MCP Gateway | MCP User-based Authentication Failure: Missing cimd_flow_id cookie – Aembit

Overview

This article addresses user-based authentication failures through the Aembit MCP Gateway. The primary symptom is a Missing cimd_flow_id cookie error during the authentication callback. This error occurs when your mcp client uses a stale, cached authentication endpoint.

Relates To

MCP Client: Claude Code
Aembit Component: MCP Identity Gateway, access policy
Resources/Tooling: User-based Authentication

Cause

Claude code maintains a local authentication cache that stores the MCP Gateway endpoint URL. This might result from stale, authentication server entries requiring the revocation for the existing cached entries.

Solution

The resolution requires clearing the Claude Code's local authentication cache to force it to retrieve the updated endpoint information.

Clear Local Authentication Cache
Execute the following command to purge the stale endpoint configuration.
```
/mcp clear authentication
```
Re-authenticate
Initiate a new connection to the target server. The client will fetch the correct MCP Gateway endpoint and complete the authentication flow successfully.