The bs>1 prefill path has multiple coupled stages: scheduler admission, page-aligned batch planning, tensor splitting, direct cache writes, index top-k, MLA reuse, and disaggregated KV handoff. Add a default-off, rate-limited debug channel so production ETE runs can identify where batching or metadata semantics diverge without permanently increasing hot-path log volume.
Constraint: Logs must be default-off and rate-limited because these paths execute per-rank and often per-layer.
Rejected: Always-on INFO logs | would flood logs and add CPU overhead during normal prefill.
Rejected: Only scheduler-side logging | insufficient to distinguish planner, index, MLA, and transfer handoff failures.
Confidence: medium
Scope-risk: moderate
Directive: Keep bs>1 debug evidence env-gated; do not add unconditional per-layer or per-token logs in these paths.
Tested: Local py_compile for touched files
Tested: git diff --check
Tested: Remote py_compile and targeted NSA CP utility tests: 5 passed
Not-tested: Full ETE correctness with debug disabled
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