Vibe Coding
Two Consecutive Claude Code Releases Ship MCP OAuth Fixes — `127.0.0.1` vs `localhost` and Pre-Registered Clients
2.1.229 fixed MCP OAuth against strict authorization servers by using `127.0.0.1` instead of `localhost` in the redirect URI, and 2.1.231 — the newest release — fixed OAuth sign-in failing with a redirect URI mismatch for servers that use a pre-registered OAuth client, naming Slack as the example. Back-to-back releases patching the same subsystem means the OAuth handshake, not the protocol itself, is where MCP integration currently breaks. If a remote MCP server has been refusing to authenticate, upgrade before debugging your own server config.
↳ Follow the thread