> ## Documentation Index
> Fetch the complete documentation index at: https://cac.nextmind.space/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# API key users

> Use cac for fingerprint isolation without a proxy.

If you connect to Claude Code using an API key and base URL (not OAuth), you can still use cac for identity isolation and telemetry blocking — no proxy needed.

## Setup

```bash theme={null}
# Install cac
npm install -g claude-cac

# Create an environment (no -p flag)
cac env create work

# Activate
cac work

# Set your API credentials (cac preserves these)
export ANTHROPIC_API_KEY=sk-ant-...
export ANTHROPIC_BASE_URL=https://your-endpoint.com

# Run Claude Code
claude
```

## What's protected

Without a proxy, cac still provides:

| Protection                                         | Status         |
| :------------------------------------------------- | :------------- |
| Device fingerprint isolation (UUID, hostname, MAC) | Active         |
| `.claude` config isolation                         | Active         |
| Telemetry blocking (DNS guard + env vars)          | Active         |
| mTLS client certificates                           | Active         |
| Claude Code version pinning                        | Active         |
| Proxy routing                                      | Not applicable |
| Health check bypass                                | Not applicable |

## How API vars are handled

When **no proxy** is configured, cac preserves your environment variables:

* `ANTHROPIC_API_KEY` — kept
* `ANTHROPIC_BASE_URL` — kept
* `ANTHROPIC_AUTH_TOKEN` — kept

When a **proxy is configured**, cac clears these variables to force OAuth authentication through the proxy. This prevents accidental API key leakage through third-party endpoints.

## Multiple API endpoints

You can create separate environments for different API endpoints:

```bash theme={null}
cac env create prod-us
cac env create prod-eu
cac env create staging
```

Each gets its own identity and `.claude` config. Switch between them:

```bash theme={null}
cac prod-us
export ANTHROPIC_BASE_URL=https://us.api.example.com
claude

# Later...
cac prod-eu
export ANTHROPIC_BASE_URL=https://eu.api.example.com
claude
```