Only solve equality constraints during slider dragging

The constraint projection was running on every _forward() call, moving
joints away from qpos0 during initialization and ground placement.
Now it only runs when locked_joint_names is provided (slider drag path).

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

Author: hshi74

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "robot-keyframe-kit"
-version = "0.3.2"
+version = "0.3.3"
 description = "A generalizable Viser-based keyframe editor for any MuJoCo robot"
 readme = "README.md"
 license = "MIT"

src/robot_keyframe_kit/editor.py

@@ -46,7 +46,7 @@
 
 from .config import EditorConfig
 from .keyframe import Keyframe
-from .math_utils import interpolate_action, solve_equality_constraints
+from .math_utils import interpolate_action
 from .sim_worker import SimWorker
 
 
@@ -1276,9 +1276,8 @@ def _get_site_transform(self, name: str) -> np.ndarray:
         raise ValueError(f"Could not find site or body named '{name}'")
 
     def _forward(self) -> None:
-        """Run forward kinematics and solve equality constraints at position level."""
+        """Run forward kinematics."""
         mujoco.mj_forward(self.model, self.data)
-        solve_equality_constraints(self.model, self.data)
 
     def _estimate_robot_height(self) -> float:
         """Estimate robot height from geom bounds in the current model state."""

src/robot_keyframe_kit/sim_worker.py

@@ -395,9 +395,14 @@ def _set_joint_angles(self, joint_angles: Dict[str, float]) -> None:
             self.data.joint(name).qpos = value
 
     def _forward(self, locked_joint_names: Optional[list[str]] = None) -> None:
-        """Run forward kinematics and solve equality constraints at position level."""
+        """Run forward kinematics, optionally solving equality constraints.
+
+        Constraint projection only runs when *locked_joint_names* is provided
+        (i.e. during slider dragging).  All other callers just need mj_forward.
+        """
         mujoco.mj_forward(self.model, self.data)
-        solve_equality_constraints(self.model, self.data, locked_joint_names=locked_joint_names)
+        if locked_joint_names is not None:
+            solve_equality_constraints(self.model, self.data, locked_joint_names=locked_joint_names)
 
     def _step(self) -> None:
         """Step physics simulation."""