Use Modellix LLM with CodeBuddy

Configure CodeBuddy to call the Modellix LLM gateway. CodeBuddy supports OpenAI-compatible custom models in the UI and in models.json, pointed at Chat Completions on POST /v1/chat/completions.

This page covers LLM text only (https://llm.modellix.ai).Modellix model IDs are provider/name (for example openai/gpt-5.5). Enter that full string as the Model Name / id. In the UI, set Endpoint to https://llm.modellix.ai/v1. When editing models.json by hand, set url to the full Chat Completions path (.../v1/chat/completions). See Models & Pricing.

Set Up CodeBuddy

Get a Modellix API Key

Create a Modellix API key in the console and export it for models.json env substitution:

export MODELLIX_API_KEY="mdlx-xxxxxxxx"

You can also paste the key directly into the CodeBuddy UI or config files.

Add a Custom Model in the UI

In CodeBuddy, open the model picker (for example Default under the input box), scroll to the bottom, and choose Configure custom models → Add Model.Set Provider to Custom, then fill in:

Field	Value
Endpoint	`https://llm.modellix.ai/v1`
API Key	Your Modellix API Key
Model Name	Exact Modellix Model ID (for example `openai/gpt-5.5`)
Advanced Settings	Enable Tool Calling for agent tool use; enable Image Input / Reasoning only if the model supports them

Save the model. Include /v1 in the Endpoint so paths resolve to /v1/chat/completions.

Persist with models.json

CodeBuddy also stores custom models in a local file. Edit this when the UI is inconvenient, or to share a project-level config.

User scope (macOS / Linux): ~/.codebuddy/models.json
User scope (Windows): %USERPROFILE%\.codebuddy\models.json
Project scope (higher priority): <project>/.codebuddy/models.json

Example:

{
  "models": [
    {
      "id": "openai/gpt-5.5",
      "name": "GPT 5.5",
      "vendor": "Modellix",
      "url": "https://llm.modellix.ai/v1/chat/completions",
      "apiKey": "${MODELLIX_API_KEY}",
      "maxInputTokens": 200000,
      "maxOutputTokens": 8192,
      "supportsToolCall": true
    }
  ],
  "availableModels": ["openai/gpt-5.5"]
}

Field	Value
`id` / `name`	Exact Modellix Model ID (`provider/name`)
`vendor`	`Modellix`
`url`	`https://llm.modellix.ai/v1/chat/completions`
`apiKey`	`${MODELLIX_API_KEY}` or your key string
`availableModels`	Must include each model `id` you want selectable

When writing models.json by hand, use the full Chat Completions URL (including /chat/completions). A host-only value or https://llm.modellix.ai/v1 without /chat/completions is less reliable than the full path. Do not point url at the media API host (https://api.modellix.ai).

Add more entries for other Modellix IDs (for example anthropic/claude-sonnet-5, google/gemini-3.6-flash) on the same gateway URL. Full catalog: Models & Pricing.

After saving, restart CodeBuddy or reopen the model picker so the list refreshes.

Select and Start

Open the model picker, choose your model under Custom Models, and send a short test message.CodeBuddy may display custom models as name:name. That is normal if the selected model responds correctly.

Optional: CodeBuddy CLI

The CLI package is CodeBuddy Code (codebuddy). It uses a separate Anthropic-compatible entry point from the desktop custom-model OpenAI path.

export CODEBUDDY_API_KEY="mdlx-xxxxxxxx"
export CODEBUDDY_BASE_URL="https://llm.modellix.ai"
export CODEBUDDY_MODEL="anthropic/claude-sonnet-5"
codebuddy

Or persist in ~/.codebuddy/settings.json:

{
  "env": {
    "CODEBUDDY_API_KEY": "mdlx-xxxxxxxx",
    "CODEBUDDY_BASE_URL": "https://llm.modellix.ai",
    "CODEBUDDY_MODEL": "anthropic/claude-sonnet-5"
  }
}

Setting	Value
`CODEBUDDY_BASE_URL`	`https://llm.modellix.ai` (without `/v1`)
`CODEBUDDY_API_KEY`	Modellix API Key
`CODEBUDDY_MODEL`	Prefer `anthropic/...` for this CLI path

Do not set CODEBUDDY_BASE_URL to an OpenAI Chat Completions path such as .../v1/chat/completions. If you see 404s on the CLI, check that the base URL is the LLM host root without /v1.

Troubleshooting

Symptom	Check
401 / auth errors	Key is a Modellix API Key; `${MODELLIX_API_KEY}` is set if used in `models.json`
Model not found / 404	Model Name / `id` is a full ID like `openai/gpt-5.5`, not bare `gpt-5.5`
UI Endpoint errors	Endpoint includes `/v1`: `https://llm.modellix.ai/v1`
`models.json` path errors	`url` ends with `/v1/chat/completions`, not the media API host
CLI 404	`CODEBUDDY_BASE_URL` is `https://llm.modellix.ai` without `/v1` or `/chat/completions`
Model missing after edit	Restart CodeBuddy or reopen the model picker; confirm `id` is listed in `availableModels`

CodeBuddy models.json — custom model schema
Models & Pricing — Model IDs and rates
LLM API guide — protocols and curl examples
Junie — another client that uses a full Chat Completions URL
Claude Code — Anthropic-style base URL without /v1 (similar to CodeBuddy CLI)

Get Started

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Use Modellix LLM with CodeBuddy

Set Up CodeBuddy

Troubleshooting

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Set Up CodeBuddy

Troubleshooting

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