c51_grad_kernel.cu line 275: lift floor from 1e-6 to 1e-3 in
\`inv_a_std = 1.0f / (a_std + 1e-3f)\`, capping the magnitude-branch
gradient amplifier at 1000 instead of ~1e6 in the degenerate case.
Why: Smoke A produced 1109 GRAD_CLIP_OUTLIER events with C51 grad
reaching 9.5e6 — the SP7 budget controller saturated at the EPS_DIV
floor instead of rebalancing proportionally. Phase-0 verification
against the actual kernel found the amplifier is NOT the spec's
claimed −log(p)/p divide (which does not exist; the kernel uses
the CE-stable expf(lp) - proj form at line 81). The actual
amplifier is inv_a_std = 1/(a_std + 1e-6) at line 275, gated by
\`if (d == 1) grad_val *= inv_a_std\` at line 282. When magnitude
advantage logits collapse near-uniform (Smoke A: var_q=9e-10),
a_std → ~1e-9, so inv_a_std → ~1e6.
Per feedback_isv_for_adaptive_bounds, this is a numerical-stability
anchor (Invariant 1: prevent division-by-near-zero amplification),
not a behavioural bound. ISV-driven bounds govern behavior; the
existing 1e-12f floor on a_std at line 274 is also a structural
anchor — same class of fix.
Validation gate: Smoke A2-A GRAD_CLIP_OUTLIER count <100 in fold 2
(was 1109 pre-fix). The 3-order-of-magnitude reduction in worst-
case amplification should bring C51 grad spikes back under SP7
budget controller authority.
Audit doc: Fix 40 added (parallel to Fix 39 for A.2 and Fix 41 for
A.3); the stale "A.1 deferred" note was removed in the A.3 commit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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