Adds two nullable TEXT columns to entity_facts —
`created_by_model` (LLM identifier) and `created_by_backend`
("local" / "hybrid" / "manual" / NULL) — so the curator can audit
which configurations produce good fact-keeping and which produce
noise.
photo_insights already carries model_version + backend, and
entity_facts.source_insight_id links to it, but:
- source_insight_id is set post-loop, so chat-continuation and
regenerated-insight facts lose the link.
- JOINing per read is more friction than embedding provenance on
the row itself.
- Manual facts (POST /knowledge/facts) have no insight at all and
need their own "manual" provenance marker.
Threading: execute_tool grows `model` + `backend` params, passed
from the three call sites (agentic insight loop, chat single-turn,
chat stream) using the loop-time `chat_backend.primary_model()` +
`effective_backend` already in scope. tool_store_fact stamps the
new fact accordingly; manual create_fact stamps backend="manual".
Legacy rows leave both NULL — pre-tracking data can't be back-
filled reliably from training_messages without burning compute.
Indexes are partial (WHERE NOT NULL) so legacy rows don't bloat
them, and "show me all facts from model X" stays fast.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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