Quick answer: Unity Animator layer weight changes ignored while a state is mid-blend? Layer weight is sampled once per evaluation - change pre-blend or use a separate animation parameter.
Reduced layer 1's weight during a transition. Animation still bleeds layer 1 fully until the transition completes.
Set weight pre-transition
Modify SetLayerWeight before triggering the state change. The new weight is sampled at transition start.
Use a sync layer
Sync Layer mirrors the timing but allows independent weight curves. The override layer adjusts smoothly without fighting the base.
Or use Avatar Mask transitions
For partial-body overrides, an avatar mask + per-state mask gives cleaner weight control than layer weight.
“Layer weight is a global. Globals interact poorly with running transitions.”
Tweak layer weights via animation curves rather than code where possible. Curves are inspectable and sample correctly through blends.