Spine Path Motion Speeds Up and Slows Down? Separate Sampling and Easing

A bone changes speed along a curve, and enabling Constant Speed still leaves a slowdown near the end. Separate how time changes the constraint position from how that position is mapped onto the path. Both stages can affect the motion you see.

Hold the path still first

The official reference describes more accurate path-position calculation with Constant Speed enabled. Unequal handle lengths and deformation can worsen accuracy when it is disabled. In a project copy, hold the path, skeleton scale and camera fixed. Use linear Position keys and remove unrelated constraint influences. Compare enabled and disabled runs with the same endpoints and duration.

Restore easing by itself

Sample the constrained bone world position at equal time intervals and compare successive travel distances. Straight segments between samples only approximate distance on a curve; sparse sampling can distort the comparison. Keep Constant Speed enabled and restore only the original key interpolation. If the slowdown returns with that curve, investigate time interpolation instead of expecting the path option to override easing.

Reintroduce path deformation

Restore weights or deform keys that change the path and repeat the sample. Record the path pose because motion of the path itself changes world-space speed. For a start position that moves after the path length changes, use the related diagnostic guide on Fixed and Percent. Review compatible character motion in the Spine Workbench, then validate path settings and performance in Spine and the receiving engine.