> For the complete documentation index, see [llms.txt](https://ai-os-and-trend-finder.gitbook.io/ai-os-and-trend-finder-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ai-os-and-trend-finder.gitbook.io/ai-os-and-trend-finder-docs/.spec_system/archive/phases/phase_29/session_09_source_death_baseline_alarm.md).

# Session 09: Source-Death Baseline Alarm

**Session ID**: `phase29-session09-source-death-baseline-alarm` **Status**: Not Started **Estimated Tasks**: \~12-25 **Estimated Duration**: 2-4 hours

***

## Objective

Distinguish a genuinely quiet run from a silent source or adapter death. Maps the Tier 3 source-death baseline alarm idea.

***

## Scope

### In Scope (MVP)

* Persist a private last-good per-source evidence-count baseline keyed by source ID.
* Warn when a configured source that previously returned evidence now returns zero accepted rows.
* Distinguish disabled/unconfigured/skipped sources from source-death warnings.
* Surface the warning in collection health and Engine Replay without exposing private baseline paths.

### Out of Scope

* Auto-disabling or re-enabling any source.
* Exposing the private baseline file path or counts beyond safe warning labels.

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## Prerequisites

* [ ] Session 07 complete (uses the narrated trace/warning path established there).

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## Deliverables

1. Private last-good per-source baseline keyed by source ID.
2. Source-death warning that excludes disabled/unconfigured/skipped sources.
3. Collection-health and Engine Replay surfacing without private paths.
4. Unit tests for zeroed-live, first-run, and disabled-source cases.

***

## Success Criteria

* [ ] A zeroed previously-live source trips a source-death warning.
* [ ] A first run and a disabled source do not trip the warning.
* [ ] No private baseline path or raw count leaks into browser-safe surfaces.
* [ ] Payload budget and privacy scans remain green.

***

## Key Files

* `scripts/extensions/trend-finder/collector.ts`
* `scripts/extensions/trend-finder/engine-trace.ts`
* `scripts/extensions/trend-finder/private-diagnostics.ts`
* `src/extensions/trend-finder/schema.ts`
* `src/extensions/trend-finder/view-model.ts`
* `src/extensions/trend-finder/views/sources-view.tsx`
* `src/extensions/trend-finder/engine-replay-model.ts`

***

## Comparison Notes (folded from comparison plan)

**Effort:** Medium. **Boundary risk:** None. Tier 3 polish. **Depends on Session 07** - uses the narrated trace/warning path established there.

**Source-death baseline alarm.** TrendingAI compares current per-source counts with `data/.source-baseline.json` and warns when a previously live source returns zero. Trend Finder adoption: persist a private last-good per-source baseline and distinguish silent adapter/feed death from a quiet run.

**TrendingAI source pointers.** `src/harvesters/orchestrator.ts` (`checkSourceDeath`).


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