diff --git a/src/server/__tests__/sessions.test.ts b/src/server/__tests__/sessions.test.ts
index 9a5b1d3d..73035777 100644
--- a/src/server/__tests__/sessions.test.ts
+++ b/src/server/__tests__/sessions.test.ts
@@ -3474,6 +3474,59 @@ describe('Sessions API', () => {
     expect((await fetch(`${baseUrl}/api/sessions/${crypto.randomUUID()}/turn-checkpoints`)).status).toBe(404)
   })
 
+  for (const origin of ['created', 'resumed']) {
+    it(`GET turn-checkpoints keeps a positive ${origin} session known immediately after retention cleanup`, async () => {
+      const { sessionService } = await import('../services/sessionService.js')
+      await fs.writeFile(path.join(tmpDir, 'settings.json'), JSON.stringify({ cleanupPeriodDays: 365 }))
+      resetSettingsCache()
+      let sessionId: string
+      if (origin === 'created') {
+        const created = await fetch(`${baseUrl}/api/sessions`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({ workDir: tmpDir }),
+        })
+        expect(created.status).toBe(201)
+        sessionId = (await created.json() as { sessionId: string }).sessionId
+      } else {
+        sessionId = crypto.randomUUID()
+        await writeSessionFile(sanitizePath(tmpDir), sessionId, [
+          { type: 'session-meta', workDir: tmpDir },
+          { type: 'user', uuid: 'restored-user', parentUuid: null, message: { role: 'user', content: 'saved before server restart' } },
+        ])
+        // Starting the runtime for an existing disk session updates metadata;
+        // this ID was never created by the current SessionService process.
+        await sessionService.appendSessionMetadata(sessionId, { workDir: tmpDir })
+      }
+      const found = await sessionService.findSessionFile(sessionId)
+      expect(found).not.toBeNull()
+      await fs.writeFile(path.join(tmpDir, 'settings.json'), JSON.stringify({ cleanupPeriodDays: 0 }))
+      resetSettingsCache()
+      await fs.unlink(found!.filePath)
+
+      // Clicking the still-open tab requests checkpoints before another prompt
+      // can refresh runtime metadata. No disk evidence must be created here.
+      for (const days of [0, 365]) {
+        await fs.writeFile(path.join(tmpDir, 'settings.json'), JSON.stringify({ cleanupPeriodDays: days }))
+        resetSettingsCache()
+        const response = await fetch(`${baseUrl}/api/sessions/${sessionId}/turn-checkpoints`)
+        expect(response.status).toBe(200)
+        expect(await response.json()).toEqual({ checkpoints: [] })
+        expect(await sessionService.getSessionMessagesWithEvidence(sessionId)).toEqual({
+          messages: [], transcriptEvidenceComplete: false,
+        })
+        expect(await sessionService.findSessionFile(sessionId)).toBeNull()
+        expect((await fetch(`${baseUrl}/api/sessions/${crypto.randomUUID()}/turn-checkpoints`)).status).toBe(404)
+      }
+
+      // Explicit deletion ends this in-process lifetime even when cleanup has
+      // already removed its file; it must not become an immortal empty session.
+      await sessionService.deleteSession(sessionId)
+      expect((await fetch(`${baseUrl}/api/sessions/${sessionId}/turn-checkpoints`)).status).toBe(404)
+      await expect(sessionService.deleteSession(sessionId)).rejects.toMatchObject({ statusCode: 404 })
+    })
+  }
+
   it('POST /api/sessions should create a session', async () => {
     const workDir = await fs.mkdtemp(path.join(tmpDir, 'api-session-'))
     const res = await fetch(`${baseUrl}/api/sessions`, {
diff --git a/src/server/services/sessionService.ts b/src/server/services/sessionService.ts
index b7a13189..d1dc71ef 100644
--- a/src/server/services/sessionService.ts
+++ b/src/server/services/sessionService.ts
@@ -588,6 +588,10 @@ export class SessionService {
   // Keep launch state available when retention disables or removes transcripts.
   // Scope keys by config directory so test/embedded server instances cannot mix state.
   private readonly memoryLaunchInfo = new Map<string, SessionLaunchInfo>()
+  // Creation or a valid runtime metadata update establishes a session lifetime
+  // independently of its transcript. Cleanup can remove that file before the
+  // next runtime update supplies memoryLaunchInfo.
+  private readonly knownSessionKeys = new Set<string>()
   private readonly privateTitles = new Map<string, Set<string>>()
 
   shouldPersistSession(): boolean {
@@ -3764,7 +3768,8 @@ export class SessionService {
       // Retention-zero sessions intentionally have no transcript. The desktop
       // still asks for turn checkpoints after each live reply; lack of saved
       // evidence is not a missing session, nor proof of an empty history.
-      if (this.memoryLaunchInfo.has(this.memorySessionKey(sessionId))) {
+      if (this.memoryLaunchInfo.has(this.memorySessionKey(sessionId)) ||
+        this.knownSessionKeys.has(this.memorySessionKey(sessionId))) {
         return { messages: [], transcriptEvidenceComplete: false }
       }
       throw ApiError.notFound(`Session not found: ${sessionId}`)
@@ -4071,6 +4076,7 @@ export class SessionService {
     if (persist && this.shouldPersistSession()) {
       await fs.writeFile(filePath, JSON.stringify(initialEntry) + '\n' + JSON.stringify(metaEntry) + '\n', 'utf-8')
     }
+    this.knownSessionKeys.add(this.memorySessionKey(sessionId))
     this.invalidateSessionListCache()
 
     return { sessionId, workDir: absWorkDir }
@@ -4081,11 +4087,13 @@ export class SessionService {
    */
   async deleteSession(sessionId: string): Promise<void> {
     const found = await this.findSessionFile(sessionId)
-    if (!found && !this.memoryLaunchInfo.has(this.memorySessionKey(sessionId))) {
+    if (!found && !this.memoryLaunchInfo.has(this.memorySessionKey(sessionId)) &&
+      !this.knownSessionKeys.has(this.memorySessionKey(sessionId))) {
       throw ApiError.notFound(`Session not found: ${sessionId}`)
     }
 
     if (found) await fs.unlink(found.filePath)
+    this.knownSessionKeys.delete(this.memorySessionKey(sessionId))
     this.memoryLaunchInfo.delete(this.memorySessionKey(sessionId))
     this.privateTitles.delete(this.memorySessionKey(sessionId))
     if (found) this.sessionListSummaryCache.delete(found.filePath)
@@ -4399,6 +4407,7 @@ export class SessionService {
   ): Promise<void> {
     const persist = this.shouldPersistSession()
     const storedInfo = await this.getSessionLaunchInfo(sessionId)
+    if (storedInfo) this.knownSessionKeys.add(this.memorySessionKey(sessionId))
     const workDir = normalizeDriveRootPathForPlatform(metadata.workDir)
     const projectDir = this.sanitizePath(workDir)
     const previousInfo = storedInfo ?? (!persist ? {