feat(rollout): add smooth_handover flag to DAgger strategy config

The DAgger phase transitions run blocking smooth handovers: on pause the
leader is driven to the follower (~2 s), and on correction start the
follower is slid to the teleop pose (~1 s), both inside the record loop.

For clutch-style teleoperators (e.g. VR controllers) that re-reference
their command frame at the current robot pose on engage, the handover is
already continuous — the interpolation only delays the start of the
correction and eats its first frames.

Add --strategy.smooth_handover (default true, existing behavior
unchanged) to let such setups skip it, mirroring the episodic strategy's
smooth_leader_to_follower_handover flag.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/source/inference.mdx

@@ -155,6 +155,7 @@ Foot pedal input is also supported via `--strategy.input_device=pedal`. Configur
 | `--strategy.record_autonomous`       | Record autonomous frames too (default: false)           |
 | `--strategy.upload_every_n_episodes` | Push to Hub every N episodes (default: 5)               |
 | `--strategy.input_device`            | Input device: `keyboard` or `pedal` (default: keyboard) |
+| `--strategy.smooth_handover`         | Smoothly hand control over at pause / correction start (default: true). Disable for clutch-style teleops that re-reference at the current robot pose on engage |
 | `--teleop.type`                      | **Required.** Teleoperator type                         |
 
 ### Episodic (`--strategy.type=episodic`)

src/lerobot/rollout/configs.py

@@ -180,6 +180,14 @@ class DAggerStrategyConfig(RolloutStrategyConfig):
     # Target video file size in MB for episode rotation (record_autonomous
     # mode only).  Defaults to DEFAULT_VIDEO_FILE_SIZE_IN_MB when None.
     target_video_file_size_mb: int | None = None
+    # Whether to turn on or off the smooth handover behavior at phase transitions:
+    # the leader is driven to the follower position on pause (teleops with
+    # `send_feedback` capability), and the follower is slid to the teleop pose when
+    # a correction starts (non-actuated teleops). Disable for clutch-style
+    # teleoperators (e.g. VR controllers) that re-reference at the current robot
+    # pose on engage: the handover is already continuous there, and the blocking
+    # interpolation only delays the start of the correction.
+    smooth_handover: bool = True
     input_device: str = "keyboard"
     keyboard: DAggerKeyboardConfig = field(default_factory=DAggerKeyboardConfig)
     pedal: DAggerPedalConfig = field(default_factory=DAggerPedalConfig)

src/lerobot/rollout/strategies/dagger.py

@@ -623,8 +623,8 @@ class DAggerStrategy(RolloutStrategy):
     # State-machine transition side-effects
     # ------------------------------------------------------------------
 
-    @staticmethod
     def _apply_transition(
+        self,
         old_phase: DAggerPhase,
         new_phase: DAggerPhase,
         engine,
@@ -634,6 +634,10 @@ class DAggerStrategy(RolloutStrategy):
     ) -> None:
         """Execute side-effects for a validated phase transition, including smooth handovers.
 
+        The smooth handovers below can be disabled with
+        ``--strategy.smooth_handover=false`` (useful for clutch-style teleops
+        that re-reference at the current robot pose on engage).
+
         AUTONOMOUS -> PAUSED (actuated teleop):
             Pause the engine, then drive the leader arm to the follower's last
             commanded position so the operator takes over without a jerk.
@@ -657,7 +661,7 @@ class DAggerStrategy(RolloutStrategy):
             logger.info("Pausing engine - robot holds position")
             engine.pause()
 
-            if teleop_supports_feedback(teleop) and prev_action is not None:
+            if self.config.smooth_handover and teleop_supports_feedback(teleop) and prev_action is not None:
                 # TODO(Maxime): prev_action is in robot action key space (output of robot_action_processor).
                 # send_feedback expects teleop feedback key space. For homogeneous setups (e.g. SO-101
                 # leader + SO-101 follower) the keys are identical so this works. If the processor pipeline
@@ -668,7 +672,11 @@ class DAggerStrategy(RolloutStrategy):
 
         elif old_phase == DAggerPhase.PAUSED and new_phase == DAggerPhase.CORRECTING:
             logger.info("Entering correction mode - human teleop control")
-            if not teleop_supports_feedback(teleop) and prev_action is not None:
+            if (
+                self.config.smooth_handover
+                and not teleop_supports_feedback(teleop)
+                and prev_action is not None
+            ):
                 logger.info("Smooth handover: sliding follower to teleop position")
                 obs = robot.get_observation()
                 teleop_action = teleop.get_action()