One backend call per SAM-style decoder layer (PE norms, token
self-attention, token-to-image cross-attention, erf-GELU feed-forward,
final norm) inside one command buffer, with the layer's f32 weights cached
on the device under their content identity and pooled transients.
gpu_two_way_layer_resident in the common backend; CUDA declines and the
per-op path stays. Body decoder loop on the M3 Max: layers 100 -> 9 ms,
frame 405 -> 266 ms, oracle parity unchanged (kp3d 1.5 mm).
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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