ToolAI CodingDev ToolsOpen Sourcezigagentscli
fx
Vercel Labs' small open-source coding agent written in Zig. It ships as one native binary of about 6.7 MiB, needs no background service, works with any model, and its terminal output reads more like a Unix shell than an IDE.
Added October 22, 2026
fx pushes back against coding CLIs that bring a daemon, a full-screen TUI and a client-server split. You get one binary with no runtime to install. fx opens an interactive shell in the project folder, and fx ask "..." runs a single request, which you can script with --json. Output is printed inline, so scrollback, tmux and copy mode keep working. Commands run in your login shell, so your aliases, functions and PATH all apply.
It doesn't lock you to one model. It works with Vercel AI Gateway, a ChatGPT or Grok subscription, and any OpenAI-compatible Chat Completions endpoint such as Ollama or OpenRouter. The built-in tools cover files, shell, web search, URL reading and subagents. Skills, MCP servers and AGENTS.md add more, and their schemas load only when needed to save context. There are also permission modes (auto, ask, full-access), session resume with fx -c, and an ACP server via fx acp.
The core can be embedded through libfx, which comes as a native Node addon and as WebAssembly. The browser demo on fx.sh runs the full CLI compiled to Wasm on top of a just-bash workspace. It's Apache-2.0, runs on macOS and Linux, and is marked experimental, so expect frequent changes.
Repo: vercel-labs/fx
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