fix(overseer): hub-inferred stale silence is captured-only, not inbox-promoted

hub/src/sync/overseerEventRecorder.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, it } from 'bun:test'
+import { OVERSEER_STALE_SILENCE_MS } from '@hapi/protocol'
 import type { Session } from '@hapi/protocol/types'
 import { Store } from '../store'
 import { OverseerEventRecorder, toSessionSnapshot } from './overseerEventRecorder'
@@ -97,6 +98,30 @@ describe('OverseerEventRecorder', () => {
         expect(event?.attentionCandidate).toBe(0)
     })
 
+    it('records hub-inferred stale silence as captured-only (not inbox-promoted)', () => {
+        const store = new Store(':memory:')
+        const recorder = new OverseerEventRecorder(store.events, store.inbox)
+        const session = store.sessions.getOrCreateSession('idle', { flavor: 'claude', path: '/tmp', host: 'local' }, null, 'default')
+
+        const now = Date.now()
+        const silentSince = now - OVERSEER_STALE_SILENCE_MS - 60_000
+        const live = makeSession(session.id, 'claude', {
+            active: true,
+            activeAt: silentSince,
+            updatedAt: silentSince
+        })
+
+        const emitted = recorder.checkStaleSessions([live], now)
+
+        expect(emitted).toHaveLength(1)
+        expect(emitted[0]?.eventType).toBe('stale')
+        expect(emitted[0]?.attentionCandidate).toBe(0)
+        expect(store.events.count()).toBe(1)
+        // captured-only: the silence event is recorded for the Overseer/replay to query,
+        // but it must NOT flood the operator inbox (one item per idle session).
+        expect(store.inbox.count()).toBe(0)
+    })
+
     it('synthesizes approval_requested from permission prompts', () => {
         const store = new Store(':memory:')
         const recorder = new OverseerEventRecorder(store.events, store.inbox)

hub/src/sync/overseerEventRecorder.ts

@@ -232,7 +232,15 @@ export class OverseerEventRecorder {
                 sourceKind: 'system',
                 sourceRef: session.id,
                 eventType: 'stale',
-                attentionCandidate: 1,
+                // Captured-only: hub-inferred silence is ambient awareness, not an
+                // operator-action signal (operatorActionRequired stays 0). Auto-promoting
+                // it floods the inbox with one item per idle session ("narrating log file"
+                // failure mode); the framing doc mandates under-surface > over-surface.
+                // The event is still recorded so the Overseer/replay can synthesize a
+                // coalesced view ("N sessions idle") when it judges it worth attention.
+                // A worker that EXPLICITLY self-reports `stalled` keeps attention_candidate=1
+                // via deriveAttentionCandidate; only this inferred sweep is captured-only.
+                attentionCandidate: 0,
                 operatorActionRequired: 0,
                 summary: `No agent output for ${Math.round((now - lastAt) / 60_000)} minutes`,
                 relatedSessionId: session.id,