Cuts Haiku classifier false-positive rate from 44.1% → 22.9% on
BrowseSafe-Bench smoke. Detection trades from 67.3% → 56.2%; the
lost TPs are all cases Haiku correctly labeled verdict=warn
(phishing targeting users, not agent hijack) — they still surface
in the WARN banner meta but no longer kill the session.
Key changes:
- combineVerdict: label-first voting for transcript_classifier. Only
meta.verdict==='block' block-votes; verdict==='warn' is a soft
signal. Missing meta.verdict never block-votes (backward-compat).
- Hallucination guard: verdict='block' at confidence < LOG_ONLY (0.40)
drops to warn-vote — prevents malformed low-conf blocks from going
authoritative.
- New THRESHOLDS.SOLO_CONTENT_BLOCK = 0.92 decoupled from BLOCK (0.85).
Label-less content classifiers (testsavant, deberta) need a higher
solo-BLOCK bar because they can't distinguish injection from
phishing-targeting-user. Transcript keeps label-gated solo path
(verdict=block AND conf >= BLOCK).
- THRESHOLDS.WARN bumped 0.60 → 0.75 — borderline fires drop out of
the 2-of-N ensemble pool.
- Haiku model pinned (claude-haiku-4-5-20251001). `claude -p` spawns
from os.tmpdir() so project CLAUDE.md doesn't poison the classifier
context (measured 44k cache_creation tokens per call before the fix,
and Haiku refusing to classify because it read "security system"
from CLAUDE.md and went meta).
- Haiku timeout 15s → 45s. Measured real latency is 17-33s end-to-end
(Claude Code session startup + Haiku); v1's 15s caused 100% timeout
when re-measured — v1's ensemble was effectively L4-only in prod.
- Haiku prompt rewritten: explicit block/warn/safe criteria, 8 few-shot
exemplars (instruction-override → block; social engineering → warn;
discussion-of-injection → safe).
Test updates:
- 5 existing combineVerdict tests adapted for label-first semantics
(transcript signals now need meta.verdict to block-vote).
- 6 new tests: warn-soft-signal, three-way-block-with-warn-transcript,
hallucination-guard-below-floor, above-floor-label-first,
backward-compat-missing-meta.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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