Retrieval eligibility (SNUG-121)

User-facing agent retrieval (RAG, MCP ask / search_knowledge, brain /ask) applies a single eligibility policy so operational metadata never masquerades as user-meaningful evidence.

Implementation: brain/src/hippo_brain/retrieval_eligibility.py. Wired through retrieval.Filters.include_excluded and env HIPPO_RETRIEVAL_INCLUDE_EXCLUDED=1.

Default policy by source family

Family	Included when	Excluded by default
shell	`events.probe_tag IS NULL`	Synthetic probe commands (`probe_tag` set)
browser	`browser_events.probe_tag IS NULL`	Probe canary page views
agentic (claude/codex/cursor/opencode)	Non-probe, non-journal, non-empty, settled segment	`probe_tag` set; `journal.jsonl` under `subagents/.../workflows/`; `message_count=0` with blank `summary_text`; `end_time` within 90s settle window of now (in-flight)
workflow (GitHub Actions)	`conclusion IS NOT NULL` or `status = completed`	In-progress status journal rows
claude-auto-memory	Active document revision (`memory_documents.state = 'active'`)	Superseded / inactive revisions

Enrichment-time filters (is_enrichment_eligible) prevent most noise from ever becoming knowledge nodes. Retrieval eligibility is defense-in-depth for rows that slip through or for hydration of linked sources.

Operator / debug mode

Set any of:

Filters(include_excluded=True) on programmatic retrieval
MCP tool param include_excluded=true on search_knowledge and ask
Environment HIPPO_RETRIEVAL_INCLUDE_EXCLUDED=1 for the brain/MCP process

Operator mode disables the eligibility gate so capture-health investigations can see probe and diagnostic rows. Never enable in production agent defaults.

Adding a new source

Add enrichment eligibility in enrichment.is_enrichment_eligible (capture path).
Add retrieval SQL helpers in retrieval_eligibility.py.
Extend knowledge_node_eligible_exists_sql with an EXISTS branch.
Add a regression test in brain/tests/test_retrieval_eligibility.py.

See also AP-6 in anti-patterns.md. Agent-facing per-source semantics: source-trust-contracts.md.