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.

Client type: Terminal agent
Protocol revision: Not published

Support

Codex CLI

stdio: Yes
Streamable HTTP: Yes
Legacy SSE: No
Revision: Not published
OAuth flow: Yes
Registration: Unknown
Metadata doc: Unknown
Client ID: Unknown
resource: Unknown
iss: Unknown
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
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
Custom headers: Both http_headers and env_http_headers are documented, plus bearer_token_env_var for the Authorization: Bearer case. Source

Primary source

This row was last verified July 31, 2026 against the 2026-07-28 revision.