perf(ci): split Dockerfile dep-install from source-copy for faster rebuilds

The dep-install layer (uv sync) now only depends on pyproject.toml,
uv.lock, and a minimal package stub — not the full src/ tree. Source
code changes only rebuild the final COPY layer (seconds, not minutes).

Also switch from type=local cache (lost on ephemeral runners) to
type=gha (persisted in GitHub Actions cache, shared across all runs).

Before: every src/ change → full uv sync rebuild (~8-10 min)
After:  src/-only change → cached dep layer, ~30s source copy

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/benchmark_tests.yml

@@ -83,8 +83,9 @@ jobs:
         with:
           cache-binary: false
 
-      # Build the benchmark-specific image; layer cache lives in the runner's
+      # Build the benchmark-specific image. Layer cache uses GHA cache (persists
-      # local Docker daemon — reused across re-runs on the same machine.
+      # across runners). The Dockerfile separates dep-install from source-copy,
+      # so code-only changes skip the slow uv-sync layer entirely.
       - name: Build Libero benchmark image
         uses: docker/build-push-action@v6 # zizmor: ignore[unpinned-uses]
         with:
@@ -93,8 +94,8 @@ jobs:
           push: false
           load: true
           tags: lerobot-benchmark-libero:ci
-          cache-from: type=local,src=/tmp/.buildx-cache-libero
+          cache-from: type=gha,scope=benchmark-libero
-          cache-to: type=local,dest=/tmp/.buildx-cache-libero,mode=max
+          cache-to: type=gha,scope=benchmark-libero,mode=max
 
       - name: Login to Hugging Face
         if: env.HF_USER_TOKEN != ''
@@ -247,8 +248,8 @@ jobs:
           push: false
           load: true
           tags: lerobot-benchmark-metaworld:ci
-          cache-from: type=local,src=/tmp/.buildx-cache-metaworld
+          cache-from: type=gha,scope=benchmark-metaworld
-          cache-to: type=local,dest=/tmp/.buildx-cache-metaworld,mode=max
+          cache-to: type=gha,scope=benchmark-metaworld,mode=max
 
       - name: Run MetaWorld smoke eval (1 episode)
         run: |

docker/Dockerfile.benchmark.libero

@@ -61,9 +61,11 @@ ENV HOME=/home/user_lerobot \
 
 RUN uv venv --python python${PYTHON_VERSION}
 
-# Install only lerobot[libero] — completely isolated from metaworld's dep tree
+# ── Dependency layer (cached unless pyproject.toml / uv.lock change) ────────
+# Copy only the files uv needs to resolve deps, plus a minimal package stub
+# so the editable install can succeed without the full source tree.
 COPY --chown=user_lerobot:user_lerobot setup.py pyproject.toml uv.lock README.md MANIFEST.in ./
-COPY --chown=user_lerobot:user_lerobot src/ src/
+RUN mkdir -p src/lerobot && touch src/lerobot/__init__.py src/lerobot/py.typed
 
 RUN uv sync --locked --extra libero --extra smolvla --no-cache
 
@@ -84,6 +86,7 @@ snapshot_download(repo_id='lerobot/libero-assets', repo_type='dataset', \
 
 RUN chmod +x /lerobot/.venv/lib/python${PYTHON_VERSION}/site-packages/triton/backends/nvidia/bin/ptxas
 
+# ── Source layer (rebuilds in seconds on code-only changes) ─────────────────
 COPY --chown=user_lerobot:user_lerobot . .
 
 CMD ["/bin/bash"]

docker/Dockerfile.benchmark.metaworld

@@ -61,14 +61,17 @@ ENV HOME=/home/user_lerobot \
 
 RUN uv venv --python python${PYTHON_VERSION}
 
-# Install only lerobot[metaworld] — completely isolated from libero's dep tree
+# ── Dependency layer (cached unless pyproject.toml / uv.lock change) ────────
+# Copy only the files uv needs to resolve deps, plus a minimal package stub
+# so the editable install can succeed without the full source tree.
 COPY --chown=user_lerobot:user_lerobot setup.py pyproject.toml uv.lock README.md MANIFEST.in ./
-COPY --chown=user_lerobot:user_lerobot src/ src/
+RUN mkdir -p src/lerobot && touch src/lerobot/__init__.py src/lerobot/py.typed
 
 RUN uv sync --locked --extra metaworld --extra smolvla --no-cache
 
 RUN chmod +x /lerobot/.venv/lib/python${PYTHON_VERSION}/site-packages/triton/backends/nvidia/bin/ptxas
 
+# ── Source layer (rebuilds in seconds on code-only changes) ─────────────────
 COPY --chown=user_lerobot:user_lerobot . .
 
 CMD ["/bin/bash"]