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MCP troubleshooting

Fix common connection and authentication issues.

Use this guide when Cursor cannot list personas or MCP requests fail after setup.

401 Unauthorized or authentication errors

Symptoms: Cursor reports unauthorized, 401, or empty persona lists despite a configured server.

Remediation:

  1. Re-run Authorize for Cursor (MCP) from the dashboard MCP CONNECT panel.
  2. Download or copy a fresh configuration — do not reuse an old token.
  3. Replace the `personaforge` entry in `~/.cursor/mcp.json` and restart Cursor.
  4. Alternatively, create a new MCP Access Key under Settings → Security, then download the updated configuration.

Wrong MCP URL

Symptoms: Connection timeouts, 404, `Cannot POST /`, "unsupported method", or SSE `Invalid content type` errors.

Remediation:

  1. Re-download configuration from Authorize for Cursor (MCP) on the dashboard or create a new key under Settings → Security — use the `url` from that artifact in your `mcp.json`.
  2. The URL must end with `/mcp` (for example `https://your-mcp-host.onrender.com/mcp`). If you see `Cannot POST /` in Cursor logs, your config is pointing at the service root without `/mcp` — re-download configuration or append `/mcp` manually.
  3. Production uses the value from `NEXT_PUBLIC_MCP_URL` — never point at localhost unless you are running `mcp-server` locally for engineering.
  4. After correcting the URL, restart Cursor.

Expired or revoked token

Symptoms: MCP worked previously but suddenly returns 401 or empty data.

Remediation:

  1. Open Settings → Security and review MCP Access Keys.
  2. Revoke compromised or unused keys.
  3. Create a new key or re-authorize from the dashboard, then replace your Cursor configuration.

Session errors (Bad Request: No valid session ID)

Symptoms: Errors mentioning session ID, SSE 404, or streamable HTTP failures.

Remediation:

  1. Restart Cursor after updating `mcp.json`.
  2. Ensure you are on the latest hosted `mcp-server` deployment (operators: redeploy Render if the endpoint is stale).
  3. Re-authorize to obtain a configuration that includes the required headers block.

SSE stream drops after several minutes (`Failed to open SSE stream`)

Symptoms: MCP connects and works briefly, then fails with `Failed to open SSE stream` / `Maximum reconnection attempts exceeded` after roughly 5–10 minutes of idle time.

Cause: Hosted proxies (e.g. Render) can close long-lived SSE connections. The MCP client then tries to reopen the notification stream on the same session.

Remediation:

  1. Restart Cursor — this starts a fresh MCP session.
  2. Operators: deploy the latest `mcp-server` (includes SSE reconnect handling).
  3. If the problem persists after a server restart or Render spin-down, re-authorize from the dashboard so Cursor picks up a new session.

Still stuck?

Email support@chamelain.com with your org name and the error message from Cursor (redact any tokens).