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Use Claude Code with Fabric AI Gateway

You can send Claude Code traffic through Fabric AI Gateway by pointing Claude Code at a gateway route and passing a gateway key as a custom header. The gateway then applies your plugins to Claude Code requests, and you can review them in the console. This topic shows you how to start Claude Code through the gateway and confirm that requests arrive.

Prerequisites

Before you begin, make sure you have the following:

  • Claude Code installed on your computer.
  • A route that uses the Anthropic Messages API, such as anthropic-route, with these three endpoints exposed: messages, count_tokens, and models. Claude Code needs only these endpoints. For the steps, see Connect an LLM provider.
  • A gateway key for the route, and the name of the request header that the route’s Key Auth plugin reads.

Configure Claude Code to use the gateway

Claude Code reads its settings from a settings.json file, which is the recommended way to point it at the gateway. To configure Claude Code, do the following:

  1. Open your Claude Code user settings file, ~/.claude/settings.json. To limit the change to one project, use .claude/settings.json in that project instead.

  2. Add an env block with the gateway base URL and the gateway key header:

    {
      "env": {
        "ANTHROPIC_BASE_URL": "https://GATEWAY_HOST/anthropic",
        "ANTHROPIC_CUSTOM_HEADERS": "fg-api-key: GATEWAY_KEY"
      }
    }

  3. Replace GATEWAY_HOST with your data plane host and GATEWAY_KEY with your gateway key.

  4. Restart Claude Code.

The settings do the following:

  • ANTHROPIC_BASE_URL sends requests to the gateway route instead of the Anthropic API. Use the base URL only, not the individual endpoint paths.
  • ANTHROPIC_CUSTOM_HEADERS adds the gateway key to each request. Use fg-api-key as the header name, unless the route’s Key Auth instance still shows an older header under Request header. For more information, see Authenticate requests with Key Auth.

Treat the gateway key as a secret. Don’t commit a settings file that contains it. For a project-level file, use .claude/settings.local.json, which Claude Code doesn’t share through version control.

To try the gateway for one session without editing a file, set the same two variables in your shell before you run claude.

How Claude Code authenticates to Anthropic

The gateway supplies the Anthropic credential. It adds the API key saved on the connection when it forwards requests to Anthropic, so you only need to send the gateway key to Fabric.

Confirm that requests pass through the gateway

To confirm that Claude Code uses the gateway, do the following:

  1. In Claude Code, send a message, for example Hello, is this working?.
  2. In the Fabric console, select Admin, and then select Traces.
  3. Find the requests from your user on the route.

Open a trace to see the request body, which includes the system prompt and the tool definitions that Claude Code sends with each request. If you attached a routing plugin to the route, the trace also shows the extra calls that the plugin makes.

Next steps