# Pi Mono Pi is a minimal, opinionated CLI coding agent created by [[Mario Zechner]]. Written in TypeScript. Emphasizes user control, observability, and simplicity over feature bloat. 8k+ GitHub stars. MIT licensed. ## Philosophy - Minimal system prompt (under 1000 tokens, vs ~10k for [[Claude Code]]) - Only four core tools: read, write, edit, bash - Full context observability — nothing injected behind the user's back - Stable, documented system prompts that don't break workflows between releases - "If I don't need it, it won't be built" - YOLO by default: unrestricted filesystem access and command execution ## Packages - **pi-ai**: Unified LLM API across providers (Anthropic, OpenAI, Google, xAI, Groq, Cerebras, OpenRouter, OpenAI-compatible) - **pi-agent-core**: Agent loop runtime with tool execution, state management, event streaming - **pi-coding-agent**: The CLI itself with session management, project context, themes - **pi-tui**: Terminal UI framework with differential rendering and flicker prevention - **pi-web-ui**: Web-based chat interface components - **pi-mom**: Slack integration routing messages to the coding agent - **pi-pods**: Deployment utility for vLLM services on GPU infrastructure ## Key features - Mid-session model switching and multi-provider support - Session branching, resuming, and HTML export - Full cost and token tracking - Hierarchical AGENTS.md files for project context - Custom slash commands as markdown templates - Headless operation via JSON streaming and RPC mode - OAuth for Claude Pro/Max subscriptions ## What Pi deliberately excludes - **No MCP support**: CLI tools with README files preferred over MCP's context overhead - **No sub-agents**: External sessions and artifacts preferred - **No background bash**: tmux recommended instead - **No plan mode**: File-based PLAN.md preferred for cross-session persistence - **No built-in to-dos**: TODO.md files instead ## References - Source code: https://github.com/badlogic/pi-mono - Author's writeup: https://mariozechner.at/posts/2025-11-30-pi-coding-agent/ - Armin Ronacher's review: https://lucumr.pocoo.org/2026/1/31/pi ## Related - [[AI Agents]] - [[Claude Code]] - [[Vibe Coding]] - [[OpenClaw]]