The cache-hit accuracy drop is not isolated to one obvious kernel boundary, so the scheduler/radix/HiCache path needs request-correlated evidence. Add default-off, rate-limited CP shared-KV debug logs for prefix matching, valid-tail flooring, pending backup attach/commit, load-back planning, and unfinished-request cache insertion. The investigation notes capture current GSM8K pass1/pass2 evidence and rejected interpretations to avoid repeated log archaeology.
Constraint: Logs must be default-off and bounded because these paths are scheduler/control hot paths.
Rejected: Always-on INFO tracing | would distort the exact latency and cache-hit behavior under investigation.
Confidence: medium
Scope-risk: moderate
Directive: Remove or keep env-gated only after the GSM8K cache-hit root cause is closed; do not leave unbounded hot-path logs.
Tested: python -m py_compile on changed runtime files.
Not-tested: Local pytest blocked before collection by missing orjson dependency; fresh restarted GSM8K verification still pending.
(cherry picked from commit bfc6d1473dc2a5d72bc3a8d6fca1e2429537be0e)
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