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Expose collaboration presets for clients --------- Co-authored-by: Josh McKinney <joshka@openai.com>
169 lines
6.8 KiB
Markdown
169 lines
6.8 KiB
Markdown
# Codex MCP Server Interface [experimental]
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This document describes Codex’s experimental MCP server interface: a JSON‑RPC API that runs over the Model Context Protocol (MCP) transport to control a local Codex engine.
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- Status: experimental and subject to change without notice
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- Server binary: `codex mcp-server` (or `codex-mcp-server`)
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- Transport: standard MCP over stdio (JSON‑RPC 2.0, line‑delimited)
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## Overview
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Codex exposes a small set of MCP‑compatible methods to create and manage conversations, send user input, receive live events, and handle approval prompts. The types are defined in `protocol/src/mcp_protocol.rs` and re‑used by the MCP server implementation in `mcp-server/`.
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At a glance:
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- Conversations
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- `newConversation` → start a Codex session
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- `sendUserMessage` / `sendUserTurn` → send user input into a conversation
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- `interruptConversation` → stop the current turn
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- `listConversations`, `resumeConversation`, `archiveConversation`
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- Configuration and info
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- `getUserSavedConfig`, `setDefaultModel`, `getUserAgent`, `userInfo`
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- `model/list` → enumerate available models and reasoning options
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- `collaborationMode/list` → enumerate collaboration mode presets (experimental)
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- Auth
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- `account/read`, `account/login/start`, `account/login/cancel`, `account/logout`, `account/rateLimits/read`
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- notifications: `account/login/completed`, `account/updated`, `account/rateLimits/updated`
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- Utilities
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- `gitDiffToRemote`, `execOneOffCommand`
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- Approvals (server → client requests)
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- `applyPatchApproval`, `execCommandApproval`
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- Notifications (server → client)
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- `loginChatGptComplete`, `authStatusChange`
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- `codex/event` stream with agent events
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See code for full type definitions and exact shapes: `protocol/src/mcp_protocol.rs`.
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## Starting the server
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Run Codex as an MCP server and connect an MCP client:
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```bash
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codex mcp-server | your_mcp_client
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```
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For a simple inspection UI, you can also try:
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```bash
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npx @modelcontextprotocol/inspector codex mcp-server
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```
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Use the separate `codex mcp` subcommand to manage configured MCP server launchers in `config.toml`.
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## Conversations
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Start a new session with optional overrides:
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Request `newConversation` params (subset):
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- `model`: string model id (e.g. "o3", "gpt-5.1", "gpt-5.1-codex")
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- `profile`: optional named profile
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- `cwd`: optional working directory
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- `approvalPolicy`: `untrusted` | `on-request` | `on-failure` | `never`
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- `sandbox`: `read-only` | `workspace-write` | `external-sandbox` (honors `networkAccess` restricted/enabled) | `danger-full-access`
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- `config`: map of additional config overrides
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- `baseInstructions`: optional instruction override
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- `compactPrompt`: optional replacement for the default compaction prompt
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- `includePlanTool` / `includeApplyPatchTool`: booleans
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Response: `{ conversationId, model, reasoningEffort?, rolloutPath }`
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Send input to the active turn:
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- `sendUserMessage` → enqueue items to the conversation
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- `sendUserTurn` → structured turn with explicit `cwd`, `approvalPolicy`, `sandboxPolicy`, `model`, optional `effort`, `summary`, and optional `outputSchema` (JSON Schema for the final assistant message)
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For v2 threads, `turn/start` also accepts `outputSchema` to constrain the final assistant message for that turn.
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Interrupt a running turn: `interruptConversation`.
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List/resume/archive: `listConversations`, `resumeConversation`, `archiveConversation`.
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## Models
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Fetch the catalog of models available in the current Codex build with `model/list`. The request accepts optional pagination inputs:
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- `pageSize` – number of models to return (defaults to a server-selected value)
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- `cursor` – opaque string from the previous response’s `nextCursor`
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Each response yields:
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- `items` – ordered list of models. A model includes:
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- `id`, `model`, `displayName`, `description`
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- `supportedReasoningEfforts` – array of objects with:
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- `reasoningEffort` – one of `minimal|low|medium|high`
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- `description` – human-friendly label for the effort
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- `defaultReasoningEffort` – suggested effort for the UI
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- `isDefault` – whether the model is recommended for most users
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- `nextCursor` – pass into the next request to continue paging (optional)
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## Collaboration modes (experimental)
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Fetch the built-in collaboration mode presets with `collaborationMode/list`. This endpoint does not accept pagination and returns the full list in one response:
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- `data` – ordered list of collaboration mode presets
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## Event stream
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While a conversation runs, the server sends notifications:
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- `codex/event` with the serialized Codex event payload. The shape matches `core/src/protocol.rs`’s `Event` and `EventMsg` types. Some notifications include a `_meta.requestId` to correlate with the originating request.
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- Auth notifications via method names `loginChatGptComplete` and `authStatusChange`.
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Clients should render events and, when present, surface approval requests (see next section).
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## Tool responses
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The `codex` and `codex-reply` tools return standard MCP `CallToolResult` payloads. For
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compatibility with MCP clients that prefer `structuredContent`, Codex mirrors the
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content blocks inside `structuredContent` alongside the `threadId`.
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Example:
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```json
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{
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"content": [{ "type": "text", "text": "Hello from Codex" }],
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"structuredContent": {
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"threadId": "019bbed6-1e9e-7f31-984c-a05b65045719",
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"content": "Hello from Codex"
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}
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}
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```
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## Approvals (server → client)
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When Codex needs approval to apply changes or run commands, the server issues JSON‑RPC requests to the client:
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- `applyPatchApproval { conversationId, callId, fileChanges, reason?, grantRoot? }`
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- `execCommandApproval { conversationId, callId, command, cwd, reason? }`
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The client must reply with `{ decision: "allow" | "deny" }` for each request.
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## Auth helpers
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For the complete request/response shapes and flow examples, see the [“Auth endpoints (v2)” section in the app‑server README](../app-server/README.md#auth-endpoints-v2).
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## Example: start and send a message
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```json
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{ "jsonrpc": "2.0", "id": 1, "method": "newConversation", "params": { "model": "gpt-5.1", "approvalPolicy": "on-request" } }
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```
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Server responds:
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```json
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{ "jsonrpc": "2.0", "id": 1, "result": { "conversationId": "c7b0…", "model": "gpt-5.1", "rolloutPath": "/path/to/rollout.jsonl" } }
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```
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Then send input:
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```json
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{ "jsonrpc": "2.0", "id": 2, "method": "sendUserMessage", "params": { "conversationId": "c7b0…", "items": [{ "type": "text", "text": "Hello Codex" }] } }
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```
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While processing, the server emits `codex/event` notifications containing agent output, approvals, and status updates.
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## Compatibility and stability
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This interface is experimental. Method names, fields, and event shapes may evolve. For the authoritative schema, consult `protocol/src/mcp_protocol.rs` and the corresponding server wiring in `mcp-server/`.
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