vercel-labs/fx

What it solves

fx provides a lightweight, native coding agent that operates directly in the terminal. It bridges the gap between a full IDE and a standard Unix shell, allowing developers to perform coding tasks via a CLI without needing a heavy graphical interface.

How it works

Written in Zig, fx is a small native binary that can be used as a standalone interactive shell or via one-shot commands (fx ask). It is model-agnostic, supporting various providers including Vercel AI Gateway, ChatGPT, Grok, and local endpoints like Ollama. It can be embedded into other systems via WebAssembly (WASM) or the Agent Client Protocol (ACP).

To manage long conversations, fx uses a sophisticated context compaction system that summarizes previous turns and tool calls while preserving key rules, facts, and decisions, ensuring the agent remains functional as the context window fills.

Who it’s for

It is designed for developers who prefer a terminal-centric workflow and those who want to embed a native coding agent into their own applications or editors.

Highlights

• Model Agnostic: Works with Vercel AI Gateway, OpenAI, xAI, and any OpenAI-compatible endpoint.
• Terminal-Native: Preserves terminal scrollback and integrates with tmux.
• Extensible: Supports MCP servers, custom skills, and subagents.
• Multimodal: Handles image attachments (PNG, JPEG, GIF, WebP) with automatic resizing logic.
• Embeddable: Available as a native binary or WASM for integration into JS hosts or ACP clients.
• Context Management: Advanced automatic compaction to prevent context overflow while maintaining session history.