Quick answer: Unity Animation Rigging constraints affecting bones in wrong order? Layer order determines evaluation - reorder in the Rig component or split into multiple Rig assets.
IK foot placement runs before the spine adjustment. Feet plant against the un-adjusted ground; spine then pushes the character above the floor.
Reorder layers
On the Rig component, constraints evaluate top-to-bottom. Drag IK below spine so spine adjusts first.
Use multiple Rig layers
Split into Rig A (base pose) and Rig B (IK). Weight blends between them; evaluation order between rigs is deterministic.
Validate with the Rig Builder
Window > Animation > Animation Rigging > Rig Builder. Shows the evaluation graph; reorder mistakes are visible.
“Animation Rigging is a constraint solver. Solvers care about order.”
Build one canonical character rig. New characters derive from it. The order is correct from the first frame because nobody re-decides it.