docs(dqn): SP1 Phase B smoke result — F1 NaN topology captured (slots 26 + 32)
Smoke smoke-test-xvzgk (commit f139a63ee) confirms Phase B
instrumentation fires correctly: backward-path slots 24-35 capture
the F1 ep2 explosion's NaN topology beyond the prior visible-only
[6, 12] (grad_buf + save_h_s2).
F1 first-fire signature: flagged=[6, 12, 26, 32]
- 26 iqn_trunk_m — apply_iqn_trunk_gradient cuBLAS bwd output
- 32 bn_d_concat_buf — Bottleneck Linear backward dy
- 6, 12 = downstream propagation (existing visible flags)
CLEAN at first-fire: slots 27 (iqn_d_h_s2_buf), 28 (d_branch_logits_buf),
33/34/35 (bw_d_h_s2 multi-point), 24/25 (d_value/adv_logits_buf),
29 (cql), 30 (aux).
Source kernels identified (drives Task 6 surgical fix):
1. apply_iqn_trunk_gradient cuBLAS sgemm (gpu_dqn_trainer.rs:6843+) —
matches session_2026-04-05 residual-8% finding, never closed.
2. Bottleneck Linear backward cuBLAS sgemm — NEW finding (not in audit's
original top-3 ranking). cuBLAS GEMM produces NaN from clean inputs;
suggests extreme intermediate products at F1's Bellman-target shift.
Both are template (f) cuBLAS-wrapper fixes — input range guard + output
sanitization, ISV-driven bounds (Q_ABS_REF_INDEX=16, Q_DIR_ABS_REF_INDEX=21,
H_S2_RMS_EMA_INDEX=96 — all existing slots, no new ISV).
F0 Sharpe regression to 34.55 (from 55.87 baseline) noted as concern.
Possible stochastic variance OR Phase B instrumentation timing impact;
calibrate with Task 6 fix smoke. No deferral per operating principles.
F2 cascade (steps 5+): flagged adds slots 2, 3, 7, 8, 24, 25, 29, 33, 34
once F1's corrupted Adam EMAs + weights flow into F2. Slots 27, 28, 35
STAY CLEAN throughout — IQN-internal backward chain is NOT the seed;
the cascade enters IQN's consumer but never the IQN producer.
2ba0eef718