Pi

Pi is a deliberately minimal terminal-based coding agent built around the idea that a harness should adapt to a developer's workflow instead of forcing one on them. Rather than shipping a large built-in feature set, Pi keeps only a handful of core tools and pushes everything else, sub-agent-style behaviors, plan modes, custom commands, into a TypeScript extension system that anyone can write, publish, and share as an npm or git package.

It talks to more than 15 model providers, including Anthropic, OpenAI, Google, Azure, Bedrock, Mistral, Groq, and Hugging Face, with mid-session switching between models and providers rather than a hard lock-in to one vendor. Sessions are tree-structured, supporting branching and compaction so a developer can explore an alternate approach without losing the original conversation thread, and Pi runs interactively, in print/JSON mode for scripting, over RPC for process integration, or embedded via SDK inside another application.

Created by Mario Zechner (creator of the libGDX game framework) and released under the MIT license with no SaaS backend, Pi is aimed at developers who want a fast, hackable, fully local coding agent they can extend with their own skills, prompt templates, and themes instead of working around a vendor's fixed feature set.