Explain OAuth client-registration failures during login (e.g. Figma 403) instead of leaking SDK JSON parse errors#298
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Logging in to a server that refuses Dynamic Client Registration (e.g. Figma's remote MCP server, which 403s any client not on its allow-list with a plain-text body) surfaced the SDK's raw JSON parse error: HTTP 403: Invalid OAuth error response: SyntaxError: Unexpected token 'F', "Forbidden" is not valid JSON. Raw body: Forbidden performOAuthFlow now rewrites registration-phase failures (detected via the SDK's typed OAuthError plus a reachedAuthorization flag set at the authorization redirect) into actionable guidance pointing at --client-id / --client-metadata-url. Allow-list wording is used only for 401/403 or OAuth-coded client rejections; other registration failures (5xx outages, rejected metadata) are reported honestly, and the server's underlying response stays visible in the message. Post-redirect errors pass through unchanged. Supersedes #297. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01AP2pmUcWvR8rNypXqNEqtk
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mcpc loginagainst a server that refuses Dynamic Client Registration (e.g. Figma's remote MCP server, which returns a plain-text403 Forbiddenfor clients not on its allow-list) surfaced the SDK's raw parse error (HTTP 403: Invalid OAuth error response: SyntaxError: ... Raw body: Forbidden). Registration-phase failures are now rewritten into actionable guidance pointing at--client-id/--client-metadata-url.OAuthErrorplus areachedAuthorizationflag; post-redirect errors pass through unchangedloginprints onlyerror.messageFixes #296, supersedes #297.
https://claude.ai/code/session_01AP2pmUcWvR8rNypXqNEqtk
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