Older MCP servers using the legacy HTTP+SSE protocol no longer get wrongly prompted into an OAuth login flow
For MCP servers (external tools Claude Code connects to) that use the older HTTP+SSE connection method rather than newer transports, Claude Code now checks whether a 401 "unauthorized" response on the connection request really means the server wants OAuth login. If the server's earlier setup request didn't return a 405 "method not allowed" response, the 401 is treated as a genuine OAuth prompt. If it did return 405, Claude Code now refuses to start an OAuth flow at all.
This avoids incorrectly launching an OAuth sign-in flow against MCP servers that don't actually require one, which previously could have interrupted the user with an unnecessary login prompt.