[BUG] Official Meta Ads MCP (mcp.facebook.com/ads) fails OAuth with "redirect_uris are not registered for this client"

Summary

Authenticating to the official hosted Meta Ads MCP server at https://mcp.facebook.com/ads fails before the browser opens, with Meta's OAuth server rejecting Claude Code's dynamic client registration:

SDK auth failed: The provided redirect_uris are not registered for this client.

Because this is the official hosted integration, there's no way for the user to override client_id, client_secret, or --callback-port — the OAuth client identity is fixed by Claude Code, so this can only be fixed on the Anthropic ↔ Meta side.

Environment

• Claude Code: 2.1.123 (per User-Agent in debug log)
• Platform: Linux / WSL2 (Ubuntu under WSL2 on Windows)
• MCP server: https://mcp.facebook.com/ads (HTTP transport, official Meta Ads MCP)

Reproduction

1. Add the official Meta Ads MCP via /mcp (project-scoped HTTP server, URL https://mcp.facebook.com/ads).
2. Run /mcp → select Meta-ads MCP Server → Authenticate.
3. Browser does not open. Dialog shows: SDK auth failed: The provided redirect_uris are not registered for this client.

Debug log (claude --debug-file ... --debug mcp)

13:12:35.817 [DEBUG] MCP server "meta-ads": Initializing HTTP transport to https://mcp.facebook.com/ads
13:12:35.820 [DEBUG] MCP server "meta-ads": HTTP transport options: {"url":"https://mcp.facebook.com/ads","headers":{"User-Agent":"claude-code/2.1.123 (cli)","Accept-Encoding":"identity"},"hasAuthProvider":true,"timeoutMs":60000}
13:12:36.573 [DEBUG] MCP server "meta-ads": HTTP Connection failed after 756ms: The provided redirect_uris are not registered for this client.
13:12:41.065 [DEBUG] MCP server "meta-ads": SDK auth error: jo: The provided redirect_uris are not registered for this client.
13:12:41.066 [DEBUG] MCP server "meta-ads": Error during auth completion: Error: SDK auth failed: The provided redirect_uris are not registered for this client.

The failure is a server-to-server response from Meta's auth endpoint within ~750ms of the handshake starting — no browser launch is attempted, so this is not a WSL browser-handoff issue.

Suggested fix

Either:

• Anthropic's OAuth client config for the hosted Meta Ads MCP is missing the redirect_uri Claude Code is registering, or
• Meta's allowlist for that client needs to include Claude Code's localhost callback pattern.

It would also help if Claude Code logged the exact redirect_uri value it tried to register — currently the rejection is logged but not the request body.