Debug physics bugs (collision, solver, joints, integration) using deterministic repro + cdb step-through. Activates when user reports bodies exploding, tunneling, not settling, false contacts, or wrong collision behavior — especially after speculative fixes failed.
Autonomous physics debugging against nudge.exe (app/scene-based) and nudge_tests.exe (unit-test pause points). Scientific method with deterministic repros, mechanical metrics, varied-input verification, and bias guards. Activate when the user asks to debug a physics bug end-to-end and wants the agent to drive from repro to verified fix.