diff --git a/src/server/__tests__/task-notification-persistence.test.ts b/src/server/__tests__/task-notification-persistence.test.ts
index 87077a0c..d3fdb549 100644
--- a/src/server/__tests__/task-notification-persistence.test.ts
+++ b/src/server/__tests__/task-notification-persistence.test.ts
@@ -82,20 +82,33 @@ describe('background task notification persistence', () => {
       timestamp: '2026-07-18T00:00:00.000Z',
     })}\n`, 'utf8')
 
+    const realOpen = fs.open
     const realWriteFile = fs.writeFile
+    let appendClosed = false
     let markAppendStarted!: () => void
     const appendStarted = new Promise<void>((resolve) => {
       markAppendStarted = resolve
     })
-    spyOn(fs, 'writeFile').mockImplementation((filePath: any, data: any, options: any) => {
-      if (options && typeof options === 'object' && options.flag === 'a') {
+    spyOn(fs, 'open').mockImplementation(async (...args) => {
+      const handle = await realOpen(...args)
+      const realClose = handle.close.bind(handle)
+      spyOn(handle, 'close').mockImplementation(async () => {
+        await realClose()
+        appendClosed = true
+      })
+      spyOn(handle, 'writeFile').mockImplementation((_data, options) => {
         markAppendStarted()
+        const signal = typeof options === 'object' ? options?.signal : undefined
         return new Promise<void>((resolve) => {
-          if (options.signal?.aborted) resolve()
-          else options.signal?.addEventListener('abort', () => resolve(), { once: true })
+          if (signal?.aborted) resolve()
+          else signal?.addEventListener('abort', () => resolve(), { once: true })
         })
-      }
-      return realWriteFile(filePath, data, options)
+      })
+      return handle
+    })
+    spyOn(fs, 'writeFile').mockImplementation((...args) => {
+      expect(appendClosed).toBe(true)
+      return realWriteFile(...args)
     })
 
     const service = new SessionService()
@@ -129,27 +142,39 @@ describe('background task notification persistence', () => {
       timestamp: '2026-07-18T00:00:00.000Z',
     })}\n`, 'utf8')
 
-    const realWriteFile = fs.writeFile
+    const realOpen = fs.open
     let appendAttempts = 0
+    let abortedAppendClosed = false
     let markAppendStarted!: () => void
     const appendStarted = new Promise<void>((resolve) => {
       markAppendStarted = resolve
     })
-    spyOn(fs, 'writeFile').mockImplementation((filePath: any, data: any, options: any) => {
-      if (options && typeof options === 'object' && options.flag === 'a') {
-        appendAttempts++
-        if (appendAttempts > 1) return realWriteFile(filePath, data, options)
+    spyOn(fs, 'open').mockImplementation(async (...args) => {
+      const handle = await realOpen(...args)
+      appendAttempts++
+      if (appendAttempts > 1) return handle
+      const realClose = handle.close.bind(handle)
+      spyOn(handle, 'close').mockImplementation(async () => {
+        await realClose()
+        abortedAppendClosed = true
+      })
+      spyOn(handle, 'writeFile').mockImplementation((_data, options) => {
         markAppendStarted()
+        const signal = typeof options === 'object' ? options?.signal : undefined
         return new Promise<void>((_resolve, reject) => {
           const rejectAbort = () => {
             const error = new Error('The operation was aborted')
             error.name = 'AbortError'
             reject(error)
           }
-          if (options.signal?.aborted) rejectAbort()
-          else options.signal?.addEventListener('abort', rejectAbort, { once: true })
+          if (signal?.aborted) rejectAbort()
+          else signal?.addEventListener('abort', rejectAbort, { once: true })
         })
-      }
+      })
+      return handle
+    })
+    spyOn(fs, 'writeFile').mockImplementation(() => {
+      expect(abortedAppendClosed).toBe(true)
       return Promise.reject(new Error('transcript replacement failed'))
     })
 
diff --git a/src/server/__tests__/websocket-handler.test.ts b/src/server/__tests__/websocket-handler.test.ts
index d546c04b..1fa52e1b 100644
--- a/src/server/__tests__/websocket-handler.test.ts
+++ b/src/server/__tests__/websocket-handler.test.ts
@@ -23,7 +23,10 @@ import {
 import { conversationService } from '../services/conversationService.js'
 import { computerUseApprovalService } from '../services/computerUseApprovalService.js'
 import { sessionService } from '../services/sessionService.js'
+import * as titleService from '../services/titleService.js'
+import { SettingsService } from '../services/settingsService.js'
 import * as teleportApi from '../../utils/teleport/api.js'
+import { resetSettingsCache, setSessionSettingsCache } from '../../utils/settings/settingsCache.js'
 
 function makeClientSocket(sessionId: string, clientKind: 'full' | 'pet' = 'full') {
   const sent: string[] = []
@@ -122,6 +125,7 @@ describe('translateCliMessage usage mapping', () => {
 
 describe('WebSocket handler session title lifecycle', () => {
   afterEach(() => {
+    resetSettingsCache()
     __resetWebSocketHandlerStateForTests()
     mock.restore()
   })
@@ -158,6 +162,85 @@ describe('WebSocket handler session title lifecycle', () => {
     )
   })
 
+  it('keeps private prompt titles in memory when settings change while title saving awaits', async () => {
+    const sessionId = `title-private-${crypto.randomUUID()}`
+    const ws = makeClientSocket(sessionId)
+    spyOn(conversationService, 'hasSession').mockReturnValue(true)
+    spyOn(conversationService, 'getPendingPermissionRequests').mockReturnValue([])
+    spyOn(conversationService, 'onOutput').mockImplementation(() => {})
+    spyOn(conversationService, 'removeOutputCallback').mockImplementation(() => {})
+    spyOn(conversationService, 'sendMessage').mockResolvedValue(true)
+    setSessionSettingsCache({ settings: { cleanupPeriodDays: 0 }, errors: [] })
+    let release!: (value: string | null) => void
+    const saving = new Promise<string | null>(resolve => { release = resolve })
+    spyOn(sessionService, 'getCustomTitle')
+      .mockResolvedValueOnce(null)
+      .mockImplementationOnce(() => saving)
+    spyOn(sessionService, 'getSessionLaunchInfo').mockResolvedValue({
+      filePath: '/tmp/private-session.jsonl', projectDir: '/tmp', workDir: '/tmp',
+      transcriptMessageCount: 0, customTitle: null,
+    })
+    const append = spyOn(sessionService, 'appendAiTitle').mockResolvedValue(undefined)
+    handleWebSocket.open(ws)
+    handleWebSocket.message(ws, JSON.stringify({ type: 'user_message', content: 'PRIVATE delayed prompt' }))
+    await flushMicrotasks(30)
+    setSessionSettingsCache({ settings: { cleanupPeriodDays: 365 }, errors: [] })
+    release(null)
+    await flushMicrotasks(30)
+    expect(append).toHaveBeenCalledWith(sessionId, 'PRIVATE delayed prompt', false)
+    expect(ws.sent.map(payload => JSON.parse(payload))).toContainEqual({
+      type: 'session_title_updated', sessionId, title: 'PRIVATE delayed prompt',
+    })
+  })
+
+  it('does not persist delayed polished titles or later refreshes derived from private turns', async () => {
+    spyOn(SettingsService.prototype, 'getUserSettings').mockResolvedValue({})
+    const sessionId = `title-private-complete-${crypto.randomUUID()}`
+    const ws = makeClientSocket(sessionId)
+    const callbacks = new Set<(message: any) => void>()
+    spyOn(conversationService, 'hasSession').mockReturnValue(true)
+    spyOn(conversationService, 'getPendingPermissionRequests').mockReturnValue([])
+    spyOn(conversationService, 'onOutput').mockImplementation((_id, callback) => { callbacks.add(callback) })
+    spyOn(conversationService, 'removeOutputCallback').mockImplementation((_id, callback) => { callbacks.delete(callback) })
+    spyOn(conversationService, 'sendMessage').mockResolvedValue(true)
+    spyOn(sessionService, 'getCustomTitle').mockResolvedValue(null)
+    spyOn(sessionService, 'getSessionLaunchInfo').mockResolvedValue({
+      filePath: '/tmp/private-session.jsonl', projectDir: '/tmp', workDir: '/tmp',
+      transcriptMessageCount: 0, customTitle: null,
+    })
+    setSessionSettingsCache({ settings: { cleanupPeriodDays: 0 }, errors: [] })
+    const append = spyOn(sessionService, 'appendAiTitle').mockResolvedValue(undefined)
+    let release!: (value: string) => void
+    const generated = new Promise<string>(resolve => { release = resolve })
+    const generate = spyOn(titleService, 'generateTitle').mockImplementation(() => generated)
+    handleWebSocket.open(ws)
+    handleWebSocket.message(ws, JSON.stringify({ type: 'user_message', content: 'PRIVATE prompt' }))
+    await flushMicrotasks(30)
+    for (const callback of [...callbacks]) callback({ type: 'result', subtype: 'success', result: 'PRIVATE reply' })
+    // Language settings load is async; wait until the controlled model seam starts.
+    for (let i = 0; i < 100 && generate.mock.calls.length === 0; i++) {
+      await new Promise(resolve => setTimeout(resolve, 1))
+    }
+    expect(generate).toHaveBeenCalledTimes(1)
+    setSessionSettingsCache({ settings: { cleanupPeriodDays: 365 }, errors: [] })
+    release('PRIVATE polished title')
+    await flushMicrotasks(30)
+    expect(append).toHaveBeenCalledWith(sessionId, 'PRIVATE polished title', false)
+    generate.mockResolvedValue('PRIVATE third-turn summary')
+    for (const content of ['PUBLIC second prompt', 'PUBLIC third prompt']) {
+      handleWebSocket.message(ws, JSON.stringify({ type: 'user_message', content }))
+      await flushMicrotasks(30)
+      for (const callback of [...callbacks]) callback({ type: 'result', subtype: 'success', result: 'PUBLIC reply' })
+      await flushMicrotasks(30)
+    }
+    for (let i = 0; i < 100 && generate.mock.calls.length < 2; i++) {
+      await new Promise(resolve => setTimeout(resolve, 1))
+    }
+    await flushMicrotasks(30)
+    expect(generate).toHaveBeenCalledTimes(2)
+    expect(append).toHaveBeenCalledWith(sessionId, 'PRIVATE third-turn summary', false)
+  })
+
   it('ignores /compact for titles without disabling the next real first-message title', async () => {
     const sessionId = `title-compact-${crypto.randomUUID()}`
     const ws = makeClientSocket(sessionId)
diff --git a/src/server/services/sessionService.retention.test.ts b/src/server/services/sessionService.retention.test.ts
new file mode 100644
index 00000000..97a5345b
--- /dev/null
+++ b/src/server/services/sessionService.retention.test.ts
@@ -0,0 +1,119 @@
+import { afterEach, beforeEach, expect, spyOn, test } from 'bun:test'
+import { mkdtemp, mkdir, readFile, readdir, rm, writeFile } from 'node:fs/promises'
+import { join } from 'node:path'
+import { SessionService } from './sessionService.js'
+import { resetSettingsCache } from '../../utils/settings/settingsCache.js'
+
+let directory: string
+let service: SessionService
+let previousConfig: string | undefined
+let previousHome: string | undefined
+
+async function retention(days: number) {
+  await writeFile(join(directory, 'settings.json'), JSON.stringify({ cleanupPeriodDays: days }))
+  resetSettingsCache()
+}
+
+beforeEach(async () => {
+  directory = await mkdtemp('/tmp/session-service-retention-')
+  previousConfig = process.env.CLAUDE_CONFIG_DIR
+  previousHome = process.env.HOME
+  process.env.CLAUDE_CONFIG_DIR = directory
+  process.env.HOME = directory
+  resetSettingsCache()
+  service = new SessionService()
+})
+
+afterEach(async () => {
+  if (previousConfig === undefined) delete process.env.CLAUDE_CONFIG_DIR
+  else process.env.CLAUDE_CONFIG_DIR = previousConfig
+  if (previousHome === undefined) delete process.env.HOME
+  else process.env.HOME = previousHome
+  resetSettingsCache()
+  await rm(directory, { recursive: true, force: true })
+})
+
+async function transcripts() {
+  return (await readdir(join(directory, 'projects'), { recursive: true }).catch(() => []))
+    .filter(file => file.endsWith('.jsonl'))
+}
+
+test('retention zero keeps workspace, runtime and title usable without snapshot/meta/title JSONL', async () => {
+  await retention(0)
+  const { sessionId, workDir } = await service.createSession(directory, undefined, 'plan')
+  await service.appendSessionMetadata(sessionId, {
+    workDir, runtimeProviderId: 'fake-provider', runtimeModelId: 'fake-model', effortLevel: 'high',
+  })
+  await service.renameSession(sessionId, 'PRIVATE-CUSTOM')
+  await service.appendAiTitle(sessionId, 'PRIVATE-PROMPT-DERIVED-TITLE')
+  expect(await transcripts()).toEqual([])
+  expect(await service.getSessionWorkDir(sessionId)).toBe(workDir)
+  expect(await service.getCustomTitle(sessionId)).toBe('PRIVATE-CUSTOM')
+  expect(await service.getSessionLaunchInfo(sessionId)).toMatchObject({
+    workDir, permissionMode: 'plan', runtimeProviderId: 'fake-provider',
+    runtimeModelId: 'fake-model', effortLevel: 'high', transcriptMessageCount: 0,
+  })
+})
+
+test('disabled metadata/title appends leave old files unchanged and clear does not recreate removed history', async () => {
+  await retention(365)
+  const { sessionId, workDir } = await service.createSession(directory)
+  const info = (await service.getSessionLaunchInfo(sessionId))!
+  const original = await readFile(info.filePath, 'utf8')
+  await retention(0)
+  await service.appendSessionMetadata(sessionId, { workDir, customTitle: 'PRIVATE-META', runtimeModelId: 'private-model' })
+  await service.appendAiTitle(sessionId, 'PRIVATE-AI')
+  expect(await readFile(info.filePath, 'utf8')).toBe(original)
+  await rm(info.filePath)
+  await service.clearSessionTranscript(sessionId, workDir, 'plan')
+  expect(await transcripts()).toEqual([])
+  expect(await service.getSessionLaunchInfo(sessionId)).toMatchObject({ workDir, permissionMode: 'plan' })
+})
+
+
+test('restoring persistence cannot copy private custom titles into metadata or save delayed private AI titles', async () => {
+  await retention(0)
+  const { sessionId, workDir } = await service.createSession(directory)
+  await service.renameSession(sessionId, 'PRIVATE-CUSTOM')
+  await retention(365)
+  const info = (await service.getSessionLaunchInfo(sessionId))!
+  // Simulate the runtime materializing only its new public turn.
+  await mkdir(join(directory, 'projects', info.projectDir), { recursive: true })
+  await writeFile(info.filePath, JSON.stringify({ type: 'user', uuid: 'public-user', message: { role: 'user', content: 'PUBLIC' } }) + '\n')
+  await service.appendSessionMetadata(sessionId, { workDir, customTitle: 'PRIVATE-CUSTOM', runtimeModelId: 'public-model' })
+  await service.appendAiTitle(sessionId, 'PRIVATE-DELAYED-AI', false)
+  await service.appendAiTitle(sessionId, 'Public title')
+  const content = await readFile(info.filePath, 'utf8')
+  expect(content).not.toContain('PRIVATE')
+  expect(content).toContain('Public title')
+  expect(await new SessionService().getSessionLaunchInfo(sessionId)).toMatchObject({ workDir, runtimeModelId: 'public-model', transcriptMessageCount: 1 })
+})
+
+test('a delayed title never recreates an old transcript deleted after lookup', async () => {
+  await retention(365)
+  const { sessionId } = await service.createSession(directory)
+  const info = (await service.getSessionLaunchInfo(sessionId))!
+  const originalFind = service.findSessionFile.bind(service)
+  const lookup = spyOn(service, 'findSessionFile').mockImplementation(async id => {
+    const found = await originalFind(id)
+    await rm(info.filePath)
+    return found
+  })
+  try {
+    await service.appendAiTitle(sessionId, 'Delayed old title')
+    expect(await transcripts()).toEqual([])
+  } finally {
+    lookup.mockRestore()
+  }
+})
+
+
+test('memory-only sessions can be deleted and cleared without creating JSONL', async () => {
+  await retention(0)
+  const { sessionId, workDir } = await service.createSession(directory)
+  await service.clearSessionTranscript(sessionId, workDir, 'plan')
+  await service.deleteSession(sessionId)
+  expect(await service.getSessionLaunchInfo(sessionId)).toBeNull()
+  expect(await service.getCustomTitle(sessionId)).toBeNull()
+  expect(await transcripts()).toEqual([])
+})
diff --git a/src/server/services/sessionService.ts b/src/server/services/sessionService.ts
index 91de87ee..11b475c1 100644
--- a/src/server/services/sessionService.ts
+++ b/src/server/services/sessionService.ts
@@ -5,7 +5,7 @@
  * 确保 Desktop App 与 CLI 的数据完全互通。
  */
 
-import { createReadStream, type Stats } from 'node:fs'
+import { constants, createReadStream, type Stats } from 'node:fs'
 import { createHash } from 'node:crypto'
 import * as fs from 'node:fs/promises'
 import * as path from 'node:path'
@@ -47,6 +47,7 @@ import {
 import { ProviderService } from './providerService.js'
 import { shouldHideCommandMetadataContent } from '../../utils/commandMetadata.js'
 import { getClaudeConfigHomeDir } from '../../utils/envUtils.js'
+import { getSettings_DEPRECATED } from '../../utils/settings/settings.js'
 import {
   extractGoalCreationTitle,
   extractTranscriptUserTitle,
@@ -584,6 +585,31 @@ function getSharedSessionMutationState(
 
 export class SessionService {
   private providerService = new ProviderService()
+  // 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>()
+  private readonly privateTitles = new Map<string, Set<string>>()
+
+  shouldPersistSession(): boolean {
+    return getSettings_DEPRECATED()?.cleanupPeriodDays !== 0
+  }
+
+  private memorySessionKey(sessionId: string): string {
+    return `${this.getConfigDir()}:${sessionId}`
+  }
+
+  private rememberPrivateTitle(sessionId: string, title: string): void {
+    const key = this.memorySessionKey(sessionId)
+    const titles = this.privateTitles.get(key) ?? new Set<string>()
+    titles.add(title)
+    this.privateTitles.set(key, titles)
+  }
+
+  private canPersistTitle(sessionId: string, title: string): boolean {
+    return this.shouldPersistSession() &&
+      !this.privateTitles.get(this.memorySessionKey(sessionId))?.has(title)
+  }
+
   private readonly pendingTaskNotificationWrites = new Map<
     string,
     Set<{
@@ -1443,16 +1469,24 @@ export class SessionService {
     entry: Record<string, unknown>,
     signal?: AbortSignal,
   ): Promise<void> {
+    if (!this.shouldPersistSession()) return
     const line = JSON.stringify(entry) + '\n'
-    if (signal) {
-      await fs.writeFile(filePath, line, {
-        encoding: 'utf-8',
-        flag: 'a',
-        signal,
-      })
-      return
+    // A delayed title/notification must not recreate a transcript removed by
+    // retention cleanup after lookup. Metadata relocation opts into creation.
+    let handle: fs.FileHandle
+    try {
+      handle = await fs.open(filePath, constants.O_WRONLY | constants.O_APPEND |
+        (entry.type === 'session-meta' ? constants.O_CREAT : 0))
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code === 'ENOENT') return
+      throw error
+    }
+    try {
+      if (!this.shouldPersistSession()) return
+      await handle.writeFile(line, { encoding: 'utf-8', signal })
+    } finally {
+      await handle.close()
     }
-    await fs.appendFile(filePath, line, 'utf-8')
   }
 
   private resolveWorkDirFromEntries(
@@ -3965,6 +3999,7 @@ export class SessionService {
     permissionMode?: string,
   ): Promise<{ sessionId: string; workDir: string }> {
     // Default to user home directory when no workDir specified
+    const persist = this.shouldPersistSession()
     const resolvedWorkDir = workDir || os.homedir()
     const sessionId = crypto.randomUUID()
 
@@ -3991,7 +4026,7 @@ export class SessionService {
     const dirPath = path.join(this.getProjectsDir(), sanitized)
 
     // Ensure the project directory exists
-    await fs.mkdir(dirPath, { recursive: true })
+    if (persist && this.shouldPersistSession()) await fs.mkdir(dirPath, { recursive: true })
 
     const filePath = path.join(dirPath, `${sessionId}.jsonl`)
     const now = new Date().toISOString()
@@ -4020,7 +4055,16 @@ export class SessionService {
       timestamp: now,
     }
 
-    await fs.writeFile(filePath, JSON.stringify(initialEntry) + '\n' + JSON.stringify(metaEntry) + '\n', 'utf-8')
+    if (!persist || !this.shouldPersistSession()) this.memoryLaunchInfo.set(this.memorySessionKey(sessionId), {
+      filePath, projectDir: sanitized, workDir: absWorkDir,
+      repository: preparedWorkspace.repository, transcriptMessageCount: 0,
+      customTitle: null,
+      ...(permissionMode && VALID_SESSION_PERMISSION_MODES.has(permissionMode)
+        ? { permissionMode } : {}),
+    })
+    if (persist && this.shouldPersistSession()) {
+      await fs.writeFile(filePath, JSON.stringify(initialEntry) + '\n' + JSON.stringify(metaEntry) + '\n', 'utf-8')
+    }
     this.invalidateSessionListCache()
 
     return { sessionId, workDir: absWorkDir }
@@ -4031,12 +4075,14 @@ export class SessionService {
    */
   async deleteSession(sessionId: string): Promise<void> {
     const found = await this.findSessionFile(sessionId)
-    if (!found) {
+    if (!found && !this.memoryLaunchInfo.has(this.memorySessionKey(sessionId))) {
       throw ApiError.notFound(`Session not found: ${sessionId}`)
     }
 
-    await fs.unlink(found.filePath)
-    this.sessionListSummaryCache.delete(found.filePath)
+    if (found) await fs.unlink(found.filePath)
+    this.memoryLaunchInfo.delete(this.memorySessionKey(sessionId))
+    this.privateTitles.delete(this.memorySessionKey(sessionId))
+    if (found) this.sessionListSummaryCache.delete(found.filePath)
     this.invalidateSessionListCache()
   }
 
@@ -4081,10 +4127,18 @@ export class SessionService {
       throw ApiError.badRequest('title is required')
     }
 
-    const found = await this.findSessionFile(sessionId)
-    if (!found) {
-      throw ApiError.notFound(`Session not found: ${sessionId}`)
+    const persist = this.shouldPersistSession()
+    const info = await this.getSessionLaunchInfo(sessionId)
+    if (!info) throw ApiError.notFound(`Session not found: ${sessionId}`)
+    if (!persist || !this.shouldPersistSession() || this.memoryLaunchInfo.has(this.memorySessionKey(sessionId))) {
+      this.memoryLaunchInfo.set(this.memorySessionKey(sessionId), { ...info, customTitle: title })
     }
+    if (!persist || !this.shouldPersistSession()) {
+      this.rememberPrivateTitle(sessionId, title)
+      return
+    }
+    const found = await this.findSessionFile(sessionId)
+    if (!found || !this.canPersistTitle(sessionId, title)) return
 
     const entry = {
       type: 'custom-title',
@@ -4099,9 +4153,13 @@ export class SessionService {
   /**
    * Append an AI-generated title entry to a session's JSONL file.
    */
-  async appendAiTitle(sessionId: string, title: string): Promise<void> {
+  async appendAiTitle(sessionId: string, title: string, persist = this.shouldPersistSession()): Promise<void> {
+    if (!persist || !this.shouldPersistSession()) {
+      this.rememberPrivateTitle(sessionId, title)
+      return
+    }
     const found = await this.findSessionFile(sessionId)
-    if (!found) return
+    if (!found || !this.canPersistTitle(sessionId, title)) return
 
     await this.appendJsonlEntry(found.filePath, {
       type: 'ai-title',
@@ -4112,6 +4170,8 @@ export class SessionService {
   }
 
   async getCustomTitle(sessionId: string): Promise<string | null> {
+    const memory = this.memoryLaunchInfo.get(this.memorySessionKey(sessionId))
+    if (memory?.customTitle) return memory.customTitle
     const found = await this.findSessionFile(sessionId)
     if (!found) return null
 
@@ -4130,6 +4190,8 @@ export class SessionService {
    * First checks for stored session-meta entry, then falls back to desanitizePath.
    */
   async getSessionWorkDir(sessionId: string): Promise<string | null> {
+    const memory = this.memoryLaunchInfo.get(this.memorySessionKey(sessionId))
+    if (memory) return memory.workDir
     const found = await this.findSessionFile(sessionId)
     if (!found) return null
 
@@ -4154,8 +4216,9 @@ export class SessionService {
    * Placeholder desktop-created sessions have zero transcript messages.
    */
   async getSessionLaunchInfo(sessionId: string): Promise<SessionLaunchInfo | null> {
+    const memory = this.memoryLaunchInfo.get(this.memorySessionKey(sessionId))
     const found = await this.findSessionFile(sessionId)
-    if (!found) return null
+    if (!found) return memory ? { ...memory, transcriptMessageCount: 0 } : null
 
     const entries = await this.readJsonlFile(found.filePath)
     const workDir = this.resolveWorkDirFromEntries(entries, found.projectDir) || process.cwd()
@@ -4195,12 +4258,13 @@ export class SessionService {
       workDir,
       repository,
       worktreeSession,
-      transcriptMessageCount,
       customTitle,
       permissionMode,
       ...(runtimeProviderId !== undefined ? { runtimeProviderId } : {}),
       ...(runtimeModelId ? { runtimeModelId } : {}),
       ...(effortLevel ? { effortLevel } : {}),
+      ...memory,
+      transcriptMessageCount,
     }
   }
 
@@ -4216,6 +4280,7 @@ export class SessionService {
     fallbackWorkDir?: string,
     preservedPermissionMode?: string,
   ): Promise<void> {
+    const persist = this.shouldPersistSession()
     const nextEpoch = (this.taskNotificationMutationEpochs.get(sessionId) ?? 0) + 1
     this.taskNotificationMutationEpochs.set(sessionId, nextEpoch)
     this.clearingTaskNotificationSessions.add(sessionId)
@@ -4225,6 +4290,23 @@ export class SessionService {
     try {
       await Promise.allSettled(pendingWrites.map((pending) => pending.promise))
 
+      if (!persist || !this.shouldPersistSession()) {
+        const storedInfo = await this.getSessionLaunchInfo(sessionId)
+        const workDir = fallbackWorkDir && normalizeDriveRootPathForPlatform(fallbackWorkDir)
+        const projectDir = workDir && this.sanitizePath(workDir)
+        const info = storedInfo ?? (workDir && projectDir ? {
+          filePath: path.join(this.getProjectsDir(), projectDir, `${sessionId}.jsonl`),
+          projectDir, workDir, transcriptMessageCount: 0, customTitle: null,
+        } : null)
+        if (info) {
+          this.memoryLaunchInfo.set(this.memorySessionKey(sessionId), {
+            ...info, transcriptMessageCount: 0, customTitle: null,
+            ...(preservedPermissionMode && VALID_SESSION_PERMISSION_MODES.has(preservedPermissionMode)
+              ? { permissionMode: preservedPermissionMode } : {}),
+          })
+        }
+        return
+      }
       let found = await this.findSessionFile(sessionId)
       if (!found && fallbackWorkDir) {
         const resolvedPath = path.resolve(normalizeDriveRootPathForPlatform(fallbackWorkDir))
@@ -4271,6 +4353,8 @@ export class SessionService {
         timestamp: now,
       }
 
+      if (!this.shouldPersistSession()) return
+      this.memoryLaunchInfo.delete(this.memorySessionKey(sessionId))
       await fs.writeFile(
         found.filePath,
         `${JSON.stringify(initialEntry)}\n${JSON.stringify(metaEntry)}\n`,
@@ -4307,6 +4391,35 @@ export class SessionService {
       effortLevel?: string
     }
   ): Promise<void> {
+    const persist = this.shouldPersistSession()
+    const storedInfo = await this.getSessionLaunchInfo(sessionId)
+    const workDir = normalizeDriveRootPathForPlatform(metadata.workDir)
+    const projectDir = this.sanitizePath(workDir)
+    const previousInfo = storedInfo ?? (!persist ? {
+      filePath: path.join(this.getProjectsDir(), projectDir, `${sessionId}.jsonl`),
+      projectDir, workDir, transcriptMessageCount: 0, customTitle: null,
+    } : null)
+    if (previousInfo && (!persist || !this.shouldPersistSession() || this.memoryLaunchInfo.has(this.memorySessionKey(sessionId)))) {
+      const normalizedWorkDir = normalizeDriveRootPathForPlatform(metadata.workDir)
+      const projectDir = this.sanitizePath(normalizedWorkDir)
+      this.memoryLaunchInfo.set(this.memorySessionKey(sessionId), {
+        ...previousInfo,
+        workDir: normalizedWorkDir, projectDir,
+        filePath: path.join(this.getProjectsDir(), projectDir, `${sessionId}.jsonl`),
+        ...(metadata.repository ? { repository: metadata.repository } : {}),
+        ...(metadata.customTitle ? { customTitle: metadata.customTitle } : {}),
+        ...(metadata.permissionMode && VALID_SESSION_PERMISSION_MODES.has(metadata.permissionMode)
+          ? { permissionMode: metadata.permissionMode } : {}),
+        ...(metadata.runtimeProviderId !== undefined ? { runtimeProviderId: metadata.runtimeProviderId } : {}),
+        ...(metadata.runtimeModelId ? { runtimeModelId: metadata.runtimeModelId } : {}),
+        ...(metadata.effortLevel && VALID_SESSION_EFFORT_LEVELS.has(metadata.effortLevel)
+          ? { effortLevel: metadata.effortLevel } : {}),
+      })
+    }
+    if (!persist || !this.shouldPersistSession()) {
+      if (metadata.customTitle) this.rememberPrivateTitle(sessionId, metadata.customTitle)
+      return
+    }
     const matches = await this.findSessionFiles(sessionId)
     if (matches.length === 0) return
 
@@ -4325,9 +4438,8 @@ export class SessionService {
     const targetProjectDir = this.sanitizePath(normalizedWorkDir)
     const targetFilePath = path.join(this.getProjectsDir(), targetProjectDir, `${sessionId}.jsonl`)
 
-    if (!metadata.customTitle) {
-      const launchInfo = await this.getSessionLaunchInfo(sessionId)
-      if (this.metadataMatchesLaunchInfo(launchInfo, {
+    if (!metadata.customTitle && !this.memoryLaunchInfo.has(this.memorySessionKey(sessionId))) {
+      if (this.metadataMatchesLaunchInfo(previousInfo, {
         ...metadata,
         workDir: normalizedWorkDir,
         repository,
@@ -4356,7 +4468,7 @@ export class SessionService {
       timestamp: new Date().toISOString(),
     })
 
-    if (metadata.customTitle) {
+    if (metadata.customTitle && this.canPersistTitle(sessionId, metadata.customTitle)) {
       await this.appendJsonlEntry(targetFilePath, {
         type: 'custom-title',
         customTitle: metadata.customTitle,
@@ -4517,7 +4629,7 @@ export class SessionService {
       notification,
       notification.timestamp ?? new Date(this.now()).toISOString(),
     )
-    if (!normalized) return
+    if (!normalized || !this.shouldPersistSession()) return
     if (this.clearingTaskNotificationSessions.has(sessionId)) return
 
     const epoch = this.taskNotificationMutationEpochs.get(sessionId) ?? 0
diff --git a/src/server/services/titleService.ts b/src/server/services/titleService.ts
index 1413676d..07d575a2 100644
--- a/src/server/services/titleService.ts
+++ b/src/server/services/titleService.ts
@@ -492,10 +492,15 @@ function looksLikeStructuredTitleFragment(text: string): boolean {
  * Returns false when a user custom title exists, because custom titles are
  * intentional and must not be replaced by automatic title refreshes.
  */
-export async function saveAiTitle(sessionId: string, title: string): Promise<boolean> {
+export async function saveAiTitle(
+  sessionId: string,
+  title: string,
+  persist = sessionService.shouldPersistSession(),
+): Promise<boolean> {
   if (await sessionService.getCustomTitle(sessionId)) {
     return false
   }
-  await sessionService.appendAiTitle(sessionId, title)
+  if (persist) await sessionService.appendAiTitle(sessionId, title)
+  else await sessionService.appendAiTitle(sessionId, title, false)
   return true
 }
diff --git a/src/server/ws/handler.ts b/src/server/ws/handler.ts
index 18b218c8..fffa1bd0 100644
--- a/src/server/ws/handler.ts
+++ b/src/server/ws/handler.ts
@@ -173,6 +173,7 @@ const sessionTitleState = new Map<string, {
   userMessageCount: number
   hasCustomTitle: boolean
   hasExistingTranscript: boolean
+  persistTitleSource: boolean
   firstUserMessage: string
   completedTurns: TitleConversationTurn[]
   activeTurn?: TitleConversationTurn & { count: number }
@@ -762,6 +763,7 @@ async function handleUserMessage(
   message: Extract<ClientMessage, { type: 'user_message' }>,
   activeTurn: ActiveUserTurnState,
 ) {
+  const persistTitleSource = sessionService.shouldPersistSession()
   const { sessionId } = ws.data
 
   const desktopSlashCommand = getDesktopSlashCommand(message.content)
@@ -820,6 +822,7 @@ async function handleUserMessage(
       userMessageCount: 0,
       hasCustomTitle,
       hasExistingTranscript: (launchInfo?.transcriptMessageCount ?? 0) > 0,
+      persistTitleSource,
       firstUserMessage: '',
       completedTurns: [],
       startedGenerationKeys: new Set<string>(),
@@ -830,6 +833,7 @@ async function handleUserMessage(
   const titleInput = getTitleInputForUserMessage(message.content, desktopSlashCommand)
   let titleTurnNumber: number | null = null
   if (titleInput) {
+    titleState.persistTitleSource &&= persistTitleSource
     titleState.userMessageCount++
     titleTurnNumber = titleState.userMessageCount
     titleState.activeTurn = {
@@ -2321,6 +2325,10 @@ function triggerTitleGeneration(
 ): void {
   const state = sessionTitleState.get(sessionId)
   if (!state || state.hasCustomTitle || state.hasExistingTranscript) return
+  // Titles summarize cumulative input. Once it includes a private turn, later
+  // refreshes must remain in memory even if retention is enabled again.
+  state.persistTitleSource &&= sessionService.shouldPersistSession()
+  const persist = state.persistTitleSource
 
   const count = phase === 'turn-complete'
     ? completedTurnCount ?? state.userMessageCount
@@ -2337,7 +2345,7 @@ function triggerTitleGeneration(
         const text = state.firstUserMessage
         const placeholder = deriveTitle(text)
         if (placeholder) {
-          const saved = await saveAiTitle(sessionId, placeholder)
+          const saved = await saveAiTitle(sessionId, placeholder, persist)
           if (!saved) {
             state.hasCustomTitle = true
             return
@@ -2375,7 +2383,7 @@ function triggerTitleGeneration(
       )
       if (generationSeq !== state.generationSeq) return
       if (aiTitle) {
-        const saved = await saveAiTitle(sessionId, aiTitle)
+        const saved = await saveAiTitle(sessionId, aiTitle, persist && state.persistTitleSource)
         if (!saved) {
           state.hasCustomTitle = true
           return
@@ -2457,8 +2465,10 @@ function bindTitleSessionOutput(
 }
 
 function appendAssistantTextForTitle(sessionId: string, cliMsg: any): void {
-  const activeTurn = sessionTitleState.get(sessionId)?.activeTurn
-  if (!activeTurn) return
+  const state = sessionTitleState.get(sessionId)
+  const activeTurn = state?.activeTurn
+  if (!state || !activeTurn) return
+  state.persistTitleSource &&= sessionService.shouldPersistSession()
 
   const streamText = extractAssistantStreamTextForTitle(cliMsg)
   if (streamText) {
diff --git a/src/utils/__tests__/sessionStorageRetention.test.ts b/src/utils/__tests__/sessionStorageRetention.test.ts
new file mode 100644
index 00000000..586da16a
--- /dev/null
+++ b/src/utils/__tests__/sessionStorageRetention.test.ts
@@ -0,0 +1,188 @@
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test'
+import { randomUUID } from 'node:crypto'
+import * as fs from 'node:fs/promises'
+import * as os from 'node:os'
+import * as path from 'node:path'
+import { switchSession } from '../../bootstrap/state.js'
+import type { SessionId } from '../../types/ids.js'
+import {
+  clearSessionMessagesCache,
+  flushSessionStorage,
+  getLastSessionLog,
+  getTranscriptPathForSession,
+  reAppendSessionMetadata,
+  recordTranscript,
+  recordSidechainTranscript,
+  getAgentTranscriptPath,
+  resetProjectForTesting,
+} from '../sessionStorage.js'
+import { resetSettingsCache, setSessionSettingsCache } from '../settings/settingsCache.js'
+
+const originalConfigDir = process.env.CLAUDE_CONFIG_DIR
+const originalTestPersistence = process.env.TEST_ENABLE_SESSION_PERSISTENCE
+const retention = (days: number) => setSessionSettingsCache({ settings: { cleanupPeriodDays: days }, errors: [] })
+let messageClock = 0
+const user = (content: string) => ({
+  type: 'user' as const,
+  uuid: randomUUID(),
+  timestamp: new Date(1_700_000_000_000 + messageClock++).toISOString(),
+  message: { role: 'user', content },
+})
+
+// Exercise the growing in-memory history used by QueryEngine without a model.
+describe('session retention transitions', () => {
+  let tmpDir: string
+  let sessionId: SessionId
+  beforeEach(async () => {
+    tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'session-retention-'))
+    process.env.CLAUDE_CONFIG_DIR = tmpDir
+    process.env.TEST_ENABLE_SESSION_PERSISTENCE = '1'
+    resetProjectForTesting()
+    clearSessionMessagesCache()
+    sessionId = randomUUID() as SessionId
+    switchSession(sessionId)
+    retention(365)
+  })
+  afterEach(async () => {
+    await flushSessionStorage()
+    resetProjectForTesting()
+    clearSessionMessagesCache()
+    resetSettingsCache()
+    if (originalConfigDir === undefined) delete process.env.CLAUDE_CONFIG_DIR
+    else process.env.CLAUDE_CONFIG_DIR = originalConfigDir
+    if (originalTestPersistence === undefined) delete process.env.TEST_ENABLE_SESSION_PERSISTENCE
+    else process.env.TEST_ENABLE_SESSION_PERSISTENCE = originalTestPersistence
+    await fs.rm(tmpDir, { recursive: true, force: true })
+  })
+
+  for (const initiallyEnabled of [false, true]) {
+    it(`never backfills disabled user/assistant/tool history (${initiallyEnabled ? 'positive→0→positive' : '0→positive'})`, async () => {
+      const history: any[] = []
+      const transcriptPath = getTranscriptPathForSession(sessionId)
+      if (initiallyEnabled) {
+        history.push(user('previously saved and then removed'))
+        await recordTranscript(history)
+        await flushSessionStorage()
+        await fs.unlink(transcriptPath)
+      }
+      retention(0)
+      const privateUser = user('PRIVATE USER CANARY')
+      const privateAssistant = {
+        type: 'assistant', uuid: randomUUID(), timestamp: new Date(1_700_000_000_000 + messageClock++).toISOString(),
+        message: { role: 'assistant', content: [{ type: 'tool_use', id: 'tool-private', name: 'Read', input: { file_path: 'PRIVATE TOOL INPUT' } }] },
+      }
+      const privateResult = {
+        ...user(''), sourceToolAssistantUUID: privateAssistant.uuid,
+        message: { role: 'user', content: [{ type: 'tool_result', tool_use_id: 'tool-private', content: 'PRIVATE TOOL RESULT' }] },
+      }
+      history.push(privateUser, privateAssistant, privateResult)
+      const disabledParent = await recordTranscript(history)
+      await flushSessionStorage()
+      expect(await fs.access(transcriptPath).then(() => true, () => false)).toBe(false)
+      retention(365)
+      // An incremental caller can retain a stale parent hint; tool results may
+      // also explicitly refer to a suppressed assistant across the transition.
+      const fresh = { ...user('NEW PUBLIC MESSAGE'), sourceToolAssistantUUID: privateAssistant.uuid }
+      history.push(fresh)
+      await recordTranscript(history, undefined, disabledParent ?? undefined)
+      await flushSessionStorage()
+      reAppendSessionMetadata()
+      const raw = await fs.readFile(transcriptPath, 'utf8')
+      expect(raw).not.toContain('PRIVATE')
+      expect(raw).not.toContain('previously saved and then removed')
+      const entries = raw.trim().split('\n').map(line => JSON.parse(line))
+      const messages = entries.filter(entry => entry.type === 'user' || entry.type === 'assistant')
+      expect(messages).toHaveLength(1)
+      expect(messages[0]).toMatchObject({ uuid: fresh.uuid, parentUuid: null })
+      const next = user('SECOND PUBLIC MESSAGE')
+      history.push(next)
+      await recordTranscript(history)
+      await flushSessionStorage()
+      const restored = await getLastSessionLog(sessionId)
+      expect(restored?.messages.map(message => message.uuid)).toEqual([fresh.uuid, next.uuid])
+    })
+  }
+
+  it('keeps an unflushed enabled prefix when a second incremental write arrives', async () => {
+    const first = user('enabled first')
+    const second = user('enabled second')
+    const parent = await recordTranscript([first] as never[])
+    await recordTranscript([first, second] as never[], undefined, parent ?? undefined)
+    await flushSessionStorage()
+    expect((await getLastSessionLog(sessionId))?.messages.map(message => message.uuid)).toEqual([first.uuid, second.uuid])
+  })
+
+  it('starts a valid new chain after cleanup even when no messages were sent while disabled', async () => {
+    const old = user('OLD REMOVED HISTORY')
+    await recordTranscript([old] as never[])
+    await flushSessionStorage()
+    retention(0)
+    const transcriptPath = getTranscriptPathForSession(sessionId)
+    await fs.unlink(transcriptPath)
+    retention(365)
+    const fresh = user('NEW AFTER IDLE CLEANUP')
+    await recordTranscript([old, fresh] as never[])
+    await flushSessionStorage()
+    const raw = await fs.readFile(transcriptPath, 'utf8')
+    expect(raw).not.toContain('OLD REMOVED HISTORY')
+    expect(JSON.parse(raw.trim())).toMatchObject({ uuid: fresh.uuid, parentUuid: null })
+    expect((await getLastSessionLog(sessionId))?.messages.map(message => message.uuid)).toEqual([fresh.uuid])
+  })
+
+  it('drops queued writes when retention is disabled before flush', async () => {
+    const message = user('QUEUED PRIVATE PROMPT')
+    await recordTranscript([message] as never[])
+    const transcriptPath = getTranscriptPathForSession(sessionId)
+    retention(0)
+    await fs.rm(transcriptPath, { force: true })
+    await flushSessionStorage()
+    expect(await fs.access(transcriptPath).then(() => true, () => false)).toBe(false)
+    retention(365)
+    await recordTranscript([message, user('new after queued discard')] as never[])
+    await flushSessionStorage()
+    expect(await fs.readFile(transcriptPath, 'utf8')).not.toContain('QUEUED PRIVATE PROMPT')
+  })
+
+  it('attributes discarded queued messages to their original session across a switch', async () => {
+    const privateMessage = user('PRIVATE QUEUED SESSION A')
+    await recordTranscript([privateMessage] as never[])
+    switchSession(randomUUID() as SessionId)
+    retention(0)
+    await flushSessionStorage()
+    switchSession(sessionId)
+    clearSessionMessagesCache()
+    retention(365)
+    const fresh = user('public session A')
+    await recordTranscript([privateMessage, fresh] as never[])
+    await flushSessionStorage()
+    const raw = await fs.readFile(getTranscriptPathForSession(sessionId), 'utf8')
+    expect(raw).not.toContain('PRIVATE')
+    expect(JSON.parse(raw.trim())).toMatchObject({ uuid: fresh.uuid, parentUuid: null })
+  })
+
+  it('keeps excluded sidechain messages private after dedup cache invalidation', async () => {
+    const privateMessage = user('PRIVATE SIDECHAIN')
+    retention(0)
+    await recordSidechainTranscript([privateMessage] as never[], 'retention-agent')
+    clearSessionMessagesCache()
+    retention(365)
+    const fresh = user('public sidechain')
+    await recordSidechainTranscript([privateMessage, fresh] as never[], 'retention-agent', privateMessage.uuid)
+    await flushSessionStorage()
+    const raw = await fs.readFile(getAgentTranscriptPath('retention-agent' as never), 'utf8')
+    expect(raw).not.toContain('PRIVATE')
+    expect(JSON.parse(raw.trim())).toMatchObject({ uuid: fresh.uuid, parentUuid: null })
+  })
+
+  it('does not rebuild a removed session through cached last-prompt metadata while disabled', async () => {
+    await recordTranscript([user('old prompt')] as never[])
+    await flushSessionStorage()
+    const transcriptPath = getTranscriptPathForSession(sessionId)
+    retention(0)
+    await fs.unlink(transcriptPath)
+    await recordTranscript([user('PRIVATE LAST PROMPT')] as never[])
+    reAppendSessionMetadata()
+    await flushSessionStorage()
+    expect(await fs.access(transcriptPath).then(() => true, () => false)).toBe(false)
+  })
+})
diff --git a/src/utils/sessionStorage.ts b/src/utils/sessionStorage.ts
index 7c635834..7b5c58f3 100644
--- a/src/utils/sessionStorage.ts
+++ b/src/utils/sessionStorage.ts
@@ -600,6 +600,48 @@ class Project {
   // Entries buffered while sessionFile is null. Flushed by materializeSessionFile
   // on the first user/assistant message — prevents metadata-only session files.
   private pendingEntries: Entry[] = []
+  // UUIDs observed while recording was disabled must never be backfilled by
+  // growing-history callers. Keep these separate from the on-disk dedup cache:
+  // excluded messages cannot become parents, even after cache invalidation.
+  private excludedMessages = new Map<string, Set<UUID>>()
+
+  isMessageExcluded(uuid: UUID, sessionId = getSessionId()): boolean {
+    return this.excludedMessages.get(sessionId)?.has(uuid) ?? false
+  }
+
+  private excludeMessageUuids(uuids: Iterable<UUID>, sessionId = getSessionId()): void {
+    let excluded = this.excludedMessages.get(sessionId)
+    if (!excluded) {
+      excluded = new Set()
+      this.excludedMessages.set(sessionId, excluded)
+    }
+    for (const uuid of uuids) excluded.add(uuid)
+  }
+
+  filterPersistableMessages(messages: Transcript, sessionId = getSessionId()): Transcript {
+    if (this.shouldSkipPersistence()) {
+      this.excludeMessageUuids(messages.map(message => message.uuid), sessionId)
+      this.pendingEntries = []
+      this.currentSessionLastPrompt = undefined
+      return []
+    }
+    return messages.filter(message => !this.isMessageExcluded(message.uuid, sessionId))
+  }
+
+  async discardDeletedTranscriptHistory(messageSet: Set<UUID>, sessionId: UUID): Promise<void> {
+    const filePath = this.sessionFile ?? getTranscriptPathForSession(sessionId)
+    // An unflushed first turn has UUIDs in the dedup cache before its file
+    // exists. Only treat a missing file as cleanup when no writes are pending.
+    if (messageSet.size === 0 || this.activeDrain || this.writeQueues.get(filePath)?.length) return
+    try {
+      await stat(filePath)
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') return
+      this.excludeMessageUuids(messageSet, sessionId)
+      messageSet.clear()
+      this.currentSessionLastPrompt = undefined
+    }
+  }
   private remoteIngressUrl: string | null = null
   private internalEventWriter: InternalEventWriter | null = null
   private internalEventReader: InternalEventReader | null = null
@@ -698,6 +740,16 @@ class Project {
         continue
       }
       const batch = queue.splice(0)
+      // Cleanup can disable recording while a batch is waiting for its timer.
+      // Discard it instead of recreating a transcript removed by cleanup.
+      if (this.shouldSkipPersistence()) {
+        for (const { entry, resolve } of batch) {
+          if ('uuid' in entry) this.filterPersistableMessages([entry as TranscriptMessage], entry.sessionId as SessionId)
+          resolve()
+        }
+        this.currentSessionLastPrompt = undefined
+        continue
+      }
 
       let content = ''
       const resolvers: Array<() => void> = []
@@ -769,7 +821,7 @@ class Project {
    * external-writer concern — their caches are authoritative.
    */
   reAppendSessionMetadata(skipTitleRefresh = false): void {
-    if (!this.sessionFile) return
+    if (!this.sessionFile || this.shouldSkipPersistence()) return
     const sessionId = getSessionId() as UUID
     if (!sessionId) return
 
@@ -1058,8 +1110,13 @@ class Project {
     startingParentUuid?: UUID | null,
     teamInfo?: { teamName?: string; agentName?: string },
   ) {
+    // Capture the policy before any async work: a later settings change must
+    // not make the history submitted while disabled eligible for persistence.
+    messages = this.filterPersistableMessages(messages)
     return this.trackWrite(async () => {
-      let parentUuid: UUID | null = startingParentUuid ?? null
+      if (messages.length === 0) return
+      let parentUuid: UUID | null = startingParentUuid && !this.isMessageExcluded(startingParentUuid)
+        ? startingParentUuid : null
 
       // First user/assistant message materializes the session file.
       // Hook progress/attachment messages alone stay buffered.
@@ -1084,6 +1141,7 @@ class Project {
       const slug = getPlanSlugCache().get(sessionId)
 
       for (const message of messages) {
+        if (this.filterPersistableMessages([message]).length === 0) continue
         const isCompactBoundary = isCompactBoundaryMessage(message)
 
         // For tool_result messages, use the assistant message UUID from the message
@@ -1092,7 +1150,8 @@ class Project {
         if (
           message.type === 'user' &&
           'sourceToolAssistantUUID' in message &&
-          message.sourceToolAssistantUUID
+          message.sourceToolAssistantUUID &&
+          !this.isMessageExcluded(message.sourceToolAssistantUUID)
         ) {
           effectiveParentUuid = message.sourceToolAssistantUUID
         }
@@ -1124,7 +1183,7 @@ class Project {
           slug,
         }
         await this.appendEntry(transcriptMessage)
-        if (isChainParticipant(message)) {
+        if (isChainParticipant(message) && !this.isMessageExcluded(message.uuid)) {
           parentUuid = message.uuid
         }
       }
@@ -1132,8 +1191,10 @@ class Project {
       // Cache this turn's user prompt for reAppendSessionMetadata —
       // the --resume picker shows what the user was last doing.
       // Overwritten every turn by design.
-      if (!isSidechain) {
-        const text = getFirstMeaningfulUserMessageTextContent(messages)
+      if (!isSidechain && !this.shouldSkipPersistence()) {
+        const text = getFirstMeaningfulUserMessageTextContent(
+          this.filterPersistableMessages(messages),
+        )
         if (text) {
           const flat = text.replace(/\n/g, ' ').trim()
           this.currentSessionLastPrompt =
@@ -1188,6 +1249,7 @@ class Project {
 
   async appendEntry(entry: Entry, sessionId: UUID = getSessionId() as UUID) {
     if (this.shouldSkipPersistence()) {
+      if ('uuid' in entry) this.filterPersistableMessages([entry as TranscriptMessage], sessionId as SessionId)
       return
     }
 
@@ -1472,13 +1534,21 @@ export async function recordTranscript(
   startingParentUuidHint?: UUID,
   allMessages?: readonly Message[],
 ): Promise<UUID | null> {
-  const cleanedMessages = cleanMessagesForLogging(messages, allMessages)
+  const project = getProject()
+  const cleanedMessages = project.filterPersistableMessages(
+    cleanMessagesForLogging(messages, allMessages),
+  )
+  if (cleanedMessages.length === 0) return null
   const sessionId = getSessionId() as UUID
   const messageSet = await getSessionMessages(sessionId)
+  await project.discardDeletedTranscriptHistory(messageSet, sessionId)
   const newMessages: typeof cleanedMessages = []
-  let startingParentUuid: UUID | undefined = startingParentUuidHint
+  let startingParentUuid: UUID | undefined = startingParentUuidHint &&
+    !project.isMessageExcluded(startingParentUuidHint) && messageSet.has(startingParentUuidHint)
+    ? startingParentUuidHint : undefined
   let seenNewMessage = false
   for (const m of cleanedMessages) {
+    if (project.isMessageExcluded(m.uuid)) continue
     if (messageSet.has(m.uuid as UUID)) {
       // Only track skipped messages that form a prefix. After compaction,
       // messagesToKeep appear AFTER new CB/summary, so this skips them.
@@ -1505,7 +1575,9 @@ export async function recordTranscript(
   // slice is all-recorded (rewind, /resume scenarios where every message is
   // already in messageSet). Progress is skipped — it's written to the JSONL
   // but nothing chains TO it (see isChainParticipant).
-  const lastRecorded = newMessages.findLast(isChainParticipant)
+  const lastRecorded = newMessages.findLast(m =>
+    isChainParticipant(m) && !project.isMessageExcluded(m.uuid),
+  )
   return (lastRecorded?.uuid as UUID | undefined) ?? startingParentUuid ?? null
 }