Fixing "Unable to Connect to Extension Server" on Claude.ai with Apify MCP Connector
If you're encountering the frustrating "Unable to connect to extension server" error when using the Apify MCP connector with Claude.ai, you're not alone. This issue prevents the connector from loading your Apify tools and actors, rendering the integration useless. This article will guide you through the steps to resolve this problem and get your Apify connector working smoothly again.
Understanding the Problem
The error typically manifests immediately after adding the Apify MCP connector to Claude.ai or when attempting to use an Apify tool within a conversation. Disabling and re-enabling the connector, or even providing a valid API token, often proves ineffective. This can be particularly confusing as the connector appears to be correctly configured, yet it fails to establish a connection with the Apify server.
Root Cause: Deprecated SSE Endpoint
The underlying cause of this issue lies in the fact that the original Apify MCP connector configuration for Claude.ai was using a deprecated Server-Sent Events (SSE) endpoint. This endpoint, specifically /sse, was removed on April 1, 2026. As a result, the Claude.ai connector, attempting to connect to this non-existent endpoint, fails and throws the "Unable to connect" error.
Solution: Switching to the Streamable HTTP Endpoint
The solution involves updating the connector's URL to utilize the current streamable HTTP endpoint. Here's a step-by-step guide:
- Remove the Existing Connector: In Claude Desktop, navigate to Settings → Connectors. Locate the Apify MCP connector and remove it.
- Add the New Connector: Click the button to add a new connector.
- Enter the Correct URL: In the connector URL field, enter the following URL:
https://mcp.apify.com - Authorize the Connection: Upon the first connection attempt, Claude.ai will likely open a browser window prompting you to authorize the connection via OAuth. Follow the on-screen instructions to grant the necessary permissions. This eliminates the need to manually input an API token directly into the URL.
By switching to the https://mcp.apify.com endpoint, you're directing the connector to the correct and actively supported server, resolving the connection issue.
Alternative: Token-Based Authentication
While OAuth is the recommended approach, you can also configure the connector using token-based authentication. This involves setting an Authorization: Bearer header with your Apify API token. Refer to the Apify documentation for detailed instructions on setting up token-based authentication.
Practical Tips and Considerations
- Clear Cache: If you continue to experience issues after updating the connector URL, try clearing your browser's cache and cookies or restarting the Claude Desktop application.
- API Token Validity: Ensure that your Apify API token is valid and has the necessary permissions to access the actors or tools you intend to use.
- Firewall/Proxy: In rare cases, firewall or proxy settings may interfere with the connection. Verify that your network configuration allows communication with
mcp.apify.com. - Connector Updates: Keep your Claude Desktop application and the Apify MCP connector updated to the latest versions to benefit from bug fixes and performance improvements.
By following these steps, you should be able to successfully resolve the "Unable to connect to extension server" error and enjoy seamless integration between Apify and Claude.ai.