Plan C Phase 2 T8. The plan-prescribed pre-T2 snapshot approach was
impossible (T2 had already landed); replacement strategy (ii) from the
dispatch brief — behavioral parity vs an analytical Boltzmann reference
computed in Rust — is used.
Setup forces direction = Long (d=2) deterministically via peaked C51
logits (Long peaked at v=+0.8 atom; other directions at v=-0.5), so
the kernel's Hold/Flat → mag_idx=0 short-circuit doesn't mask the
magnitude branch's Boltzmann sampling. q_values are crafted with each
branch (mag/ord/urg) peaked at a single bin with magnitude 1.0:
Mag Q = [0.0, 0.0, 1.0] peak at Full (mag=2)
Order Q = [1.0, 0.0, 0.0] peak at Market (ord=0)
Urgency Q = [0.0, 1.0, 0.0] peak at urg=1
With q_range=1.0 in all three branches, tau collapses to 1.0 and the
analytical Boltzmann probabilities are:
P(best) = 1/(1 + 2/e) ≈ 0.5767
P(other) = 1/e/(1 + 2/e) ≈ 0.2117
Tolerance: at batch=8192 the 1-σ Bernoulli noise is ~0.0055 for p≈0.58;
±5% absolute tolerance covers ~9σ. Algorithmic divergence (e.g. an
inadvertent strict-argmax substitution) would shift P(best) to 1.0 —
trivially detected by the ±5% tolerance.
Assertions:
- dir_idx == Long for every sample (eval argmax E[Q] over peaked C51)
- mag/ord/urg histograms each within ±5% of the Boltzmann reference
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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