# fx on a MicroVM: The 6MB Unix-like Coding Agent > fx is a 6.4 MiB Zig coding agent that behaves like a shell, not an IDE. Run it always-on in a Firecracker guest. BYOK, from $25/mo. - Published: 2026-08-19 · Updated: 2026-08-19 · jurniti - Canonical: https://www.jurniti.com/blog/fx-on-a-microvm Most coding agents want to be an IDE in your terminal. **fx wants to be a shell.** That is the whole product. A 6.4 MiB Zig binary. Cold start measured in microseconds. Output that scrolls like a Unix tool instead of a full-screen TUI. Apache-2.0, model-agnostic, installable with one curl. ## The laptop problem, again A tiny binary is easy to install locally. That is not the same as easy to *leave running*. - You close the lid and the turn dies with it. - Device-code login works, but you still do not want the agent editing files on the machine that holds your password manager. - You want the same `~/.fx` — settings, skills, sessions — reachable tomorrow from a phone. fx is small enough to feel disposable. The work it does is not. ## What we actually run jurniti gives fx its own computer — a Firecracker microVM, the same isolation primitive AWS uses for Lambda. Not a container. Not a shared box with someone else's agent in the next namespace. On provision you get: - A fresh Ubuntu microVM with `fx` already on `PATH`. The binary is **pre-baked**, so first boot is not a CDN fetch. - A live in-browser terminal. Run `fx login` (Vercel device-code — PTY-safe) or `fx setup` to paste an AI Gateway key. - A persistent home. `~/.fx/settings.json`, `~/.fx/skills/`, and your project's `AGENTS.md` survive stop/start. - Pinned CPU and RAM. Your reservation. BYOK throughout. fx talks to Vercel AI Gateway with *your* login or *your* key. We never proxy model spend. ## Why the form factor matters fx's own pitch is "closer to a Unix shell than a heavy IDE in the terminal." That is not marketing fluff. A 6MB agent with a 10µs cold start is the shape you want when you `fx ask` from a script, or when you pack many instances onto one machine. The managed version of that is not "more UI." It is the same small binary, left on, isolated, with a disk that outlives the process. `fx acp` is there too — Agent Client Protocol over stdio — so an editor host can drive the same box you already use from the shell. ## Snapshot it, fork it, share it Once the box is yours — model, permissions, skills, MCP servers in `~/.fx/mcp.json` — snapshot it into a template. A template forks into a fresh paid VM in about three minutes. Credentials do not travel. Public capture drops `~/.fx/auth.json` (the Vercel OAuth session) and `~/.fx/api-key` (the Linux file store). Session transcripts and usage records go with them. What survives is the reusable layer: settings, skills, project `AGENTS.md`. ## Honest limits - **Experimental upstream.** fx.sh itself says experimental. The binary we bake is a real `X.Y.Z` (0.0.3 on first ship) and we watch GitHub releases, but expect frequent changes. - **Terminal-first.** There is no web dashboard to proxy. You work in the in-browser terminal. - **No free tier.** From $25/mo. The de-risk is a 30-day money-back guarantee on your first purchase, not a trial that expires while you are still evaluating. ## Get the box Pick a plan, choose fx, pay. The VM is up in a few minutes with `fx` on your PATH. Then: ```bash fx login fx ``` ## Frequently asked questions ### What is fx? fx is Vercel Labs' tiny, open, native coding-agent CLI. It is written in Zig, ships as a ~6.4 MiB binary, and aims at Unix-shell ergonomics rather than a full TUI IDE. ### How do I authenticate on a remote box? `fx login` uses Vercel OAuth device-code — it prints a URL and a short code. That works in a remote PTY. You can also run `fx setup` and paste an AI Gateway API key, or export AI_GATEWAY_API_KEY. ### Does fx need Node? No. The official installer drops a static binary into ~/.local/bin. There is no npm tree and no nvm bootstrap. ### Pricing? From $25/mo, BYOK (your Vercel login or AI Gateway key), 30-day money-back on your first purchase. No free trial and no free tier.