[BUG] MCP oAuth2.1 Dynamic client registration fails

[struckoff]

What happened?

OAuth dynamic client registration fails: registrationUrl dropped in WWW-Authenticate discovery path

What did you expect to happen?

When connecting to an MCP server that advertises registration_endpoint in its OAuth Authorization Server Metadata (RFC 8414), gemini-cli should successfully discover and use that endpoint for
dynamic client registration (RFC 7591) without requiring manual configuration.

Specifically, after the WWW-Authenticate discovery path succeeds (discoverOAuthFromWWWAuthenticate returns a config with registrationUrl), the registrationUrl should be preserved through the entire
flow and used for registerClient().

Client information

Client Information

Run gemini to enter the interactive CLI, then run the /about command.

> /about
About Gemini CLI                                                                                                                                                                                                                                                                                  │
│                                                                                                                                                                                                                                                                                                   │
│ CLI Version                                                                                          0.29.7                                                                                                                                                                                       │
│ Git Commit                                                                                           118984025f                                                                                                                                                                                   │
│ Model                                                                                                Auto (Gemini 3)                                                                                                                                                                              │
│ Sandbox                                                                                              no sandbox                                                                                                                                                                                   │
│ OS                                                                                                   linux                                                                                                                                                                                        │
│ Auth Method                                                                                          Logged in with Google (as5423.ru@gmail.com)                                                                                                                                                  │
│ Tier                                                                                                 Gemini Code Assist for individuals                                                                                

Login information

No response

Anything else we need to know?

No response

[struckoff]

/assign

[gemini-cli]

👋 @struckoff, thanks for your interest in this issue! We're reserving self-assignment for issues that have been marked with the help wanted label. Feel free to check out our list of issues that need attention.

[struckoff]

Hi @jacob314, sorry for tag.
Is it possible to assign me on a fix? I have a working fix already, but missing required tag in a issue. Fix quite straightforward, just need to update registration URL mapping.
Geminit CLI itself supports dynamic registration if I put everything in json config manually, all is missing is a discovery on mcp add command.

[TomHsiung]

It's been a month and more, pal. Did you solve this problem? Thanks

[struckoff]

I had to rely on my fork here: #20992, so I guess answer will be - no.

[TomHsiung]

Okay! Thanks.