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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.

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.

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.

Config file location

Claude Code's config file is settings.json.

~/.claude/settings.json
C:\Users\YourUsername\.claude\settings.json

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):

{
  "env": {
    "ANTHROPIC_AUTH_TOKEN": "sk-your-lmu-ai-api-key",
    "ANTHROPIC_BASE_URL": "https://api.lmuai.com",
    "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:

FieldDescription
ANTHROPIC_AUTH_TOKENThe LMU AI API Key — enter your own sk- key
ANTHROPIC_BASE_URLThe LMU AI API address; for Claude Code, use https://api.lmuai.com, without /v1
ANTHROPIC_DEFAULT_OPUS_MODEL / ANTHROPIC_DEFAULT_OPUS_MODEL_NAMEMaps Claude Code's Opus default model to gpt-5.6-sol
ANTHROPIC_DEFAULT_SONNET_MODEL / ANTHROPIC_DEFAULT_SONNET_MODEL_NAMEMaps the Sonnet default model to gpt-5.5
ANTHROPIC_DEFAULT_HAIKU_MODEL / ANTHROPIC_DEFAULT_HAIKU_MODEL_NAMEMaps the Haiku default model to gpt-5.4
modelThe model tier selected when Claude Code launches; here it's opus, which maps to gpt-5.6-sol above

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

Option 2 — Minimal config

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

{
  "env": {
    "ANTHROPIC_AUTH_TOKEN": "sk-your-lmu-ai-api-key",
    "ANTHROPIC_BASE_URL": "https://api.lmuai.com"
  },
  "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:

/model gpt-5.6-sol

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

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.

Common issues

Should the Base URL include /v1?

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

https://api.lmuai.com

Do not use https://api.lmuai.com/v1.

Can I just set model to gpt-5.6-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?

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.com
  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.

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On this page

Config file locationOption 1 — Full config (recommended)Option 2 — Minimal configCommon issuesShould the Base URL include /v1?Can I just set model to gpt-5.6-sol?What if it still doesn't work after configuring?