whereismyai
fx
fx is a tiny open source coding agent CLI written in Zig for research and system embedding.
fx is a coding agent harness and command-line interface written in Zig, built for research and embeddability within larger systems. It focuses on minimalism and performance, featuring a small binary size and model-agnostic operation that supports local models, gateways, direct provider API access, and subscriptions. The system provides concise tool schemas, dynamic loading of skill instructions and Model Context Protocol servers, and a shell-like terminal user interface that preserves scroll history. Users can run the agent in the terminal, CI pipelines, or agent sandboxes, or compile it to WebAssembly using the Zig toolchain to run in the browser via libfx. It is open source under the Apache-2.0 license and designed for developers who need a performant and extensible coding agent.
fx at a glance
- Best for: Software engineer
- Runs on: CLI, Web
- Pricing: Free
- Released: August 2026
- Category: AI coding tool
- Website: fx.sh
Key features
- Written in Zig with a small binary size
- Model and provider agnostic operation
- WebAssembly support for browser usage
- Shell-like terminal user interface
- Concise tool schemas for context efficiency
- Support for Model Context Protocol servers
- Embeddable core with libfx
Use it for
- Research coding agent behavior and system design
- Embed coding agents into larger software systems
- Run coding tasks in CI pipelines and sandboxes
- Execute agent sessions directly in the browser
Companions
Tools that articles about fx recommend using with it, each with its job.
- Context7 — Provides up-to-date documentation for AI agents and code editors.
- Ollama — Run local models at zero marginal cost, with code kept on your machine.
- OpenRouter — Access over 500 models and 80 providers through one unified API.
- Daytona — Runs sessions in isolated sandboxes synced to git branches.
- Composio — Equips AI agents with tools, managed user auth, and sandboxes across 1,500+ apps
- Oh My OpenCode Slim — Lightweight multi-agent orchestration and background tasks.
Alternatives to fx
- OpenCode — Works with 75+ model providers, local models, and existing subscriptions
- ZCode — Integrates GLM-5.3 with multi-agent workflows and remote chat control.
- Fx0 — Generates durable design sessions with automatic recovery if interrupted.
- jevgrep — Reduces coding agent costs by providing targeted, relevant repository context.
- Freebuff — Access multiple coding AI models for free without subscriptions.
- Command Code — Repairs open model tool calls and learns developer patterns automatically.
- Cline — Open source, any model, with approval on every step
- CodeGraph — It eliminates file crawling, reducing AI agent tool calls by 88% and cutting costs.
- Zed — Very fast native editor with parallel agents and multiplayer
- Warp — AI terminal plus cloud agents with built-in evals and benchmarks
- SmallCode — Runs fully local with budget-managed context and a forgiving parser for small models.
- Weft — It enables safe parallel coding agent work without file locks.
All fx alternatives