vercel-labs/fx is a Unix-family coding agent written in Zig. The latest release is v0.0.14. The available information lists no changes in this version, so the release contents cannot be pinned down. The description below is the project feature set as documented in the repository README.
fx ships as a single native binary, so no separate language runtime installation is needed. It prints conversation output to the terminal scrollback, keeping scrolling, search, copy, and tmux bindings. The README explains that commands such as fx help and fx status --json are expected to stay under 2 milliseconds on Linux or CI fails, and that Apple Silicon stable releases must respect a defined binary size limit. It also provides fx ask for scripts, ACP for editor communication, and libfx, built as a JavaScript native addon and as WebAssembly. The license is Apache-2.0.
Concurrency-sensitive modules such as the session manager and the indexer are modeled in TLA+ and verified. However, the README designates the project as experimental and warns users to accept the risks. Even though performance conventions and design verification are documented, this information alone cannot tell you how stable or fast it is in real usage environments. So for now it is more reasonable to view it as an experimental implementation rather than a mature agent.