Signal Detector — Ambient Brain Capture

After the user enables automatic capture, apply this lightweight pass to substantive inbound messages within their chosen scope. It watches for:

1. Original thinking — the user's ideas, observations, theses, frameworks
2. Entity mentions — people, companies, media references

Original thinking is AT LEAST as valuable as entity extraction. Ideas are the intellectual capital. Entities are bookkeeping. Both compound over time.

Contract

This skill guarantees:

• Applies only after explicit automatic-capture opt-in (skips: no recorded choice, capture off, chat-only requests, and purely operational messages)
• Spawns as a sub-agent where the harness supports it; otherwise runs the detection inline before composing the reply. Never blocking the response is the intent, not a runtime contract
• Checks the user's stored capture choice before writing and honors narrower per-message instructions; a first-fire announcement is not consent
• Captures ideas with the user's EXACT phrasing (no paraphrasing)
• Detects entity mentions and creates/enriches brain pages
• Logs a one-line summary of what was captured
• Back-links all entity mentions (Iron Law)
• Citations on every fact written

Ambient routing is a harness convention that a well-behaved agent follows, not a mechanical guarantee; nothing in the gbrain runtime blocks a reply if the skill never loads. On harnesses without per-message ambient routing (Claude Code, Codex), apply this skill as an agent convention or wire it via a prompt-submit hook. When the operator has enabled memory.auto_writeback (off by default; gbrain config set memory.auto_writeback salient), the MCP server's initialize instructions and the managed bootstrap instruction blocks carry the ambient-writeback contract to the agent, and on Claude Code a Stop-hook extraction backstop catches turns the convention missed. That is still a convention on the agent side — server-delivered instructions plus a backstop, not a mechanical guarantee.

Convention: See skills/conventions/quality.md for Iron Law back-linking.

Every time this skill creates or updates a brain page that mentions a person or company:

1. Check if that person/company has a brain page
2. If yes → add a back-link FROM their page TO the page you just created/updated
3. Format: - **YYYY-MM-DD** | Referenced in [page title](path) — brief context
4. An unlinked mention is a broken brain.

Enablement before capture

Automatic capture is off by default. Before writing, establish an explicit user choice for this brain and capture scope. A stored opt-in or an explicitly enabled memory.auto_writeback mode can supply that choice; off, a missing or unreadable choice cannot. Reading this skill, installing GBrain, an available API key, silence, or an announcement that capture is on does not authorize it.

If the user asks to enable capture, explain what will be retained and record the accepted choice. Honor an existing choice without asking again. A request to remember one fact authorizes that fact, not future ambient capture. Delegation and paid enrichment are separate capabilities: capture opt-in alone does not authorize spawning workers or making paid provider calls.

After activation, confirm the chosen scope once and explain how to turn it off. Do not capture the current turn while awaiting a required answer.

Per-User Storage Policy

If the user turns capture off, record the requested setting and stop capture: no content pages, links, or timeline entries. A chat-only instruction suppresses capture for that message without changing the standing setting; do not save the chat-only content as a preference. Re-enable only on request. Explicit remembering and relevant recall remain available when capture is off.

Phases

Phase 1: Idea/Observation Detection (PRIMARY)

When the user expresses a novel thought, observation, thesis, or framework:

• If it's the user's original thinking (they generated it) → create/update originals/{slug}
• If it's a world concept they're referencing → create/update concepts/{slug}
• If it's a product or business idea → create/update ideas/{slug}

Capture exact phrasing. The user's language IS the insight. Don't paraphrase.

Cross-linking (MANDATORY): Every original MUST link to related people, companies, meetings, and concepts. An original without cross-links is a dead original.

Phase 2: Entity Detection (SECONDARY)

1. Extract entity mentions (people, companies, media titles)
2. For each entity:
   • gbrain search "name" — does a page exist?
   • If NO page → check notability. If notable, save the supplied information with provenance.
   • If page exists but THIN → enrich only within separately authorized capabilities and spending
   • If page exists and RICH → no action
3. For new FACTS with specific dates → call gbrain timeline-add <slug> <date> "<summary>"

Auto-link (v0.10.1): When you write/update an originals or ideas page that references a person or company, the auto-link post-hook on put_page automatically creates the link from the new page to that entity. You don't need to call gbrain link manually. Timeline entries still need explicit calls.

Phase 3: Signal Logging

Always log a one-line summary:

• Signals: 0 ideas, 0 entities, 0 facts (skipped: operational)
• Signals: 0 ideas, 0 entities, 0 facts (skipped: capture off)
• Signals: 1 idea (captured → originals/x), 2 entities (enriched → people/y, companies/z)

This makes the ambient capture loop debuggable.

Output Format

After opt-in, report observed writes and their provenance. Keep the signal log brief and verify captured content with an actual readback. Without opt-in, perform no capture writes; a skipped-capture diagnostic is not a reason to interrupt every response or ask for enablement repeatedly.

When it fails

Follow the agent operator protocol for any gbrain error code, exit code, [AGENT] block or notice block. Specific to this skill:

• No automatic-capture opt-in on record: do nothing. An API key, silence or a first-fire announcement is not consent.
• A capture write returns write_pending (exit 10) or revision_conflict: never block the main reply; poll the receipt or re-read and merge on the next turn.
• Paid enrichment of a thin page needs its own authorization; on no_pricing or a cost-cap refusal, skip enrichment and leave the page thin.

Anti-Patterns

• Blocking the main response to wait for signal detection to complete
• Paraphrasing the user's original thinking instead of capturing exact phrasing
• Creating pages for non-notable entities (one-off mentions)
• Skipping back-links after creating/updating pages
• Running on purely operational messages ("ok", "thanks", "do it")
• Capturing without explicit opt-in, after capture was disabled, or on a chat-only turn
• Treating a first-fire announcement, one explicit memory, or an API key as standing authorization
• Starting paid enrichment or delegation just because capture is enabled

Tools Used

• search — check if entity page exists
• query — semantic search for related context
• get_page — load existing entity pages
• put_page — create/update brain pages
• add_link — cross-reference entities
• add_timeline_entry — record events on entity timelines