fx
A lightweight, open-source, embeddable command-line coding agent framework
About fx
fx is a coding agent framework and command-line tool written in Zig, designed for research and suitable for embedding in larger systems. The project uses the Apache-2.0 open-source license and is model-agnostic, connecting to local or cloud inference. It emphasizes a command-line form close to a Unix shell, with a lightweight binary and 10µs cold start for resource-constrained environments and programmatic calls. Its current official status is experimental, so features may change frequently.
Best for
Best use cases
Research-oriented coding agent experiments
Embedding an agent in a larger system
Local or cloud inference
Running agents in resource-constrained environments
Features
Lightweight embedding
Designed for instant installation and embedding, making it suitable for resource-constrained environments and agent sandboxes.
Fast startup
Around 10µs cold start, with no unnecessary work or I/O before accepting user input.
Multi-environment inference
Model-agnostic and suitable for local and cloud inference.
Command-line form
CLI output and behavior for end users are closer to a Unix shell.
Pros
- Apache-2.0 open source
- Model-agnostic
- Supports local and cloud inference
- Lightweight and easy to embed
Cons
- The current status is experimental; the official warning says to use it at your own risk
- Installation support covers x86_64 and arm64 on macOS and Linux