MCP status and sign-in requests can ask for a live-only reply

What

MCP servers are outside programs that give Claude Code extra tools. Programs that control Claude Code, such as the SDK or a remote client, can send it requests. Two of these requests now accept a new liveReply option:

• mcp_status (which reports the state of each MCP server) took no options before. With liveReply set, and when Claude Code is writing through a cloud session, the answer goes only to the clients attached at that moment. It is sent as a control_response marked live_only: true and is not stored in the session history. On cloud workers this answer includes each server's configuration, such as URLs, headers and OAuth (sign-in) settings. In headless mode, a successful mcp_status with liveReply is answered through this separate path.
• mcp_authenticate (which starts signing in to an MCP server) with liveReply set sends the sign-in URL through a different reply path than the usual final answer.
• The remote-session client keeps track of these live-only requests separately from other requests.

The MCP connection check also now treats a new replaced server state as finished, and takes into account whether a request was relayed.

Why

A program can ask for MCP status, which may include server URLs and headers, without that answer being saved in the session history. It can also receive a sign-in link before the sign-in flow completes.