Mario Zechner's Pi Lets Developers Build and Extend Their Own Coding Agent
Pi is a minimal, aggressively extensible coding agent harness with unified access to 15+ LLM providers, tree-structured sessions, and self-modifying customization.
PRO- Pi is a minimal, self-extending coding agent harness from Earendil, MIT licensed, at github.com/earendil-works/pi
- Unified pi-ai package covers 15+ providers including Anthropic, OpenAI, Google, Bedrock, Mistral, Groq, Ollama
- Tree-structured sessions let you rewind, branch, and share via
/tree,/export, and/share - Sub-agents, plan mode, MCP, and permission gates are extensions, not core features
- Four run modes: interactive TUI, print/JSON, RPC over stdin, and embeddable SDK
- Skills, AGENTS.md, prompt templates, and swappable compaction enable real context engineering
Most coding agents ship as sealed products with baked-in opinions about sub-agents, plan mode, permission popups, and MCP. Pi, the agent harness formerly published as pi-mono by Mario Zechner (badlogic), takes the opposite bet: strip the harness down to primitives, then let the agent extend itself on the fly. The repo has crossed 95k stars and moved under the earendil-works organization with a dedicated site at pi.dev.
The landing page sums up the philosophy: there are many agent harnesses, but this one is yours. Rather than shipping features, Pi ships primitives and hands you the tools to bolt on whatever behavior you actually need.
What is actually in the box
Pi is a TypeScript monorepo split into a handful of packages you can adopt independently:
- @earendil-works/pi-coding-agent: the interactive coding agent CLI, installable via
curl, npm, pnpm, or bun - @earendil-works/pi-agent-core: the agent runtime with tool calling and state management
- @earendil-works/pi-ai: a unified multi-provider LLM API covering Anthropic, OpenAI, Google, and others
- @earendil-works/pi-tui: a terminal UI library with differential rendering
- @earendil-works/pi-telemetry: vendor-neutral telemetry contracts and typed schemas
Installing the CLI is a one-liner: curl -fsSL https://pi.dev/install.sh | sh. The project is MIT licensed and the coding agent is on npm as
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