# Configure GPT models in Claude Code

> Use GPT models (e.g. gpt-5.6-sol) in Claude Code via the LMU AI API: plan prerequisites, the settings.json config, and switching with /model.

URL: https://docs.lmuai.ai/docs/tools/claude-code-gpt



Claude Code can call GPT models through the LMU AI API, for example `gpt-5.6-sol`, `gpt-5.6-terra`, and `gpt-5.5`.

<Callout type="warn" title="Prerequisites">
  You need to meet one of the following:

  * Have subscribed to a **GPT plan**
  * Use pay-as-you-go billing and have selected the **GPT group** in the LMU AI console

  If your current plan or group doesn't include GPT models, you may still get a no-permission or model-unavailable error even after configuring.
</Callout>

***

## Config file location [#config-file-location]

Claude Code's config file is `settings.json`.

<Tabs items="['Mac/Linux', 'Windows']">
  <Tab value="Mac/Linux">
    ```bash
    ~/.claude/settings.json
    ```
  </Tab>

  <Tab value="Windows">
    ```powershell
    C:\Users\YourUsername\.claude\settings.json
    ```
  </Tab>
</Tabs>

***

## Option 1 — Full config (recommended) [#option-1--full-config-recommended]

The full config maps Claude Code's internal Opus / Sonnet / Haiku default models to GPT models. Once configured, launching Claude Code uses the corresponding GPT model by default.

Open `settings.json` in a text editor and add the following (replace the key with your own LMU AI API Key):

```json
{
  "env": {
    "ANTHROPIC_AUTH_TOKEN": "sk-your-lmu-ai-api-key",
    "ANTHROPIC_BASE_URL": "https://api.lmuai.ai",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "gpt-5.4",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL_NAME": "gpt-5.4",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "gpt-5.6-sol",
    "ANTHROPIC_DEFAULT_OPUS_MODEL_NAME": "gpt-5.6-sol",
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "gpt-5.5",
    "ANTHROPIC_DEFAULT_SONNET_MODEL_NAME": "gpt-5.5"
  },
  "skipDangerousModePermissionPrompt": true,
  "model": "opus"
}
```

**Field reference:**

| Field                                                                    | Description                                                                                            |
| ------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------ |
| `ANTHROPIC_AUTH_TOKEN`                                                   | The LMU AI API Key — enter your own `sk-` key                                                          |
| `ANTHROPIC_BASE_URL`                                                     | The LMU AI API address; for Claude Code, use `https://api.lmuai.ai`, without `/v1`                     |
| `ANTHROPIC_DEFAULT_OPUS_MODEL` / `ANTHROPIC_DEFAULT_OPUS_MODEL_NAME`     | Maps Claude Code's Opus default model to `gpt-5.6-sol`                                                 |
| `ANTHROPIC_DEFAULT_SONNET_MODEL` / `ANTHROPIC_DEFAULT_SONNET_MODEL_NAME` | Maps the Sonnet default model to `gpt-5.5`                                                             |
| `ANTHROPIC_DEFAULT_HAIKU_MODEL` / `ANTHROPIC_DEFAULT_HAIKU_MODEL_NAME`   | Maps the Haiku default model to `gpt-5.4`                                                              |
| `model`                                                                  | The model tier selected when Claude Code launches; here it's `opus`, which maps to `gpt-5.6-sol` above |

<Callout type="info" title="Model mapping">
  With the full config above:

  * Selecting `opus` in Claude Code → actually calls `gpt-5.6-sol`
  * Selecting `sonnet` in Claude Code → actually calls `gpt-5.5`
  * Selecting `haiku` in Claude Code → actually calls `gpt-5.4`
</Callout>

***

## Option 2 — Minimal config [#option-2--minimal-config]

If you just want to configure the key and Base URL first, you can use the minimal config:

```json
{
  "env": {
    "ANTHROPIC_AUTH_TOKEN": "sk-your-lmu-ai-api-key",
    "ANTHROPIC_BASE_URL": "https://api.lmuai.ai"
  },
  "skipDangerousModePermissionPrompt": true,
  "model": "opus"
}
```

The minimal config doesn't map `opus` to `gpt-5.6-sol` ahead of time. After launching Claude Code, run this manually in Claude Code:

```bash
/model gpt-5.6-sol
```

The current session then switches to `gpt-5.6-sol`.

<Callout type="info" title="When to use the minimal config?">
  If you often switch between different GPT models, use the minimal config and specify one with `/model <model-name>` after each launch, e.g. `/model gpt-5.6-sol`.

  If you want `gpt-5.6-sol` to be the default on every launch, use the full config above.
</Callout>

***

## Common issues [#common-issues]

### Should the Base URL include `/v1`? [#should-the-base-url-include-v1]

Claude Code connects to the LMU AI API using the Anthropic protocol, so use:

```text
https://api.lmuai.ai
```

Do not use `https://api.lmuai.ai/v1`.

### Can I just set `model` to `gpt-5.6-sol`? [#can-i-just-set-model-to-gpt-56-sol]

We recommend one of two approaches instead:

* Use the full config, mapping `ANTHROPIC_DEFAULT_OPUS_MODEL` to `gpt-5.6-sol` and keeping `"model": "opus"`
* Use the minimal config and run `/model gpt-5.6-sol` after launch

Both fit Claude Code's model-tier configuration approach better, and make switching and reverting clearer.

### What if it still doesn't work after configuring? [#what-if-it-still-doesnt-work-after-configuring]

Check the following:

1. Whether the API Key is a key generated in the LMU AI console
2. Whether `ANTHROPIC_BASE_URL` is `https://api.lmuai.ai`
3. Whether you've subscribed to a GPT plan, or, on pay-as-you-go, selected the GPT group
4. Whether the model name is spelled correctly, e.g. `gpt-5.6-sol`

To see the currently supported models, check the [Model Gallery](/docs/guide/models).