feat: crash-safe state persistence via periodic flush#303
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Persist remaining volatile session state across process restarts without relying on shutdown handlers (which SIGKILL/crashes bypass). Three-tier persistence strategy: - Immediate: session identity (fingerprint, header promotion) — rare - 30s periodic (dirty-flag gated): gradient calibration, cache warming state, and cost tracker snapshot via idle tick DB migration v24 adds 12 columns to session_state for identity (3), cache warming (2), and gradient calibration (7) fields. Review fixes: - Atomic gradient restore (lastTurnAt > 0 proxy, not per-field sentinels) - Dirty flag on SessionState — only flush changed sessions on 30s tick - Moved cost persistence from per-turn to 30s tick (reduces write amplification) - Validate TTL from DB, log.warn on corrupt warmup JSON
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## Summary Follow-up to #303. Fixes a pre-existing bug where `headerSessionIndex` was empty after process restart, causing Tier 1 session identification to fail and orphan persisted session state. - Load header→session mappings from `session_state` table in `initIfNeeded()` (before the first `identifySession()` call) - Clear `headerSessionIndex` in `resetPipelineState()` for test isolation - New `loadHeaderSessionIndex()` DB function + tests
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Summary
Closes #299
Persist remaining volatile session state across process restarts without relying on shutdown handlers (which
SIGKILL/crashes bypass).Changes
session_state— session identity (3), cache warming (2), gradient calibration (7)gradient.ts: NewsaveGradientState()+ atomic restore of gradient fields from DB on firstgetSessionState()access (useslastTurnAt > 0as "ever flushed" proxy)pipeline.ts: Restore session identity + cache warming from DB on session creation; persist fingerprint/headers immediately on mutation; dirty-flag marking on each turnidle.ts: 30s tick flushes gradient + cache warming + cost state for dirty sessions only (skips unchanged sessions)types.ts:_dirtyflag onSessionStatefor periodic flush gating