Under the hood
Useful2 Signal3
OAuth docs now note that Claude Code sends a surface parameter and its own user agent.
What's wrong with this entry?
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surface=claude_code
What
The OAuth device-authorization documentation for third-party server implementors now records that the request body may carry a surface extension parameter, that Claude Code sends surface=claude_code, and that it sends a claude-code user agent on metadata, device, token and refresh requests.
Evidence
surface=claude_code
Strings lifted out of the shipped bundle, so the claim above can be checked against them.