Rune

Rune is an open-source, keyboard-driven IDE for power users, built by Unstable Build. It describes itself as the Unix way finished as a product: a GPU-rendered character-grid interface that puts code, terminals, CLI tools, language intelligence, debugging, and AI agents in one composable, multi-workspace environment. It ships with three built-in editing modes — standard (VS Code/Sublime style), vim, and emacs — and the bindings apply everywhere in the app, including terminals, input boxes, and the file explorer.

Everything ships in the box: LSP-based language intelligence, debugging, terminal splits, workspace slots, and a fuzzy command prompt. Rune Agent, the built-in AI coding assistant, is deliberately distributed as an extension (the rune-agent package) rather than baked into the core editor. It can read and edit files, search the codebase, run commands, and hold multi-step conversations, with support for OpenAI, Anthropic, Gemini, Amazon Bedrock, local models, custom providers, MCP servers, skills, and sub-agents.

Compared to paid AI IDEs like Cursor and Windsurf, Rune is fully open source under GPLv3 and free to download, with a paid tier (Rune Pro, $10/month) that only extends Rune Network node limits from 2 to 10 — the editor itself is not paywalled. Compared to JetBrains IDEs and Sublime Text, Rune trades a large plugin marketplace and GUI polish for a terminal-native, composable workflow that feels closer to tmux plus Neovim, with LSP and agent support built in. Extensions are written against the Apache-2.0 licensed rune-go-sdk, and the docs are served from inside the IDE via a docs:/// workspace.