Perch: Semantic Code Linting with Jev

Semantic code linting with Jev.

Create an API key at console.typesafe.ai and set

it as PERCH_API_KEY.

npm install -g @lakeday/perch

export PERCH_API_KEY=<your TypeSafe API key>$ perch scan

checkout.py

ID Line Severity Type Confidence Problem Method

bdc67421 14 P1 (0.8) defect 81% wrong_order place_order

ddc5c917 24 P1 (0.8) defect 92% inverted_condition can_fulfil

cart.py

ID Line Severity Type Confidence Problem Method

287bfb9d 9 P1 (1.0) defect 90% off_by_one subtotal

80d6ebbb 29 P1 (1.4) defect 89% unhandled_null cheapest

✖ 20 problems in 5 files, all failingperch issues lists them worst first. perch issues <id> opens one up. perch check <id> asks again after a fix, and records what it finds nowhere.

perch setup claude-code # .claude/skills/perch/SKILL.md

perch setup codex # .codex/skills/perch/SKILL.md

perch setup pi # .pi/skills/perch/SKILL.md

perch setup cursor # .cursor/rules/perch.mdcExtend perch with custom rules, in perch.yaml:

- name: env-read-once

where: "src/**/*.js"

each: method

min: 70

ensure: >

This method takes its configuration as arguments. Reading process.env is the

command line's job.npm run check # lint, typecheck, test

npm run build # bundle src/cli.js into dist/cli.mjsFrom a checkout: npm install && npm run build && npm link puts perch on the

path.