Coding agent · CLI / WASM
fx
fx is a CLI / WASM in the 2026 agents.dancingteeth catalog. Terminal-first users who want a tiny embeddable Zig coding agent (CLI, ACP, WASM) with AGENTS.md/skills/MCP — closer to a Unix shell than a heavy TUI or IDE fork.
Last updated
Verified
Best for
Terminal-first users who want a tiny embeddable Zig coding agent (CLI, ACP, WASM) with AGENTS.md/skills/MCP — closer to a Unix shell than a heavy TUI or IDE fork.
Skip if
You need Windows-native installs, OpenCode-class paste-a-key-for-every-lab as the only auth story (fx defaults to Vercel AI Gateway but docs cite Codex/Grok and custom connections preview), or a battle-tested IDE/TUI (Cursor / Claude Code / Crush).
Who it fits
- Terminal-first users who want a tiny embeddable Zig coding agent (CLI, ACP, WASM) with AGENTS.md/skills/MCP — closer to a Unix shell than a heavy TUI or IDE fork.
- Terminal-first engineers who live in the shell and git
- Builders who start in the browser without a local IDE setup
Pros
Tiny ~6.4 MiB Zig coding agent with ~10µs cold start and single-digit MB baseline — built to embed in sandboxes and pack many local instances; shell-like CLI (not a heavy TUI) plus ACP for editors, `fx ask` headless, and an experimental WASM SDK; first-class AGENTS.md (global, workspace, and target-scoped), SKILL.md discovery across Claude/Codex/OpenCode/agents dirs, MCP, and session-backed subagents; context-efficient prompt/tools for cheaper TTFT; permission modes with a command sandbox.
Cons
Officially experimental (v0.0.x) with frequent breaking changes; default auth and model catalog path is hosted Vercel AI Gateway (login or gateway key), with docs also citing Codex/Grok and a custom-connections preview — not OpenCode-class paste-a-key-for-every-lab on day one; native install is macOS/Linux only; WASM embed drops native MCP, skills, subagents, and OS sandbox vs the local CLI.
Facts
- Locality:
- Hybrid (local + cloud)
- Surfaces:
- CLI, Web
- Maturity:
- Experimental
- Open source:
- Source available
- Free tier:
- Free option available
- MCP:
- Model Context Protocol support
- Verified:
- Sep 2026
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Frequently asked questions
What is fx?
- fx is a CLI / WASM covered in the agents.dancingteeth 2026 catalog. Tiny ~6.
Who is fx best for?
- Terminal-first users who want a tiny embeddable Zig coding agent (CLI, ACP, WASM) with AGENTS.md/skills/MCP — closer to a Unix shell than a heavy TUI or IDE fork.
When should I skip fx?
- You need Windows-native installs, OpenCode-class paste-a-key-for-every-lab as the only auth story (fx defaults to Vercel AI Gateway but docs cite Codex/Grok and custom connections preview), or a battle-tested IDE/TUI (Cursor / Claude Code / Crush).
What are the main trade-offs of fx?
- Pros: Tiny ~6. Cons: Officially experimental (v0.
Does fx support AGENTS.md, SKILL.md, or MCP?
- This card lists AGENTS.md as Full Support, SKILL.md as Supported, and rules/memory as ~/.fx/AGENTS.md plus workspace and target-scoped AGENTS.md; skills catalog; MCP; saved sessions with resume/compaction; permission/sandbox grants.. Free options: 100% Free (Open-source, Apache-2.0); model spend primarily via Vercel login or AI Gateway key (default); docs also describe Codex/Grok and custom-connection preview paths..
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