._meta.video_keys) > 0:
+            for ep_idx in requested_episodes:
+                for vid_key in self._meta.video_keys:
+                    video_path = self.root / self._meta.get_video_file_path(ep_idx, vid_key)
+                    if not video_path.exists():
+                        return False
+
+        return True
+
+    def get_episodes_file_paths(self) -> list[Path]:
+        """Return deduplicated file paths (data + video) for selected episodes.
+
+        Used to build the ``allow_patterns`` list for ``snapshot_download``.
+        """
+        episodes = self.episodes if self.episodes is not None else list(range(self._meta.total_episodes))
+        fpaths = [str(self._meta.get_data_file_path(ep_idx)) for ep_idx in episodes]
+        if len(self._meta.video_keys) > 0:
+            video_files = [
+                str(self._meta.get_video_file_path(ep_idx, vid_key))
+                for vid_key in self._meta.video_keys
+                for ep_idx in episodes
+            ]
+            fpaths += video_files
+        # episodes are stored in the same files, so we return unique paths only
+        fpaths = list(set(fpaths))
+        return fpaths
+
+    def _get_query_indices(
+        self, abs_idx: int, ep_idx: int
+    ) -> tuple[dict[str, list[int]], dict[str, torch.Tensor]]:
+        """Compute query indices for delta timestamps."""
+        ep = self._meta.episodes[ep_idx]
+        ep_start = ep["dataset_from_index"]
+        ep_end = ep["dataset_to_index"]
+        query_indices = {
+            key: [max(ep_start, min(ep_end - 1, abs_idx + delta)) for delta in delta_idx]
+            for key, delta_idx in self.delta_indices.items()
+        }
+        padding = {
+            f"{key}_is_pad": torch.BoolTensor(
+                [(abs_idx + delta < ep_start) | (abs_idx + delta >= ep_end) for delta in delta_idx]
+            )
+            for key, delta_idx in self.delta_indices.items()
+        }
+        return query_indices, padding
+
+    def _get_query_timestamps(
+        self,
+        current_ts: float,
+        query_indices: dict[str, list[int]] | None = None,
+    ) -> dict[str, list[float]]:
+        query_timestamps = {}
+        for key in self._meta.video_keys:
+            if query_indices is not None and key in query_indices:
+                if self._absolute_to_relative_idx is not None:
+                    relative_indices = [self._absolute_to_relative_idx[idx] for idx in query_indices[key]]
+                    timestamps = self.hf_dataset[relative_indices]["timestamp"]
+                else:
+                    timestamps = self.hf_dataset[query_indices[key]]["timestamp"]
+                query_timestamps[key] = torch.stack(timestamps).tolist()
+            else:
+                query_timestamps[key] = [current_ts]
+
+        return query_timestamps
+
+    def _query_hf_dataset(self, query_indices: dict[str, list[int]]) -> dict:
+        """Query dataset for indices across keys, skipping video keys."""
+        result: dict = {}
+        for key, q_idx in query_indices.items():
+            if key in self._meta.video_keys:
+                continue
+            relative_indices = (
+                q_idx
+                if self._absolute_to_relative_idx is None
+                else [self._absolute_to_relative_idx[idx] for idx in q_idx]
+            )
+            try:
+                result[key] = torch.stack(self.hf_dataset[key][relative_indices])
+            except (KeyError, TypeError, IndexError):
+                result[key] = torch.stack(self.hf_dataset[relative_indices][key])
+        return result
+
+    def _query_videos(self, query_timestamps: dict[str, list[float]], ep_idx: int) -> dict[str, torch.Tensor]:
+        """Note: When using data workers (e.g. DataLoader with num_workers>0), do not call this function
+        in the main process (e.g. by using a second Dataloader with num_workers=0). It will result in a
+        Segmentation Fault.
+        """
+        ep = self._meta.episodes[ep_idx]
+        item = {}
+        for vid_key, query_ts in query_timestamps.items():
+            from_timestamp = ep[f"videos/{vid_key}/from_timestamp"]
+            shifted_query_ts = [from_timestamp + ts for ts in query_ts]
+
+            video_path = self.root / self._meta.get_video_file_path(ep_idx, vid_key)
+            frames = decode_video_frames(video_path, shifted_query_ts, self._tolerance_s, self._video_backend)
+            item[vid_key] = frames.squeeze(0)
+
+        return item
+
+    def get_item(self, idx) -> dict:
+        """Core __getitem__ logic. Assumes hf_dataset is loaded.
+
+        ``idx`` is a *relative* index into the (possibly episode-filtered)
+        HF dataset, **not** the absolute frame index stored in the ``index``
+        column.  The absolute index is retrieved from the row itself.
+        """
+        item = self.hf_dataset[idx]
+        ep_idx = item["episode_index"].item()
+        abs_idx = item["index"].item()
+
+        query_indices = None
+        if self.delta_indices is not None:
+            query_indices, padding = self._get_query_indices(abs_idx, ep_idx)
+            query_result = self._query_hf_dataset(query_indices)
+            item = {**item, **padding}
+            for key, val in query_result.items():
+                item[key] = val
+
+        if len(self._meta.video_keys) > 0:
+            current_ts = item["timestamp"].item()
+            query_timestamps = self._get_query_timestamps(current_ts, query_indices)
+            video_frames = self._query_videos(query_timestamps, ep_idx)
+            item = {**video_frames, **item}
+
+        if self._image_transforms is not None:
+            image_keys = self._meta.camera_keys
+            for cam in image_keys:
+                item[cam] = self._image_transforms(item[cam])
+
+        # Add task as a string
+        task_idx = item["task_index"].item()
+        item["task"] = self._meta.tasks.iloc[task_idx].name
+
+        # add subtask information if available
+        if "subtask_index" in self._meta.features and self._meta.subtasks is not None:
+            subtask_idx = item["subtask_index"].item()
+            item["subtask"] = self._meta.subtasks.iloc[subtask_idx].name
+
+        return item

src/lerobot/datasets/dataset_tools.py

@@ -37,23 +37,30 @@ import torch
 from tqdm import tqdm
 
 from lerobot.datasets.aggregate import aggregate_datasets
-from lerobot.datasets.compute_stats import aggregate_stats
-from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
+from lerobot.datasets.compute_stats import (
+    aggregate_stats,
+    compute_episode_stats,
+    compute_relative_action_stats,
+)
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.io_utils import (
+    get_parquet_file_size_in_mb,
+    load_episodes,
+    write_info,
+    write_stats,
+    write_tasks,
+)
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.datasets.utils import (
     DATA_DIR,
     DEFAULT_CHUNK_SIZE,
     DEFAULT_DATA_FILE_SIZE_IN_MB,
     DEFAULT_DATA_PATH,
     DEFAULT_EPISODES_PATH,
-    get_parquet_file_size_in_mb,
-    load_episodes,
     update_chunk_file_indices,
-    write_info,
-    write_stats,
-    write_tasks,
 )
 from lerobot.datasets.video_utils import encode_video_frames, get_video_info
-from lerobot.utils.constants import HF_LEROBOT_HOME, OBS_IMAGE
+from lerobot.utils.constants import ACTION, HF_LEROBOT_HOME, OBS_IMAGE, OBS_STATE
 
 
 def _load_episode_with_stats(src_dataset: LeRobotDataset, episode_idx: int) -> dict:
@@ -888,7 +895,7 @@ def _copy_and_reindex_episodes_metadata(
 
         total_frames += src_episode["length"]
 
-    dst_meta._close_writer()
+    dst_meta.finalize()
 
     dst_meta.info.update(
         {
@@ -915,7 +922,8 @@ def _write_parquet(df: pd.DataFrame, path: Path, meta: LeRobotDatasetMetadata) -
 
     This ensures images are properly embedded and the file can be loaded correctly by HF datasets.
     """
-    from lerobot.datasets.utils import embed_images, get_hf_features_from_features
+    from lerobot.datasets.feature_utils import get_hf_features_from_features
+    from lerobot.datasets.io_utils import embed_images
 
     hf_features = get_hf_features_from_features(meta.features)
     ep_dataset = datasets.Dataset.from_dict(df.to_dict(orient="list"), features=hf_features, split="train")
@@ -1529,6 +1537,114 @@ def modify_tasks(
     return dataset
 
 
+def recompute_stats(
+    dataset: LeRobotDataset,
+    skip_image_video: bool = True,
+    relative_action: bool = False,
+    relative_exclude_joints: list[str] | None = None,
+    chunk_size: int = 50,
+    num_workers: int = 0,
+) -> LeRobotDataset:
+    """Recompute stats.json from scratch by iterating all episodes.
+
+    Args:
+        dataset: The LeRobotDataset to recompute stats for.
+        skip_image_video: If True (default), only recompute stats for numeric features
+            (action, state, etc.) and keep existing image/video stats unchanged.
+        relative_action: If True, compute action stats in relative space by
+            iterating all valid action chunks and subtracting the current state.
+            This matches the normalization distribution the model sees during
+            training with ``use_relative_actions=True``.
+        relative_exclude_joints: Joint names to exclude from relative conversion when
+            relative_action=True. These dims keep absolute stats.
+        chunk_size: Action chunk size used for relative stats computation. Should match
+            ``policy.chunk_size``. Only used when ``relative_action=True``.
+        num_workers: Number of parallel threads for relative action stats computation.
+            Values ≤1 mean single-threaded. Only used when ``relative_action=True``.
+
+    Returns:
+        The same dataset with updated stats.
+    """
+    features = dataset.meta.features
+    meta_keys = {"index", "episode_index", "task_index", "frame_index", "timestamp"}
+    numeric_features = {
+        k: v
+        for k, v in features.items()
+        if v["dtype"] not in ["image", "video", "string"] and k not in meta_keys
+    }
+
+    if skip_image_video:
+        features_to_compute = numeric_features
+    else:
+        features_to_compute = {
+            k: v for k, v in features.items() if v["dtype"] != "string" and k not in meta_keys
+        }
+
+    # When relative_action is enabled, compute action stats via chunk-based sampling
+    # (matching what the model sees during training) and skip action in the
+    # per-episode pass below.
+    relative_action_stats = None
+    if relative_action and ACTION in features and OBS_STATE in features:
+        if relative_exclude_joints is None:
+            relative_exclude_joints = ["gripper"]
+        relative_action_stats = compute_relative_action_stats(
+            hf_dataset=dataset.hf_dataset,
+            features=features,
+            chunk_size=chunk_size,
+            exclude_joints=relative_exclude_joints,
+            num_workers=num_workers,
+        )
+        features_to_compute.pop(ACTION, None)
+
+    logging.info(f"Recomputing stats for features: {list(features_to_compute.keys())}")
+
+    data_dir = dataset.root / DATA_DIR
+    parquet_files = sorted(data_dir.glob("*/*.parquet"))
+    if not parquet_files:
+        raise ValueError(f"No parquet files found in {data_dir}")
+
+    all_episode_stats = []
+    numeric_keys = [k for k, v in features_to_compute.items() if v["dtype"] not in ["image", "video"]]
+
+    for parquet_path in tqdm(parquet_files, desc="Computing stats from data files"):
+        df = pd.read_parquet(parquet_path)
+
+        for ep_idx in sorted(df["episode_index"].unique()):
+            ep_df = df[df["episode_index"] == ep_idx]
+            episode_data = {}
+            for key in numeric_keys:
+                if key in ep_df.columns:
+                    values = ep_df[key].values
+                    if hasattr(values[0], "__len__"):
+                        episode_data[key] = np.stack(values)
+                    else:
+                        episode_data[key] = np.array(values)
+
+            ep_stats = compute_episode_stats(episode_data, features_to_compute)
+            all_episode_stats.append(ep_stats)
+
+    if features_to_compute and not all_episode_stats:
+        logging.warning("No episode stats computed")
+        return dataset
+
+    new_stats = aggregate_stats(all_episode_stats) if all_episode_stats else {}
+
+    if relative_action_stats is not None:
+        new_stats[ACTION] = relative_action_stats
+
+    # Merge: keep existing stats for features we didn't recompute
+    if dataset.meta.stats:
+        for key, value in dataset.meta.stats.items():
+            if key not in new_stats:
+                new_stats[key] = value
+
+    write_stats(new_stats, dataset.root)
+    dataset.meta.stats = new_stats
+
+    logging.info("Stats recomputed successfully")
+    return dataset
+
+
 def convert_image_to_video_dataset(
     dataset: LeRobotDataset,
     output_dir: Path | None = None,

src/lerobot/datasets/dataset_writer.py

@@ -0,0 +1,634 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Private writer component for LeRobotDataset. Handles sequential recording (episode buffer, ParquetWriter, image writer, video encoding)."""
+
+from __future__ import annotations
+
+import concurrent.futures
+import contextlib
+import logging
+import shutil
+import tempfile
+from pathlib import Path
+
+import datasets
+import numpy as np
+import pandas as pd
+import PIL.Image
+import pyarrow.parquet as pq
+import torch
+
+from lerobot.datasets.compute_stats import compute_episode_stats
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import (
+    get_hf_features_from_features,
+    validate_episode_buffer,
+    validate_frame,
+)
+from lerobot.datasets.image_writer import AsyncImageWriter, write_image
+from lerobot.datasets.io_utils import (
+    embed_images,
+    get_file_size_in_mb,
+    load_episodes,
+    write_info,
+)
+from lerobot.datasets.utils import (
+    DEFAULT_EPISODES_PATH,
+    DEFAULT_IMAGE_PATH,
+    update_chunk_file_indices,
+)
+from lerobot.datasets.video_utils import (
+    StreamingVideoEncoder,
+    concatenate_video_files,
+    encode_video_frames,
+    get_video_duration_in_s,
+)
+
+logger = logging.getLogger(__name__)
+
+
+def _encode_video_worker(
+    video_key: str,
+    episode_index: int,
+    root: Path,
+    fps: int,
+    vcodec: str = "libsvtav1",
+    encoder_threads: int | None = None,
+) -> Path:
+    temp_path = Path(tempfile.mkdtemp(dir=root)) / f"{video_key}_{episode_index:03d}.mp4"
+    fpath = DEFAULT_IMAGE_PATH.format(image_key=video_key, episode_index=episode_index, frame_index=0)
+    img_dir = (root / fpath).parent
+    encode_video_frames(
+        img_dir, temp_path, fps, vcodec=vcodec, overwrite=True, encoder_threads=encoder_threads
+    )
+    shutil.rmtree(img_dir)
+    return temp_path
+
+
+class DatasetWriter:
+    """Encapsulates write-side state and methods for LeRobotDataset.
+
+    Owns: episode_buffer, image_writer, _pq_writer (ParquetWriter), _latest_episode,
+    _current_file_start_frame, _streaming_encoder, _episodes_since_last_encoding, _recorded_frames.
+    """
+
+    def __init__(
+        self,
+        meta: LeRobotDatasetMetadata,
+        root: Path,
+        vcodec: str,
+        encoder_threads: int | None,
+        batch_encoding_size: int,
+        streaming_encoder: StreamingVideoEncoder | None = None,
+        initial_frames: int = 0,
+    ):
+        """Initialize the writer with metadata, codec, and encoding config.
+
+        Args:
+            meta: Dataset metadata instance (used for feature schema, chunk
+                settings, and episode persistence).
+            root: Local dataset root directory.
+            vcodec: Video codec for encoding (e.g. ``'libsvtav1'``, ``'h264'``).
+            encoder_threads: Threads per encoder instance. ``None`` for auto.
+            batch_encoding_size: Number of episodes to accumulate before
+                batch-encoding videos.
+            streaming_encoder: Optional pre-built :class:`StreamingVideoEncoder`
+                for real-time encoding. ``None`` disables streaming mode.
+            initial_frames: Starting frame count (non-zero when resuming).
+        """
+        self._meta = meta
+        self._root = root
+        self._vcodec = vcodec
+        self._encoder_threads = encoder_threads
+        self._batch_encoding_size = batch_encoding_size
+        self._streaming_encoder = streaming_encoder
+
+        # Writer state
+        self.image_writer: AsyncImageWriter | None = None
+        self.episode_buffer: dict = self._create_episode_buffer()
+        self._pq_writer: pq.ParquetWriter | None = None
+        self._latest_episode: dict | None = None
+        self._current_file_start_frame: int | None = None
+        self._episodes_since_last_encoding: int = 0
+        self._recorded_frames: int = initial_frames
+        self._finalized = False
+
+    def _create_episode_buffer(self, episode_index: int | None = None) -> dict:
+        current_ep_idx = self._meta.total_episodes if episode_index is None else episode_index
+        ep_buffer = {}
+        ep_buffer["size"] = 0
+        ep_buffer["task"] = []
+        for key in self._meta.features:
+            ep_buffer[key] = current_ep_idx if key == "episode_index" else []
+        return ep_buffer
+
+    def _get_image_file_path(self, episode_index: int, image_key: str, frame_index: int) -> Path:
+        fpath = DEFAULT_IMAGE_PATH.format(
+            image_key=image_key, episode_index=episode_index, frame_index=frame_index
+        )
+        return self._root / fpath
+
+    def _get_image_file_dir(self, episode_index: int, image_key: str) -> Path:
+        return self._get_image_file_path(episode_index, image_key, frame_index=0).parent
+
+    def _save_image(
+        self, image: torch.Tensor | np.ndarray | PIL.Image.Image, fpath: Path, compress_level: int = 1
+    ) -> None:
+        if self.image_writer is None:
+            if isinstance(image, torch.Tensor):
+                image = image.cpu().numpy()
+            write_image(image, fpath, compress_level=compress_level)
+        else:
+            self.image_writer.save_image(image=image, fpath=fpath, compress_level=compress_level)
+
+    def add_frame(self, frame: dict) -> None:
+        """
+        Add a single frame to the current episode buffer.
+
+        Apart from images written to a temporary directory, nothing is written to disk
+        until ``save_episode()`` is called.
+
+        The caller must provide all user-defined features plus ``"task"``, and must
+        not provide ``"timestamp"`` or ``"frame_index"``; those are computed
+        automatically.
+        """
+        # Convert torch to numpy if needed
+        for name in frame:
+            if isinstance(frame[name], torch.Tensor):
+                frame[name] = frame[name].numpy()
+
+        validate_frame(frame, self._meta.features)
+
+        if self.episode_buffer is None:
+            self.episode_buffer = self._create_episode_buffer()
+
+        # Automatically add frame_index and timestamp to episode buffer
+        frame_index = self.episode_buffer["size"]
+        timestamp = frame_index / self._meta.fps
+        self.episode_buffer["frame_index"].append(frame_index)
+        self.episode_buffer["timestamp"].append(timestamp)
+        self.episode_buffer["task"].append(frame.pop("task"))
+
+        # Start streaming encoder on first frame of episode
+        if frame_index == 0 and self._streaming_encoder is not None:
+            self._streaming_encoder.start_episode(
+                video_keys=list(self._meta.video_keys),
+                temp_dir=self._root,
+            )
+
+        # Add frame features to episode_buffer
+        for key in frame:
+            if key not in self._meta.features:
+                raise ValueError(
+                    f"An element of the frame is not in the features. '{key}' not in '{self._meta.features.keys()}'."
+                )
+
+            if self._meta.features[key]["dtype"] == "video" and self._streaming_encoder is not None:
+                self._streaming_encoder.feed_frame(key, frame[key])
+                self.episode_buffer[key].append(None)
+            elif self._meta.features[key]["dtype"] in ["image", "video"]:
+                img_path = self._get_image_file_path(
+                    episode_index=self.episode_buffer["episode_index"], image_key=key, frame_index=frame_index
+                )
+                if frame_index == 0:
+                    img_path.parent.mkdir(parents=True, exist_ok=True)
+                compress_level = 1 if self._meta.features[key]["dtype"] == "video" else 6
+                self._save_image(frame[key], img_path, compress_level)
+                self.episode_buffer[key].append(str(img_path))
+            else:
+                self.episode_buffer[key].append(frame[key])
+
+        self.episode_buffer["size"] += 1
+
+    def save_episode(
+        self,
+        episode_data: dict | None = None,
+        parallel_encoding: bool = True,
+    ) -> None:
+        """Save the current episode in self.episode_buffer to disk."""
+        episode_buffer = episode_data if episode_data is not None else self.episode_buffer
+
+        validate_episode_buffer(episode_buffer, self._meta.total_episodes, self._meta.features)
+
+        # size and task are special cases that won't be added to hf_dataset
+        episode_length = episode_buffer.pop("size")
+        tasks = episode_buffer.pop("task")
+        episode_tasks = list(set(tasks))
+        episode_index = episode_buffer["episode_index"]
+
+        episode_buffer["index"] = np.arange(self._meta.total_frames, self._meta.total_frames + episode_length)
+        episode_buffer["episode_index"] = np.full((episode_length,), episode_index)
+
+        # Update tasks and task indices with new tasks if any
+        self._meta.save_episode_tasks(episode_tasks)
+
+        # Given tasks in natural language, find their corresponding task indices
+        episode_buffer["task_index"] = np.array([self._meta.get_task_index(task) for task in tasks])
+
+        for key, ft in self._meta.features.items():
+            if key in ["index", "episode_index", "task_index"] or ft["dtype"] in ["image", "video"]:
+                continue
+            episode_buffer[key] = np.stack(episode_buffer[key])
+
+        # Wait for image writer to end, so that episode stats over images can be computed
+        self._wait_image_writer()
+
+        has_video_keys = len(self._meta.video_keys) > 0
+        use_streaming = self._streaming_encoder is not None and has_video_keys
+        use_batched_encoding = self._batch_encoding_size > 1
+
+        if use_streaming:
+            non_video_buffer = {
+                k: v
+                for k, v in episode_buffer.items()
+                if self._meta.features.get(k, {}).get("dtype") not in ("video",)
+            }
+            non_video_features = {k: v for k, v in self._meta.features.items() if v["dtype"] != "video"}
+            ep_stats = compute_episode_stats(non_video_buffer, non_video_features)
+        else:
+            ep_stats = compute_episode_stats(episode_buffer, self._meta.features)
+
+        ep_metadata = self._save_episode_data(episode_buffer)
+
+        if use_streaming:
+            streaming_results = self._streaming_encoder.finish_episode()
+            for video_key in self._meta.video_keys:
+                temp_path, video_stats = streaming_results[video_key]
+                if video_stats is not None:
+                    ep_stats[video_key] = {
+                        k: v if k == "count" else np.squeeze(v.reshape(1, -1, 1, 1) / 255.0, axis=0)
+                        for k, v in video_stats.items()
+                    }
+                ep_metadata.update(self._save_episode_video(video_key, episode_index, temp_path=temp_path))
+        elif has_video_keys and not use_batched_encoding:
+            num_cameras = len(self._meta.video_keys)
+            if parallel_encoding and num_cameras > 1:
+                with concurrent.futures.ProcessPoolExecutor(max_workers=num_cameras) as executor:
+                    future_to_key = {
+                        executor.submit(
+                            _encode_video_worker,
+                            video_key,
+                            episode_index,
+                            self._root,
+                            self._meta.fps,
+                            self._vcodec,
+                            self._encoder_threads,
+                        ): video_key
+                        for video_key in self._meta.video_keys
+                    }
+
+                    results = {}
+                    for future in concurrent.futures.as_completed(future_to_key):
+                        video_key = future_to_key[future]
+                        try:
+                            temp_path = future.result()
+                            results[video_key] = temp_path
+                        except Exception as exc:
+                            logger.error(f"Video encoding failed for {video_key}: {exc}")
+                            raise exc
+
+                for video_key in self._meta.video_keys:
+                    temp_path = results[video_key]
+                    ep_metadata.update(
+                        self._save_episode_video(video_key, episode_index, temp_path=temp_path)
+                    )
+            else:
+                for video_key in self._meta.video_keys:
+                    ep_metadata.update(self._save_episode_video(video_key, episode_index))
+
+        # `meta.save_episode` need to be executed after encoding the videos
+        self._meta.save_episode(episode_index, episode_length, episode_tasks, ep_stats, ep_metadata)
+
+        if has_video_keys and use_batched_encoding:
+            self._episodes_since_last_encoding += 1
+            if self._episodes_since_last_encoding == self._batch_encoding_size:
+                start_ep = self._meta.total_episodes - self._batch_encoding_size
+                end_ep = self._meta.total_episodes
+                self._batch_save_episode_video(start_ep, end_ep)
+                self._episodes_since_last_encoding = 0
+
+        if episode_data is None:
+            self.clear_episode_buffer(delete_images=len(self._meta.image_keys) > 0)
+
+    def _batch_save_episode_video(self, start_episode: int, end_episode: int | None = None) -> None:
+        """Batch save videos for multiple episodes."""
+        if end_episode is None:
+            end_episode = self._meta.total_episodes
+
+        logger.info(
+            f"Batch encoding {self._batch_encoding_size} videos for episodes {start_episode} to {end_episode - 1}"
+        )
+
+        chunk_idx = self._meta.episodes[start_episode]["data/chunk_index"]
+        file_idx = self._meta.episodes[start_episode]["data/file_index"]
+        episode_df_path = self._root / DEFAULT_EPISODES_PATH.format(
+            chunk_index=chunk_idx, file_index=file_idx
+        )
+        episode_df = pd.read_parquet(episode_df_path)
+
+        for ep_idx in range(start_episode, end_episode):
+            logger.info(f"Encoding videos for episode {ep_idx}")
+
+            if (
+                self._meta.episodes[ep_idx]["data/chunk_index"] != chunk_idx
+                or self._meta.episodes[ep_idx]["data/file_index"] != file_idx
+            ):
+                episode_df.to_parquet(episode_df_path)
+                self._meta.episodes = load_episodes(self._root)
+
+                chunk_idx = self._meta.episodes[ep_idx]["data/chunk_index"]
+                file_idx = self._meta.episodes[ep_idx]["data/file_index"]
+                episode_df_path = self._root / DEFAULT_EPISODES_PATH.format(
+                    chunk_index=chunk_idx, file_index=file_idx
+                )
+                episode_df = pd.read_parquet(episode_df_path)
+
+            video_ep_metadata = {}
+            for video_key in self._meta.video_keys:
+                video_ep_metadata.update(self._save_episode_video(video_key, ep_idx))
+            video_ep_metadata.pop("episode_index")
+            video_ep_df = pd.DataFrame(video_ep_metadata, index=[ep_idx]).convert_dtypes(
+                dtype_backend="pyarrow"
+            )
+
+            episode_df = episode_df.combine_first(video_ep_df)
+            episode_df.to_parquet(episode_df_path)
+            self._meta.episodes = load_episodes(self._root)
+
+    def _save_episode_data(self, episode_buffer: dict) -> dict:
+        """Save episode data to a parquet file."""
+        # Use metadata features as the authoritative schema
+        hf_features = get_hf_features_from_features(self._meta.features)
+        ep_dict = {key: episode_buffer[key] for key in hf_features}
+        ep_dataset = datasets.Dataset.from_dict(ep_dict, features=hf_features, split="train")
+        ep_dataset = embed_images(ep_dataset)
+        ep_num_frames = len(ep_dataset)
+
+        if self._latest_episode is None:
+            chunk_idx, file_idx = 0, 0
+            global_frame_index = 0
+            self._current_file_start_frame = 0
+            if self._meta.episodes is not None and len(self._meta.episodes) > 0:
+                latest_ep = self._meta.episodes[-1]
+                global_frame_index = latest_ep["dataset_to_index"]
+                chunk_idx = latest_ep["data/chunk_index"]
+                file_idx = latest_ep["data/file_index"]
+
+                chunk_idx, file_idx = update_chunk_file_indices(chunk_idx, file_idx, self._meta.chunks_size)
+                self._current_file_start_frame = global_frame_index
+        else:
+            latest_ep = self._latest_episode
+            chunk_idx = latest_ep["data/chunk_index"]
+            file_idx = latest_ep["data/file_index"]
+            global_frame_index = latest_ep["index"][-1] + 1
+
+            latest_path = self._root / self._meta.data_path.format(chunk_index=chunk_idx, file_index=file_idx)
+            latest_size_in_mb = get_file_size_in_mb(latest_path)
+
+            frames_in_current_file = global_frame_index - self._current_file_start_frame
+            av_size_per_frame = (
+                latest_size_in_mb / frames_in_current_file if frames_in_current_file > 0 else 0
+            )
+
+            if latest_size_in_mb + av_size_per_frame * ep_num_frames >= self._meta.data_files_size_in_mb:
+                chunk_idx, file_idx = update_chunk_file_indices(chunk_idx, file_idx, self._meta.chunks_size)
+                self.close_writer()
+                self._current_file_start_frame = global_frame_index
+
+        ep_dict["data/chunk_index"] = chunk_idx
+        ep_dict["data/file_index"] = file_idx
+
+        path = self._root / self._meta.data_path.format(chunk_index=chunk_idx, file_index=file_idx)
+        path.parent.mkdir(parents=True, exist_ok=True)
+
+        table = ep_dataset.with_format("arrow")[:]
+        if not self._pq_writer:
+            self._pq_writer = pq.ParquetWriter(
+                path, schema=table.schema, compression="snappy", use_dictionary=True
+            )
+        self._pq_writer.write_table(table)
+
+        metadata = {
+            "data/chunk_index": chunk_idx,
+            "data/file_index": file_idx,
+            "dataset_from_index": global_frame_index,
+            "dataset_to_index": global_frame_index + ep_num_frames,
+        }
+
+        self._latest_episode = {**ep_dict, **metadata}
+        self._recorded_frames += ep_num_frames
+
+        return metadata
+
+    def _save_episode_video(
+        self,
+        video_key: str,
+        episode_index: int,
+        temp_path: Path | None = None,
+    ) -> dict:
+        if temp_path is None:
+            ep_path = self._encode_temporary_episode_video(video_key, episode_index)
+        else:
+            ep_path = temp_path
+
+        ep_size_in_mb = get_file_size_in_mb(ep_path)
+        ep_duration_in_s = get_video_duration_in_s(ep_path)
+
+        if (
+            episode_index == 0
+            or self._meta.latest_episode is None
+            or f"videos/{video_key}/chunk_index" not in self._meta.latest_episode
+        ):
+            chunk_idx, file_idx = 0, 0
+            if self._meta.episodes is not None and len(self._meta.episodes) > 0:
+                old_chunk_idx = self._meta.episodes[-1][f"videos/{video_key}/chunk_index"]
+                old_file_idx = self._meta.episodes[-1][f"videos/{video_key}/file_index"]
+                chunk_idx, file_idx = update_chunk_file_indices(
+                    old_chunk_idx, old_file_idx, self._meta.chunks_size
+                )
+            latest_duration_in_s = 0.0
+            new_path = self._root / self._meta.video_path.format(
+                video_key=video_key, chunk_index=chunk_idx, file_index=file_idx
+            )
+            new_path.parent.mkdir(parents=True, exist_ok=True)
+            shutil.move(str(ep_path), str(new_path))
+        else:
+            latest_ep = self._meta.latest_episode
+            chunk_idx = latest_ep[f"videos/{video_key}/chunk_index"][0]
+            file_idx = latest_ep[f"videos/{video_key}/file_index"][0]
+
+            latest_path = self._root / self._meta.video_path.format(
+                video_key=video_key, chunk_index=chunk_idx, file_index=file_idx
+            )
+            latest_size_in_mb = get_file_size_in_mb(latest_path)
+            latest_duration_in_s = latest_ep[f"videos/{video_key}/to_timestamp"][0]
+
+            if latest_size_in_mb + ep_size_in_mb >= self._meta.video_files_size_in_mb:
+                chunk_idx, file_idx = update_chunk_file_indices(chunk_idx, file_idx, self._meta.chunks_size)
+                new_path = self._root / self._meta.video_path.format(
+                    video_key=video_key, chunk_index=chunk_idx, file_index=file_idx
+                )
+                new_path.parent.mkdir(parents=True, exist_ok=True)
+                shutil.move(str(ep_path), str(new_path))
+                latest_duration_in_s = 0.0
+            else:
+                concatenate_video_files(
+                    [latest_path, ep_path],
+                    latest_path,
+                )
+
+        # Remove temporary directory
+        shutil.rmtree(str(ep_path.parent))
+
+        # Update video info (only needed when first episode is encoded)
+        if episode_index == 0:
+            self._meta.update_video_info(video_key)
+            write_info(self._meta.info, self._meta.root)
+
+        metadata = {
+            "episode_index": episode_index,
+            f"videos/{video_key}/chunk_index": chunk_idx,
+            f"videos/{video_key}/file_index": file_idx,
+            f"videos/{video_key}/from_timestamp": latest_duration_in_s,
+            f"videos/{video_key}/to_timestamp": latest_duration_in_s + ep_duration_in_s,
+        }
+        return metadata
+
+    def clear_episode_buffer(self, delete_images: bool = True) -> None:
+        """Discard the current episode buffer and optionally delete temp images.
+
+        Args:
+            delete_images: If ``True``, remove temporary image directories
+                written for the current episode.
+        """
+        # Cancel streaming encoder if active
+        if self._streaming_encoder is not None:
+            self._streaming_encoder.cancel_episode()
+
+        if delete_images:
+            if self.image_writer is not None:
+                self._wait_image_writer()
+            episode_index = self.episode_buffer["episode_index"]
+            # episode_index is `int` when freshly created, but becomes `np.ndarray` after
+            # save_episode() mutates the buffer. Handle both types here.
+            if isinstance(episode_index, np.ndarray):
+                episode_index = episode_index.item() if episode_index.size == 1 else episode_index[0]
+            for cam_key in self._meta.image_keys:
+                img_dir = self._get_image_file_dir(episode_index, cam_key)
+                if img_dir.is_dir():
+                    shutil.rmtree(img_dir)
+
+        self.episode_buffer = self._create_episode_buffer()
+
+    def start_image_writer(self, num_processes: int = 0, num_threads: int = 4) -> None:
+        """Start an :class:`AsyncImageWriter` for background image persistence.
+
+        Args:
+            num_processes: Number of subprocesses. ``0`` means threads only.
+            num_threads: Number of threads per process.
+        """
+        if isinstance(self.image_writer, AsyncImageWriter):
+            logger.warning(
+                "You are starting a new AsyncImageWriter that is replacing an already existing one in the dataset."
+            )
+
+        self.image_writer = AsyncImageWriter(
+            num_processes=num_processes,
+            num_threads=num_threads,
+        )
+
+    def stop_image_writer(self) -> None:
+        """Stop the image writer (needed before pickling the dataset for DataLoader)."""
+        if self.image_writer is not None:
+            self.image_writer.stop()
+            self.image_writer = None
+
+    def _wait_image_writer(self) -> None:
+        """Wait for asynchronous image writer to finish."""
+        if self.image_writer is not None:
+            self.image_writer.wait_until_done()
+
+    def _encode_temporary_episode_video(self, video_key: str, episode_index: int) -> Path:
+        """Use ffmpeg to convert frames stored as png into mp4 videos."""
+        return _encode_video_worker(
+            video_key, episode_index, self._root, self._meta.fps, self._vcodec, self._encoder_threads
+        )
+
+    def close_writer(self) -> None:
+        """Close and cleanup the parquet writer if it exists."""
+        if self._pq_writer is not None:
+            self._pq_writer.close()
+            self._pq_writer = None
+
+    def flush_pending_videos(self) -> None:
+        """Flush any pending video encoding (streaming or batch).
+
+        For streaming encoding: closes the encoder.
+        For batch encoding: encodes any remaining episodes that haven't been batch-encoded yet.
+        """
+        if self._streaming_encoder is not None:
+            self._streaming_encoder.close()
+        elif self._episodes_since_last_encoding > 0:
+            start_ep = self._meta.total_episodes - self._episodes_since_last_encoding
+            end_ep = self._meta.total_episodes
+            logger.info(
+                f"Encoding remaining {self._episodes_since_last_encoding} episodes, "
+                f"from episode {start_ep} to {end_ep - 1}"
+            )
+            self._batch_save_episode_video(start_ep, end_ep)
+
+    def cancel_pending_videos(self) -> None:
+        """Cancel any in-progress streaming encoding without flushing."""
+        if self._streaming_encoder is not None:
+            self._streaming_encoder.cancel_episode()
+
+    def cleanup_interrupted_episode(self, episode_index: int) -> None:
+        """Remove temporary image directories for an interrupted episode."""
+        for key in self._meta.video_keys:
+            img_dir = self._get_image_file_path(
+                episode_index=episode_index, image_key=key, frame_index=0
+            ).parent
+            if img_dir.exists():
+                logger.debug(
+                    f"Cleaning up interrupted episode images for episode {episode_index}, camera {key}"
+                )
+                shutil.rmtree(img_dir)
+
+    def finalize(self) -> None:
+        """Flush all pending work and release all resources.
+
+        Idempotent — safe to call multiple times.
+        """
+        if getattr(self, "_finalized", False):
+            return
+        # 1. Wait for async image writes to complete, then stop
+        if self.image_writer is not None:
+            self.image_writer.wait_until_done()
+            self.image_writer.stop()
+            self.image_writer = None
+        # 2. Flush pending video encoding (streaming or batch)
+        self.flush_pending_videos()
+        # 3. Close own parquet writer
+        self.close_writer()
+        # 4. Finalize metadata (idempotent)
+        self._meta.finalize()
+        self._finalized = True
+
+    def __del__(self):
+        """Safety net: release resources on garbage collection."""
+        # During interpreter shutdown, referenced objects may already be collected.
+        with contextlib.suppress(Exception):
+            self.finalize()

src/lerobot/datasets/factory.py

@@ -20,11 +20,9 @@ import torch
 
 from lerobot.configs.policies import PreTrainedConfig
 from lerobot.configs.train import TrainPipelineConfig
-from lerobot.datasets.lerobot_dataset import (
-    LeRobotDataset,
-    LeRobotDatasetMetadata,
-    MultiLeRobotDataset,
-)
+from lerobot.datasets.dataset_metadata import LeRobotDatasetMetadata
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+from lerobot.datasets.multi_dataset import MultiLeRobotDataset
 from lerobot.datasets.streaming_dataset import StreamingLeRobotDataset
 from lerobot.datasets.transforms import ImageTransforms
 from lerobot.utils.constants import ACTION, OBS_PREFIX, REWARD

src/lerobot/datasets/feature_utils.py

@@ -0,0 +1,556 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from pprint import pformat
+from typing import Any
+
+import datasets
+import numpy as np
+from PIL import Image as PILImage
+
+from lerobot.configs.types import FeatureType, PolicyFeature
+from lerobot.datasets.utils import (
+    DEFAULT_CHUNK_SIZE,
+    DEFAULT_DATA_FILE_SIZE_IN_MB,
+    DEFAULT_DATA_PATH,
+    DEFAULT_FEATURES,
+    DEFAULT_VIDEO_FILE_SIZE_IN_MB,
+    DEFAULT_VIDEO_PATH,
+)
+from lerobot.utils.constants import ACTION, OBS_ENV_STATE, OBS_STR
+from lerobot.utils.utils import is_valid_numpy_dtype_string
+
+
+def get_hf_features_from_features(features: dict) -> datasets.Features:
+    """Convert a LeRobot features dictionary to a `datasets.Features` object.
+
+    Args:
+        features (dict): A LeRobot-style feature dictionary.
+
+    Returns:
+        datasets.Features: The corresponding Hugging Face `datasets.Features` object.
+
+    Raises:
+        ValueError: If a feature has an unsupported shape.
+    """
+    hf_features = {}
+    for key, ft in features.items():
+        if ft["dtype"] == "video":
+            continue
+        elif ft["dtype"] == "image":
+            hf_features[key] = datasets.Image()
+        elif ft["shape"] == (1,):
+            hf_features[key] = datasets.Value(dtype=ft["dtype"])
+        elif len(ft["shape"]) == 1:
+            hf_features[key] = datasets.Sequence(
+                length=ft["shape"][0], feature=datasets.Value(dtype=ft["dtype"])
+            )
+        elif len(ft["shape"]) == 2:
+            hf_features[key] = datasets.Array2D(shape=ft["shape"], dtype=ft["dtype"])
+        elif len(ft["shape"]) == 3:
+            hf_features[key] = datasets.Array3D(shape=ft["shape"], dtype=ft["dtype"])
+        elif len(ft["shape"]) == 4:
+            hf_features[key] = datasets.Array4D(shape=ft["shape"], dtype=ft["dtype"])
+        elif len(ft["shape"]) == 5:
+            hf_features[key] = datasets.Array5D(shape=ft["shape"], dtype=ft["dtype"])
+        else:
+            raise ValueError(f"Corresponding feature is not valid: {ft}")
+
+    return datasets.Features(hf_features)
+
+
+def _validate_feature_names(features: dict[str, dict]) -> None:
+    """Validate that feature names do not contain invalid characters.
+
+    Args:
+        features (dict): The LeRobot features dictionary.
+
+    Raises:
+        ValueError: If any feature name contains '/'.
+    """
+    invalid_features = {name: ft for name, ft in features.items() if "/" in name}
+    if invalid_features:
+        raise ValueError(f"Feature names should not contain '/'. Found '/' in '{invalid_features}'.")
+
+
+def hw_to_dataset_features(
+    hw_features: dict[str, type | tuple], prefix: str, use_video: bool = True
+) -> dict[str, dict]:
+    """Convert hardware-specific features to a LeRobot dataset feature dictionary.
+
+    This function takes a dictionary describing hardware outputs (like joint states
+    or camera image shapes) and formats it into the standard LeRobot feature
+    specification.
+
+    Args:
+        hw_features (dict): Dictionary mapping feature names to their type (float for
+            joints) or shape (tuple for images).
+        prefix (str): The prefix to add to the feature keys (e.g., "observation"
+            or "action").
+        use_video (bool): If True, image features are marked as "video", otherwise "image".
+
+    Returns:
+        dict: A LeRobot features dictionary.
+    """
+    features = {}
+    joint_fts = {
+        key: ftype
+        for key, ftype in hw_features.items()
+        if ftype is float or (isinstance(ftype, PolicyFeature) and ftype.type != FeatureType.VISUAL)
+    }
+    cam_fts = {key: shape for key, shape in hw_features.items() if isinstance(shape, tuple)}
+
+    if joint_fts and prefix == ACTION:
+        features[prefix] = {
+            "dtype": "float32",
+            "shape": (len(joint_fts),),
+            "names": list(joint_fts),
+        }
+
+    if joint_fts and prefix == OBS_STR:
+        features[f"{prefix}.state"] = {
+            "dtype": "float32",
+            "shape": (len(joint_fts),),
+            "names": list(joint_fts),
+        }
+
+    for key, shape in cam_fts.items():
+        features[f"{prefix}.images.{key}"] = {
+            "dtype": "video" if use_video else "image",
+            "shape": shape,
+            "names": ["height", "width", "channels"],
+        }
+
+    _validate_feature_names(features)
+    return features
+
+
+def build_dataset_frame(
+    ds_features: dict[str, dict], values: dict[str, Any], prefix: str
+) -> dict[str, np.ndarray]:
+    """Construct a single data frame from raw values based on dataset features.
+
+    A "frame" is a dictionary containing all the data for a single timestep,
+    formatted as numpy arrays according to the feature specification.
+
+    Args:
+        ds_features (dict): The LeRobot dataset features dictionary.
+        values (dict): A dictionary of raw values from the hardware/environment.
+        prefix (str): The prefix to filter features by (e.g., "observation"
+            or "action").
+
+    Returns:
+        dict: A dictionary representing a single frame of data.
+    """
+    frame = {}
+    for key, ft in ds_features.items():
+        if key in DEFAULT_FEATURES or not key.startswith(prefix):
+            continue
+        elif ft["dtype"] == "float32" and len(ft["shape"]) == 1:
+            frame[key] = np.array([values[name] for name in ft["names"]], dtype=np.float32)
+        elif ft["dtype"] in ["image", "video"]:
+            frame[key] = values[key.removeprefix(f"{prefix}.images.")]
+
+    return frame
+
+
+def dataset_to_policy_features(features: dict[str, dict]) -> dict[str, PolicyFeature]:
+    """Convert dataset features to policy features.
+
+    This function transforms the dataset's feature specification into a format
+    that a policy can use, classifying features by type (e.g., visual, state,
+    action) and ensuring correct shapes (e.g., channel-first for images).
+
+    Args:
+        features (dict): The LeRobot dataset features dictionary.
+
+    Returns:
+        dict: A dictionary mapping feature keys to `PolicyFeature` objects.
+
+    Raises:
+        ValueError: If an image feature does not have a 3D shape.
+    """
+    # TODO(aliberts): Implement "type" in dataset features and simplify this
+    policy_features = {}
+    for key, ft in features.items():
+        shape = ft["shape"]
+        if ft["dtype"] in ["image", "video"]:
+            type = FeatureType.VISUAL
+            if len(shape) != 3:
+                raise ValueError(f"Number of dimensions of {key} != 3 (shape={shape})")
+
+            names = ft["names"]
+            # Backward compatibility for "channel" which is an error introduced in LeRobotDataset v2.0 for ported datasets.
+            if names[2] in ["channel", "channels"]:  # (h, w, c) -> (c, h, w)
+                shape = (shape[2], shape[0], shape[1])
+        elif key == OBS_ENV_STATE:
+            type = FeatureType.ENV
+        elif key.startswith(OBS_STR):
+            type = FeatureType.STATE
+        elif key.startswith(ACTION):
+            type = FeatureType.ACTION
+        else:
+            continue
+
+        policy_features[key] = PolicyFeature(
+            type=type,
+            shape=shape,
+        )
+
+    return policy_features
+
+
+def combine_feature_dicts(*dicts: dict) -> dict:
+    """Merge LeRobot grouped feature dicts.
+
+    - For 1D numeric specs (dtype not image/video/string) with "names": we merge the names and recompute the shape.
+    - For others (e.g. `observation.images.*`), the last one wins (if they are identical).
+
+    Args:
+        *dicts: A variable number of LeRobot feature dictionaries to merge.
+
+    Returns:
+        dict: A single merged feature dictionary.
+
+    Raises:
+        ValueError: If there's a dtype mismatch for a feature being merged.
+    """
+    out: dict = {}
+    for d in dicts:
+        for key, value in d.items():
+            if not isinstance(value, dict):
+                out[key] = value
+                continue
+
+            dtype = value.get("dtype")
+            shape = value.get("shape")
+            is_vector = (
+                dtype not in ("image", "video", "string")
+                and isinstance(shape, tuple)
+                and len(shape) == 1
+                and "names" in value
+            )
+
+            if is_vector:
+                # Initialize or retrieve the accumulating dict for this feature key
+                target = out.setdefault(key, {"dtype": dtype, "names": [], "shape": (0,)})
+                # Ensure consistent data types across merged entries
+                if "dtype" in target and dtype != target["dtype"]:
+                    raise ValueError(f"dtype mismatch for '{key}': {target['dtype']} vs {dtype}")
+
+                # Merge feature names: append only new ones to preserve order without duplicates
+                seen = set(target["names"])
+                for n in value["names"]:
+                    if n not in seen:
+                        target["names"].append(n)
+                        seen.add(n)
+                # Recompute the shape to reflect the updated number of features
+                target["shape"] = (len(target["names"]),)
+            else:
+                # For images/videos and non-1D entries: override with the latest definition
+                out[key] = value
+    return out
+
+
+def create_empty_dataset_info(
+    codebase_version: str,
+    fps: int,
+    features: dict,
+    use_videos: bool,
+    robot_type: str | None = None,
+    chunks_size: int | None = None,
+    data_files_size_in_mb: int | None = None,
+    video_files_size_in_mb: int | None = None,
+) -> dict:
+    """Create a template dictionary for a new dataset's `info.json`.
+
+    Args:
+        codebase_version (str): The version of the LeRobot codebase.
+        fps (int): The frames per second of the data.
+        features (dict): The LeRobot features dictionary for the dataset.
+        use_videos (bool): Whether the dataset will store videos.
+        robot_type (str | None): The type of robot used, if any.
+
+    Returns:
+        dict: A dictionary with the initial dataset metadata.
+    """
+    return {
+        "codebase_version": codebase_version,
+        "robot_type": robot_type,
+        "total_episodes": 0,
+        "total_frames": 0,
+        "total_tasks": 0,
+        "chunks_size": chunks_size or DEFAULT_CHUNK_SIZE,
+        "data_files_size_in_mb": data_files_size_in_mb or DEFAULT_DATA_FILE_SIZE_IN_MB,
+        "video_files_size_in_mb": video_files_size_in_mb or DEFAULT_VIDEO_FILE_SIZE_IN_MB,
+        "fps": fps,
+        "splits": {},
+        "data_path": DEFAULT_DATA_PATH,
+        "video_path": DEFAULT_VIDEO_PATH if use_videos else None,
+        "features": features,
+    }
+
+
+def check_delta_timestamps(
+    delta_timestamps: dict[str, list[float]], fps: int, tolerance_s: float, raise_value_error: bool = True
+) -> bool:
+    """Check if delta timestamps are multiples of 1/fps +/- tolerance.
+
+    This ensures that adding these delta timestamps to any existing timestamp in
+    the dataset will result in a value that aligns with the dataset's frame rate.
+
+    Args:
+        delta_timestamps (dict): A dictionary where values are lists of time
+            deltas in seconds.
+        fps (int): The frames per second of the dataset.
+        tolerance_s (float): The allowed tolerance in seconds.
+        raise_value_error (bool): If True, raises an error on failure.
+
+    Returns:
+        bool: True if all deltas are valid, False otherwise.
+
+    Raises:
+        ValueError: If any delta is outside the tolerance and `raise_value_error` is True.
+    """
+    outside_tolerance = {}
+    for key, delta_ts in delta_timestamps.items():
+        within_tolerance = [abs(ts * fps - round(ts * fps)) / fps <= tolerance_s for ts in delta_ts]
+        if not all(within_tolerance):
+            outside_tolerance[key] = [
+                ts for ts, is_within in zip(delta_ts, within_tolerance, strict=True) if not is_within
+            ]
+
+    if len(outside_tolerance) > 0:
+        if raise_value_error:
+            raise ValueError(
+                f"""
+                The following delta_timestamps are found outside of tolerance range.
+                Please make sure they are multiples of 1/{fps} +/- tolerance and adjust
+                their values accordingly.
+                \n{pformat(outside_tolerance)}
+                """
+            )
+        return False
+
+    return True
+
+
+def get_delta_indices(delta_timestamps: dict[str, list[float]], fps: int) -> dict[str, list[int]]:
+    """Convert delta timestamps in seconds to delta indices in frames.
+
+    Args:
+        delta_timestamps (dict): A dictionary of time deltas in seconds.
+        fps (int): The frames per second of the dataset.
+
+    Returns:
+        dict: A dictionary of frame delta indices.
+    """
+    delta_indices = {}
+    for key, delta_ts in delta_timestamps.items():
+        delta_indices[key] = [round(d * fps) for d in delta_ts]
+
+    return delta_indices
+
+
+def validate_frame(frame: dict, features: dict) -> None:
+    # DEFAULT_FEATURES (timestamp, frame_index, episode_index, index, task_index) are
+    # auto-populated by the recording pipeline (add_frame / save_episode) and must not
+    # be supplied by the caller. Excluding them here means any frame dict that contains
+    # these keys will be rejected as extra features.
+    expected_features = set(features) - set(DEFAULT_FEATURES)
+    actual_features = set(frame)
+
+    # task is a special required field that's not part of regular features
+    if "task" not in actual_features:
+        raise ValueError("Feature mismatch in `frame` dictionary:\nMissing features: {'task'}\n")
+
+    # Remove task from actual_features for regular feature validation
+    actual_features_for_validation = actual_features - {"task"}
+
+    error_message = validate_features_presence(actual_features_for_validation, expected_features)
+
+    common_features = actual_features_for_validation & expected_features
+    for name in common_features:
+        error_message += validate_feature_dtype_and_shape(name, features[name], frame[name])
+
+    if error_message:
+        raise ValueError(error_message)
+
+
+def validate_features_presence(actual_features: set[str], expected_features: set[str]) -> str:
+    """Check for missing or extra features in a frame.
+
+    Args:
+        actual_features (set[str]): The set of feature names present in the frame.
+        expected_features (set[str]): The set of feature names expected in the frame.
+
+    Returns:
+        str: An error message string if there's a mismatch, otherwise an empty string.
+    """
+    error_message = ""
+    missing_features = expected_features - actual_features
+    extra_features = actual_features - expected_features
+
+    if missing_features or extra_features:
+        error_message += "Feature mismatch in `frame` dictionary:\n"
+        if missing_features:
+            error_message += f"Missing features: {missing_features}\n"
+        if extra_features:
+            error_message += f"Extra features: {extra_features}\n"
+
+    return error_message
+
+
+def validate_feature_dtype_and_shape(
+    name: str, feature: dict, value: np.ndarray | PILImage.Image | str
+) -> str:
+    """Validate the dtype and shape of a single feature's value.
+
+    Args:
+        name (str): The name of the feature.
+        feature (dict): The feature specification from the LeRobot features dictionary.
+        value: The value of the feature to validate.
+
+    Returns:
+        str: An error message if validation fails, otherwise an empty string.
+
+    Raises:
+        NotImplementedError: If the feature dtype is not supported for validation.
+    """
+    expected_dtype = feature["dtype"]
+    expected_shape = feature["shape"]
+    if is_valid_numpy_dtype_string(expected_dtype):
+        return validate_feature_numpy_array(name, expected_dtype, expected_shape, value)
+    elif expected_dtype in ["image", "video"]:
+        return validate_feature_image_or_video(name, expected_shape, value)
+    elif expected_dtype == "string":
+        return validate_feature_string(name, value)
+    else:
+        raise NotImplementedError(f"The feature dtype '{expected_dtype}' is not implemented yet.")
+
+
+def validate_feature_numpy_array(
+    name: str, expected_dtype: str, expected_shape: list[int], value: np.ndarray
+) -> str:
+    """Validate a feature that is expected to be a numpy array.
+
+    Args:
+        name (str): The name of the feature.
+        expected_dtype (str): The expected numpy dtype as a string.
+        expected_shape (list[int]): The expected shape.
+        value (np.ndarray): The numpy array to validate.
+
+    Returns:
+        str: An error message if validation fails, otherwise an empty string.
+    """
+    error_message = ""
+    if isinstance(value, np.ndarray):
+        actual_dtype = value.dtype
+        actual_shape = value.shape
+
+        if actual_dtype != np.dtype(expected_dtype):
+            error_message += f"The feature '{name}' of dtype '{actual_dtype}' is not of the expected dtype '{expected_dtype}'.\n"
+
+        if actual_shape != expected_shape:
+            error_message += f"The feature '{name}' of shape '{actual_shape}' does not have the expected shape '{expected_shape}'.\n"
+    else:
+        error_message += f"The feature '{name}' is not a 'np.ndarray'. Expected type is '{expected_dtype}', but type '{type(value)}' provided instead.\n"
+
+    return error_message
+
+
+def validate_feature_image_or_video(
+    name: str, expected_shape: list[str], value: np.ndarray | PILImage.Image
+) -> str:
+    """Validate a feature that is expected to be an image or video frame.
+
+    Accepts `np.ndarray` (channel-first or channel-last) or `PIL.Image.Image`.
+
+    Args:
+        name (str): The name of the feature.
+        expected_shape (list[str]): The expected shape (C, H, W).
+        value: The image data to validate.
+
+    Returns:
+        str: An error message if validation fails, otherwise an empty string.
+    """
+    # Note: The check of pixels range ([0,1] for float and [0,255] for uint8) is done by the image writer threads.
+    error_message = ""
+    if isinstance(value, np.ndarray):
+        actual_shape = value.shape
+        c, h, w = expected_shape
+        if len(actual_shape) != 3 or (actual_shape != (c, h, w) and actual_shape != (h, w, c)):
+            error_message += f"The feature '{name}' of shape '{actual_shape}' does not have the expected shape '{(c, h, w)}' or '{(h, w, c)}'.\n"
+    elif isinstance(value, PILImage.Image):
+        pass
+    else:
+        error_message += f"The feature '{name}' is expected to be of type 'PIL.Image' or 'np.ndarray' channel first or channel last, but type '{type(value)}' provided instead.\n"
+
+    return error_message
+
+
+def validate_feature_string(name: str, value: str) -> str:
+    """Validate a feature that is expected to be a string.
+
+    Args:
+        name (str): The name of the feature.
+        value (str): The value to validate.
+
+    Returns:
+        str: An error message if validation fails, otherwise an empty string.
+    """
+    if not isinstance(value, str):
+        return f"The feature '{name}' is expected to be of type 'str', but type '{type(value)}' provided instead.\n"
+    return ""
+
+
+def validate_episode_buffer(episode_buffer: dict, total_episodes: int, features: dict) -> None:
+    """Validate the episode buffer before it's written to disk.
+
+    Ensures the buffer has the required keys, contains at least one frame, and
+    has features consistent with the dataset's specification.
+
+    Args:
+        episode_buffer (dict): The buffer containing data for a single episode.
+        total_episodes (int): The current total number of episodes in the dataset.
+        features (dict): The LeRobot features dictionary for the dataset.
+
+    Raises:
+        ValueError: If the buffer is invalid.
+        NotImplementedError: If the episode index is manually set and doesn't match.
+    """
+    if "size" not in episode_buffer:
+        raise ValueError("size key not found in episode_buffer")
+
+    if "task" not in episode_buffer:
+        raise ValueError("task key not found in episode_buffer")
+
+    if episode_buffer["episode_index"] != total_episodes:
+        # TODO(aliberts): Add option to use existing episode_index
+        raise NotImplementedError(
+            "You might have manually provided the episode_buffer with an episode_index that doesn't "
+            "match the total number of episodes already in the dataset. This is not supported for now."
+        )
+
+    if episode_buffer["size"] == 0:
+        raise ValueError("You must add one or several frames with `add_frame` before calling `add_episode`.")
+
+    buffer_keys = set(episode_buffer.keys()) - {"task", "size"}
+    if not buffer_keys == set(features):
+        raise ValueError(
+            f"Features from `episode_buffer` don't match the ones in `features`."
+            f"In episode_buffer not in features: {buffer_keys - set(features)}"
+            f"In features not in episode_buffer: {set(features) - buffer_keys}"
+        )

src/lerobot/datasets/image_writer.py

@@ -13,6 +13,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import logging
 import multiprocessing
 import queue
 import threading
@@ -22,6 +23,8 @@ import numpy as np
 import PIL.Image
 import torch
 
+logger = logging.getLogger(__name__)
+
 
 def safe_stop_image_writer(func):
     def wrapper(*args, **kwargs):
@@ -29,10 +32,10 @@ def safe_stop_image_writer(func):
             return func(*args, **kwargs)
         except Exception as e:
             dataset = kwargs.get("dataset")
-            image_writer = getattr(dataset, "image_writer", None) if dataset else None
-            if image_writer is not None:
-                print("Waiting for image writer to terminate...")
-                image_writer.stop()
+            writer = getattr(dataset, "writer", None) if dataset else None
+            if writer is not None and writer.image_writer is not None:
+                logger.warning("Waiting for image writer to terminate...")
+                writer.image_writer.stop()
             raise e
 
     return wrapper
@@ -89,8 +92,7 @@ def write_image(image: np.ndarray | PIL.Image.Image, fpath: Path, compress_level
             PIL.Image.Image object.
 
     Side Effects:
-        Prints an error message to the console if the image writing process
-        fails for any reason.
+        Logs an error message if the image writing process fails for any reason.
     """
     try:
         if isinstance(image, np.ndarray):
@@ -101,7 +103,7 @@ def write_image(image: np.ndarray | PIL.Image.Image, fpath: Path, compress_level
             raise TypeError(f"Unsupported image type: {type(image)}")
         img.save(fpath, compress_level=compress_level)
     except Exception as e:
-        print(f"Error writing image {fpath}: {e}")
+        logger.error("Error writing image %s: %s", fpath, e)
 
 
 def worker_thread_loop(queue: queue.Queue):

src/lerobot/datasets/io_utils.py

@@ -0,0 +1,342 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import json
+from pathlib import Path
+from typing import Any
+
+import datasets
+import numpy as np
+import pandas
+import pandas as pd
+import pyarrow.dataset as pa_ds
+import pyarrow.parquet as pq
+import torch
+from datasets import Dataset
+from datasets.table import embed_table_storage
+from PIL import Image as PILImage
+from torchvision import transforms
+
+from lerobot.datasets.utils import (
+    DEFAULT_DATA_FILE_SIZE_IN_MB,
+    DEFAULT_EPISODES_PATH,
+    DEFAULT_SUBTASKS_PATH,
+    DEFAULT_TASKS_PATH,
+    EPISODES_DIR,
+    INFO_PATH,
+    STATS_PATH,
+    flatten_dict,
+    serialize_dict,
+    unflatten_dict,
+)
+from lerobot.utils.utils import SuppressProgressBars
+
+
+def get_parquet_file_size_in_mb(parquet_path: str | Path) -> float:
+    metadata = pq.read_metadata(parquet_path)
+    total_uncompressed_size = 0
+    for row_group in range(metadata.num_row_groups):
+        rg_metadata = metadata.row_group(row_group)
+        for column in range(rg_metadata.num_columns):
+            col_metadata = rg_metadata.column(column)
+            total_uncompressed_size += col_metadata.total_uncompressed_size
+    return total_uncompressed_size / (1024**2)
+
+
+def get_hf_dataset_size_in_mb(hf_ds: Dataset) -> int:
+    return hf_ds.data.nbytes // (1024**2)
+
+
+def load_nested_dataset(
+    pq_dir: Path, features: datasets.Features | None = None, episodes: list[int] | None = None
+) -> Dataset:
+    """Find parquet files in provided directory {pq_dir}/chunk-xxx/file-xxx.parquet
+    Convert parquet files to pyarrow memory mapped in a cache folder for efficient RAM usage
+    Concatenate all pyarrow references to return HF Dataset format
+
+    Args:
+        pq_dir: Directory containing parquet files
+        features: Optional features schema to ensure consistent loading of complex types like images
+        episodes: Optional list of episode indices to filter. Uses PyArrow predicate pushdown for efficiency.
+    """
+    paths = sorted(pq_dir.glob("*/*.parquet"))
+    if len(paths) == 0:
+        raise FileNotFoundError(f"Provided directory does not contain any parquet file: {pq_dir}")
+
+    with SuppressProgressBars():
+        # We use .from_parquet() memory-mapped loading for efficiency
+        filters = pa_ds.field("episode_index").isin(episodes) if episodes is not None else None
+        return Dataset.from_parquet([str(path) for path in paths], filters=filters, features=features)
+
+
+def get_parquet_num_frames(parquet_path: str | Path) -> int:
+    metadata = pq.read_metadata(parquet_path)
+    return metadata.num_rows
+
+
+def get_file_size_in_mb(file_path: Path) -> float:
+    """Get file size on disk in megabytes.
+
+    Args:
+        file_path (Path): Path to the file.
+    """
+    file_size_bytes = file_path.stat().st_size
+    return file_size_bytes / (1024**2)
+
+
+def embed_images(dataset: datasets.Dataset) -> datasets.Dataset:
+    """Embed image bytes into the dataset table before saving to Parquet.
+
+    This function prepares a Hugging Face dataset for serialization by converting
+    image objects into an embedded format that can be stored in Arrow/Parquet.
+
+    Args:
+        dataset (datasets.Dataset): The input dataset, possibly containing image features.
+
+    Returns:
+        datasets.Dataset: The dataset with images embedded in the table storage.
+    """
+    # Embed image bytes into the table before saving to parquet
+    format = dataset.format
+    dataset = dataset.with_format("arrow")
+    dataset = dataset.map(embed_table_storage, batched=False)
+    dataset = dataset.with_format(**format)
+    return dataset
+
+
+def load_json(fpath: Path) -> Any:
+    """Load data from a JSON file.
+
+    Args:
+        fpath (Path): Path to the JSON file.
+
+    Returns:
+        Any: The data loaded from the JSON file.
+    """
+    with open(fpath) as f:
+        return json.load(f)
+
+
+def write_json(data: dict, fpath: Path) -> None:
+    """Write data to a JSON file.
+
+    Creates parent directories if they don't exist.
+
+    Args:
+        data (dict): The dictionary to write.
+        fpath (Path): The path to the output JSON file.
+    """
+    fpath.parent.mkdir(exist_ok=True, parents=True)
+    with open(fpath, "w") as f:
+        json.dump(data, f, indent=4, ensure_ascii=False)
+
+
+def write_info(info: dict, local_dir: Path) -> None:
+    write_json(info, local_dir / INFO_PATH)
+
+
+def load_info(local_dir: Path) -> dict:
+    """Load dataset info metadata from its standard file path.
+
+    Also converts shape lists to tuples for consistency.
+
+    Args:
+        local_dir (Path): The root directory of the dataset.
+
+    Returns:
+        dict: The dataset information dictionary.
+    """
+    info = load_json(local_dir / INFO_PATH)
+    for ft in info["features"].values():
+        ft["shape"] = tuple(ft["shape"])
+    return info
+
+
+def write_stats(stats: dict, local_dir: Path) -> None:
+    """Serialize and write dataset statistics to their standard file path.
+
+    Args:
+        stats (dict): The statistics dictionary (can contain tensors/numpy arrays).
+        local_dir (Path): The root directory of the dataset.
+    """
+    serialized_stats = serialize_dict(stats)
+    write_json(serialized_stats, local_dir / STATS_PATH)
+
+
+def cast_stats_to_numpy(stats: dict) -> dict[str, dict[str, np.ndarray]]:
+    """Recursively cast numerical values in a stats dictionary to numpy arrays.
+
+    Args:
+        stats (dict): The statistics dictionary.
+
+    Returns:
+        dict: The statistics dictionary with values cast to numpy arrays.
+    """
+    stats = {key: np.array(value) for key, value in flatten_dict(stats).items()}
+    return unflatten_dict(stats)
+
+
+def load_stats(local_dir: Path) -> dict[str, dict[str, np.ndarray]] | None:
+    """Load dataset statistics and cast numerical values to numpy arrays.
+
+    Returns None if the stats file doesn't exist.
+
+    Args:
+        local_dir (Path): The root directory of the dataset.
+
+    Returns:
+        A dictionary of statistics or None if the file is not found.
+    """
+    if not (local_dir / STATS_PATH).exists():
+        return None
+    stats = load_json(local_dir / STATS_PATH)
+    return cast_stats_to_numpy(stats)
+
+
+def write_tasks(tasks: pandas.DataFrame, local_dir: Path) -> None:
+    path = local_dir / DEFAULT_TASKS_PATH
+    path.parent.mkdir(parents=True, exist_ok=True)
+    tasks.to_parquet(path)
+
+
+def load_tasks(local_dir: Path) -> pandas.DataFrame:
+    tasks = pd.read_parquet(local_dir / DEFAULT_TASKS_PATH)
+    tasks.index.name = "task"
+    return tasks
+
+
+def load_subtasks(local_dir: Path) -> pandas.DataFrame | None:
+    """Load subtasks from subtasks.parquet if it exists."""
+    subtasks_path = local_dir / DEFAULT_SUBTASKS_PATH
+    if subtasks_path.exists():
+        return pd.read_parquet(subtasks_path)
+    return None
+
+
+def write_episodes(episodes: Dataset, local_dir: Path) -> None:
+    """Write episode metadata to a parquet file in the LeRobot v3.0 format.
+    This function writes episode-level metadata to a single parquet file.
+    Used primarily during dataset conversion (v2.1 → v3.0) and in test fixtures.
+
+    Args:
+        episodes: HuggingFace Dataset containing episode metadata
+        local_dir: Root directory where the dataset will be stored
+    """
+    episode_size_mb = get_hf_dataset_size_in_mb(episodes)
+    if episode_size_mb > DEFAULT_DATA_FILE_SIZE_IN_MB:
+        raise NotImplementedError(
+            f"Episodes dataset is too large ({episode_size_mb} MB) to write to a single file. "
+            f"The current limit is {DEFAULT_DATA_FILE_SIZE_IN_MB} MB. "
+            "This function only supports single-file episode metadata. "
+        )
+
+    fpath = local_dir / DEFAULT_EPISODES_PATH.format(chunk_index=0, file_index=0)
+    fpath.parent.mkdir(parents=True, exist_ok=True)
+    episodes.to_parquet(fpath)
+
+
+def load_episodes(local_dir: Path) -> datasets.Dataset:
+    episodes = load_nested_dataset(local_dir / EPISODES_DIR)
+    # Select episode features/columns containing references to episode data and videos
+    # (e.g. tasks, dataset_from_index, dataset_to_index, data/chunk_index, data/file_index, etc.)
+    # This is to speedup access to these data, instead of having to load episode stats.
+    episodes = episodes.select_columns([key for key in episodes.features if not key.startswith("stats/")])
+    return episodes
+
+
+def load_image_as_numpy(
+    fpath: str | Path, dtype: np.dtype = np.float32, channel_first: bool = True
+) -> np.ndarray:
+    """Load an image from a file into a numpy array.
+
+    Args:
+        fpath (str | Path): Path to the image file.
+        dtype (np.dtype): The desired data type of the output array. If floating,
+            pixels are scaled to [0, 1].
+        channel_first (bool): If True, converts the image to (C, H, W) format.
+            Otherwise, it remains in (H, W, C) format.
+
+    Returns:
+        np.ndarray: The image as a numpy array.
+    """
+    img = PILImage.open(fpath).convert("RGB")
+    img_array = np.array(img, dtype=dtype)
+    if channel_first:  # (H, W, C) -> (C, H, W)
+        img_array = np.transpose(img_array, (2, 0, 1))
+    if np.issubdtype(dtype, np.floating):
+        img_array /= 255.0
+    return img_array
+
+
+def hf_transform_to_torch(items_dict: dict[str, list[Any]]) -> dict[str, list[torch.Tensor | str]]:
+    """Convert a batch from a Hugging Face dataset to torch tensors.
+
+    This transform function converts items from Hugging Face dataset format (pyarrow)
+    to torch tensors. Importantly, images are converted from PIL objects (H, W, C, uint8)
+    to a torch image representation (C, H, W, float32) in the range [0, 1]. Other
+    types are converted to torch.tensor.
+
+    Args:
+        items_dict (dict): A dictionary representing a batch of data from a
+            Hugging Face dataset.
+
+    Returns:
+        dict: The batch with items converted to torch tensors.
+    """
+    for key in items_dict:
+        first_item = items_dict[key][0]
+        if isinstance(first_item, PILImage.Image):
+            to_tensor = transforms.ToTensor()
+            items_dict[key] = [to_tensor(img) for img in items_dict[key]]
+        elif first_item is None:
+            pass
+        else:
+            items_dict[key] = [x if isinstance(x, str) else torch.tensor(x) for x in items_dict[key]]
+    return items_dict
+
+
+def to_parquet_with_hf_images(
+    df: pandas.DataFrame, path: Path, features: datasets.Features | None = None
+) -> None:
+    """This function correctly writes to parquet a panda DataFrame that contains images encoded by HF dataset.
+    This way, it can be loaded by HF dataset and correctly formatted images are returned.
+
+    Args:
+        df: DataFrame to write to parquet.
+        path: Path to write the parquet file.
+        features: Optional HuggingFace Features schema. If provided, ensures image columns
+                  are properly typed as Image() in the parquet schema.
+    """
+    # TODO(qlhoest): replace this weird synthax by `df.to_parquet(path)` only
+    ds = datasets.Dataset.from_dict(df.to_dict(orient="list"), features=features)
+    ds.to_parquet(path)
+
+
+def item_to_torch(item: dict) -> dict:
+    """Convert all items in a dictionary to PyTorch tensors where appropriate.
+
+    This function is used to convert an item from a streaming dataset to PyTorch tensors.
+
+    Args:
+        item (dict): Dictionary of items from a dataset.
+
+    Returns:
+        dict: Dictionary with all tensor-like items converted to torch.Tensor.
+    """
+    for key, val in item.items():
+        if isinstance(val, (np.ndarray | list)) and key not in ["task"]:
+            # Convert numpy arrays and lists to torch tensors
+            item[key] = torch.tensor(val)
+    return item

src/lerobot/datasets/multi_dataset.py

@@ -0,0 +1,229 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+from collections.abc import Callable
+from pathlib import Path
+
+import datasets
+import torch
+import torch.utils
+
+from lerobot.datasets.compute_stats import aggregate_stats
+from lerobot.datasets.feature_utils import get_hf_features_from_features
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+from lerobot.datasets.video_utils import VideoFrame
+from lerobot.utils.constants import HF_LEROBOT_HOME
+
+logger = logging.getLogger(__name__)
+
+
+class MultiLeRobotDataset(torch.utils.data.Dataset):
+    """A dataset consisting of multiple underlying `LeRobotDataset`s.
+
+    The underlying `LeRobotDataset`s are effectively concatenated, and this class adopts much of the API
+    structure of `LeRobotDataset`.
+    """
+
+    def __init__(
+        self,
+        repo_ids: list[str],
+        root: str | Path | None = None,
+        episodes: dict | None = None,
+        image_transforms: Callable | None = None,
+        delta_timestamps: dict[str, list[float]] | None = None,
+        tolerances_s: dict | None = None,
+        download_videos: bool = True,
+        video_backend: str | None = None,
+    ):
+        super().__init__()
+        self.repo_ids = repo_ids
+        self.root = Path(root) if root else HF_LEROBOT_HOME
+        self.tolerances_s = tolerances_s if tolerances_s else dict.fromkeys(repo_ids, 0.0001)
+        # Construct the underlying datasets passing everything but `transform` and `delta_timestamps` which
+        # are handled by this class.
+        self._datasets = [
+            LeRobotDataset(
+                repo_id,
+                root=self.root / repo_id,
+                episodes=episodes[repo_id] if episodes else None,
+                image_transforms=image_transforms,
+                delta_timestamps=delta_timestamps,
+                tolerance_s=self.tolerances_s[repo_id],
+                download_videos=download_videos,
+                video_backend=video_backend,
+            )
+            for repo_id in repo_ids
+        ]
+
+        # Disable any data keys that are not common across all of the datasets. Note: we may relax this
+        # restriction in future iterations of this class. For now, this is necessary at least for being able
+        # to use PyTorch's default DataLoader collate function.
+        self.disabled_features = set()
+        intersection_features = set(self._datasets[0].features)
+        for ds in self._datasets:
+            intersection_features.intersection_update(ds.features)
+        if len(intersection_features) == 0:
+            raise RuntimeError(
+                "Multiple datasets were provided but they had no keys common to all of them. "
+                "The multi-dataset functionality currently only keeps common keys."
+            )
+        for repo_id, ds in zip(self.repo_ids, self._datasets, strict=True):
+            extra_keys = set(ds.features).difference(intersection_features)
+            if extra_keys:
+                logger.warning(
+                    f"keys {extra_keys} of {repo_id} were disabled as they are not contained in all the "
+                    "other datasets."
+                )
+                self.disabled_features.update(extra_keys)
+
+        self.delta_timestamps = delta_timestamps
+        # TODO(rcadene, aliberts): We should not perform this aggregation for datasets
+        # with multiple robots of different ranges. Instead we should have one normalization
+        # per robot.
+        self.stats = aggregate_stats([dataset.meta.stats for dataset in self._datasets])
+        self.set_image_transforms(image_transforms)
+
+    def set_image_transforms(self, image_transforms: Callable | None) -> None:
+        """Replace the transform for this dataset and its children."""
+        if image_transforms is not None and not callable(image_transforms):
+            raise TypeError("image_transforms must be callable or None.")
+        self.image_transforms = image_transforms
+        for dataset in getattr(self, "_datasets", []):
+            dataset.set_image_transforms(self.image_transforms)
+
+    def clear_image_transforms(self) -> None:
+        """Remove the transform from this dataset and its children."""
+        self.set_image_transforms(None)
+
+    @property
+    def repo_id_to_index(self):
+        """Return a mapping from dataset repo_id to a dataset index automatically created by this class.
+
+        This index is incorporated as a data key in the dictionary returned by `__getitem__`.
+        """
+        return {repo_id: i for i, repo_id in enumerate(self.repo_ids)}
+
+    @property
+    def fps(self) -> int:
+        """Frames per second used during data collection.
+
+        NOTE: Fow now, this relies on a check in __init__ to make sure all sub-datasets have the same info.
+        """
+        return self._datasets[0].meta.info["fps"]
+
+    @property
+    def video(self) -> bool:
+        """Returns True if this dataset loads video frames from mp4 files.
+
+        Returns False if it only loads images from png files.
+
+        NOTE: Fow now, this relies on a check in __init__ to make sure all sub-datasets have the same info.
+        """
+        return self._datasets[0].meta.info.get("video", False)
+
+    @property
+    def features(self) -> datasets.Features:
+        features = {}
+        for dataset in self._datasets:
+            features.update(
+                {
+                    k: v
+                    for k, v in get_hf_features_from_features(dataset.features).items()
+                    if k not in self.disabled_features
+                }
+            )
+        return features
+
+    @property
+    def camera_keys(self) -> list[str]:
+        """Keys to access image and video stream from cameras."""
+        keys = []
+        for key, feats in self.features.items():
+            if isinstance(feats, (datasets.Image | VideoFrame)):
+                keys.append(key)
+        return keys
+
+    @property
+    def video_frame_keys(self) -> list[str]:
+        """Keys to access video frames that requires to be decoded into images.
+
+        Note: It is empty if the dataset contains images only,
+        or equal to `self.cameras` if the dataset contains videos only,
+        or can even be a subset of `self.cameras` in a case of a mixed image/video dataset.
+        """
+        video_frame_keys = []
+        for key, feats in self.features.items():
+            if isinstance(feats, VideoFrame):
+                video_frame_keys.append(key)
+        return video_frame_keys
+
+    @property
+    def num_frames(self) -> int:
+        """Number of samples/frames."""
+        return sum(d.num_frames for d in self._datasets)
+
+    @property
+    def num_episodes(self) -> int:
+        """Number of episodes."""
+        return sum(d.num_episodes for d in self._datasets)
+
+    @property
+    def tolerance_s(self) -> float:
+        """Tolerance in seconds used to discard loaded frames when their timestamps
+        are not close enough from the requested frames. It is only used when `delta_timestamps`
+        is provided or when loading video frames from mp4 files.
+        """
+        # 1e-4 to account for possible numerical error
+        return 1 / self.fps - 1e-4
+
+    def __len__(self):
+        return self.num_frames
+
+    def __getitem__(self, idx: int) -> dict[str, torch.Tensor]:
+        if idx >= len(self):
+            raise IndexError(f"Index {idx} out of bounds.")
+        # Determine which dataset to get an item from based on the index.
+        start_idx = 0
+        dataset_idx = 0
+        for dataset in self._datasets:
+            if idx >= start_idx + dataset.num_frames:
+                start_idx += dataset.num_frames
+                dataset_idx += 1
+                continue
+            break
+        else:
+            raise AssertionError("We expect the loop to break out as long as the index is within bounds.")
+        item = self._datasets[dataset_idx][idx - start_idx]
+        item["dataset_index"] = torch.tensor(dataset_idx)
+        for data_key in self.disabled_features:
+            if data_key in item:
+                del item[data_key]
+
+        return item
+
+    def __repr__(self):
+        return (
+            f"{self.__class__.__name__}(\n"
+            f"  Repository IDs: '{self.repo_ids}',\n"
+            f"  Number of Samples: {self.num_frames},\n"
+            f"  Number of Episodes: {self.num_episodes},\n"
+            f"  Type: {'video (.mp4)' if self.video else 'image (.png)'},\n"
+            f"  Recorded Frames per Second: {self.fps},\n"
+            f"  Camera Keys: {self.camera_keys},\n"
+            f"  Video Frame Keys: {self.video_frame_keys if self.video else 'N/A'},\n"
+            f"  Transformations: {self.image_transforms},\n"
+            f")"
+        )

src/lerobot/datasets/online_buffer.py

@@ -1,382 +0,0 @@
-#!/usr/bin/env python
-
-# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-"""An online buffer for the online training loop in train.py
-
-Note to maintainers: This duplicates some logic from LeRobotDataset and EpisodeAwareSampler. We should
-consider converging to one approach. Here we have opted to use numpy.memmap to back the data buffer. It's much
-faster than using HuggingFace Datasets as there's no conversion to an intermediate non-python object. Also it
-supports in-place slicing and mutation which is very handy for a dynamic buffer.
-"""
-
-import os
-from pathlib import Path
-from typing import Any
-
-import numpy as np
-import torch
-
-from lerobot.datasets.lerobot_dataset import LeRobotDataset
-
-
-def _make_memmap_safe(**kwargs) -> np.memmap:
-    """Make a numpy memmap with checks on available disk space first.
-
-    Expected kwargs are: "filename", "dtype" (must by np.dtype), "mode" and "shape"
-
-    For information on dtypes:
-    https://numpy.org/doc/stable/reference/arrays.dtypes.html#arrays-dtypes-constructing
-    """
-    if kwargs["mode"].startswith("w"):
-        required_space = kwargs["dtype"].itemsize * np.prod(kwargs["shape"])  # bytes
-        stats = os.statvfs(Path(kwargs["filename"]).parent)
-        available_space = stats.f_bavail * stats.f_frsize  # bytes
-        if required_space >= available_space * 0.8:
-            raise RuntimeError(
-                f"You're about to take up {required_space} of {available_space} bytes available."
-            )
-    return np.memmap(**kwargs)
-
-
-class OnlineBuffer(torch.utils.data.Dataset):
-    """FIFO data buffer for the online training loop in train.py.
-
-    Follows the protocol of LeRobotDataset as much as is required to have it be used by the online training
-    loop in the same way that a LeRobotDataset would be used.
-
-    The underlying data structure will have data inserted in a circular fashion. Always insert after the
-    last index, and when you reach the end, wrap around to the start.
-
-    The data is stored in a numpy memmap.
-    """
-
-    NEXT_INDEX_KEY = "_next_index"
-    OCCUPANCY_MASK_KEY = "_occupancy_mask"
-    INDEX_KEY = "index"
-    FRAME_INDEX_KEY = "frame_index"
-    EPISODE_INDEX_KEY = "episode_index"
-    TIMESTAMP_KEY = "timestamp"
-    IS_PAD_POSTFIX = "_is_pad"
-
-    def __init__(
-        self,
-        write_dir: str | Path,
-        data_spec: dict[str, Any] | None,
-        buffer_capacity: int | None,
-        fps: float | None = None,
-        delta_timestamps: dict[str, list[float]] | dict[str, np.ndarray] | None = None,
-    ):
-        """
-        The online buffer can be provided from scratch or you can load an existing online buffer by passing
-        a `write_dir` associated with an existing buffer.
-
-        Args:
-            write_dir: Where to keep the numpy memmap files. One memmap file will be stored for each data key.
-                Note that if the files already exist, they are opened in read-write mode (used for training
-                resumption.)
-            data_spec: A mapping from data key to data specification, like {data_key: {"shape": tuple[int],
-                "dtype": np.dtype}}. This should include all the data that you wish to record into the buffer,
-                but note that "index", "frame_index" and "episode_index" are already accounted for by this
-                class, so you don't need to include them.
-            buffer_capacity: How many frames should be stored in the buffer as a maximum. Be aware of your
-                system's available disk space when choosing this.
-            fps: Same as the fps concept in LeRobot dataset. Here it needs to be provided for the
-                 delta_timestamps logic. You can pass None if you are not using delta_timestamps.
-            delta_timestamps: Same as the delta_timestamps concept in LeRobotDataset. This is internally
-                converted to dict[str, np.ndarray] for optimization purposes.
-
-        """
-        self.set_delta_timestamps(delta_timestamps)
-        self._fps = fps
-        # Tolerance in seconds used to discard loaded frames when their timestamps are not close enough from
-        # the requested frames. It is only used when `delta_timestamps` is provided.
-        # minus 1e-4 to account for possible numerical error
-        self.tolerance_s = 1 / self.fps - 1e-4 if fps is not None else None
-        self._buffer_capacity = buffer_capacity
-        data_spec = self._make_data_spec(data_spec, buffer_capacity)
-        Path(write_dir).mkdir(parents=True, exist_ok=True)
-        self._data = {}
-        for k, v in data_spec.items():
-            self._data[k] = _make_memmap_safe(
-                filename=Path(write_dir) / k,
-                dtype=v["dtype"] if v is not None else None,
-                mode="r+" if (Path(write_dir) / k).exists() else "w+",
-                shape=tuple(v["shape"]) if v is not None else None,
-            )
-
-    @property
-    def delta_timestamps(self) -> dict[str, np.ndarray] | None:
-        return self._delta_timestamps
-
-    def set_delta_timestamps(self, value: dict[str, list[float]] | None):
-        """Set delta_timestamps converting the values to numpy arrays.
-
-        The conversion is for an optimization in the __getitem__. The loop is much slower if the arrays
-        need to be converted into numpy arrays.
-        """
-        if value is not None:
-            self._delta_timestamps = {k: np.array(v) for k, v in value.items()}
-        else:
-            self._delta_timestamps = None
-
-    def _make_data_spec(self, data_spec: dict[str, Any], buffer_capacity: int) -> dict[str, dict[str, Any]]:
-        """Makes the data spec for np.memmap."""
-        if any(k.startswith("_") for k in data_spec):
-            raise ValueError(
-                "data_spec keys should not start with '_'. This prefix is reserved for internal logic."
-            )
-        preset_keys = {
-            OnlineBuffer.INDEX_KEY,
-            OnlineBuffer.FRAME_INDEX_KEY,
-            OnlineBuffer.EPISODE_INDEX_KEY,
-            OnlineBuffer.TIMESTAMP_KEY,
-        }
-        if len(intersection := set(data_spec).intersection(preset_keys)) > 0:
-            raise ValueError(
-                f"data_spec should not contain any of {preset_keys} as these are handled internally. "
-                f"The provided data_spec has {intersection}."
-            )
-        complete_data_spec = {
-            # _next_index will be a pointer to the next index that we should start filling from when we add
-            # more data.
-            OnlineBuffer.NEXT_INDEX_KEY: {"dtype": np.dtype("int64"), "shape": ()},
-            # Since the memmap is initialized with all-zeros, this keeps track of which indices are occupied
-            # with real data rather than the dummy initialization.
-            OnlineBuffer.OCCUPANCY_MASK_KEY: {"dtype": np.dtype("?"), "shape": (buffer_capacity,)},
-            OnlineBuffer.INDEX_KEY: {"dtype": np.dtype("int64"), "shape": (buffer_capacity,)},
-            OnlineBuffer.FRAME_INDEX_KEY: {"dtype": np.dtype("int64"), "shape": (buffer_capacity,)},
-            OnlineBuffer.EPISODE_INDEX_KEY: {"dtype": np.dtype("int64"), "shape": (buffer_capacity,)},
-            OnlineBuffer.TIMESTAMP_KEY: {"dtype": np.dtype("float64"), "shape": (buffer_capacity,)},
-        }
-        for k, v in data_spec.items():
-            complete_data_spec[k] = {"dtype": v["dtype"], "shape": (buffer_capacity, *v["shape"])}
-        return complete_data_spec
-
-    def add_data(self, data: dict[str, np.ndarray]):
-        """Add new data to the buffer, which could potentially mean shifting old data out.
-
-        The new data should contain all the frames (in order) of any number of episodes. The indices should
-        start from 0 (note to the developer: this can easily be generalized). See the `rollout` and
-        `eval_policy` functions in `eval.py` for more information on how the data is constructed.
-
-        Shift the incoming data index and episode_index to continue on from the last frame. Note that this
-        will be done in place!
-        """
-        if len(missing_keys := (set(self.data_keys).difference(set(data)))) > 0:
-            raise ValueError(f"Missing data keys: {missing_keys}")
-        new_data_length = len(data[self.data_keys[0]])
-        if not all(len(data[k]) == new_data_length for k in self.data_keys):
-            raise ValueError("All data items should have the same length")
-
-        next_index = self._data[OnlineBuffer.NEXT_INDEX_KEY]
-
-        # Sanity check to make sure that the new data indices start from 0.
-        assert data[OnlineBuffer.EPISODE_INDEX_KEY][0].item() == 0
-        assert data[OnlineBuffer.INDEX_KEY][0].item() == 0
-
-        # Shift the incoming indices if necessary.
-        if self.num_frames > 0:
-            last_episode_index = self._data[OnlineBuffer.EPISODE_INDEX_KEY][next_index - 1]
-            last_data_index = self._data[OnlineBuffer.INDEX_KEY][next_index - 1]
-            data[OnlineBuffer.EPISODE_INDEX_KEY] += last_episode_index + 1
-            data[OnlineBuffer.INDEX_KEY] += last_data_index + 1
-
-        # Insert the new data starting from next_index. It may be necessary to wrap around to the start.
-        n_surplus = max(0, new_data_length - (self._buffer_capacity - next_index))
-        for k in self.data_keys:
-            if n_surplus == 0:
-                slc = slice(next_index, next_index + new_data_length)
-                self._data[k][slc] = data[k]
-                self._data[OnlineBuffer.OCCUPANCY_MASK_KEY][slc] = True
-            else:
-                self._data[k][next_index:] = data[k][:-n_surplus]
-                self._data[OnlineBuffer.OCCUPANCY_MASK_KEY][next_index:] = True
-                self._data[k][:n_surplus] = data[k][-n_surplus:]
-        if n_surplus == 0:
-            self._data[OnlineBuffer.NEXT_INDEX_KEY] = next_index + new_data_length
-        else:
-            self._data[OnlineBuffer.NEXT_INDEX_KEY] = n_surplus
-
-    @property
-    def data_keys(self) -> list[str]:
-        keys = set(self._data)
-        keys.remove(OnlineBuffer.OCCUPANCY_MASK_KEY)
-        keys.remove(OnlineBuffer.NEXT_INDEX_KEY)
-        return sorted(keys)
-
-    @property
-    def fps(self) -> float | None:
-        return self._fps
-
-    @property
-    def num_episodes(self) -> int:
-        return len(
-            np.unique(self._data[OnlineBuffer.EPISODE_INDEX_KEY][self._data[OnlineBuffer.OCCUPANCY_MASK_KEY]])
-        )
-
-    @property
-    def num_frames(self) -> int:
-        return np.count_nonzero(self._data[OnlineBuffer.OCCUPANCY_MASK_KEY])
-
-    def __len__(self):
-        return self.num_frames
-
-    def _item_to_tensors(self, item: dict) -> dict:
-        item_ = {}
-        for k, v in item.items():
-            if isinstance(v, torch.Tensor):
-                item_[k] = v
-            elif isinstance(v, np.ndarray):
-                item_[k] = torch.from_numpy(v)
-            else:
-                item_[k] = torch.tensor(v)
-        return item_
-
-    def __getitem__(self, idx: int) -> dict[str, torch.Tensor]:
-        if idx >= len(self) or idx < -len(self):
-            raise IndexError
-
-        item = {k: v[idx] for k, v in self._data.items() if not k.startswith("_")}
-
-        if self.delta_timestamps is None:
-            return self._item_to_tensors(item)
-
-        episode_index = item[OnlineBuffer.EPISODE_INDEX_KEY]
-        current_ts = item[OnlineBuffer.TIMESTAMP_KEY]
-        episode_data_indices = np.where(
-            np.bitwise_and(
-                self._data[OnlineBuffer.EPISODE_INDEX_KEY] == episode_index,
-                self._data[OnlineBuffer.OCCUPANCY_MASK_KEY],
-            )
-        )[0]
-        episode_timestamps = self._data[OnlineBuffer.TIMESTAMP_KEY][episode_data_indices]
-
-        for data_key in self.delta_timestamps:
-            # Note: The logic in this loop is copied from `load_previous_and_future_frames`.
-            # Get timestamps used as query to retrieve data of previous/future frames.
-            query_ts = current_ts + self.delta_timestamps[data_key]
-
-            # Compute distances between each query timestamp and all timestamps of all the frames belonging to
-            # the episode.
-            dist = np.abs(query_ts[:, None] - episode_timestamps[None, :])
-            argmin_ = np.argmin(dist, axis=1)
-            min_ = dist[np.arange(dist.shape[0]), argmin_]
-
-            is_pad = min_ > self.tolerance_s
-
-            # Check violated query timestamps are all outside the episode range.
-            assert (
-                (query_ts[is_pad] < episode_timestamps[0]) | (episode_timestamps[-1] < query_ts[is_pad])
-            ).all(), (
-                f"One or several timestamps unexpectedly violate the tolerance ({min_} > {self.tolerance_s=}"
-                ") inside the episode range."
-            )
-
-            # Load frames for this data key.
-            item[data_key] = self._data[data_key][episode_data_indices[argmin_]]
-
-            item[f"{data_key}{OnlineBuffer.IS_PAD_POSTFIX}"] = is_pad
-
-        return self._item_to_tensors(item)
-
-    def get_data_by_key(self, key: str) -> torch.Tensor:
-        """Returns all data for a given data key as a Tensor."""
-        return torch.from_numpy(self._data[key][self._data[OnlineBuffer.OCCUPANCY_MASK_KEY]])
-
-
-def compute_sampler_weights(
-    offline_dataset: LeRobotDataset,
-    offline_drop_n_last_frames: int = 0,
-    online_dataset: OnlineBuffer | None = None,
-    online_sampling_ratio: float | None = None,
-    online_drop_n_last_frames: int = 0,
-) -> torch.Tensor:
-    """Compute the sampling weights for the online training dataloader in train.py.
-
-    Args:
-        offline_dataset: The LeRobotDataset used for offline pre-training.
-        online_drop_n_last_frames: Number of frames to drop from the end of each offline dataset episode.
-        online_dataset: The OnlineBuffer used in online training.
-        online_sampling_ratio: The proportion of data that should be sampled from the online dataset. If an
-            online dataset is provided, this value must also be provided.
-        online_drop_n_first_frames: See `offline_drop_n_last_frames`. This is the same, but for the online
-            dataset.
-    Returns:
-        Tensor of weights for [offline_dataset; online_dataset], normalized to 1.
-
-    Notes to maintainers:
-        - This duplicates some logic from EpisodeAwareSampler. We should consider converging to one approach.
-        - When used with `torch.utils.data.WeightedRandomSampler`, it could completely replace
-          `EpisodeAwareSampler` as the online dataset related arguments are optional. The only missing feature
-          is the ability to turn shuffling off.
-        - Options `drop_first_n_frames` and `episode_indices_to_use` can be added easily. They were not
-          included here to avoid adding complexity.
-    """
-    if len(offline_dataset) == 0 and (online_dataset is None or len(online_dataset) == 0):
-        raise ValueError("At least one of `offline_dataset` or `online_dataset` should be contain data.")
-    if (online_dataset is None) ^ (online_sampling_ratio is None):
-        raise ValueError(
-            "`online_dataset` and `online_sampling_ratio` must be provided together or not at all."
-        )
-    offline_sampling_ratio = 0 if online_sampling_ratio is None else 1 - online_sampling_ratio
-
-    weights = []
-
-    if len(offline_dataset) > 0:
-        offline_data_mask_indices = []
-        for start_index, end_index in zip(
-            offline_dataset.meta.episodes["dataset_from_index"],
-            offline_dataset.meta.episodes["dataset_to_index"],
-            strict=True,
-        ):
-            offline_data_mask_indices.extend(range(start_index, end_index - offline_drop_n_last_frames))
-        offline_data_mask = torch.zeros(len(offline_dataset), dtype=torch.bool)
-        offline_data_mask[torch.tensor(offline_data_mask_indices)] = True
-        weights.append(
-            torch.full(
-                size=(len(offline_dataset),),
-                fill_value=offline_sampling_ratio / offline_data_mask.sum(),
-            )
-            * offline_data_mask
-        )
-
-    if online_dataset is not None and len(online_dataset) > 0:
-        online_data_mask_indices = []
-        episode_indices = online_dataset.get_data_by_key("episode_index")
-        for episode_idx in torch.unique(episode_indices):
-            where_episode = torch.where(episode_indices == episode_idx)
-            start_index = where_episode[0][0]
-            end_index = where_episode[0][-1] + 1
-            online_data_mask_indices.extend(
-                range(start_index.item(), end_index.item() - online_drop_n_last_frames)
-            )
-        online_data_mask = torch.zeros(len(online_dataset), dtype=torch.bool)
-        online_data_mask[torch.tensor(online_data_mask_indices)] = True
-        weights.append(
-            torch.full(
-                size=(len(online_dataset),),
-                fill_value=online_sampling_ratio / online_data_mask.sum(),
-            )
-            * online_data_mask
-        )
-
-    weights = torch.cat(weights)
-
-    if weights.sum() == 0:
-        weights += 1 / len(weights)
-    else:
-        weights /= weights.sum()
-
-    return weights

src/lerobot/datasets/pipeline_features.py

@@ -17,8 +17,9 @@ from collections.abc import Sequence
 from typing import Any
 
 from lerobot.configs.types import PipelineFeatureType
-from lerobot.datasets.utils import hw_to_dataset_features
-from lerobot.processor import DataProcessorPipeline, RobotAction, RobotObservation
+from lerobot.datasets.feature_utils import hw_to_dataset_features
+from lerobot.processor import DataProcessorPipeline
+from lerobot.types import RobotAction, RobotObservation
 from lerobot.utils.constants import ACTION, OBS_IMAGES, OBS_STATE, OBS_STR
 
 
@@ -43,11 +44,11 @@ def create_initial_features(
     return features
 
 
-# Helper to filter state/action keys based on regex patterns.
-def should_keep(key: str, patterns: tuple[str]) -> bool:
+# Helper to filter state/action keys based on compiled regex patterns.
+def should_keep(key: str, patterns: tuple[re.Pattern] | None) -> bool:
     if patterns is None:
         return True
-    return any(re.search(pat, key) for pat in patterns)
+    return any(pat.search(key) for pat in patterns)
 
 
 def strip_prefix(key: str, prefixes_to_strip: tuple[str]) -> str:
@@ -88,6 +89,8 @@ def aggregate_pipeline_dataset_features(
     Returns:
         A dictionary of features formatted for a Hugging Face LeRobot Dataset.
     """
+    compiled_patterns = tuple(re.compile(p) for p in patterns) if patterns is not None else None
+
     all_features = pipeline.transform_features(initial_features)
 
     # Intermediate storage for categorized and filtered features.
@@ -119,7 +122,7 @@ def aggregate_pipeline_dataset_features(
             # 2. Apply filtering rules.
             if is_image and not use_videos:
                 continue
-            if not is_image and not should_keep(key, patterns):
+            if not is_image and not should_keep(key, compiled_patterns):
                 continue
 
             # 3. Add the feature to the appropriate group with a clean name.

src/lerobot/datasets/push_dataset_to_hub/utils.py

@@ -1,73 +0,0 @@
-#!/usr/bin/env python
-
-# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import datasets
-import torch
-
-
-# TODO(aliberts): remove
-def calculate_episode_data_index(hf_dataset: datasets.Dataset) -> dict[str, torch.Tensor]:
-    """
-    Calculate episode data index for the provided HuggingFace Dataset. Relies on episode_index column of hf_dataset.
-
-    Parameters:
-    - hf_dataset (datasets.Dataset): A HuggingFace dataset containing the episode index.
-
-    Returns:
-    - episode_data_index: A dictionary containing the data index for each episode. The dictionary has two keys:
-        - "from": A tensor containing the starting index of each episode.
-        - "to": A tensor containing the ending index of each episode.
-    """
-    episode_data_index = {"from": [], "to": []}
-
-    current_episode = None
-    """
-    The episode_index is a list of integers, each representing the episode index of the corresponding example.
-    For instance, the following is a valid episode_index:
-      [0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2]
-
-    Below, we iterate through the episode_index and populate the episode_data_index dictionary with the starting and
-    ending index of each episode. For the episode_index above, the episode_data_index dictionary will look like this:
-        {
-            "from": [0, 3, 7],
-            "to": [3, 7, 12]
-        }
-    """
-    if len(hf_dataset) == 0:
-        episode_data_index = {
-            "from": torch.tensor([]),
-            "to": torch.tensor([]),
-        }
-        return episode_data_index
-    for idx, episode_idx in enumerate(hf_dataset["episode_index"]):
-        if episode_idx != current_episode:
-            # We encountered a new episode, so we append its starting location to the "from" list
-            episode_data_index["from"].append(idx)
-            # If this is not the first episode, we append the ending location of the previous episode to the "to" list
-            if current_episode is not None:
-                episode_data_index["to"].append(idx)
-            # Let's keep track of the current episode index
-            current_episode = episode_idx
-        else:
-            # We are still in the same episode, so there is nothing for us to do here
-            pass
-    # We have reached the end of the dataset, so we append the ending location of the last episode to the "to" list
-    episode_data_index["to"].append(idx + 1)
-
-    for k in ["from", "to"]:
-        episode_data_index[k] = torch.tensor(episode_data_index[k])
-
-    return episode_data_index

src/lerobot/datasets/sampler.py

@@ -13,10 +13,13 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import logging
 from collections.abc import Iterator
 
 import torch
 
+logger = logging.getLogger(__name__)
+
 
 class EpisodeAwareSampler:
     def __init__(
@@ -39,13 +42,35 @@ class EpisodeAwareSampler:
             drop_n_last_frames: Number of frames to drop from the end of each episode.
             shuffle: Whether to shuffle the indices.
         """
+        if drop_n_first_frames < 0:
+            raise ValueError(f"drop_n_first_frames must be >= 0, got {drop_n_first_frames}")
+        if drop_n_last_frames < 0:
+            raise ValueError(f"drop_n_last_frames must be >= 0, got {drop_n_last_frames}")
+
         indices = []
         for episode_idx, (start_index, end_index) in enumerate(
             zip(dataset_from_indices, dataset_to_indices, strict=True)
         ):
             if episode_indices_to_use is None or episode_idx in episode_indices_to_use:
+                ep_length = end_index - start_index
+                if drop_n_first_frames + drop_n_last_frames >= ep_length:
+                    logger.warning(
+                        "Episode %d has %d frames but drop_n_first_frames=%d and "
+                        "drop_n_last_frames=%d removes all frames. Skipping.",
+                        episode_idx,
+                        ep_length,
+                        drop_n_first_frames,
+                        drop_n_last_frames,
+                    )
+                    continue
                 indices.extend(range(start_index + drop_n_first_frames, end_index - drop_n_last_frames))
 
+        if not indices:
+            raise ValueError(
+                "No valid frames remain after applying drop_n_first_frames and drop_n_last_frames. "
+                "All episodes were either filtered out or had too few frames."
+            )
+
         self.indices = indices
         self.shuffle = shuffle
 

src/lerobot/datasets/streaming_dataset.py

@@ -13,7 +13,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from collections.abc import Callable, Generator, Iterator
+from collections import deque
+from collections.abc import Callable, Generator, Iterable, Iterator
 from pathlib import Path
 
 import datasets
@@ -21,16 +22,13 @@ import numpy as np
 import torch
 from datasets import load_dataset
 
-from lerobot.datasets.lerobot_dataset import CODEBASE_VERSION, LeRobotDatasetMetadata
+from lerobot.datasets.dataset_metadata import CODEBASE_VERSION, LeRobotDatasetMetadata
+from lerobot.datasets.feature_utils import get_delta_indices
+from lerobot.datasets.io_utils import item_to_torch
 from lerobot.datasets.utils import (
-    Backtrackable,
-    LookAheadError,
-    LookBackError,
     check_version_compatibility,
     find_float_index,
-    get_delta_indices,
     is_float_in_list,
-    item_to_torch,
     safe_shard,
 )
 from lerobot.datasets.video_utils import (
@@ -40,6 +38,164 @@ from lerobot.datasets.video_utils import (
 from lerobot.utils.constants import HF_LEROBOT_HOME, LOOKAHEAD_BACKTRACKTABLE, LOOKBACK_BACKTRACKTABLE
 
 
+class LookBackError(Exception):
+    """
+    Exception raised when trying to look back in the history of a Backtrackable object.
+    """
+
+    pass
+
+
+class LookAheadError(Exception):
+    """
+    Exception raised when trying to look ahead in the future of a Backtrackable object.
+    """
+
+    pass
+
+
+class Backtrackable[T]:
+    """
+    Wrap any iterator/iterable so you can step back up to `history` items
+    and look ahead up to `lookahead` items.
+
+    This is useful for streaming datasets where you need to access previous and future items
+    but can't load the entire dataset into memory.
+
+    Example:
+    -------
+    ```python
+    ds = load_dataset("c4", "en", streaming=True, split="train")
+    rev = Backtrackable(ds, history=3, lookahead=2)
+
+    x0 = next(rev)  # forward
+    x1 = next(rev)
+    x2 = next(rev)
+
+    # Look ahead
+    x3_peek = rev.peek_ahead(1)  # next item without moving cursor
+    x4_peek = rev.peek_ahead(2)  # two items ahead
+
+    # Look back
+    x1_again = rev.peek_back(1)  # previous item without moving cursor
+    x0_again = rev.peek_back(2)  # two items back
+
+    # Move backward
+    x1_back = rev.prev()  # back one step
+    next(rev)  # returns x2, continues forward from where we were
+    ```
+    """
+
+    __slots__ = ("_source", "_back_buf", "_ahead_buf", "_cursor", "_history", "_lookahead")
+
+    def __init__(self, iterable: Iterable[T], *, history: int = 1, lookahead: int = 0):
+        if history < 1:
+            raise ValueError("history must be >= 1")
+        if lookahead <= 0:
+            raise ValueError("lookahead must be > 0")
+
+        self._source: Iterator[T] = iter(iterable)
+        self._back_buf: deque[T] = deque(maxlen=history)
+        self._ahead_buf: deque[T] = deque(maxlen=lookahead) if lookahead > 0 else deque()
+        self._cursor: int = 0
+        self._history = history
+        self._lookahead = lookahead
+
+    def __iter__(self) -> "Backtrackable[T]":
+        return self
+
+    def __next__(self) -> T:
+        # If we've stepped back, consume from back buffer first
+        if self._cursor < 0:  # -1 means "last item", etc.
+            self._cursor += 1
+            return self._back_buf[self._cursor]
+
+        # If we have items in the ahead buffer, use them first
+        item = self._ahead_buf.popleft() if self._ahead_buf else next(self._source)
+
+        # Add current item to back buffer and reset cursor
+        self._back_buf.append(item)
+        self._cursor = 0
+        return item
+
+    def prev(self) -> T:
+        """
+        Step one item back in history and return it.
+        Raises IndexError if already at the oldest buffered item.
+        """
+        if len(self._back_buf) + self._cursor <= 1:
+            raise LookBackError("At start of history")
+
+        self._cursor -= 1
+        return self._back_buf[self._cursor]
+
+    def peek_back(self, n: int = 1) -> T:
+        """
+        Look `n` items back (n=1 == previous item) without moving the cursor.
+        """
+        if n < 0 or n + 1 > len(self._back_buf) + self._cursor:
+            raise LookBackError("peek_back distance out of range")
+
+        return self._back_buf[self._cursor - (n + 1)]
+
+    def peek_ahead(self, n: int = 1) -> T:
+        """
+        Look `n` items ahead (n=1 == next item) without moving the cursor.
+        Fills the ahead buffer if necessary.
+        """
+        if n < 1:
+            raise LookAheadError("peek_ahead distance must be 1 or more")
+        elif n > self._lookahead:
+            raise LookAheadError("peek_ahead distance exceeds lookahead limit")
+
+        # Fill ahead buffer if we don't have enough items
+        while len(self._ahead_buf) < n:
+            try:
+                item = next(self._source)
+                self._ahead_buf.append(item)
+
+            except StopIteration as err:
+                raise LookAheadError("peek_ahead: not enough items in source") from err
+
+        return self._ahead_buf[n - 1]
+
+    def history(self) -> list[T]:
+        """
+        Return a copy of the buffered history (most recent last).
+        The list length ≤ `history` argument passed at construction.
+        """
+        if self._cursor == 0:
+            return list(self._back_buf)
+
+        # When cursor<0, slice so the order remains chronological
+        return list(self._back_buf)[: self._cursor or None]
+
+    def can_peek_back(self, steps: int = 1) -> bool:
+        """
+        Check if we can go back `steps` items without raising an IndexError.
+        """
+        return steps <= len(self._back_buf) + self._cursor
+
+    def can_peek_ahead(self, steps: int = 1) -> bool:
+        """
+        Check if we can peek ahead `steps` items.
+        This may involve trying to fill the ahead buffer.
+        """
+        if self._lookahead > 0 and steps > self._lookahead:
+            return False
+
+        # Try to fill ahead buffer to check if we can peek that far
+        try:
+            while len(self._ahead_buf) < steps:
+                if self._lookahead > 0 and len(self._ahead_buf) >= self._lookahead:
+                    return False
+                item = next(self._source)
+                self._ahead_buf.append(item)
+            return True
+        except StopIteration:
+            return False
+
+
 class StreamingLeRobotDataset(torch.utils.data.IterableDataset):
     """LeRobotDataset with streaming capabilities.
 
@@ -99,7 +255,9 @@ class StreamingLeRobotDataset(torch.utils.data.IterableDataset):
 
         Args:
             repo_id (str): This is the repo id that will be used to fetch the dataset.
-            root (Path | None, optional): Local directory to use for downloading/writing files.
+            root (Path | None, optional): Local directory to use for local datasets. When omitted, Hub
+                metadata is resolved through a revision-safe snapshot cache under
+                ``$HF_LEROBOT_HOME/hub``.
             episodes (list[int] | None, optional): If specified, this will only load episodes specified by
                 their episode_index in this list.
             image_transforms (Callable | None, optional): Transform to apply to image data.
@@ -115,7 +273,8 @@ class StreamingLeRobotDataset(torch.utils.data.IterableDataset):
         """
         super().__init__()
         self.repo_id = repo_id
-        self.root = Path(root) if root else HF_LEROBOT_HOME / repo_id
+        self._requested_root = Path(root) if root else None
+        self.root = self._requested_root if self._requested_root is not None else HF_LEROBOT_HOME / repo_id
         self.streaming_from_local = root is not None
 
         self.image_transforms = image_transforms
@@ -132,12 +291,15 @@ class StreamingLeRobotDataset(torch.utils.data.IterableDataset):
         # We cache the video decoders to avoid re-initializing them at each frame (avoiding a ~10x slowdown)
         self.video_decoder_cache = None
 
-        self.root.mkdir(exist_ok=True, parents=True)
+        if self._requested_root is not None:
+            self.root.mkdir(exist_ok=True, parents=True)
 
         # Load metadata
         self.meta = LeRobotDatasetMetadata(
-            self.repo_id, self.root, self.revision, force_cache_sync=force_cache_sync
+            self.repo_id, self._requested_root, self.revision, force_cache_sync=force_cache_sync
         )
+        self.root = self.meta.root
+        self.revision = self.meta.revision
         # Check version
         check_version_compatibility(self.repo_id, self.meta._version, CODEBASE_VERSION)
 

src/lerobot/datasets/video_utils.py

@@ -37,6 +37,8 @@ import torchvision
 from datasets.features.features import register_feature
 from PIL import Image
 
+logger = logging.getLogger(__name__)
+
 # List of hardware encoders to probe for auto-selection. Availability depends on the platform and FFmpeg build.
 # Determines the order of preference for auto-selection when vcodec="auto" is used.
 HW_ENCODERS = [
@@ -94,7 +96,7 @@ def detect_available_hw_encoders() -> list[str]:
             av.codec.Codec(codec_name, "w")
             available.append(codec_name)
         except Exception:  # nosec B110
-            pass  # nosec B110
+            logger.debug("HW encoder '%s' not available", codec_name)  # nosec B110
     return available
 
 
@@ -103,14 +105,14 @@ def resolve_vcodec(vcodec: str) -> str:
     if vcodec not in VALID_VIDEO_CODECS:
         raise ValueError(f"Invalid vcodec '{vcodec}'. Must be one of: {sorted(VALID_VIDEO_CODECS)}")
     if vcodec != "auto":
-        logging.info(f"Using video codec: {vcodec}")
+        logger.info(f"Using video codec: {vcodec}")
         return vcodec
     available = detect_available_hw_encoders()
     for encoder in HW_ENCODERS:
         if encoder in available:
-            logging.info(f"Auto-selected video codec: {encoder}")
+            logger.info(f"Auto-selected video codec: {encoder}")
             return encoder
-    logging.info("No hardware encoder available, falling back to software encoder 'libsvtav1'")
+    logger.info("No hardware encoder available, falling back to software encoder 'libsvtav1'")
     return "libsvtav1"
 
 
@@ -118,7 +120,7 @@ def get_safe_default_codec():
     if importlib.util.find_spec("torchcodec"):
         return "torchcodec"
     else:
-        logging.warning(
+        logger.warning(
             "'torchcodec' is not available in your platform, falling back to 'pyav' as a default decoder"
         )
         return "pyav"
@@ -208,7 +210,7 @@ def decode_video_frames_torchvision(
     for frame in reader:
         current_ts = frame["pts"]
         if log_loaded_timestamps:
-            logging.info(f"frame loaded at timestamp={current_ts:.4f}")
+            logger.info(f"frame loaded at timestamp={current_ts:.4f}")
         loaded_frames.append(frame["data"])
         loaded_ts.append(current_ts)
         if current_ts >= last_ts:
@@ -244,7 +246,7 @@ def decode_video_frames_torchvision(
     closest_ts = loaded_ts[argmin_]
 
     if log_loaded_timestamps:
-        logging.info(f"{closest_ts=}")
+        logger.info(f"{closest_ts=}")
 
     # convert to the pytorch format which is float32 in [0,1] range (and channel first)
     closest_frames = closest_frames.type(torch.float32) / 255
@@ -348,7 +350,7 @@ def decode_video_frames_torchcodec(
         loaded_frames.append(frame)
         loaded_ts.append(pts.item())
         if log_loaded_timestamps:
-            logging.info(f"Frame loaded at timestamp={pts:.4f}")
+            logger.info(f"Frame loaded at timestamp={pts:.4f}")
 
     query_ts = torch.tensor(timestamps)
     loaded_ts = torch.tensor(loaded_ts)
@@ -374,7 +376,7 @@ def decode_video_frames_torchcodec(
     closest_ts = loaded_ts[argmin_]
 
     if log_loaded_timestamps:
-        logging.info(f"{closest_ts=}")
+        logger.info(f"{closest_ts=}")
 
     # convert to float32 in [0,1] range
     closest_frames = (closest_frames / 255.0).type(torch.float32)
@@ -408,14 +410,14 @@ def encode_video_frames(
     imgs_dir = Path(imgs_dir)
 
     if video_path.exists() and not overwrite:
-        logging.warning(f"Video file already exists: {video_path}. Skipping encoding.")
+        logger.warning(f"Video file already exists: {video_path}. Skipping encoding.")
         return
 
     video_path.parent.mkdir(parents=True, exist_ok=True)
 
     # Encoders/pixel formats incompatibility check
     if (vcodec == "libsvtav1" or vcodec == "hevc") and pix_fmt == "yuv444p":
-        logging.warning(
+        logger.warning(
             f"Incompatible pixel format 'yuv444p' for codec {vcodec}, auto-selecting format 'yuv420p'"
         )
         pix_fmt = "yuv420p"
@@ -508,7 +510,7 @@ def concatenate_video_files(
     output_video_path = Path(output_video_path)
 
     if output_video_path.exists() and not overwrite:
-        logging.warning(f"Video file already exists: {output_video_path}. Skipping concatenation.")
+        logger.warning(f"Video file already exists: {output_video_path}. Skipping concatenation.")
         return
 
     output_video_path.parent.mkdir(parents=True, exist_ok=True)
@@ -693,7 +695,7 @@ class _CameraEncoderThread(threading.Thread):
                 self.result_queue.put(("ok", None))
 
         except Exception as e:
-            logging.error(f"Encoder thread error: {e}")
+            logger.error(f"Encoder thread error: {e}")
             if container is not None:
                 with contextlib.suppress(Exception):
                     container.close()
@@ -739,6 +741,7 @@ class StreamingVideoEncoder:
         self._video_paths: dict[str, Path] = {}
         self._dropped_frames: dict[str, int] = {}
         self._episode_active = False
+        self._closed = False
 
     def start_episode(self, video_keys: list[str], temp_dir: Path) -> None:
         """Start encoder threads for a new episode.
@@ -819,7 +822,7 @@ class StreamingVideoEncoder:
             count = self._dropped_frames[video_key]
             # Log periodically to avoid spam (1st, then every 10th)
             if count == 1 or count % 10 == 0:
-                logging.warning(
+                logger.warning(
                     f"Encoder queue full for {video_key}, dropped {count} frame(s). "
                     f"Consider using vcodec='auto' for hardware encoding or increasing encoder_queue_maxsize."
                 )
@@ -841,7 +844,7 @@ class StreamingVideoEncoder:
         # Report dropped frames
         for video_key, count in self._dropped_frames.items():
             if count > 0:
-                logging.warning(f"Episode finished with {count} dropped frame(s) for {video_key}.")
+                logger.warning(f"Episode finished with {count} dropped frame(s) for {video_key}.")
 
         # Send sentinel to all queues
         for video_key in self._frame_queues:
@@ -851,7 +854,7 @@ class StreamingVideoEncoder:
         for video_key in self._threads:
             self._threads[video_key].join(timeout=120)
             if self._threads[video_key].is_alive():
-                logging.error(f"Encoder thread for {video_key} did not finish in time")
+                logger.error(f"Encoder thread for {video_key} did not finish in time")
                 self._stop_events[video_key].set()
                 self._threads[video_key].join(timeout=5)
                 results[video_key] = (self._video_paths[video_key], None)
@@ -863,7 +866,7 @@ class StreamingVideoEncoder:
                     raise RuntimeError(f"Encoder thread for {video_key} failed: {data}")
                 results[video_key] = (self._video_paths[video_key], data)
             except queue.Empty:
-                logging.error(f"No result from encoder thread for {video_key}")
+                logger.error(f"No result from encoder thread for {video_key}")
                 results[video_key] = (self._video_paths[video_key], None)
 
         self._cleanup()
@@ -893,8 +896,11 @@ class StreamingVideoEncoder:
 
     def close(self) -> None:
         """Close the encoder, canceling any in-progress episode."""
+        if self._closed:
+            return
         if self._episode_active:
             self.cancel_episode()
+        self._closed = True
 
     def _cleanup(self) -> None:
         """Clean up queues and thread tracking dicts."""
@@ -1061,43 +1067,19 @@ class VideoEncodingManager:
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
-        streaming_encoder = getattr(self.dataset, "_streaming_encoder", None)
+        writer = self.dataset.writer
+        if writer is not None:
+            if exc_type is not None and writer._streaming_encoder is not None:
+                writer.cancel_pending_videos()
 
-        if streaming_encoder is not None:
-            # Handle streaming encoder cleanup
-            if exc_type is not None:
-                streaming_encoder.cancel_episode()
-            streaming_encoder.close()
-        elif self.dataset.episodes_since_last_encoding > 0:
-            # Handle any remaining episodes that haven't been batch encoded
-            if exc_type is not None:
-                logging.info("Exception occurred. Encoding remaining episodes before exit...")
-            else:
-                logging.info("Recording stopped. Encoding remaining episodes...")
+            # finalize() handles flush_pending_videos + parquet + metadata
+            self.dataset.finalize()
 
-            start_ep = self.dataset.num_episodes - self.dataset.episodes_since_last_encoding
-            end_ep = self.dataset.num_episodes
-            logging.info(
-                f"Encoding remaining {self.dataset.episodes_since_last_encoding} episodes, "
-                f"from episode {start_ep} to {end_ep - 1}"
-            )
-            self.dataset._batch_save_episode_video(start_ep, end_ep)
-
-        # Finalize the dataset to properly close all writers
-        self.dataset.finalize()
-
-        # Clean up episode images if recording was interrupted (only for non-streaming mode)
-        if exc_type is not None and streaming_encoder is None:
-            interrupted_episode_index = self.dataset.num_episodes
-            for key in self.dataset.meta.video_keys:
-                img_dir = self.dataset._get_image_file_path(
-                    episode_index=interrupted_episode_index, image_key=key, frame_index=0
-                ).parent
-                if img_dir.exists():
-                    logging.debug(
-                        f"Cleaning up interrupted episode images for episode {interrupted_episode_index}, camera {key}"
-                    )
-                    shutil.rmtree(img_dir)
+            # Clean up episode images if recording was interrupted (only for non-streaming mode)
+            if exc_type is not None and writer._streaming_encoder is None:
+                writer.cleanup_interrupted_episode(self.dataset.num_episodes)
+        else:
+            self.dataset.finalize()
 
         # Clean up any remaining images directory if it's empty
         img_dir = self.dataset.root / "images"
@@ -1105,8 +1087,8 @@ class VideoEncodingManager:
             png_files = list(img_dir.rglob("*.png"))
             if len(png_files) == 0:
                 shutil.rmtree(img_dir)
-                logging.debug("Cleaned up empty images directory")
+                logger.debug("Cleaned up empty images directory")
             else:
-                logging.debug(f"Images directory is not empty, containing {len(png_files)} PNG files")
+                logger.debug(f"Images directory is not empty, containing {len(png_files)} PNG files")
 
         return False  # Don't suppress the original exception

src/lerobot/envs/configs.py

@@ -12,11 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
 import abc
+import importlib
 from dataclasses import dataclass, field, fields
 from typing import Any
 
 import draccus
+import gymnasium as gym
+from gymnasium.envs.registration import registry as gym_registry
 
 from lerobot.configs.types import FeatureType, PolicyFeature
 from lerobot.robots import RobotConfig
@@ -67,6 +72,49 @@ class EnvConfig(draccus.ChoiceRegistry, abc.ABC):
     def gym_kwargs(self) -> dict:
         raise NotImplementedError()
 
+    def create_envs(
+        self,
+        n_envs: int,
+        use_async_envs: bool = False,
+    ) -> dict[str, dict[int, gym.vector.VectorEnv]]:
+        """Create {suite: {task_id: VectorEnv}}.
+
+        Default: single-task env via gym.make(). Multi-task benchmarks override.
+        """
+        env_cls = gym.vector.AsyncVectorEnv if use_async_envs else gym.vector.SyncVectorEnv
+
+        if self.gym_id not in gym_registry:
+            print(f"gym id '{self.gym_id}' not found, attempting to import '{self.package_name}'...")
+            try:
+                importlib.import_module(self.package_name)
+            except ModuleNotFoundError as e:
+                raise ModuleNotFoundError(
+                    f"Package '{self.package_name}' required for env '{self.type}' not found. "
+                    f"Please install it or check PYTHONPATH."
+                ) from e
+
+            if self.gym_id not in gym_registry:
+                raise gym.error.NameNotFound(
+                    f"Environment '{self.gym_id}' not registered even after importing '{self.package_name}'."
+                )
+
+        def _make_one():
+            return gym.make(self.gym_id, disable_env_checker=self.disable_env_checker, **self.gym_kwargs)
+
+        try:
+            from gymnasium.vector import AutoresetMode
+
+            vec = env_cls([_make_one for _ in range(n_envs)], autoreset_mode=AutoresetMode.SAME_STEP)
+        except ImportError:
+            vec = env_cls([_make_one for _ in range(n_envs)])
+        return {self.type: {0: vec}}
+
+    def get_env_processors(self):
+        """Return (preprocessor, postprocessor) for this env. Default: identity."""
+        from lerobot.processor.pipeline import PolicyProcessorPipeline
+
+        return PolicyProcessorPipeline(steps=[]), PolicyProcessorPipeline(steps=[])
+
 
 @dataclass
 class HubEnvConfig(EnvConfig):
@@ -338,6 +386,12 @@ class LiberoEnv(EnvConfig):
         else:
             raise ValueError(f"Unsupported obs_type: {self.obs_type}")
 
+        if self.camera_name_mapping is not None:
+            mapped_agentview = self.camera_name_mapping.get("agentview_image", "image")
+            mapped_eye_in_hand = self.camera_name_mapping.get("robot0_eye_in_hand_image", "image2")
+            self.features_map[LIBERO_KEY_PIXELS_AGENTVIEW] = f"{OBS_IMAGES}.{mapped_agentview}"
+            self.features_map[LIBERO_KEY_PIXELS_EYE_IN_HAND] = f"{OBS_IMAGES}.{mapped_eye_in_hand}"
+
     @property
     def gym_kwargs(self) -> dict:
         kwargs: dict[str, Any] = {"obs_type": self.obs_type, "render_mode": self.render_mode}
@@ -345,6 +399,33 @@ class LiberoEnv(EnvConfig):
             kwargs["task_ids"] = self.task_ids
         return kwargs
 
+    def create_envs(self, n_envs: int, use_async_envs: bool = False):
+        from lerobot.envs.libero import create_libero_envs
+
+        if self.task is None:
+            raise ValueError("LiberoEnv requires a task to be specified")
+        env_cls = gym.vector.AsyncVectorEnv if use_async_envs else gym.vector.SyncVectorEnv
+        return create_libero_envs(
+            task=self.task,
+            n_envs=n_envs,
+            camera_name=self.camera_name,
+            init_states=self.init_states,
+            gym_kwargs=self.gym_kwargs,
+            env_cls=env_cls,
+            control_mode=self.control_mode,
+            episode_length=self.episode_length,
+            camera_name_mapping=self.camera_name_mapping,
+        )
+
+    def get_env_processors(self):
+        from lerobot.processor.env_processor import LiberoProcessorStep
+        from lerobot.processor.pipeline import PolicyProcessorPipeline
+
+        return (
+            PolicyProcessorPipeline(steps=[LiberoProcessorStep()]),
+            PolicyProcessorPipeline(steps=[]),
+        )
+
 
 @EnvConfig.register_subclass("metaworld")
 @dataclass
@@ -387,6 +468,19 @@ class MetaworldEnv(EnvConfig):
             "render_mode": self.render_mode,
         }
 
+    def create_envs(self, n_envs: int, use_async_envs: bool = False):
+        from lerobot.envs.metaworld import create_metaworld_envs
+
+        if self.task is None:
+            raise ValueError("MetaWorld requires a task to be specified")
+        env_cls = gym.vector.AsyncVectorEnv if use_async_envs else gym.vector.SyncVectorEnv
+        return create_metaworld_envs(
+            task=self.task,
+            n_envs=n_envs,
+            gym_kwargs=self.gym_kwargs,
+            env_cls=env_cls,
+        )
+
 
 @EnvConfig.register_subclass("isaaclab_arena")
 @dataclass
@@ -454,3 +548,18 @@ class IsaaclabArenaEnv(HubEnvConfig):
     @property
     def gym_kwargs(self) -> dict:
         return {}
+
+    def get_env_processors(self):
+        from lerobot.processor.env_processor import IsaaclabArenaProcessorStep
+        from lerobot.processor.pipeline import PolicyProcessorPipeline
+
+        state_keys = tuple(k.strip() for k in (self.state_keys or "").split(",") if k.strip())
+        camera_keys = tuple(k.strip() for k in (self.camera_keys or "").split(",") if k.strip())
+        if not state_keys and not camera_keys:
+            raise ValueError("At least one of state_keys or camera_keys must be specified.")
+        return (
+            PolicyProcessorPipeline(
+                steps=[IsaaclabArenaProcessorStep(state_keys=state_keys, camera_keys=camera_keys)]
+            ),
+            PolicyProcessorPipeline(steps=[]),
+        )