Append a "Plan Accuracy Errata" section to the SP19+20 plan
documenting the 6 deviations from the original Phase 2 plan that
emerged during implementation. Each entry captures the gap, the
decision made, and the rationale, so future implementers see what
was actually built vs what was specified.
Gaps documented:
1. Task 2.0 (label-at-open infrastructure) was NEW — split out from
Task 2.2 to land buffer + alloc + reset + write site atomically
before Task 2.2's consumer ships. Sign convention mapping detail
captured (kernel emits {0, 1, -1}, SP20 spec uses {-1, 0, +1}).
2. Per-env alpha plumbing was not in Task 2.2 plan scope — built in
Task 2.2 (NOT deferred to Phase 4) to preserve the
`feedback_no_partial_refactor` contract atomicity. Touches 5
files in one commit.
3. Per-bar SP18 D-leg sites — KEEP for Phase 2 per `feedback_no_stubs`.
Plan's wording "DELETE [these helpers]" was overbroad; only the
trade-close-site call is deleted. The phantom
`compute_sp12_reward_with_cost` doesn't exist as a function (the
SP12 v3 reward is the inlined block).
4. `sp20_compute_event_reward` placement — new dedicated
`sp20_reward.cuh` header (NOT inside `experience_kernels.cu`,
NOT inside `trade_physics.cuh`). Mirrors the
compute_asymmetric_capped_pnl / compute_min_hold_penalty
header-only pattern; needed for GPU oracle test wrapper to share
the function bit-for-bit per `feedback_no_cpu_test_fallbacks`.
5. Task 2.3 was subsumed by Task 2.2 — the existing Path C chain
consumes the new `alpha` field automatically once `alpha_per_env`
is wired; no separate `sp20_emas_compute` producer call needed.
6. `min_hold_*` kernel-arg trio cleanup deferred to Task 2.4 — the 3
kernel args were deleted in Task 2.2 (per `feedback_no_hiding`)
but the upstream producer chain (`min_hold_temperature_update_kernel`,
ISV[460], `read_min_hold_temperature_from_isv`, `config.min_hold_*`)
deferred to Task 2.4 because it touches SP14 ISV slot registry +
StateResetRegistry + ISV layout fingerprint bump.
Implementation-level details remain in `docs/dqn-wire-up-audit.md`
Task 2.0 / 2.1 / 2.2 entries; this errata is the plan-level
"what was actually built vs what was specified".
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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