MCP connections can skip the listening request when a server says it does not accept it
If an MCP server's last reply says it does not accept GET requests, Claude Code stops sending the GET that opens a listening stream and answers it itself
You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
MCPArea: what it touches
ImprovementsKind: in v2.1.309,
ImprovementsSection of the release
Unclear It is not stated what condition switches this behaviour on.
What
An MCP server is an outside program that gives Claude Code extra tools. Over some connections, Claude Code sends a GET request (one kind of web request) to open a listening stream, a long-lived connection the server can use to send messages back on its own.
Claude Code now remembers whether the server's most recent reply carried an Allow header, the part of a reply that lists which kinds of request the server accepts, and whether that list left out GET. If it did, Claude Code stops sending later GET requests to that server. It answers each one itself with a 405 "method not allowed" result and logs the reason. This only happens under a certain condition.
Why
It saves Claude Code from repeatedly trying to open a listening stream with a server that has already said it does not support one.
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtIt is not stated what condition switches this behaviour on.
