Use Modellix LLM with OpenCode

Configure OpenCode to call the Modellix LLM gateway. The recommended approach is a custom provider using @ai-sdk/openai-compatible (Chat Completions at /v1/chat/completions).

Modellix model IDs are provider/name (for example openai/gpt-5.5). Put that full string in the custom provider models map so OpenCode sends it unchanged in the request body. See Models & Pricing.

Set Up OpenCode

Store Credentials

In OpenCode, run /connect, choose Other, and enter a provider ID such as modellix. Paste your Modellix API key from the console.The provider ID from /connect must match the key under provider in opencode.json.Alternatively, set the key in config with options.apiKey (for example {env:MODELLIX_API_KEY}).

Add a Custom Provider

Create or update opencode.json (project) or ~/.config/opencode/opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "model": "modellix/openai/gpt-5.5",
  "provider": {
    "modellix": {
      "npm": "@ai-sdk/openai-compatible",
      "name": "Modellix",
      "options": {
        "baseURL": "https://llm.modellix.ai/v1",
        "apiKey": "{env:MODELLIX_API_KEY}"
      },
      "models": {
        "openai/gpt-5.5": {
          "name": "GPT 5.5"
        },
        "openai/gpt-5.6-sol": {
          "name": "GPT 5.6 Sol"
        },
        "openai/gpt-5.6-terra": {
          "name": "GPT 5.6 Terra"
        },
        "openai/gpt-5.6-luna": {
          "name": "GPT 5.6 Luna"
        },
        "anthropic/claude-sonnet-5": {
          "name": "Claude Sonnet 5"
        },
        "google/gemini-3.6-flash": {
          "name": "Gemini 3.6 Flash"
        },
        "xai/grok-4.5": {
          "name": "Grok 4.5"
        }
      }
    }
  }
}

Field	Value
Provider ID	Any string (for example `modellix`); must match `/connect`
`npm`	`@ai-sdk/openai-compatible` for Chat Completions
`options.baseURL`	`https://llm.modellix.ai/v1`
`options.apiKey`	Modellix API Key (or rely on `/connect` auth)
`models` keys	Exact Modellix Model IDs (`provider/name`)
Top-level `model`	`modellix/<model-id>` (provider ID + model key)

Add or remove entries under models as needed. Full catalog: Models & Pricing.

If you prefer Responses instead of Chat Completions, set npm to @ai-sdk/openai (see OpenCode custom provider). Most setups should keep @ai-sdk/openai-compatible.

Select a Modellix Model

Run /models and select a Modellix model.You do not need a separate Anthropic baseURL without /v1 for OpenCode. Register anthropic/... and google/... IDs on the same Modellix custom provider above; traffic goes through OpenAI-compatible Chat Completions on https://llm.modellix.ai/v1.Native Anthropic Messages (ANTHROPIC_BASE_URL without /v1) is for the Anthropic SDK and Claude Code, not required here.

Troubleshooting

Check	Detail
Provider ID	`/connect` ID matches `provider.modellix` (or your chosen ID) in config
`npm` package	Use `@ai-sdk/openai-compatible` for `/v1/chat/completions`
`baseURL`	Must be `https://llm.modellix.ai/v1`
Model keys	Must be full IDs like `openai/gpt-5.5`, not bare `gpt-5.5`
Auth	`opencode auth list`, or `options.apiKey`

OpenCode custom provider — official setup
Models & Pricing — Model IDs and rates
LLM API guide — protocols and curl examples
OpenAI SDK — same /v1 Chat Completions gateway

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Use Modellix LLM with OpenCode

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