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1# Hooks

3Hooks are an extensibility framework for Codex. They allow

4you to inject your own scripts into the agentic loop, enabling features such as:

6- Send the conversation to a custom logging/analytics engine

7- Scan your team's prompts to block accidentally pasting API keys

8- Summarize conversations to create persistent memories automatically

9- Run a custom validation check when a conversation turn stops, enforcing standards

10- Customize prompting when in a certain directory

12Hooks are behind a feature flag in `config.toml`:

14```toml

15[features]

16codex_hooks = true

17```

19Runtime behavior to keep in mind:

21- Matching hooks from multiple files all run.

22- Multiple matching command hooks for the same event are launched concurrently,

23 so one hook cannot prevent another matching hook from starting.

24- `PreToolUse`, `PermissionRequest`, `PostToolUse`, `UserPromptSubmit`, and

25 `Stop` run at turn scope.

27## Where Codex looks for hooks

29Codex discovers hooks next to active config layers in either of these forms:

31- `hooks.json`

32- inline `[hooks]` tables inside `config.toml`

34In practice, the four most useful locations are:

36- `~/.codex/hooks.json`

37- `~/.codex/config.toml`

38- `<repo>/.codex/hooks.json`

39- `<repo>/.codex/config.toml`

41If more than one hook source exists, Codex loads all matching hooks.

42Higher-precedence config layers do not replace lower-precedence hooks.

43If a single layer contains both `hooks.json` and inline `[hooks]`, Codex

44merges them and warns at startup. Prefer one representation per layer.

46Project-local hooks load only when the project `.codex/` layer is trusted. In

47untrusted projects, Codex still loads user and system hooks from their own

48active config layers.

50## Config shape

52Hooks are organized in three levels:

54- A hook event such as `PreToolUse`, `PostToolUse`, or `Stop`

55- A matcher group that decides when that event matches

56- One or more hook handlers that run when the matcher group matches

58```json

59{

60 "hooks": {

61 "SessionStart": [

62 {

63 "matcher": "startup|resume",

64 "hooks": [

65 {

66 "type": "command",

67 "command": "python3 ~/.codex/hooks/session_start.py",

68 "statusMessage": "Loading session notes"

69 }

70 ]

71 }

72 ],

73 "PreToolUse": [

74 {

75 "matcher": "Bash",

76 "hooks": [

77 {

78 "type": "command",

79 "command": "/usr/bin/python3 \"$(git rev-parse --show-toplevel)/.codex/hooks/pre_tool_use_policy.py\"",

80 "statusMessage": "Checking Bash command"

81 }

82 ]

83 }

84 ],

85 "PermissionRequest": [

86 {

87 "matcher": "Bash",

88 "hooks": [

89 {

90 "type": "command",

91 "command": "/usr/bin/python3 \"$(git rev-parse --show-toplevel)/.codex/hooks/permission_request.py\"",

92 "statusMessage": "Checking approval request"

93 }

94 ]

95 }

96 ],

97 "PostToolUse": [

98 {

99 "matcher": "Bash",

100 "hooks": [

101 {

102 "type": "command",

103 "command": "/usr/bin/python3 \"$(git rev-parse --show-toplevel)/.codex/hooks/post_tool_use_review.py\"",

104 "statusMessage": "Reviewing Bash output"

105 }

106 ]

107 }

108 ],

109 "UserPromptSubmit": [

110 {

111 "hooks": [

112 {

113 "type": "command",

114 "command": "/usr/bin/python3 \"$(git rev-parse --show-toplevel)/.codex/hooks/user_prompt_submit_data_flywheel.py\""

115 }

116 ]

117 }

118 ],

119 "Stop": [

120 {

121 "hooks": [

122 {

123 "type": "command",

124 "command": "/usr/bin/python3 \"$(git rev-parse --show-toplevel)/.codex/hooks/stop_continue.py\"",

125 "timeout": 30

126 }

127 ]

128 }

129 ]

130 }

131}

132```

133

134Notes:

135

136- `timeout` is in seconds.

137- If `timeout` is omitted, Codex uses `600` seconds.

138- `statusMessage` is optional.

139- Commands run with the session `cwd` as their working directory.

140- For repo-local hooks, prefer resolving from the git root instead of using a

141 relative path such as `.codex/hooks/...`. Codex may be started from a

142 subdirectory, and a git-root-based path keeps the hook location stable.

143

144Equivalent inline TOML in `config.toml`:

145

146```toml

147[features]

148codex_hooks = true

149

150[[hooks.PreToolUse]]

151matcher = "^Bash$"

152

153[[hooks.PreToolUse.hooks]]

154type = "command"

155command = '/usr/bin/python3 "$(git rev-parse --show-toplevel)/.codex/hooks/pre_tool_use_policy.py"'

156timeout = 30

157statusMessage = "Checking Bash command"

158

159[[hooks.PostToolUse]]

160matcher = "^Bash$"

161

162[[hooks.PostToolUse.hooks]]

163type = "command"

164command = '/usr/bin/python3 "$(git rev-parse --show-toplevel)/.codex/hooks/post_tool_use_review.py"'

165timeout = 30

166statusMessage = "Reviewing Bash output"

167```

168

169## Managed hooks from `requirements.toml`

170

171Enterprise-managed requirements can also define hooks inline under `[hooks]`.

172This is useful when admins want to enforce the hook configuration while

173delivering the actual scripts through MDM or another device-management system.

174

175```toml

176[features]

177codex_hooks = true

178

179[hooks]

180managed_dir = "/enterprise/hooks"

181windows_managed_dir = 'C:\enterprise\hooks'

182

183[[hooks.PreToolUse]]

184matcher = "^Bash$"

185

186[[hooks.PreToolUse.hooks]]

187type = "command"

188command = "python3 /enterprise/hooks/pre_tool_use_policy.py"

189timeout = 30

190statusMessage = "Checking managed Bash command"

191```

192

193Notes for managed hooks:

194

195- `managed_dir` is used on macOS and Linux.

196- `windows_managed_dir` is used on Windows.

197- Codex does not distribute the scripts in `managed_dir`; your enterprise

198 tooling must install and update them separately.

199- Managed hook commands should use absolute script paths under the configured

200 managed directory.

201

202## Matcher patterns

203

204The `matcher` field is a regex string that filters when hooks fire. Use `"*"`,

205`""`, or omit `matcher` entirely to match every occurrence of a supported

206event.

207

208Only some current Codex events honor `matcher`:

209

210| Event | What `matcher` filters | Notes |

211| --- | --- | --- |

212| `PermissionRequest` | tool name | Support includes `Bash`, `apply_patch`\*, and MCP tool names |

213| `PostToolUse` | tool name | Support includes `Bash`, `apply_patch`\*, and MCP tool names |

214| `PreToolUse` | tool name | Support includes `Bash`, `apply_patch`\*, and MCP tool names |

215| `SessionStart` | start source | Current runtime values are `startup`, `resume`, and `clear` |

216| `UserPromptSubmit` | not supported | Any configured `matcher` is ignored for this event |

217| `Stop` | not supported | Any configured `matcher` is ignored for this event |

218

219\*For `apply_patch`, matchers can also use `Edit` or `Write`.

220

221Examples:

222

223- `Bash`

224- `^apply_patch$`

225- `Edit|Write`

226- `mcp__filesystem__read_file`

227- `mcp__filesystem__.*`

228- `startup|resume|clear`

229

230## Common input fields

231

232Every command hook receives one JSON object on `stdin`.

233

234These are the shared fields you will usually use:

235

236| Field | Type | Meaning |

237| --- | --- | --- |

238| `session_id` | `string` | Current session or thread id. |

240| `cwd` | `string` | Working directory for the session |

241| `hook_event_name` | `string` | Current hook event name |

242| `model` | `string` | Active model slug |

243

244Turn-scoped hooks list `turn_id` in their event-specific tables.

245

246If you need the full wire format, see [Schemas](#schemas).

247

248## Common output fields

249

250`SessionStart`, `UserPromptSubmit`, and `Stop` support these shared JSON

251fields:

252

253```json

254{

255 "continue": true,

256 "stopReason": "optional",

257 "systemMessage": "optional",

258 "suppressOutput": false

259}

260```

261

262| Field | Effect |

263| ---------------- | ----------------------------------------------- |

264| `continue` | If `false`, marks that hook run as stopped |

265| `stopReason` | Recorded as the reason for stopping |

266| `systemMessage` | Surfaced as a warning in the UI or event stream |

267| `suppressOutput` | Parsed today but not yet implemented |

268

269Exit `0` with no output is treated as success and Codex continues.

270

271`PreToolUse` and `PermissionRequest` support `systemMessage`, but `continue`,

272`stopReason`, and `suppressOutput` aren't currently supported for those events.

273

274`PostToolUse` supports `systemMessage`, `continue: false`, and `stopReason`.

275`suppressOutput` is parsed but not currently supported for that event.

276

277## Hooks

278

279### SessionStart

280

281`matcher` is applied to `source` for this event.

282

283Fields in addition to [Common input fields](#common-input-fields):

284

285| Field | Type | Meaning |

286| --- | --- | --- |

287| `source` | `string` | How the session started: `startup` or `resume` |

288

289Plain text on `stdout` is added as extra developer context.

290

291JSON on `stdout` supports [Common output fields](#common-output-fields) and this

292hook-specific shape:

293

294```json

295{

296 "hookSpecificOutput": {

297 "hookEventName": "SessionStart",

298 "additionalContext": "Load the workspace conventions before editing."

299 }

300}

301```

302

303That `additionalContext` text is added as extra developer context.

304

305### PreToolUse

306

307`PreToolUse` can intercept Bash, file edits performed through `apply_patch`,

308and MCP tool calls. It is still a guardrail rather than a complete enforcement

309boundary because Codex can often perform equivalent work through another

310supported tool path.

311

312This doesn't intercept all shell calls yet, only the simple ones. The newer

313 `unified_exec` mechanism allows richer streaming stdin/stdout handling of

314 shell, but interception is incomplete. Similarly, this doesn't intercept

315 `WebSearch` or other non-shell, non-MCP tool calls.

316

317`matcher` is applied to `tool_name` and matcher aliases. For file edits through

318`apply_patch`, matchers can use `apply_patch`, `Edit`, or `Write`; hook input

319still reports `tool_name: "apply_patch"`.

320

321Fields in addition to [Common input fields](#common-input-fields):

322

323| Field | Type | Meaning |

324| --- | --- | --- |

325| `turn_id` | `string` | Codex-specific extension. Active Codex turn id |

326| `tool_name` | `string` | Canonical hook tool name, such as `Bash`, `apply_patch`, or an MCP name like `mcp__fs__read` |

327| `tool_use_id` | `string` | Tool-call id for this invocation |

328| `tool_input` | `JSON value` | Tool-specific input. `Bash` and `apply_patch` use `tool_input.command` while MCP tools send all the args. |

329

330Plain text on `stdout` is ignored.

331

332JSON on `stdout` can use `systemMessage` and can block a Bash command with this

333hook-specific shape:

334

335```json

336{

337 "hookSpecificOutput": {

338 "hookEventName": "PreToolUse",

339 "permissionDecision": "deny",

340 "permissionDecisionReason": "Destructive command blocked by hook."

341 }

342}

343```

344

345Codex also accepts this older block shape:

346

347```json

348{

349 "decision": "block",

350 "reason": "Destructive command blocked by hook."

351}

352```

353

354You can also use exit code `2` and write the blocking reason to `stderr`.

355

356`permissionDecision: "allow"` and `"ask"`, legacy `decision: "approve"`,

357`updatedInput`, `additionalContext`, `continue: false`, `stopReason`, and

358`suppressOutput` are parsed but not supported yet, so they fail open.

359

360### PermissionRequest

361

362`PermissionRequest` runs when Codex is about to ask for approval, such as a

363shell escalation or managed-network approval. It can allow the request, deny

364the request, or decline to decide and let the normal approval prompt continue.

365It doesn't run for commands that don't need approval.

366

367`matcher` is applied to `tool_name` and matcher aliases. Current canonical

368values include `Bash`, `apply_patch`, and MCP tool names such as

369`mcp__server__tool`; `apply_patch` also matches `Edit` and `Write`.

370

371Fields in addition to [Common input fields](#common-input-fields):

372

373| Field | Type | Meaning |

374| --- | --- | --- |

375| `turn_id` | `string` | Codex-specific extension. Active Codex turn id |

376| `tool_name` | `string` | Canonical hook tool name, such as `Bash`, `apply_patch`, or an MCP name like `mcp__fs__read` |

377| `tool_input` | `JSON value` | Tool-specific input. `Bash` and `apply_patch` use `tool_input.command` while MCP tools send all the args. |

379

380Plain text on `stdout` is ignored.

381

382To approve the request, return:

383

384```json

385{

386 "hookSpecificOutput": {

387 "hookEventName": "PermissionRequest",

388 "decision": {

389 "behavior": "allow"

390 }

391 }

392}

393```

394

395To deny the request, return:

396

397```json

398{

399 "hookSpecificOutput": {

400 "hookEventName": "PermissionRequest",

401 "decision": {

402 "behavior": "deny",

403 "message": "Blocked by repository policy."

404 }

405 }

406}

407```

408

409If multiple matching hooks return decisions, any `deny` wins. Otherwise, an

410`allow` lets the request proceed without surfacing the approval prompt. If no

411matching hook decides, Codex uses the normal approval flow.

412

413Don't return `updatedInput`, `updatedPermissions`, or `interrupt` for

414`PermissionRequest`; those fields are reserved for future behavior and fail

415closed today.

416

417### PostToolUse

418

419`PostToolUse` runs after supported tools produce output, including Bash,

420`apply_patch`, and MCP tool calls. For Bash, it also runs after commands that

421exit with a non-zero status. It can't undo side effects from the tool that

422already ran.

423

424This doesn't intercept all shell calls yet, only the simple ones. The newer

425 `unified_exec` mechanism allows richer streaming stdin/stdout handling of

426 shell, but interception is incomplete. Similarly, this doesn't intercept

427 `WebSearch` or other non-shell, non-MCP tool calls.

428

429`matcher` is applied to `tool_name` and matcher aliases. For file edits through

430`apply_patch`, matchers can use `apply_patch`, `Edit`, or `Write`; hook input

431still reports `tool_name: "apply_patch"`.

432

433Fields in addition to [Common input fields](#common-input-fields):

434

435| Field | Type | Meaning |

436| --- | --- | --- |

437| `turn_id` | `string` | Codex-specific extension. Active Codex turn id |

438| `tool_name` | `string` | Canonical hook tool name, such as `Bash`, `apply_patch`, or an MCP name like `mcp__fs__read` |

439| `tool_use_id` | `string` | Tool-call id for this invocation |

440| `tool_input` | `JSON value` | Tool-specific input. `Bash` and `apply_patch` use `tool_input.command` while MCP tools send all the args. |

441| `tool_response` | `JSON value` | Tool-specific output. For MCP tools, this is the MCP call result. |

442

443Plain text on `stdout` is ignored.

444

445JSON on `stdout` can use `systemMessage` and this hook-specific shape:

446

447```json

448{

449 "decision": "block",

450 "reason": "The Bash output needs review before continuing.",

451 "hookSpecificOutput": {

452 "hookEventName": "PostToolUse",

453 "additionalContext": "The command updated generated files."

454 }

455}

456```

457

458That `additionalContext` text is added as extra developer context.

459

460For this event, `decision: "block"` doesn't undo the completed Bash command.

461Instead, Codex records the feedback, replaces the tool result with that

462feedback, and continues the model from the hook-provided message.

463

464You can also use exit code `2` and write the feedback reason to `stderr`.

465

466To stop normal processing of the original tool result after the command has

467already run, return `continue: false`. Codex will replace the tool result with

468your feedback or stop text and continue from there.

469

470`updatedMCPToolOutput` and `suppressOutput` are parsed but not supported yet,

471so they fail open.

472

473### UserPromptSubmit

474

475`matcher` isn't currently used for this event.

476

477Fields in addition to [Common input fields](#common-input-fields):

478

479| Field | Type | Meaning |

480| --- | --- | --- |

481| `turn_id` | `string` | Codex-specific extension. Active Codex turn id |

482| `prompt` | `string` | User prompt that's about to be sent |

483

484Plain text on `stdout` is added as extra developer context.

485

486JSON on `stdout` supports [Common output fields](#common-output-fields) and

487this hook-specific shape:

488

489```json

490{

491 "hookSpecificOutput": {

492 "hookEventName": "UserPromptSubmit",

493 "additionalContext": "Ask for a clearer reproduction before editing files."

494 }

495}

496```

497

498That `additionalContext` text is added as extra developer context.

499

500To block the prompt, return:

501

502```json

503{

504 "decision": "block",

505 "reason": "Ask for confirmation before doing that."

506}

507```

508

509You can also use exit code `2` and write the blocking reason to `stderr`.

510

511### Stop

512

513`matcher` isn't currently used for this event.

514

515Fields in addition to [Common input fields](#common-input-fields):

516

517| Field | Type | Meaning |

518| --- | --- | --- |

519| `turn_id` | `string` | Codex-specific extension. Active Codex turn id |

520| `stop_hook_active` | `boolean` | Whether this turn was already continued by `Stop` |

522

523`Stop` expects JSON on `stdout` when it exits `0`. Plain text output is invalid

524for this event.

525

526JSON on `stdout` supports [Common output fields](#common-output-fields). To keep

527Codex going, return:

528

529```json

530{

531 "decision": "block",

532 "reason": "Run one more pass over the failing tests."

533}

534```

535

536You can also use exit code `2` and write the continuation reason to `stderr`.

537

538For this event, `decision: "block"` doesn't reject the turn. Instead, it tells

539Codex to continue and automatically creates a new continuation prompt that acts

540as a new user prompt, using your `reason` as that prompt text.

541

542If any matching `Stop` hook returns `continue: false`, that takes precedence

543over continuation decisions from other matching `Stop` hooks.

544

545## Schemas

546

547If you need the exact current wire format, see the generated schemas in the

548[Codex GitHub repository](https://github.com/openai/codex/tree/main/codex-rs/hooks/schema/generated).

hooks.md Codex Docs, 2026-03-20 00:35 UTC → 2026-04-29 12:40 UTC