app-server.md Codex Docs, 2026-03-07 18:10 UTC → 2026-03-18 12:23 UTC

21Requests include `method`, `params`, and `id`:21Requests include `method`, `params`, and `id`:

22 22 

23```json23```json

24{ "method": "thread/start", "id": 10, "params": { "model": "gpt-5.1-codex" } }24{ "method": "thread/start", "id": 10, "params": { "model": "gpt-5.4" } }

25```25```

26 26 

27Responses echo the `id` with either `result` or `error`:27Responses echo the `id` with either `result` or `error`:

99 },99 },

100});100});

101send({ method: "initialized", params: {} });101send({ method: "initialized", params: {} });

102send({ method: "thread/start", id: 1, params: { model: "gpt-5.1-codex" } });102send({ method: "thread/start", id: 1, params: { model: "gpt-5.4" } });

103```103```

104 104 

105## Core primitives105## Core primitives

123 123 

124Clients must send a single `initialize` request per transport connection before invoking any other method on that connection, then acknowledge with an `initialized` notification. Requests sent before initialization receive a `Not initialized` error, and repeated `initialize` calls on the same connection return `Already initialized`.124Clients must send a single `initialize` request per transport connection before invoking any other method on that connection, then acknowledge with an `initialized` notification. Requests sent before initialization receive a `Not initialized` error, and repeated `initialize` calls on the same connection return `Already initialized`.

125 125 

126The server returns the user agent string it will present to upstream services. Set `clientInfo` to identify your integration.126The server returns the user agent string it will present to upstream services plus `platformFamily` and `platformOs` values that describe the runtime target. Set `clientInfo` to identify your integration.

127 127 

128`initialize.params.capabilities` also supports per-connection notification opt-out via `optOutNotificationMethods`, which is a list of exact method names to suppress for that connection. Matching is exact (no wildcards/prefixes). Unknown method names are accepted and ignored.128`initialize.params.capabilities` also supports per-connection notification opt-out via `optOutNotificationMethods`, which is a list of exact method names to suppress for that connection. Matching is exact (no wildcards/prefixes). Unknown method names are accepted and ignored.

129 129 

159 },159 },

160 "capabilities": {160 "capabilities": {

161 "experimentalApi": true,161 "experimentalApi": true,

162 "optOutNotificationMethods": [162 "optOutNotificationMethods": ["thread/started", "item/agentMessage/delta"]

163 "codex/event/session_configured",

164 "item/agentMessage/delta"

165 ]

166 }163 }

167 }164 }

168}165}

204- `thread/read` - read a stored thread by id without resuming it; set `includeTurns` to return full turn history. Returned `thread` objects include runtime `status`.201- `thread/read` - read a stored thread by id without resuming it; set `includeTurns` to return full turn history. Returned `thread` objects include runtime `status`.

205- `thread/list` - page through stored thread logs; supports cursor-based pagination plus `modelProviders`, `sourceKinds`, `archived`, and `cwd` filters. Returned `thread` objects include runtime `status`.202- `thread/list` - page through stored thread logs; supports cursor-based pagination plus `modelProviders`, `sourceKinds`, `archived`, and `cwd` filters. Returned `thread` objects include runtime `status`.

206- `thread/loaded/list` - list the thread ids currently loaded in memory.203- `thread/loaded/list` - list the thread ids currently loaded in memory.

204- `thread/name/set` - set or update a thread's user-facing name for a loaded thread or a persisted rollout; emits `thread/name/updated`.

207- `thread/archive` - move a thread's log file into the archived directory; returns `{}` on success and emits `thread/archived`.205- `thread/archive` - move a thread's log file into the archived directory; returns `{}` on success and emits `thread/archived`.

208- `thread/unsubscribe` - unsubscribe this connection from thread turn/item events. If this was the last subscriber, the server unloads the thread and emits `thread/closed`.206- `thread/unsubscribe` - unsubscribe this connection from thread turn/item events. If this was the last subscriber, the server unloads the thread and emits `thread/closed`.

209- `thread/unarchive` - restore an archived thread rollout back into the active sessions directory; returns the restored `thread` and emits `thread/unarchived`.207- `thread/unarchive` - restore an archived thread rollout back into the active sessions directory; returns the restored `thread` and emits `thread/unarchived`.

215- `turn/interrupt` - request cancellation of an in-flight turn; success is `{}` and the turn ends with `status: "interrupted"`.213- `turn/interrupt` - request cancellation of an in-flight turn; success is `{}` and the turn ends with `status: "interrupted"`.

216- `review/start` - kick off the Codex reviewer for a thread; emits `enteredReviewMode` and `exitedReviewMode` items.214- `review/start` - kick off the Codex reviewer for a thread; emits `enteredReviewMode` and `exitedReviewMode` items.

217- `command/exec` - run a single command under the server sandbox without starting a thread/turn.215- `command/exec` - run a single command under the server sandbox without starting a thread/turn.

216- `command/exec/write` - write stdin bytes to a running `command/exec` session or close stdin.

217- `command/exec/resize` - resize a running PTY-backed `command/exec` session.

218- `command/exec/terminate` - terminate a running `command/exec` session.

218- `model/list` - list available models (set `includeHidden: true` to include entries with `hidden: true`) with effort options, optional `upgrade`, and `inputModalities`.219- `model/list` - list available models (set `includeHidden: true` to include entries with `hidden: true`) with effort options, optional `upgrade`, and `inputModalities`.

219- `experimentalFeature/list` - list feature flags with lifecycle stage metadata and cursor pagination.220- `experimentalFeature/list` - list feature flags with lifecycle stage metadata and cursor pagination.

220- `collaborationMode/list` - list collaboration mode presets (experimental, no pagination).221- `collaborationMode/list` - list collaboration mode presets (experimental, no pagination).

221- `skills/list` - list skills for one or more `cwd` values (supports `forceReload` and optional `perCwdExtraUserRoots`).222- `skills/list` - list skills for one or more `cwd` values (supports `forceReload` and optional `perCwdExtraUserRoots`).

223- `plugin/list` - list discovered plugin marketplaces and plugin state, including install/auth policy metadata.

224- `plugin/read` - read one plugin by marketplace path and plugin name, including bundled skills, apps, and MCP server names.

222- `app/list` - list available apps (connectors) with pagination plus accessibility/enabled metadata.225- `app/list` - list available apps (connectors) with pagination plus accessibility/enabled metadata.

223- `skills/config/write` - enable or disable skills by path.226- `skills/config/write` - enable or disable skills by path.

224- `mcpServer/oauth/login` - start an OAuth login for a configured MCP server; returns an authorization URL and emits `mcpServer/oauthLogin/completed` on completion.227- `mcpServer/oauth/login` - start an OAuth login for a configured MCP server; returns an authorization URL and emits `mcpServer/oauthLogin/completed` on completion.

233- `config/value/write` - write a single configuration key/value to the user's `config.toml` on disk.236- `config/value/write` - write a single configuration key/value to the user's `config.toml` on disk.

234- `config/batchWrite` - apply configuration edits atomically to the user's `config.toml` on disk.237- `config/batchWrite` - apply configuration edits atomically to the user's `config.toml` on disk.

235- `configRequirements/read` - fetch requirements from `requirements.toml` and/or MDM, including allow-lists, pinned `featureRequirements`, and residency/network requirements (or `null` if you haven't set any up).238- `configRequirements/read` - fetch requirements from `requirements.toml` and/or MDM, including allow-lists, pinned `featureRequirements`, and residency/network requirements (or `null` if you haven't set any up).

239- `fs/readFile`, `fs/writeFile`, `fs/createDirectory`, `fs/getMetadata`, `fs/readDirectory`, `fs/remove`, and `fs/copy` - operate on absolute filesystem paths through the app-server v2 filesystem API.

236 240 

237## Models241## Models

238 242 

315 319 

316```json320```json

317{ "method": "thread/start", "id": 10, "params": {321{ "method": "thread/start", "id": 10, "params": {

318 "model": "gpt-5.1-codex",322 "model": "gpt-5.4",

319 "cwd": "/Users/me/project",323 "cwd": "/Users/me/project",

320 "approvalPolicy": "never",324 "approvalPolicy": "never",

321 "sandbox": "workspaceWrite",325 "sandbox": "workspaceWrite",

570 "writableRoots": ["/Users/me/project"],574 "writableRoots": ["/Users/me/project"],

571 "networkAccess": true575 "networkAccess": true

572 },576 },

573 "model": "gpt-5.1-codex",577 "model": "gpt-5.4",

574 "effort": "medium",578 "effort": "medium",

575 "summary": "concise",579 "summary": "concise",

576 "personality": "friendly",580 "personality": "friendly",

713- The server rejects empty `command` arrays.717- The server rejects empty `command` arrays.

714- `sandboxPolicy` accepts the same shape used by `turn/start` (for example, `dangerFullAccess`, `readOnly`, `workspaceWrite`, `externalSandbox`).718- `sandboxPolicy` accepts the same shape used by `turn/start` (for example, `dangerFullAccess`, `readOnly`, `workspaceWrite`, `externalSandbox`).

715- When omitted, `timeoutMs` falls back to the server default.719- When omitted, `timeoutMs` falls back to the server default.

720- Set `tty: true` for PTY-backed sessions, and use `processId` when you plan to follow up with `command/exec/write`, `command/exec/resize`, or `command/exec/terminate`.

721- Set `streamStdoutStderr: true` to receive `command/exec/outputDelta` notifications while the command is running.

716 722 

717### Read admin requirements (`configRequirements/read`)723### Read admin requirements (`configRequirements/read`)

718 724 

773 779 

774- Exact-match only: `item/agentMessage/delta` suppresses only that method.780- Exact-match only: `item/agentMessage/delta` suppresses only that method.

775- Unknown method names are ignored.781- Unknown method names are ignored.

776- Applies to both legacy (`codex/event/*`) and v2 (`thread/*`, `turn/*`, `item/*`, etc.) notifications.782- Applies to the current `thread/*`, `turn/*`, `item/*`, and related v2 notifications.

777- Doesn't apply to requests, responses, or errors.783- Doesn't apply to requests, responses, or errors.

778 784 

779### Fuzzy file search events (experimental)785### Fuzzy file search events (experimental)