feat(extraction): EXP-06 — generic event anchors for As-of facts

[moralespanitz]

Summary

When a fact begins with As of <date>, ... and no DESCRIPTOR_RULE matches but a subject is recoverable, emit a generic event.occurred anchor with the date and subject. Behind a new feature flag genericEventAnchorEnabled (default false).

This is EXP-06 from the Sprint 2 phase-2 implementation plan.

Why this exists

event-anchor-facts.ts ships a list of LoCoMo-style DESCRIPTOR_RULES (mentorship, internship, networking, Paris/Rome trips, etc.). Any BEAM fact with an As of <date>, prefix that doesn't match one of those rules is emitted without an anchor and is invisible to the temporal-anchor retrieval path.

The Stage 7 dry-run on iter 7 v3 measured TR 1/2 and EO 0/2; manual inspection of the failing facts showed clear temporal phrasing (As of January 2026, user is using PostgreSQL, As of March 15 2025, user completed the API migration) that the rules silently dropped.

The fall-through anchor restores those facts at retrieval time without any new LLM call.

The rule

In inferDescriptors:

1. Run the existing DESCRIPTOR_RULES loop.
2. If descriptors.length === 0 AND options.genericEventAnchorEnabled === true, push { label: 'event.occurred', subject, eventDateIso } and let the rest of the pipeline build the anchor fact.
3. The subject is recovered through the existing inferSubject helper, which already returns null (no anchor) when neither a person entity nor \buser\b is present in the fact text.

The recorded-date prefix parser is widened to accept Month Year (e.g. January 2026) in addition to the existing Month Day Year form. When only month-year is present, the synthesized event date is the first day of the month — sufficient for retrieval keying.

Risks

• Anchor inflation. With the flag on, every As of <date>, fact becomes at least one anchor. The flag is off by default to bound this.
• Subject collapse to User. inferSubject falls back to User when no person entity is present. This weakens multi-event ordering (an EO concern, addressed by EXP-13). Subject extraction returns null rather than guessing for ambiguous inputs.
• Co-existence with DESCRIPTOR_RULES. The descriptors.length === 0 guard ensures we never double-emit on a single fact. Existing LoCoMo regression tests still pass with the flag on.
• Co-existence with EXP-13 boundary fields. Anchors are post-extraction synthetic artifacts and intentionally do not carry the event_boundary / boundary_prob fields the LLM-judged extraction adds — anchors get their own retrieval boost.

Test cases

src/services/__tests__/event-anchor-facts.test.ts — extended:

• Generic anchor emitted for As of January 2026, user is using PostgreSQL. (month-year prefix, flag on).
• Generic anchor emitted for As of March 15 2025, user completed the API migration. (full-date prefix, flag on).
• No anchor emitted when flag is off.
• No anchor emitted for facts without an As of <date> prefix (flag on).
• DESCRIPTOR_RULE regression: mentorship.received still fires for the existing LoCoMo fixture, and the generic fall-through does not also fire on the same source fact when the flag is on.
• Subject-extraction fallback returns [] (no anchor) on As of January 2026, the situation continues. rather than crashing or guessing.
• Non-prefixed weird input (Random unstructured text without temporal prefix.) returns [] without throwing.

All 12 tests pass (5 existing regression + 7 new). Related runtime-config tests for consensusExtractFacts were updated to thread the new field through and all 18 of those continue to pass.

Config override

To enable for a single ingest call without restarting the server:

{
  "config_override": {
    "genericEventAnchorEnabled": true
  }
}

Or via env:

GENERIC_EVENT_ANCHOR_ENABLED=true

The field is also added to INTERNAL_POLICY_CONFIG_FIELDS so PUT /v1/memories/config accepts it on dev/test deployments.

Wiring

• RuntimeConfig.genericEventAnchorEnabled: boolean (default false).
• IngestRuntimeConfig extended with the same field; MemoryServiceDeps.config already pulls it through & IngestRuntimeConfig.
• ConsensusExtractionConfig.genericEventAnchorEnabled: boolean — buildExtractionOptions forwards it into extractFacts(...).
• ExtractionOptions.genericEventAnchorEnabled?: boolean (in observation-date-extraction.ts, the existing pattern).
• extraction.ts:323 forwards the flag into enrichExtractedFacts(..., { genericEventAnchorEnabled }).
• enrichExtractedFacts and inferEventAnchorFacts accept the new option; default-off preserves bit-identical output.
• quickExtractFacts accepts an optional EnrichmentOptions; memory-ingest.ts:performQuickIngest threads deps.config.genericEventAnchorEnabled through so the quick path also benefits.

Test plan

• npx tsc --noEmit — exit 0
• npx vitest run src/services/__tests__/event-anchor-facts.test.ts — 12/12 passing
• npx vitest run src/services/__tests__/consensus-extraction-runtime-config.test.ts observation-date-extraction.test.ts quick-extraction-assistant.test.ts — 18/18 passing
• npx vitest run src/services/__tests__/extraction.test.ts extraction-enrichment.test.ts extraction-cache.test.ts — 64/64 passing
• npx vitest run src/services/__tests__/memory-ingest-runtime-config.test.ts ingest-trace-branches.test.ts — 12/12 passing
• BEAM TR/EO sweep with the flag on (follow-up: dispatcher run after merge)