Per feedback_no_functionality_removal.md: R5 was originally scoped as
DELETE in the Phase 2 plan and the Track 2 triage because
reward_contrib[3] = 0.000 across 60 / 60 smoke epochs and
dqn-smoketest.toml sets micro_reward_scale = 0.0. Re-examination during
Phase 2 Task 2.3 rejected the DELETE path:
- dqn-production.toml already sets micro_reward_scale = 0.1, so R5 is
load-bearing in production, not dead code. The 0.0 value in smoke is
deliberate test-isolation (td_propagation / magnitude_distribution /
reward_component_audit all want the sparse-reward TD path isolated).
- The state-vector OFI block at state[SL_OFI_START..SL_OFI_START+SL_OFI_DIM)
= [42..62) provides representation features for the encoder (policy
side). R5 is a per-bar reward gradient on the critic (critic side).
Different mechanisms — production deploys both together.
- R5 also reads PREV_MID (retrospective hold quality), which is NOT in
the state vector. That signal exists only in the kernel branch.
Changes — pure documentation, no behavior change:
- experience_kernels.cu: ~30-line comment block at the R5 wiring site
(~L1915) documenting the parameter-not-flag status, production vs
smoke values, why state-vector OFI is complementary not redundant,
and the feedback_no_functionality_removal.md seal.
- experience_kernels.cu: fix stale kernel-signature comment that claimed
OFI was at state[66..74). Correct range is [42..62) per state_layout.cuh.
- config.rs: extend DQNHyperparameters::micro_reward_scale docstring and
add a comment at the Default impl pointing back at the kernel site.
- gpu_experience_collector.rs: extend reward_contrib_fractions docstring
to mark the micro=0.000 slot as a SEMANTIC value when the loaded profile
has micro_reward_scale=0.0, not a wiring regression.
- track2-triage.md: R5 verdict changed from DELETE to FIX-documented-disable
with the rationale above; "Proposed Phase 2 changes" section 1 and
"Next Track 2 steps" updated accordingly.
Smoke tests: 3 / 4 pass (reward_component_audit, controller_activity,
exploration_coverage). magnitude_distribution is failing on baseline
HEAD c0fee5a9b as well — pre-existing H10 magnitude-head collapse
regression (eval dist_mag ef=0.000, eh=0.000), unrelated to R5.
Verified via git-stash round-trip: baseline fails, changes do not
introduce new failures.
Closes Track 2 R5 verdict (originally DELETE, now FIX-documented-disable).
7b74290dd0