fix(ai-vault): fail an OpenCode capture it cannot read the message parts of

`readOpenCodeSessionMessages` returned an empty list when the message-part
schema probe failed. The sink-aware reader treats that as a complete read,
so the consumer committed nothing and marked the source `current`: the
session stayed out of the index with nothing on its row to say why and no
retry. The part limit a few lines below already throws for exactly this
reason, so the two now agree.

The preview path is unchanged and still degrades to no messages, which is
what a list read should do.

Also throws from the fixture's `appendOpenCodeSqliteTurn` when the session
id names no row, instead of falling back to the fixture epoch and appending
orphan messages a test would then assert over.

src/main/ai-vault/session-scanner-opencode-sqlite-capture.ts

@@ -173,7 +173,12 @@ export function readOpenCodeSessionMessages(
   sessionId: string
 ): TranscriptMessage[] {
   if (!canReadOpenCodeMessageParts(db)) {
-    return []
+    // Thrown for the same reason the part limit below throws: an empty capture
+    // returned here is committed under a complete-read cursor, so the session
+    // stays out of search with nothing on its row to say why and no retry.
+    throw new Error(
+      `OpenCode session ${sessionId} uses an unreadable message-part schema; its transcript was not read.`
+    )
   }
   const rows = db.prepare(buildCaptureQuery()).all(sessionId, OPENCODE_CAPTURE_PART_LIMIT + 1)
   if (rows.length > OPENCODE_CAPTURE_PART_LIMIT) {

src/main/ai-vault/session-scanner-opencode-sqlite-fixture.ts

@@ -210,8 +210,17 @@ export function appendOpenCodeSqliteTurn(
   }
 }
 
+// Throws rather than falling back to the epoch: a mistyped id would otherwise
+// append orphan rows and update nothing, leaving a test asserting over a
+// transcript that no session owns.
 function currentUpdatedMs(db: SyncDatabase, sessionId: string): number {
   const row = db.prepare('SELECT time_updated FROM session WHERE id = ?').get(sessionId)
-  const updated = row === undefined ? undefined : Object.values(row)[0]
-  return typeof updated === 'number' ? updated : OPENCODE_FIXTURE_EPOCH_MS
+  if (row === undefined) {
+    throw new Error(`OpenCode fixture has no session ${sessionId} to append to`)
+  }
+  const updated = Object.values(row)[0]
+  if (typeof updated !== 'number') {
+    throw new Error(`OpenCode fixture session ${sessionId} has no numeric time_updated`)
+  }
+  return updated
 }

src/main/ai-vault/session-scanner-opencode-sqlite.test.ts

@@ -6,6 +6,7 @@ import Database from '../sqlite/sync-database'
 import { buildOpenCodeSqliteCandidatePath } from './session-scanner-opencode-sqlite-paths'
 import { listOpenCodeSqliteSessions } from './session-scanner-opencode-sqlite-discovery'
 import { parseOpenCodeSqliteSession } from './session-scanner-opencode-sqlite'
+import { captureOpenCodeSqliteSession } from './session-scanner-opencode-sqlite-capture'
 import { withFullFirstUserPromptCapture } from './session-scanner-first-user-prompt-capture'
 import type { AiVaultScanIssue } from '../../shared/ai-vault-types'
 
@@ -479,6 +480,20 @@ describe('parseOpenCodeSqliteSession', () => {
     expect(session!.previewMessages).toEqual([])
   })
 
+  // The preview may degrade to nothing, but the search index may not: an empty
+  // capture is committed under a complete-read cursor, so the session would stay
+  // unsearchable with nothing on its row to say why and no retry.
+  it('refuses to capture a transcript it cannot read the message parts of', async () => {
+    const { db, path } = createTempDb()
+    applyMinimalOpenCodeSchema(db)
+    db.prepare(`INSERT INTO session VALUES ('ses_minimal', 1777634000000, 1777634001000)`).run()
+    db.close()
+
+    await expect(
+      captureOpenCodeSqliteSession({ dbPath: path, sessionId: 'ses_minimal', platform: 'darwin' })
+    ).rejects.toThrow(/unreadable message-part schema/)
+  })
+
   it('extracts model from older modelID schema', async () => {
     const { db, path } = createTempDb()
     applyOpenCodeSchema(db)