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

# Switch from Anthropic Claude SDK to Meliai Inference

> Point the Anthropic SDK at Meliai by setting ANTHROPIC_BASE_URL and your API key. Claude model names are mapped to open-weight equivalents automatically.

Meliai exposes a fully Anthropic-compatible endpoint at `/v1/messages`, accepting the exact request shape and returning the exact response shape that the Anthropic SDK expects. You migrate by setting two environment variables — `ANTHROPIC_API_KEY` and `ANTHROPIC_BASE_URL` — and your existing code continues to run without modification. Claude model names such as `claude-sonnet-4` are mapped automatically to open-weight equivalents served from EU infrastructure.

<Steps>
  <Step title="Get a Meliai API key">
    Create a key at [meliai.ai/account/api/keys](https://meliai.ai/account/api/keys). Your key will have the format `sk-mel-<KEY>`.

    <Tip>
      Keep your existing `ANTHROPIC_API_KEY` value if any other services in your stack still call Anthropic directly. You can hold both variables in your environment simultaneously.
    </Tip>
  </Step>

  <Step title="Set your environment variables">
    Override the two values the Anthropic SDK reads to locate the API:

    ```bash theme={null}
    export ANTHROPIC_API_KEY="sk-mel-<YOUR_KEY>"
    export ANTHROPIC_BASE_URL="https://api.meliai.ai"
    ```

    The SDK picks these up automatically — no code changes needed at this stage. `ANTHROPIC_BASE_URL` must point to the root URL (without a `/v1` suffix); the SDK appends the path itself.
  </Step>

  <Step title="Run your existing code">
    Your Anthropic SDK calls work unchanged. Here's a minimal example to confirm the connection:

    ```python theme={null}
    import os
    from anthropic import Anthropic

    client = Anthropic(
        api_key=os.environ["ANTHROPIC_API_KEY"],
        base_url="https://api.meliai.ai",
    )

    response = client.messages.create(
        model="claude-sonnet-4",
        max_tokens=256,
        messages=[{"role": "user", "content": "Name three Hanseatic cities."}],
    )
    print(response.content[0].text)
    ```

    Streaming, tool use, vision inputs, and system prompts all work through the same `/v1/messages` endpoint with no modifications to your feature-specific code.
  </Step>

  <Step title="Understand model name mapping">
    Meliai does not serve Anthropic's proprietary Claude weights. Instead, when you pass a Claude model name, Meliai maps it to the closest open-weight equivalent available on EU infrastructure. For example:

    | Anthropic model name | Meliai equivalent                          |
    | -------------------- | ------------------------------------------ |
    | `claude-sonnet-4`    | Open-weight model of comparable capability |
    | `claude-haiku-3-5`   | Fast, lightweight open-weight model        |
    | `claude-opus-4`      | High-capability open-weight model          |

    You can also supply a Meliai-native model ID directly — browse the full mapping at [meliai.ai/hub](https://meliai.ai/hub) or retrieve it programmatically:

    ```bash theme={null}
    curl https://api.meliai.ai/v1/models \
      -H "Authorization: Bearer $ANTHROPIC_API_KEY"
    ```
  </Step>
</Steps>

<Note>
  The Anthropic SDK's `beta.messages.create` interface (used for extended thinking, prompt caching, and other beta features) targets the same `/v1/messages` endpoint on Meliai. Pass the corresponding `betas` header values as you normally would; Meliai forwards them to the underlying model where supported.
</Note>

<Info>
  Meliai also exposes `POST /v1/messages/count_tokens`, the Anthropic-compatible token-count preflight endpoint. Call it before a full completion to estimate token usage and cost without incurring inference charges.
</Info>

## What changes and what stays the same

| Aspect                  | Before (Anthropic)      | After (Meliai)                     |
| ----------------------- | ----------------------- | ---------------------------------- |
| SDK                     | `anthropic` Python / JS | Same SDK, unchanged                |
| Endpoint                | `api.anthropic.com`     | `api.meliai.ai`                    |
| API key format          | `sk-ant-...`            | `sk-mel-...`                       |
| Model weights           | Proprietary Claude      | Open-weight equivalents            |
| Data residency          | Anthropic (US)          | EU-only, GDPR-compliant            |
| Environmental telemetry | Not available           | Per-response `environment_impact`  |
| Response shape          | Anthropic Messages      | Identical Anthropic Messages shape |