The dueling A'[i] = A[i] - mean(A) gives identical -1/9 gradient to all
8 non-selected exposure outputs, causing i%3 Q-value degeneracy.
For d==0 (exposure, 9 outputs): skip mean subtraction entirely.
Non-selected outputs get ZERO C51 gradient — only the separate aux
optimizer updates them with unique per-output directional signal.
Branches d=1,2 (order=3, urgency=3) keep mean subtraction — the -1/2
gradient (33%) is strong enough to differentiate 3 outputs.
4 locations patched in the C51 loss kernel.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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