MCP login for Claude Code not working

# Bug report <!-- ⚠️ We receive a lot of bug reports which have already been solved or discussed. If you are looking for help, please try these first: - Docs: https://docs.supabase.com - Discussions: https://github.com/supabase/supabase/discussions - Discord: https://discord.supabase.com Before opening a bug report, please verify the following: --> - [X] I confirm this is a bug with Supabase, not with my own application. - [X] I confirm I have searched the [Docs](https://docs.supabase.com), GitHub [Discussions](https://github.com/supabase/supabase/discussions), and [Discord](https://discord.supabase.com). ## Describe the bug A clear and concise description of what the bug is. ## To Reproduce Can you see if there's any issues with the Supabase MCP? I try to log in, and it's not logging in. I'll check what's going on with the Supabase MCP connection. Ran 2 shell commands The Supabase MCP server is showing ! Needs authentication — the OAuth handshake isn't completing. Let me dig into why. Ran 3 shell commands Server is healthy (responds with a proper OAuth challenge). So it's a local token problem. Let me inspect the stored OAuth state. Ran 1 shell command Found something concrete — there are two Supabase entries in the keychain, and only one has tokens. Let me see what distinguishes them. Ran 1 shell command Both point at the same server URL, but one is a half-finished registration (client registered, no tokens ever issued). Let me test whether the good token actually works and whether its refresh path is alive. Ran 2 shell commands The token in entry 1 works perfectly — HTTP 200, full handshake. So the server and your Supabase authorization are both fine. The problem is entirely local: Claude Code is reading a different keychain slot than the one holding your working token. Let me pin down why there are two slots. Ran 2 shell commands The picture is clear now. Let me confirm the key detail — that the plugin version is embedded in the MCP config. Ran…