A webhook-style connection route now replies 'method not allowed' instead of 'not found' for wrong HTTP methods
Claude Code has an internal route used to look up a live MCP (Model Context Protocol, the system that lets Claude use external tools) transport connection by secret and ID. If a request to a valid, known connection used the wrong HTTP method (anything other than POST), it used to get the same generic "not found" response as a request to a connection that doesn't exist at all. Now it gets a proper "method not allowed" response, with an Allow: POST header telling the caller what method it should have used.
This makes it possible to tell the difference between "this connection doesn't exist" and "this connection exists but you called it the wrong way," which is clearer for anything talking to this route programmatically.