Pi
Pi is an open-source AI coding agent toolkit built by Mario Zechner. The pi-coding-agent CLI ships a minimal four-tool core: Read, Write, Edit, and Bash. It self-extends at runtime through TypeScript Extensions, Skills, Prompt Templates, and Themes. Pi is bring-your-own-key: it integrates with 20+ providers including Anthropic, OpenAI, Google, xAI, DeepSeek, Mistral, and Groq, and supports /login for Claude Pro/Max, ChatGPT Plus/Pro, and GitHub Copilot subscriptions instead of API keys.
Overview
Open-source AI agent toolkit with a minimal 4-tool core (Read, Write, Edit, Bash) that self-extends at runtime. Includes coding agent CLI, unified LLM API, TUI/web UI, and Slack bot.
Try Pi
npm install -g @mariozechner/pi-coding-agentExport ANTHROPIC_API_KEY, OPENAI_API_KEY, or GEMINI_API_KEY, or run /login for Claude Pro/Max, ChatGPT Plus/Pro, or GitHub Copilot subscriptions.
Featured Model Specs
| Model | Lab | Released | Context | Reasoning | Open source |
|---|---|---|---|---|---|
| DeepSeek V4 Flash | DeepSeek | 2026-04-24 | 1M | Yes | Yes |
| DeepSeek V4 Pro | DeepSeek | 2026-04-24 | 1M | Yes | Yes |
| Claude Opus 4.7 | Anthropic | 2026-04-16 | 1M | Yes | No |
| Claude Sonnet 4.6 | Anthropic | 2026-02-17 | 1M | Yes | No |
| Claude Opus 4.6 | Anthropic | 2026-02-05 | 1M | Yes | No |
Model Compatibility Matrix
| Model | Lab | Default | Access tier | Notes |
|---|---|---|---|---|
| DeepSeek V4 Pro | DeepSeek | No | Free | Via DEEPSEEK_API_KEY |
| DeepSeek V4 Flash | DeepSeek | No | Free | Via DEEPSEEK_API_KEY |
| Claude Opus 4.7 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
| Claude Sonnet 4.6 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
| Claude Opus 4.6 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
| Claude 3.5 Sonnet v2 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login). Pi API ID: claude-3-5-sonnet-20241022 |
| Claude Opus 4.5 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
| Claude Haiku 4.5 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
| Claude Sonnet 4.5 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
| Grok 4 Fast | xAI | No | Free | Via XAI_API_KEY |
| Llama 3.3 70B Instruct | AI at Meta | No | Free | Via GROQ_API_KEY (Groq inference) |
| GPT-5 | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| Claude Opus 4.1 | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
| Gemini 2.5 Flash Lite | Google DeepMind | No | Free | Via GEMINI_API_KEY |
| Grok 4 | xAI | No | Free | Via XAI_API_KEY |
| Devstral Medium 2507 | MistralAI | No | Free | Via MISTRAL_API_KEY; coding-focused Mistral model |
| Gemini 2.5 Pro | Google DeepMind | No | Free | Via GEMINI_API_KEY |
| Gemini 2.5 Flash | Google DeepMind | No | Free | Via GEMINI_API_KEY |
| Claude 4 Opus | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login). Pi API ID: claude-opus-4-20250514 |
| Claude 4 Sonnet | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login). Pi API ID: claude-sonnet-4-20250514 |
| o4-mini | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| Grok-3 | xAI | No | Free | Via XAI_API_KEY |
| Llama 4 Maverick 17B Instruct | AI at Meta | No | Free | Via GROQ_API_KEY (Groq inference) |
| Llama 4 Scout 17B Instruct | AI at Meta | No | Free | Via GROQ_API_KEY (Groq inference) |
| GPT-4.1 | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| GPT-4.1 Mini | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| GPT-4.1 Nano | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| o3 | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| o3 Mini | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| Grok 3 Mini | xAI | No | Free | Via XAI_API_KEY |
| Gemini 2.0 Flash | Google DeepMind | No | Free | Via GEMINI_API_KEY |
| DeepSeek R1 Distill Llama 70B | DeepSeek | No | Free | Via GROQ_API_KEY (Groq inference) |
| Claude 3.5 Haiku | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login). Pi API ID: claude-3-5-haiku-20241022 |
| Grok-2 | xAI | No | Free | Via XAI_API_KEY |
| GPT-4o-mini | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| GPT-4o | OpenAI | No | Free | Via OPENAI_API_KEY or OpenAI ChatGPT Plus/Pro subscription (/login) |
| Claude 3.7 Sonnet | Anthropic | No | Free | Via ANTHROPIC_API_KEY or Anthropic Claude Pro/Max subscription (/login) |
Underlying Models
Compare to Similar Harnesses
FAQ
What is the Pi harness?
Pi is an open-source AI agent toolkit by Mario Zechner. Its pi-coding-agent package is an interactive coding-agent CLI built on a four-tool core: Read, Write, Edit, and Bash. It self-extends at runtime through TypeScript Extensions, Skills, Prompt Templates, and Themes.
Which LLMs does Pi support?
Pi integrates with 20+ providers through its unified pi-ai API, including Anthropic, OpenAI, Azure OpenAI, Google Gemini and Vertex, xAI, DeepSeek, Amazon Bedrock, Mistral, Groq, OpenRouter, and Hugging Face. LLMReference tracks 37 verified model associations spanning Claude, GPT-5, o3, Gemini, Grok, DeepSeek, Llama, and Devstral.
How do I install and authenticate Pi?
Install the CLI with npm install -g @mariozechner/pi-coding-agent. Authenticate by exporting provider keys such as ANTHROPIC_API_KEY, OPENAI_API_KEY, or GEMINI_API_KEY, or run /login inside the CLI to use Claude Pro/Max, ChatGPT Plus/Pro, or GitHub Copilot subscriptions instead of pay-per-token API access.
Is Pi free? Does it cost anything to run?
Pi itself is free and open source under the badlogic/pi-mono repository. Costs come only from the underlying model API or subscription you connect; there are no Pi license fees, seats, or hosted-runtime charges.
How is Pi different from Claude Code, Cursor, or Codex CLI?
Pi is provider-agnostic and bring-your-own-key by design: one CLI can run the same agent loop against Claude, GPT-5, Gemini, Grok, or local models instead of being tied to a single lab's models or subscription. Pi also exposes its agent runtime, unified LLM API, and TUI library as separate packages developers can build on.