Use Modellix LLM with CodeBuddy

Add Modellix as a CodeBuddy custom model with an OpenAI-compatible endpoint, models.json, and provider/name model IDs.

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

1. 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.

2. 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.

3. 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.

4. 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.

5. 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

Related

• 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)