fix(profiling): preserve policy mode for deterministic forward

src/lerobot/utils/profiling_utils.py

@@ -193,16 +193,15 @@ def write_deterministic_forward_artifacts(
     if device_type == "cuda":
         activities.append(torch.profiler.ProfilerActivity.CUDA)
 
-    was_training = policy.training
+    # Keep the caller-selected module mode so the fingerprint matches the actual
-    policy.eval()
+    # train-path forward used by the policy. Some policies, such as ACT with VAE,
+    # only materialize their full forward outputs while in training mode.
     with torch.random.fork_rng(devices=[] if device_type != "cuda" else None):
         torch.manual_seed(0)
         if device_type == "cuda":
             torch.cuda.manual_seed_all(0)
         with torch.no_grad(), torch.profiler.profile(activities=activities) as profiler:
             loss, output_dict = policy.forward(reference_batch)
-    if was_training:
-        policy.train()
 
     operator_entries = []
     for event in profiler.key_averages():

tests/scripts/test_model_profiling.py

@@ -23,6 +23,8 @@ import subprocess
 import sys
 from pathlib import Path
 
+import torch
+
 
 def _import_model_profiling_script():
     script_path = Path(__file__).resolve().parents[2] / "scripts" / "ci" / "run_model_profiling.py"
@@ -184,3 +186,37 @@ def test_model_profiling_main_smoke_writes_row(monkeypatch, tmp_path):
     assert row["step_timing_summary"]["forward_s"]["mean"] == 0.1
     assert row["deterministic_forward"]["operator_fingerprint"] == "ops-fingerprint"
     assert "policy_setup" in row["artifact_paths"]["cprofile_summaries"]
+
+
+def test_deterministic_forward_artifacts_preserve_policy_mode(tmp_path):
+    from lerobot.utils.profiling_utils import write_deterministic_forward_artifacts
+
+    class _TrainingOnlyPolicy(torch.nn.Module):
+        def __init__(self):
+            super().__init__()
+            self.forward_calls = 0
+
+        def forward(self, batch):
+            self.forward_calls += 1
+            assert self.training
+            return batch["value"].sum(), {"value": batch["value"]}
+
+    dataset = [{"value": torch.tensor([1.0, 2.0])}]
+    policy = _TrainingOnlyPolicy()
+    policy.train()
+
+    write_deterministic_forward_artifacts(
+        policy=policy,
+        dataset=dataset,
+        batch_size=2,
+        preprocessor=lambda batch: batch,
+        output_dir=tmp_path,
+        device_type="cpu",
+    )
+
+    payload = json.loads((tmp_path / "deterministic_forward.json").read_text())
+    assert policy.training is True
+    assert policy.forward_calls == 1
+    assert payload["reference_batch_size"] == 2
+    assert "operator_fingerprint" in payload
+    assert payload["outputs"]["loss"]["numel"] == 1