Open-source · AGPL-3.0

KERN

Write code review judgment once. Run it everywhere.

KERN is an open-source language for opinions about code. The same .kern rules run in your CLI, editor, CI, and agents.

Try in PlaygroundRead the docs
SEMANTICKERN IRACTIONEFFECTGUARDCONFREVIEWCOMPILEEVOLVEOne IR, three outputs

One rule, many places

Define the judgment once.

A .kern rule compiles into checks that run wherever your team works.

rules/no-unguarded-effect.kern

rule no-unguarded-effect
  match db.write or net.send
  require auth.guard within 3 hops
  severity error
CLI check

kern review src/ — local audit, exit codes for CI

GitHub PR annotation

Same rule, posted as a PR comment with file:line evidence

VS Code · Sight

Inline diagnostic + autofix, free extension

MCP for AI agents

Agents call review tools to catch their own mistakes

Compiles to

12 targets, your stack covered.

Next.js·React·Vue·Nuxt·Express·FastAPI·Native·CLI·Tailwind·Terminal·Ink·MCP server
See how compilation works →

Install

One line. No config.

npm install -g @kernlang/cli
kern review src/

Or skip install:

Try in Playground

Open source · AGPL-3.0 · Built by a small team.

GitHub →Hosted PR review (KERN Guard) →