# Reviewer Risk Register

Updated 2026-05-25 after Window 1.

| Risk | Severity | Evidence | Mitigation |
|---|---|---|---|
| ~~Session sequentiality not proven~~ | resolved | A1 instrumentation lands per-request t_dispatch/t_first_token/t_finish unix timestamps + proxy_request_id. Smoke validation 2026-05-25 confirms 30/30 join coverage. | All Window 1 runs already use this; Window 2 inherits. |
| ~~Cache reuse decomposition incomplete~~ | resolved | Real reuse decomposition computed in `window_1_results/lmetric_reuse.json` from joined records carrying session_id + hash_ids + cached_tokens. | — |
| APC across hot-sweep policies may be contaminated by prior policy runs | low | First-turn cached_tokens distribution shows < 1% empirical contamination; load_only and sticky vLLMs were not restarted between policies. `unified` and `capped` are isolated cold-start. | Window 2 will isolate each policy launch by default; document in paper that lmetric/load_only/sticky reflect "warm-cache" condition. |
| Unified missing `interference_index` due to analyzer truncate-write bug | medium | The original `b3_analyze.sh` unconditionally `slice_engine_state.py`'d each policy and used `open("w")`, overwriting unified's correctly-written engine_state with the empty-window slice from the (hot-sweep) shared dir. | Fixed in commit `df32499`. B2 microbench provides the cleaner same-vs-different interference proof, so we do not need to rerun unified. |
| GPU 0 ghost memory after vLLM crash | low | EngineCore subprocess name is `VLLM::EngineCor`; `pkill -f "vllm serve"` misses it. Killed manually on 2026-05-25; cleanup logic in `b3_sweep.sh` and `b3_isolated_policy.sh` now also targets `EngineCore`. | — |
| w600 trace is a 1k-request sample, not the full GLM-5.1 trace | low | All B3 + B2 percentiles are on this sample. Full-trace KV-footprint and reuse claims use the 2.11M-request full trace. | Window 2 SRR sweep uses w600; full-trace SRR would need a larger sample and more GPU budget. |
| Trace-timestamp dispatch with strict session sequentiality stretches replay wall time | medium | lmetric's 600s trace dispatched over 49 min; system over-saturates and the dispatch window expands. | Window 2 uses A4 open-loop Poisson loadgen with explicit arrival rate, decoupling load level from trace structure. |
| Capped cap=8 may be too soft | low | Reviewer might prefer cap=2 or cap=4 to test "no multi-turn" extreme. Cap=8 was chosen to sit between turns/session p90 (1) and p99 (18). | Re-run with a stricter cap if reviewer pushes back; underlying capped script is parameterized. |
| B2 microbench uses synthetic short-prompt decode load (256 tokens) | low | This bounds the realism of the "decode" workload. Production decode tokens come from prior turns of long context. | The signal magnitude is robust enough that prompt length shouldn't qualitatively change conclusions; B3 sticky's failure breakdown is the production-trace confirmation. |
| Reading B2 same-worker interference from TPOT p90 alone gives a non-monotone curve | low | TPOT p90 idx peaks at 32k (7.89×) then drops at 65k (2.26×) even though TTFT idx grows monotonically (94.6× → 218×) and TPOT p99 grows monotonically (59 → 169.5 ms). The drop is regime shift (cost migrates from TPOT to TTFT once prefill blocks first-token long enough), not interference relief. | Reports must lead with TTFT idx; TPOT p99 is the right tail indicator for TPOT. See window_1_results.md §"TPOT idx peaks at 32k, not 65k". |
