Claude Code

The most configurable client here on every axis except protocol revision: four transports, its own client metadata document, flags for a client ID and callback port, an override for the discovery chain, and a command hook that generates headers at connection time.

Client type: Terminal agent
Protocol revision: initialize era

Support

Claude Code

stdio: Yes
Streamable HTTP: Yes
Legacy SSE: Partial
Revision: initialize era
OAuth flow: Yes
Registration: Yes
Metadata doc: Yes
Client ID: Yes
resource: Yes
iss: Unknown
Headers: Yes

Protocol revision: Not published. Claude Code still runs the initialize handshake.

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: Available as claude mcp add --transport sse, with a documented note that the transport is deprecated and HTTP servers are the replacement. Claude Code also has a fourth transport nothing else here has: WebSocket, which takes headers only and runs no OAuth flow. Source
Metadata document: Claude Code publishes its own document at https://claude.ai/oauth/claude-code-client-metadata and uses it as its client_id, so it holds no Anthropic-issued credentials. It also discovers a server's support automatically. Source
Sends resource (RFC 8707): An open bug report says Claude Code appends a trailing slash to the resource value on both the authorization redirect and the token exchange, which makes Microsoft Entra ID answer AADSTS9010010 for any server whose metadata uses an unslashed resource URI. Treat this as a bug report rather than documented behavior. Source
Custom headers: Beyond a static headers map, headersHelper runs a command at connection time and merges its output into the headers, which is the path for Kerberos, short-lived tokens, and internal single sign-on. One ordering rule matters: if you configure headers.Authorization and the server rejects it, Claude Code fails the connection instead of falling back to OAuth. Source

Primary source

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