Pi Coding Agent + APIMaster.ai

Configure Pi Coding Agent with models.json and auth.json for APIMaster OpenAI-compatible API on Windows and macOS.

Pi Coding Agent is a terminal coding agent. Add provider apimaster via ~/.pi/agent/models.json to use APIMaster’s OpenAI-compatible API.

Get an API Key first. Model ids match marketplace and GET /v1/models.

Config directory

Platform	Path
Windows	`C:\Users\<username>\.pi\agent\`
macOS / Linux	`~/.pi/agent/`

Files: models.json (provider + models), auth.json (optional API key store).

models.json

Top level must be providers. Use UTF-8 without BOM on Windows.

{
  "providers": {
    "apimaster": {
      "baseUrl": "https://apimaster.ai/v1",
      "api": "openai-completions",
      "apiKey": "$APIMASTER_API_KEY",
      "models": [
        { "id": "claude-haiku-4-5", "name": "Claude Haiku 4.5 via apimaster", "reasoning": true, "contextWindow": 128000, "maxTokens": 16384 },
        { "id": "claude-opus-4-7", "name": "Claude Opus 4.7 via apimaster", "reasoning": true, "contextWindow": 128000, "maxTokens": 16384 },
        { "id": "claude-opus-4-8", "name": "Claude Opus 4.8 via apimaster", "reasoning": true, "contextWindow": 128000, "maxTokens": 16384 },
        { "id": "claude-sonnet-4-6", "name": "Claude Sonnet 4.6 via apimaster", "reasoning": true, "contextWindow": 128000, "maxTokens": 16384 },
        { "id": "gpt-5.4", "name": "GPT 5.4 via apimaster", "reasoning": true, "contextWindow": 128000, "maxTokens": 16384 },
        { "id": "gpt-5.5", "name": "GPT 5.5 via apimaster", "reasoning": true, "contextWindow": 128000, "maxTokens": 16384 },
        { "id": "minimax-m3", "name": "MiniMax M3 via apimaster", "reasoning": true, "contextWindow": 128000, "maxTokens": 16384 }
      ]
    }
  }
}

auth.json (optional)

{
  "apimaster": {
    "type": "api_key",
    "key": "your_apimaster_key"
  }
}

Environment variables

Windows (PowerShell, session):

$env:APIMASTER_API_KEY="your_apimaster_key"

Windows (persistent):

[Environment]::SetEnvironmentVariable("APIMASTER_API_KEY", "your_apimaster_key", "User")

macOS / Linux:

export APIMASTER_API_KEY="your_apimaster_key"
echo 'export APIMASTER_API_KEY="your_apimaster_key"' >> ~/.zshrc

Verify

pi --list-models
pi --provider apimaster --model gpt-5.5

Troubleshooting

models.json must use providers root — not a bare apiKey object.
UTF-8 BOM on Windows breaks JSON.parse — save without BOM.
Missing models — check path ~/.pi/agent/models.json (or Windows user profile equivalent).