Pi is a minimal, self-extensible agent harness centred on an interactive terminal coding agent. It is a monorepo of packages: the coding-agent CLI, an agent-core runtime that handles tool calling and state management, a unified multi-provider LLM API (pi-ai) spanning OpenAI, Anthropic, and Google, and a terminal UI library with differential rendering. It supports skills and AGENTS.md files, and sessions can be rewound to a prior message, branched from there, and shared.
Pi includes no built-in permission system for restricting filesystem, process, network, or credential access; by default it runs with the permissions of the user and process that launched it. For stronger isolation the README documents three patterns: a Gondolin extension routing built-in tools into a local Linux micro-VM, running the whole process in plain Docker, and running it in the OpenShell policy-controlled sandbox.