---
title: "Codex CLI — MCP compatibility"
description: "Two kinds of server, a local process or an address, with per-server tool allowlists and short default timeouts: 10 seconds to start a server and 60 seconds for a tool call."
canonicalUrl: "https://zuplo.com/learn/mcp/compatibility/clients/codex-cli"
pageType: "mcp-client"
kind: "Terminal agent"
verified: "2026-07-31"
---

# Codex CLI

> Two kinds of server, a local process or an address, with per-server tool allowlists and short default timeouts: 10 seconds to start a server and 60 seconds for a tool call.

_Terminal agent. Protocol revision: Not published._

## Support

- **stdio** — Yes
- **Streamable HTTP** — Yes
- **Legacy HTTP+SSE** — No
- **Protocol revision** — Not published
- **Runs the OAuth flow** — Yes
- **Registration (RFC 7591)** — Unknown
- **Metadata document** — Unknown
- **Pre-registered client ID** — Unknown
- **Sends resource (RFC 8707)** — Unknown
- **Validates iss (RFC 9207)** — Unknown
- **Custom headers** — Yes

**Protocol revision.** Not published. Neither the MCP page nor the configuration reference states a revision.

## Caveats and sources

Each one names the column it qualifies and cites the page it comes from, which is often not the page in the row's primary source.

### Legacy HTTP+SSE

Documented as absent by omission: the configuration offers a local process or an address, and SSE isn't among the options.

[Source](https://learn.chatgpt.com/docs/extend/mcp?surface=cli)

### Registration and discovery

An `auth` key exists on an HTTP server entry, but the documentation doesn't describe its shape, so registration, metadata documents, pre-registered IDs, and `resource` are all unknown rather than absent.

[Source](https://learn.chatgpt.com/docs/extend/mcp?surface=cli)

### Custom headers

Both `http_headers` and `env_http_headers` are documented, plus `bearer_token_env_var` for the `Authorization: Bearer` case.

[Source](https://learn.chatgpt.com/docs/extend/mcp?surface=cli)

[Primary source](https://learn.chatgpt.com/docs/extend/mcp?surface=cli)

_This row was last verified 2026-07-31 against the 2026-07-28 revision._

- **Clients** — [every client in the matrix](/learn/mcp/compatibility/clients)