Custom connector authorize flow redirects to unregistered /authorize path instead of registered authorization_endpoint

### MCP server URL or name

https://websitedesignbedford.co.uk/wp-json/mcp/novamira-oauth

### How are you connecting to this server?

From a custom connector URL I entered manually

### Where does the issue occur?

When pressing the Connect button

### When did you last reproduce this?

0850hrs 25th July 2026 BST

### Browser and OS

macOS

### Describe the issue

Connecting a custom connector to a self-hosted WordPress MCP server (Novamira plugin). I've fully verified the server-side OAuth implementation is correct via curl:

- Discovery: /.well-known/oauth-authorization-server returns valid metadata with authorization_endpoint = https://websitedesignbedford.co.uk/wp-admin/admin.php?page=novamira-oauth-authorize
- That endpoint, tested directly, correctly 302-redirects unauthenticated requests to wp-login.php with a proper redirect_to parameter
- Client registration via /wp-json/novamira/v1/oauth/register returns a valid client_id (201)

However, when connecting through Claude's connector UI (both on the original attempt and after fully removing and re-adding the connector from scratch, with the client_id supplied manually in Advanced settings), the browser opens https://websitedesignbedford.co.uk/authorize?... instead — a bare root path that was never present in the discovery metadata. That path returns a genuine WordPress 404 (route not registered). Confirmed via curl this is a real 404, not a hosting/CDN block.

Given the discovery metadata and manual testing confirm the server-side flow is correct, this appears to be a client-side issue where Claude constructs or falls back to a guessed /authorize path rather than using the authorization_endpoint value returned by discovery.

### Error details

```shell
"Couldn't register with novamira-websitedesignbed's sign-in service. You can try again, or add an OAuth Client ID in the connector settings."
ofid_91c883b8e0c77ffc (original attempt)
```

### Expected behavior

Claude should navigate to the authorization_endpoint returned by the discovery metadata (https://websitedesignbedford.co.uk/wp-admin/admin.php?page=novamira-oauth-authorize), which correctly redirects to login when unauthenticated — rather than a guessed/default /authorize path that doesn't exist on the server.

### Additional context

_No response_