Claude connector issue with https://mcp.emporiaenergy.com/streamable

### What happened?

The actual finding — confirmed: Request URL is https://claude.ai/api/mcp/auth_callback?code=66476e7a-2f8c-4e07-a99a-106c5010d071 — nothing else. No state= parameter anywhere in it. Status: 400 Bad Request, matching the exact error we've been chasing.

This settles it: Emporia's OAuth server authenticated you and redirected back with code but silently dropped state — even though Claude's backend correctly sent it out originally (that cookie in the request, mcp_oauth_state_mlhqajv5dczs_YXg=..., is Claude's frontend caching the original value specifically to check against the return trip, and there's nothing to check it against because Emporia never sent it back). This is a bug in Emporia's beta OAuth implementation, not Anthropic's.

This is a clean, well-evidenced bug report for Emporia: their /oauth/authorize endpoint isn't echoing the state parameter on the redirect back to the client's redirect_uri, violating standard OAuth behavior. Send it to info@emporiaenergy.com or file it at github.com/emporiaenergy/emporia-mcp/issues, with: the authorize request (state present), the callback request (state absent), and the 400 response.

Given it's their bug, not something either of us can route around

### What did you expect to happen?

Goal was to connect the custom connector in Claude.ai with the MCP link: https://mcp.emporiaenergy.com/streamable

### Steps to reproduce

1. Set up connector
2. pasted in the mcp: github.com/emporiaenergy/emporia-mcp/issues
3. received this error: {"type":"error","error":{"type":"invalid_request_error","message":"state: Field required"},"request_id":"req_011CdKBMdyhwSRdPPR8uctHK"}

### Area

MCP Connector (adding/managing servers)

### MCP Server (if applicable)

_No response_

### Error messages or logs

```shell
{"type":"error","error":{"type":"invalid_request_error","message":"state: Field required"},"request_id":"req_011CdKBMdyhwSRdPPR8uctHK"}
```

### Additional context

Attempted several attempts even in inprivate window