Controlled use_harness on/off on dense 27B (same workload/SLO/substrate, only the flag
differs). Harness ON: TP2 -> TP4 (0.34 req/s/GPU) in 2 iters, rejected two worse
refinements, premature LLM stop vetoed then honored -> converged, no regression.
Naive OFF: kept TP=1 and cranked runtime knobs (mbt 16k->65k, seqs, caching), all 5
trials infeasible (same TPOT/TTFT compute bottleneck), one engine OOM crash, no feasible
config found. The bottleneck is compute; the harness steered to the knob family that
adds compute (TP) while naive wandered in knobs that cannot. Reproduces the paper's
Fig-18 finding. Substrate is compressed (process comparison, not peak-rate); naive run
was infra-interrupted at trial-5 (already conclusive). Read from cpfs via dash1.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Gahow Wang
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