crosskill

Write AI coding-agent skills once. Compile to every tool.

Claude Code · Cursor · Codex (AGENTS.md) · Windsurf · Aider · OpenCode · Gemini CLI

The problem

You use Claude Code at work, Cursor at home, Codex on a server, and Aider in the terminal.

Every one of them wants its own skill / rules / instructions file:

.claude/skills/code-review.md
.cursor/rules/code-review.mdc
AGENTS.md
.windsurf/rules.md
.aider.conf.yml
.opencode/skills/code-review.md

So you copy-paste. You forget one. They drift. You can't share. Your team can't enforce.

crosskill fixes that. Write a skill once. Compile to all of them.

Try it instantly

Surface	How
🌐 Web playground	Open crosskill.dev — paste a skill, see every output, download a ZIP. No install.
⌨ CLI	`npx crosskill init`
🖥 Desktop app	crosskill.app — Tauri 2 native app with watch mode. Win/macOS/Linux installers on GitHub Releases.

Install

npx crosskill init

That's it. No keys. No accounts. No Docker. No services.

Desktop app

Native installers for Windows, macOS, and Linux are on GitHub Releases. The desktop app uses the same compiler as the CLI, plus a workspace tree, keyboard-driven save, and a "Watch" toggle that recompiles every time a *.skill.md file changes on disk.

First-run warnings (we don't have code-signing yet)

Windows: SmartScreen may warn "Windows protected your PC". Click "More info" → "Run anyway".
macOS: "App can't be opened because Apple cannot check it for malicious software". Right-click the app → Open → Open.
Linux: No warning. chmod +x the AppImage if it isn't executable.

Usage

# 1. Scaffold a skill in your repo
npx crosskill init

# 2. Edit ./crosskill/code-reviewer.skill.md

# 3. Compile to every target tool you use
npx crosskill build

# 4. Lint before shipping
npx crosskill lint

# 5. Snapshot compiled outputs (run with -u the first time)
npx crosskill test

# 6. In CI: verify outputs match crosskill.lock
npx crosskill check

# 7. Install a bundled starter skill...
npx crosskill add code-reviewer

# ...or a skill from any public GitHub repo (with optional @ref to pin)
npx crosskill add azizme-com/some-skill-repo
npx crosskill add azizme-com/some-skill-repo@v0.1.0 --sha <hex>

What gets generated

From one code-reviewer.skill.md:

✓ .claude/skills/code-reviewer/SKILL.md
✓ .cursor/rules/code-reviewer.mdc
✓ AGENTS.md                    (Codex / OpenAI)
✓ .windsurf/rules/code-reviewer.md
✓ .aider/skills/code-reviewer.md
✓ .opencode/skills/code-reviewer.md
✓ .gemini/skills/code-reviewer.md

All from this:

---
name: code-reviewer
version: 0.1.0
description: Review code for bugs, performance, and style issues
tags: [code-review, quality]
targets:
  claude: true
  cursor: true
  codex: true
  windsurf: true
  aider: true
  opencode: true
  gemini: true
---

You are an expert code reviewer.

When given code:

1. Identify bugs and edge cases — line by line.
2. Suggest performance improvements with measured impact.
3. Flag style and consistency issues, link to the project style guide.
4. Output a structured review: `## Bugs`, `## Performance`, `## Style`, `## Nits`.

## Examples

**Input:** a Python function with a race condition.
**Output:** flag the shared mutable state, propose a lock or queue, show the patch.

Why crosskill

Cross-platform from day one. One spec, many compilers. Drop in new targets as the ecosystem evolves.
Local-first. No LLM required to use crosskill itself. Compile and lint are deterministic.
One-liner install. npx crosskill init. No keys, no Docker, no services.
Versionable. Skills get a version, a lockfile, and reproducible builds across your team.
Lintable. Catches vague verbs, missing examples, format ambiguity, length issues.
Starter pack included. 10+ production-ready skills shipped in ./skills/.

Built-in skills

Run npx crosskill add @crosskill/<name> to drop any of these into your repo:

Skill	What it does
`code-reviewer`	Structured code review with bugs / perf / style sections
`commit-message`	Conventional Commits with scoped subjects
`pr-summarizer`	PR descriptions with context, changes, risks, screenshots
`test-writer`	Unit & integration tests with edge cases
`refactor-helper`	Targeted refactors that respect existing patterns
`doc-writer`	README, docstrings, API docs
`debug-buddy`	Reproduce + isolate + minimal repro
`readme-generator`	Polished READMEs that ship traffic
`api-designer`	REST + GraphQL endpoint design with examples
`arabic-najdi-writer`	Saudi Najdi-dialect copywriting & content

Supported targets

Tool	Status	Output
Claude Code	✅ Stable	`.claude/skills/<name>/SKILL.md`
Cursor	✅ Stable	`.cursor/rules/<name>.mdc`
Codex / OpenAI	✅ Stable	`AGENTS.md`
Windsurf	✅ Stable	`.windsurf/rules/<name>.md`
Aider	✅ Stable	`.aider/skills/<name>.md`
OpenCode	✅ Stable	`.opencode/skills/<name>.md`
Gemini CLI	✅ Stable	`.gemini/skills/<name>.md`
Copilot Workspace	✅ Stable	`.github/copilot-instructions.md`
Continue.dev	✅ Stable	`.continue/<name>.md`
Zed Assistant	🚧 Planned	—
Cline	🚧 Planned	—

Want another target? Open an issue.

Skill format (`*.skill.md`)

---
name: string                  # kebab-case, unique
version: string               # semver, e.g. 0.1.0
description: string           # one line, under 120 chars
author?: string               # github handle or name
tags?: string[]               # for registry search
license?: string              # SPDX id, defaults to MIT
targets:
  claude?: boolean
  cursor?: boolean
  codex?: boolean
  windsurf?: boolean
  aider?: boolean
  opencode?: boolean
  gemini?: boolean
tools?: string[]              # tools the skill expects (read_file, grep, etc)
inputs?: string[]             # named inputs the skill consumes
---

# Body: the actual prompt / instructions in Markdown

Full spec: docs/format.md.

Config (`crosskill.config.json`)

{
  "skillsDir": "./crosskill",
  "outputs": {
    "claude": ".claude/skills",
    "cursor": ".cursor/rules",
    "codex": "AGENTS.md",
    "windsurf": ".windsurf/rules",
    "aider": ".aider/skills",
    "opencode": ".opencode/skills",
    "gemini": ".gemini/skills"
  },
  "lint": {
    "minBodyLength": 80,
    "maxBodyLength": 8000,
    "requireExamples": true
  }
}

GitHub Action

Drop crosskill into a PR workflow to catch skill drift before it lands. Lint, lockfile-drift check, and snapshot-drift check — one composite step:

# .github/workflows/skills.yml
name: skills
on:
  pull_request:
    paths: ["crosskill/**", "crosskill.config.json", "crosskill.lock"]
  push:
    branches: [main]
    paths: ["crosskill/**", "crosskill.config.json", "crosskill.lock"]

jobs:
  skills:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: alkhunizan/crosskill/.github/actions/crosskill@main
        with:
          mode: all # lint | check | test | all
          # version: 0.1.0   # pin for reproducibility; omit for `latest`

Inputs:

Input	Default	Notes
`mode`	`all`	`lint`, `check`, `test`, or `all` (lint → check → test, fail fast)
`version`	`latest`	Any version published to npm
`skills-dir`	`""`	Override; usually leave empty and use `crosskill.config.json`
`working-directory`	`"."`	Run from a subdirectory if your skills live there

Roadmap

Compilers for 7 platforms
Lint command
10 built-in skills
crosskill test — snapshot every compiled output; --eval pipes examples: through local Ollama
crosskill.lock for reproducible team builds (crosskill build writes; crosskill check / build --frozen verifies)
crosskill.dev — public skill registry & search
GitHub Action for skill CI on PRs (alkhunizan/crosskill/.github/actions/crosskill)
VS Code & Cursor extension with live multi-target preview
Private team registries (optional paid tier)

Contributing

PRs welcome — especially new compiler targets. See CONTRIBUTING.md.

Easiest first PR: add a new starter skill to ./packages/skills/.

Repository layout

This repo is a Bun-workspace monorepo:

packages/core/ — @crosskill/core library (browser-safe parser, linter, compilers; Node-only helpers live at @crosskill/core/node)
packages/cli/ — crosskill CLI binary, depends on @crosskill/core via workspace:*
packages/skills/ — @crosskill/skills, the starter skills shipped to every consumer
apps/web/ — crosskill.dev web playground (Next.js 14 static export, Monaco editor)
apps/desktop/ — crosskill.app Tauri 2 native desktop app (bun run --filter '@crosskill/desktop' tauri:dev to run locally; requires Rust)

bun install            # install all workspace deps
bun run build          # build @crosskill/core then crosskill
bun test               # 85 tests across packages
bun run typecheck      # strict TS, no any

License

One skill. Every tool. No lock-in.

Website · Skill Registry · Docs · Twitter

Name		Name	Last commit message	Last commit date
.github		.github
PLAN		PLAN
apps		apps
docs		docs
examples		examples
packages		packages
scripts		scripts
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
CLAUDE.md		CLAUDE.md
CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
SECURITY.md		SECURITY.md
bun.lock		bun.lock
package.json		package.json
tsconfig.base.json		tsconfig.base.json

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crosskill

The problem

Try it instantly

Install

Desktop app

First-run warnings (we don't have code-signing yet)

Usage

What gets generated

Why crosskill

Built-in skills

Supported targets

Skill format (`*.skill.md`)

Config (`crosskill.config.json`)

GitHub Action

Roadmap

Contributing

Repository layout

License

About

Releases

Packages

Used by

Contributors

Languages

Latest commit

History

Folders and files

Repository files navigation

crosskill

The problem

Try it instantly

Install

Desktop app

First-run warnings (we don't have code-signing yet)

Usage

What gets generated

Why crosskill

Built-in skills

Supported targets

Skill format (*.skill.md)

Config (crosskill.config.json)

GitHub Action

Roadmap

Contributing

Repository layout

License

About

Topics

Resources

Code of conduct

Contributing

Security policy

Stars

Watchers

Forks

Releases

Packages

Used by

Contributors

Languages

Skill format (`*.skill.md`)

Config (`crosskill.config.json`)