Claude Code now asks every local MCP server for the 2026-07-28 protocol

Claude Code 2.1.292 (October 6, 2026) changes how it connects to local MCP servers. Stdio servers are now asked to negotiate MCP protocol revision 2026-07-28 by default, on every install, including Bedrock, Vertex, and Foundry.

Servers that support the newer revision use it. Servers that don't connect the older way, as before.

What changes for a slow server

A stdio server that ignores the newer protocol check can make startup wait. The release notes say that after one slow connect, Claude Code now remembers that server for seven days and connects to it the older way without the wait.

Channel servers

A channel server that negotiates the newer revision can't deliver channel messages, so Claude Code doesn't register it as a channel. A channel server that doesn't support the revision connects on the earlier handshake and registers as before. If you run a stdio channel server and want it kept on the earlier handshake, opt out.

Opting out

Set MCP_PROTOCOL_NEGOTIATION to legacy to keep every server on the earlier protocol:

export MCP_PROTOCOL_NEGOTIATION=legacy

The variable takes auto or legacy. auto probes HTTP, claude.ai connector, and stdio servers. legacy probes none. Any other value is ignored with a warning in the debug log.

The variable applies to the v2 MCP client runtime only. To choose the runtime itself, set MCP_SDK_GENERATION to v1 or v2. Per the MCP docs, v2 is the default on Claude Code 2.1.274 or later in sessions that don't fetch feature flags.

See the Claude Code sheet for the current MCP and environment-variable surface.