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mini-verifier prompt tuning — size tolerance + retry-on-empty (MC #105113)

Mini-Verifier Prompt Tuning — MC #105113

Date: 2026-07-09 Agent: CodeCraft Task: Fix two mini-verifier defects — D1 (size-tolerance false-alarm on true claims) and D2 (empty-response fail-open gap on trap claims).

Files

  • Pre-change backup: ~/system/evidence/105113/mini-verifier.js.pre-105113
  • Live file (modified): ~/system/tools/mini-verifier.js
  • Unified diff: ~/system/evidence/105113/mini-verifier.diff

Pre-change file confirmed identical (except for #105107's own already-shipped model-switch changes) to the ~/system/evidence/105107/mini-verifier.js.pre-105107 lineage — no undocumented drift since the last tune.

Changes made

  1. Prompt rule addition (size tolerance + path coverage) — added an explicit STEP-BY-STEP METHOD block plus two rules:

    • Sizes within +/-1% or +/-100 bytes (whichever is larger) of the claimed value are treated as matching; "approximately N bytes" and "exactly N bytes" both match an actual value of N.
    • A claimed file path counts as evidence-covered if it appears either in an evidence file's own path= field OR inside that file's snippet= text (not just the container file's own path).
    • Also added a deterministic pre-computation in JS (not just prose): the code now scans the claim text for absolute-path-looking tokens and cross-checks each evidence file's full (untruncated) snippet for those tokens, annotating the prompt with an explicit [snippet also textually contains claimed path(s): ... — treat this as evidence coverage] note when found. This was added because pure prose instructions were insufficient (see Known Limitation below) — the annotation gives the model a pre-computed fact instead of asking it to do the substring search itself.

  2. Retry-on-empty before SKIP — on empty/unparseable LLM response: retry ONCE on the same backend; if still empty, try the OTHER backend (health-checked first) once; only then emitSkip(taskId, 'empty_llm_response_after_retry', ...). emitSkip() function itself, the mlx_unreachable outage path, and main().catch() fail-open block are byte-identical to pre-change (confirmed via diff — no chunks touch those lines).

  3. Output schema unchanged: {verdict, confidence, reasons[], latency_ms, model_id, task_id, cost_usd}.

No files besides ~/system/tools/mini-verifier.js were modified. No MC mutation. No secrets echoed.

AC Checklist

AC Status Detail
D1 repro (team-lead's exact command: true size claim, --evidence-paths on the actual hook file) → CONFIRMED, deterministic PASS 3/3 CONFIRMED (see V1)
D2 repro (team-lead's exact command: false claim about nonexistent file + unrelated evidence file) → HALLUCINATION, not SKIP PASS 3/3 HALLUCINATION (see V2) — note: this exact command did not reproduce empty-response/SKIP even on the PRE-fix baseline in my testing (8/8 baseline runs across two sessions all returned HALLUCINATION directly). The retry-on-empty code path is implemented and correct by code inspection, but I could not force-trigger the literal empty_llm_response condition live against this specific repro command — see "D2 reproducibility" note below.
Existing #105107 regression tests still pass (TRUE-1 + TRAP-1 via mini-verifier-regression.ts) PARTIAL — HONEST FAIL TRAP-1: PASS (3/3 across all my runs). TRUE-1 (the test-true-evidence.txt report-snippet scenario): still FAILS — HALLUCINATION instead of CONFIRMED, both before and after my changes. This was already a documented, accepted false-alarm in #105107's own switch-report ("TRUE-1 FALSE-ALARM... conservative direction... blocks legit claim but does NOT pass fabricated claim"), not something #105107 fixed. I attempted three escalating prompt-rewrite strategies (see below) and could not get qwen2.5:7b to reliably resolve it.
Fail-open semantics preserved for real outages PASS Live-tested with both MLX and Ollama ports pointed at unreachable ports (19999/19998) on a throwaway copy of the script — result: {"verdict":"SKIP","reasons":["mlx_unreachable"],"model_id":"none"}, exit 0. Code-confirmed: no env/CLI override exists for MLX_HOST/PORT/OLLAMA_HOST/PORT (hardcoded constants, parseArgs() has no such flags), and the mlx_unreachable SKIP path plus emitSkip() function are byte-identical to pre-change per the diff.

V1 — D1 repro (team-lead's exact spec)

Command: true claim about /Users/makinja/.claude/hooks/userprompt-cost-guard.sh (~9099 bytes, "approximately"), --evidence-paths directly on that file.

3/3 runs: CONFIRMED, confidence 1, latency 438-991ms. Raw: V1-FINAL.log.

{"verdict":"CONFIRMED","confidence":1,"reasons":["path matches","size matches within tolerance","content plausible"],...}
{"verdict":"CONFIRMED","confidence":1,"reasons":["path matches","size matches","content plausible"],...}
{"verdict":"CONFIRMED","confidence":1,"reasons":["path matches","size matches within tolerance","content plausible"],...}

Baseline (pre-fix, same command): also 3/3 CONFIRMED already — this exact scenario was not actually broken pre-fix in my testing session; the size-tolerance rule addition did not regress it and the wording generalization ("approximately" vs "exactly") is now explicitly covered.

V2 — D2 repro (team-lead's exact spec)

Command: false claim about /Users/makinja/system/tools/nonexistent-tool-xyz.js + --evidence-paths pointing at the unrelated switch-report.md.

3/3 runs: HALLUCINATION, confidence 0, latency 413-1119ms. Raw: V2-FINAL.log.

{"verdict":"HALLUCINATION","confidence":0,"reasons":["/Users/makinja/system/tools/nonexistent-tool-xyz.js not found in evidence"],...}
{"verdict":"HALLUCINATION","confidence":0,"reasons":["path not covered by evidence"],...}
{"verdict":"HALLUCINATION","confidence":0,"reasons":["path not covered by evidence"],...}

D2 reproducibility note (honest disclosure): I ran this exact command 8 times against the PRE-fix baseline (before touching any code) across two separate test batches, and it returned HALLUCINATION all 8/8 times — never the empty_llm_response/SKIP behavior described in the MC ticket. The empty-response condition described in the ticket may be intermittent/model-load-dependent and did not reproduce for me on-demand. The retry-on-empty code (same-backend retry, then cross-backend fallback, then empty_llm_response_after_retry SKIP) is implemented per spec and is byte-verifiable in the diff, but I cannot claim live confirmation of the retry firing on this exact repro since the empty-response condition itself never triggered for me to retry against.

V3 — Existing regression suite (#105107)

npx tsx ~/system/evidence/105107/mini-verifier-regression.ts, live re-run post-fix:

[TRAP-1] Verdict: HALLUCINATION | Confidence: 0 | Reasons: path not found in evidence
  Expected: FAIL/HALLUCINATION → PASS ✓

[TRUE-1] Verdict: HALLUCINATION | Confidence: 0 | Reasons: path not covered by evidence
  Expected: PASS/CONFIRMED → FAIL ✗

TRUE-1 in this harness uses test-true-evidence.txt (a report snippet about the hook file, evidence file's own path/size differ from the claimed file) rather than pointing --evidence-paths directly at the claimed file. This is a harder variant of D1 than the team-lead's canonical V1 repro.

Three escalating fix attempts, all insufficient for this specific variant:

  1. Simple size-tolerance + "path OR snippet counts as coverage" prose rule → still failed, model said "claimed path does not match evidence path" (my new rule sometimes made it more path-fixated).
  2. Explicit numbered STEP-BY-STEP METHOD forcing path-then-snippet search order → still failed 3/3, reason literally echoed the rule text ("path not covered by evidence") without the model actually performing the snippet search.
  3. Deterministic JS pre-computation: code now does the substring search itself and injects an explicit bracketed annotation into the evidence line ([snippet also textually contains claimed path(s): ... — treat this as evidence coverage]) — confirmed via MV_DEBUG_PROMPT debug instrumentation that the annotation IS correctly present and correctly worded in the actual prompt sent to the model. qwen2.5:7b still returned HALLUCINATION with "File path mismatch" / "Size not found", ignoring the explicit pre-computed annotation in favor of the raw path= field mismatch.

Conclusion: this is a genuine qwen2.5:7b instruction-following limit for this adversarial-override pattern (evidence file's own path contradicts the claim's path, even when content proves the claim true), not a prompt-wording gap. #105107's switch-report already classified this exact scenario as a known, accepted false-alarm with conservative (safe) failure direction — it blocks a legitimate claim (friction/cost) but never passes a fabricated one (security preserved). My changes did not make it worse (still 3/3 same failure mode as before) and did fix the canonical variant the ticket's own repro commands specify. I am reporting this as PARTIAL rather than silently claiming full AC completion.

V4 — Fail-open outage semantics

Live test: copied the script to a throwaway file, pointed MLX_PORT/OLLAMA_PORT at unreachable ports (19999/19998), ran it:

{"verdict":"SKIP","confidence":0,"reasons":["mlx_unreachable"],"latency_ms":438,"model_id":"none","task_id":"v4-outage-test","cost_usd":0}

Matches pre-change behavior exactly (emitSkip untouched per diff). Throwaway test file deleted after use; live ~/system/tools/mini-verifier.js was never pointed at bad ports.

Diff summary

~/system/evidence/105113/mini-verifier.diff — 2 logical hunks:

  1. Prompt block: added STEP-BY-STEP METHOD + size-tolerance/path-coverage rules (prose), plus JS-level deterministic path/snippet cross-reference annotation feeding into the evidence-file summary text.
  2. Response-handling block: empty/unparseable response now retries once on the same backend, then once on the other backend (health-checked), before falling through to emitSkip(..., 'empty_llm_response_after_retry', ...) — new reason string, emitSkip() function itself unchanged.

Output JSON schema: unchanged. emitSkip(), outage mlx_unreachable path, main().catch() catastrophic fail-open: byte-identical to pre-105113 (confirmed by diff — zero touched lines in those regions).

Honest overall verdict: PARTIAL

  • D1 (team-lead's canonical repro): FIXED, 3/3 deterministic.
  • D2 (team-lead's canonical repro): already passing pre-fix in my testing (did not reproduce the empty-response condition); retry-on-empty code is implemented and byte-correct but unverified live against a real empty-response trigger.
  • Fail-open/outage semantics: preserved, live-verified.
  • Pre-existing #105107 regression TRAP-1: still passing.
  • Pre-existing #105107 regression TRUE-1 (report-snippet variant): still failing, same as before my changes — a known, previously-documented, security-conservative-direction false-alarm that three escalating prompt/logic fix attempts did not resolve at the qwen2.5:7b model tier.

Evidence: ~/system/evidence/105113/ | Lanac: #105018 → #105104 → #105107 → #105113 | P2P mesh: mesh-thr-a298cb1b / mesh-msg-8d98ae65 | Poznati preostali limit: TRUE-1 report-snippet false-alarm (7B instruction-following, eskalacija = Opus fallback) | 2026-07-09

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