Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add instructions/vercel-labs/zerolang/agents-mdgit clone --depth 1 https://github.com/vercel-labs/zerolangWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/instructions/vercel-labs/zerolang/agents-md)<a href="https://agentmods.dev/instructions/vercel-labs/zerolang/agents-md"><img src="https://agentmods.dev/badge/instructions/vercel-labs/zerolang/agents-md.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.01256 | $0.01256 |
| Opus 5 | $0.00628 | $0.00628 |
| Sonnet 5 | $0.00251 | $0.00251 |
| Haiku 4.5 | $0.00126 | $0.00126 |
Grade A, and why
zerolang AGENTS.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 140 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Contributor Notes
Zero is a pre-1 experiment in building an agent-first programming language. Keep public-facing changes honest about what works today without weakening that positioning.
Project Direction
Zero is still being shaped around the needs of agents. Breaking changes are acceptable when they move the language, standard library, compiler, or tooling closer to that goal.
Do not preserve legacy behavior by default. Prefer the clearer agent-facing design over compatibility shims, migration layers, or carrying old paths forward. Keep examples, docs, tests, and command contracts aligned with the new behavior so the repository describes one coherent current system.
This does not mean broad churn for its own sake. Make direct changes that advance Zero's agent-first goals: on-the-fly learnability, deterministic inspection and repair, strong standard-library coverage, exceptional developer experience, and regular patterns over syntactic convenience.
Safety Expectations
Security vulnerabilities should be expected. Zero is not ready for production systems, sensitive data, or trusted infrastructure.
Run and develop Zero in safe environments: isolated workspaces, disposable inputs, and systems where compiler crashes, malformed output, or unsafe runtime behavior cannot damage production state. Treat generated artifacts and examples as experimental unless they have been reviewed for the specific environment where they will run.
Development
- Build the local compiler with
make -C native/zero-c. - Use
bin/zerofor focused checks; it execs the local native compiler at.zero/bin/zero. - Keep examples runnable and docs copyable.
- Prefer small, direct changes over broad refactors.
- Use direct emitters for compiler output.
- For broad local validation, run
pnpm run agent:checks. It mirrors the CI buckets in parallel, including conformance, command contracts, native test shards, sanitizer smoke, and workspace checks. It uses isolated/tmpworkspaces so agents can validate uncommitted changes without local artifact races. - Before ending any agent turn that changes the repository, run
pnpm run conformanceunlesspnpm run agent:checksalready passed for the same changes. If validation cannot complete, report the blocker and the failing command.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 140 lines · 1,256 tokens per session scan A 0c4ef0386cc9
zerolang AGENTS.md is an instructions file published in the GitHub repository vercel-labs/zerolang (5,346 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 1,256 tokens to every session, about $0.0063 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
next.js AGENTS.md
Instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.