FlowWM/causal_droidstd/step_5000/FINDING.md

step 5000 — root cause: wrong Phi bootstrap latent

The rollout seeded its autoregressive Phi history with zero_flow_latent.pt, which is the VAE encoding of a WHITE image (the legacy Middlebury colour wheel renders zero flow white). causal_mode's Phi is raw (u,v,dz) clipped to [-1,1] — the VAE's own input range — so its "no motion" point is the ZEROS image, i.e. mid-GREY.

	norm	L2 to quietest real GT Phi
old zero_flow_latent (white)	88.4	90.5
new zero_phi_latent (grey)	46.1	33.0
quietest real GT Phi frame	44.2	0

Effect (same checkpoint, same seed, only the bootstrap changed):

	PSNR mean	min
white bootstrap	14.14 dB	10.55
grey bootstrap	16.08 dB	14.62

Video drift is gone. TRAINING WAS NEVER AFFECTED — it takes cond_f from the dataset's GT Phi latent, never from the bootstrap — so no training compute was wasted.

Still open: decoded Phi is high-frequency noise rather than the sparse grey+patches of GT, at 8% of training. Watch; do not conclude yet.