Use Modellix LLM with Pi Agent

Configure Pi to call the Modellix LLM gateway. Pi does not ship a built-in Modellix provider, so add a custom provider in ~/.pi/agent/models.json that points at Chat Completions on POST /v1/chat/completions.

This page covers LLM text only (https://llm.modellix.ai). For Pi media packages and skills (image, video, speech), see Plugin and Skill.Modellix model IDs are provider/name (for example openai/gpt-5.5). Put that full string in each model id under your custom provider. See Models & Pricing.

Set Up Pi

Get a Modellix API Key

Create a Modellix API key in the console and export it so models.json can resolve $MODELLIX_API_KEY:

export MODELLIX_API_KEY="mdlx-xxxxxxxx"

Add the same line to your shell profile (for example ~/.zshrc) for persistent use.

Add a Custom Provider

Create or update ~/.pi/agent/models.json:

{
  "providers": {
    "modellix": {
      "baseUrl": "https://llm.modellix.ai/v1",
      "api": "openai-completions",
      "apiKey": "$MODELLIX_API_KEY",
      "models": [
        { "id": "openai/gpt-5.5", "name": "GPT 5.5", "contextWindow": 200000 },
        { "id": "openai/gpt-5.6-sol", "name": "GPT 5.6 Sol", "contextWindow": 200000 },
        { "id": "openai/gpt-5.6-terra", "name": "GPT 5.6 Terra", "contextWindow": 200000 },
        { "id": "openai/gpt-5.6-luna", "name": "GPT 5.6 Luna", "contextWindow": 200000 },
        { "id": "anthropic/claude-sonnet-5", "name": "Claude Sonnet 5", "contextWindow": 200000 },
        { "id": "google/gemini-3.6-flash", "name": "Gemini 3.6 Flash", "contextWindow": 200000 },
        { "id": "xai/grok-4.5", "name": "Grok 4.5", "contextWindow": 200000 }
      ]
    }
  }
}

Merge the modellix entry into an existing providers object if you already use custom models. Add or remove entries under models as needed.

Field	Value
Provider key	`modellix` (custom; do not use built-in `openai`, `anthropic`, or `openrouter`)
`baseUrl`	`https://llm.modellix.ai/v1`
`api`	`openai-completions`
`apiKey`	`$MODELLIX_API_KEY` (or `${MODELLIX_API_KEY}`)
`models[].id`	Exact Modellix Model IDs (`provider/name`)

Use a custom provider key such as modellix. Overwriting Pi’s built-in openai or anthropic providers sends traffic to the vendor endpoints instead of Modellix.

You do not need a separate Anthropic base URL. Register anthropic/... and google/... IDs on the same Modellix provider; traffic goes through OpenAI-compatible Chat Completions on https://llm.modellix.ai/v1.

Select a Modellix Model

In an interactive Pi session, run /model and choose a Modellix entry (for example openai/gpt-5.5 under the modellix provider).Or start Pi with the provider and model on the command line:

pi --provider modellix --model openai/gpt-5.5

Pi reloads models.json each time you open /model, so you can edit the file during a session without restarting.

If a Modellix model appears in the file but stays unavailable in /model, confirm $MODELLIX_API_KEY is set. Pi requires auth before custom models become selectable.

Start Pi

Start Pi as usual:

pi

Or with Modellix selected up front:

pi --provider modellix --model openai/gpt-5.5

Troubleshooting

Symptom	Check
401 / auth errors	`MODELLIX_API_KEY` is set; `apiKey` uses `$MODELLIX_API_KEY` or `${MODELLIX_API_KEY}`
Model listed but unavailable in `/model`	Auth is configured (env var, `apiKey` in `models.json`, or `--api-key`)
Model not found / 404	`models[].id` is a full ID like `openai/gpt-5.5`, not bare `gpt-5.5`; ID is in the live catalog
Traffic hits OpenAI or OpenRouter	Provider key is `modellix`; you did not select a built-in `openai` / `openrouter` model
Wrong path / URL errors	`baseUrl` is `https://llm.modellix.ai/v1` (include `/v1`), not the media API host
Developer role / 400 errors	Set provider `compat.supportsDeveloperRole` to `false` (see Pi Custom Models)

Pi Custom Models — models.json schema and examples
Pi Providers — auth and custom providers overview
Models & Pricing — Model IDs and rates
LLM API guide — protocols and curl examples
OpenClaw · OpenCode — other OpenAI-compatible custom setups
Plugin · Skill — Pi media capabilities

Get Started

API

Agent

SDK

Framework

IDE

Tool

Use Modellix LLM with Pi Agent

Set Up Pi

Troubleshooting

​Set Up Pi

​Troubleshooting

​Related

Set Up Pi

Troubleshooting

Related