CRITICAL: backward_full used state_dim for goff_b_s1 offset but
compute_param_sizes uses s1_input_dim (smaller with bottleneck active).
All downstream gradient offsets were misaligned. Fixed: sd → s1d.
HIGH: q_attn_params used alloc_f32 (potentially non-zero) instead of
alloc_zeros. Cross-branch Q-attention residual connection needs near-zero
init for stability. Fixed: alloc_zeros.
MEDIUM (deferred): VSN masking bypassed for magnitude branch — mag_concat
reads raw h_s2 instead of vsn_masked. No impact while W_vsn2 is zero-init
(identity mask). Will fix when VSN backward is wired.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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