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 |
| Grok 4 | xAI | 2026-03-01 | 256K | Yes | No |
| Grok 4 Fast | xAI | 2026-03-01 | 2M | No | No |
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.