Handle corrupt JSONL sidecars during list

packages/invariants/src/index.ts

@@ -118,6 +118,9 @@ function checkEvent(trace: SessionTrace, event: SessionEvent): void {
       if (trace.openTurn !== null) {
         throw new InvariantError(`turn/start ${event.data.turn} while turn ${trace.openTurn} is still open`)
       }
+      // Current sessions replay full logs, so numbering starts at 1 and remains
+      // contiguous. If a future compaction/fork stores a partial log, it must
+      // seed `nextTurn` from retained metadata before this check runs.
       if (event.data.turn !== trace.nextTurn) {
         throw new InvariantError(`turn/start expected turn ${trace.nextTurn}, got ${event.data.turn}`)
       }
@@ -143,6 +146,7 @@ function checkEvent(trace: SessionTrace, event: SessionEvent): void {
       if (trace.openStep !== null) {
         throw new InvariantError(`step/start ${event.data.step} while step ${trace.openStep} is still open`)
       }
+      // Steps are checked under the same full-log assumption as turns above.
       if (event.data.step !== trace.nextStep) {
         throw new InvariantError(`step/start expected step ${trace.nextStep} in turn ${event.data.turn}, got ${event.data.step}`)
       }

packages/session-persistence-jsonl/src/index.ts

@@ -354,7 +354,7 @@ export class SessionPersistenceJsonl extends SessionPersistence {
         if (first === undefined) continue // empty/half-written file
         const meta = parseHeaderMeta(first)
         if (meta === undefined) continue // not a session header
-        const summary = await this.readSidecar(meta.id, meta.cwd)
+        const summary = await this.readSidecarForList(meta.id, meta.cwd)
         metas.push({ ...meta, ...summary })
       }
     }
@@ -600,11 +600,9 @@ export class SessionPersistenceJsonl extends SessionPersistence {
   }
 
   /**
-   * Read the mutable-summary sidecar, or `undefined` if it is absent/unreadable
+   * Read the mutable-summary sidecar, or `undefined` if it is absent (a session
-   * (a session that has never been `update()`d, or a failed sidecar write). The
+   * that has never been `update()`d). Non-ENOENT failures surface on strict
-   * caller keeps the header-derived `updatedAt` (the session's createdAt) in
+   * load/adopt paths so corrupt metadata does not masquerade as a clean default.
-   * that case rather than overlaying `0` — reporting an active session as
-   * updated at the Unix epoch would be wrong.
    */
   private async readSidecar(id: SessionId, cwd: string | undefined): Promise<SessionSummary | undefined> {
     try {
@@ -616,6 +614,19 @@ export class SessionPersistenceJsonl extends SessionPersistence {
     }
   }
 
+  /**
+   * Best-effort summary read for list(): a corrupt sidecar should degrade one
+   * row to header metadata, not hide every session from a picker.
+   */
+  private async readSidecarForList(id: SessionId, cwd: string | undefined): Promise<SessionSummary | undefined> {
+    try {
+      return await this.readSidecar(id, cwd)
+    } catch (error: unknown) {
+      this.ctx.logger.warn(`session-persistence-jsonl: ignoring unreadable summary for session "${id}" while listing: ${String(error)}`)
+      return undefined
+    }
+  }
+
   // --- discovery helpers ---
 
   /** Find a session's log file across cwd buckets (when cwd is unknown). */

packages/session-persistence-jsonl/tests/jsonl.spec.ts

@@ -765,6 +765,27 @@ describe('SessionPersistenceJsonl: edge cases', () => {
     expect(ids).toEqual(['p1', 'p2', 'p3'])
   })
 
+  it('list tolerates one corrupt sidecar and still returns other sessions', async () => {
+    const warn = vi.spyOn(ctx.logger, 'warn').mockImplementation(() => undefined)
+    const bad = meta('bad-list-summary', '/proj')
+    await ctx.sessionPersistence.create(bad)
+    await ctx.sessionPersistence.append(bad.id, oneTurnLog())
+    await ctx.sessionPersistence.update(bad.id, { title: 'hidden by corrupt sidecar' })
+    await writeFile(sidecarPath(root, '/proj', bad.id), '{not json')
+    const good = meta('good-list-summary', '/proj')
+    await ctx.sessionPersistence.create(good)
+    await ctx.sessionPersistence.append(good.id, oneTurnLog())
+    await ctx.sessionPersistence.update(good.id, { title: 'visible' })
+
+    const listed = await ctx.sessionPersistence.list()
+
+    const badListed = listed.find(m => m.id === bad.id)
+    expect(badListed).toMatchObject({ id: bad.id })
+    expect(badListed).not.toHaveProperty('title')
+    expect(listed.find(m => m.id === good.id)).toMatchObject({ id: good.id, title: 'visible' })
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining('bad-list-summary'))
+  })
+
   it('list on an empty root returns nothing', async () => {
     expect(await ctx.sessionPersistence.list()).toEqual([])
   })