Zero.

The thesis.

Zero is Vercel Labs’ bet that the bottleneck in agentic coding is not the language but the channel between the compiler and the agent. The standard loop is fragile: the compiler emits prose written for human engineers, the agent parses it as text, the agent guesses at a fix, the next compile produces a new prose error in a slightly different format. Zero’s answer is to replace the prose channel with a structured one. zero check --json emits a stable error code (NAM003), a human-readable message, a line number, and a typed repair object an agent can act on. zero fix --plan --json returns a machine-readable edit plan. zero explain returns structured explanations against the installed compiler version.

Humans read the message. Agents read the JSON.

The distinctive move sits at the language level, not the toolchain level: Zero collapses the syntactic and verification camps into a single product decision. The language documents itself as preferring “one obvious way to express most things, even when that makes code more explicit than a human might choose,” which is syntactic-camp framing; but the obviousness is bought with capability objects on main, explicit raises markers, and effect-visible signatures, which is verification-camp machinery. Where MoonBit, the catalogue’s other industrially backed verification entry, invests in semantic-aware token sampling, Zero invests in making the surface area small enough that an agent doesn’t need help generating it in the first place.

What it looks like.

pub fun main(world: World) -> Void raises {
  check world.out.write("hello from zero\n")
}

Distinctive moves.

• Stable diagnostic codes. Errors carry codes (NAM003 for unknown identifier) that are contractually stable across compiler versions. Agents can match on the code, not the prose.
• Typed repair plans. zero fix --plan --json returns a structured edit plan, not advice. The agent applies the plan rather than inferring it from the message.
• Version-matched skills. zero skills get zero --full returns syntax, diagnostics, build, package, stdlib, testing, and edit-loop guidance pinned to the installed compiler version. The guidance lives in the toolchain, not on a webpage that may have drifted.
• No LLVM, sub-10 KiB binaries. Direct emitters for ELF, Mach-O, PE, and WebAssembly. The size budget is a load-bearing design constraint, not a marketing claim.
• One CLI surface. zero check, zero run, zero build, zero graph, zero size, zero routes, zero skills, zero explain, zero fix, zero doctor — all subcommands of a single binary that all support --json.

Maturity.

v0.1.1, Apache-2.0, released 15 May 2026, 3.3k stars on vercel-labs/zerolang at first cataloguing. The README and homepage are explicit that this is a “pre-1 experiment”: syntax and APIs are not a contract, breaking changes are expected, and security vulnerabilities should be expected — Vercel Labs recommends running Zero only in isolated environments. The repo maintains two compilers: zero-c, the C bootstrap; and compiler-zero, a self-hosting compiler written in Zero. Cross-compilation is limited to a documented target subset; there is no package registry yet; VS Code syntax highlighting ships in-repo. Named contributors are Chris Tate and Matt Van Horn.

The bet is that structured agent-first compiler output becomes table stakes once developers see what it does for repair loops. Even if Zero itself doesn’t win, the design pattern — stable codes, typed repairs, version-matched skills — is a concrete argument for what every other compiler should ship.

Agent tooling.

The toolchain is the agent tooling. zero check --json returns diagnostics; zero explain <code> returns explanations; zero fix --plan --json returns edit plans; zero skills get zero --full returns version-matched workflows. zero graph --json, zero size --json, zero routes --json, and zero doctor --json round out the inspection surface. Vercel’s separately released skills.sh ecosystem is consumable by Claude Code, Cursor, Codex, and other agent harnesses through the same Agent Skills spec that zero skills follows.