# 02 — VideoVAE+ tactile-finetuned encoder artifact diagnosis

3 tests to pin down the right-bottom hotspot + ti=0 boundary bleed.

- **A_synthetic_input_bias**: encode uniform gray (0/64/128/192/255) + noise, look at ‖z‖.
  gray-192 argmax = **(15, 15) right-bottom corner** — encoder positional bias on
  non-zero uniform input.
- **B_per_row_vmax_ep000**: same 3+3 sample frames rendered with global vs
  per-row vmax vs log-scale — proves the "contact frame right-bottom disappears"
  observation is a colormap artifact (GroupNorm suppression).
- **C_temporal_identity_ep000**: encode 16 identical p01 ref frames → 4 latent
  frames. left/right per-frame max = [52.67, 16.73, 10.17, 10.32] / [57.26,
  17.09, 10.18, 10.22]. **ti=0 is 5× baseline**, ti=1 is 1.7×. Boundary bleed
  from temporal encoder's front-replicate pad + spatial encoder's
  `TemporalAttention` position bias.