Express: Perch rule pack
3 saved requirements for Express. Inspect the selectors and adapt the example paths to your repository.
- name: stock-never-negative
where: "reserve.cjs"
ensure: >-
The stock UPDATE must include available >= the requested quantity in its WHERE predicate, so concurrent reservations cannot decrement below zero.
- name: transaction-releases-client
where: "transaction.cjs"
ensure: >-
The withTransaction helper returns every acquired PostgreSQL client to its pool by executing client.release() in finally, including when the operation or rollback throws. A finally block containing only a comment leaves the acquired client unreleased.
- name: discount-limit
where: "server.cjs"
ensure: >-
The checkout route rejects discountPercent unless it is a finite number in the inclusive range 0 to 20, before calculating the discounted total.
Download the rule pack ZIP · Download YAML · Agent repair task · Implementation, integration requirements and captured checks
Install the rule without replacing your configuration
npm install -g @lakeday/perch
perch login
curl -fL 'https://reporules.fyi/express/rule-pack.zip' -o 'perch-guide-express.zip'
unzip -n 'perch-guide-express.zip'Keep your existing perch.yaml. Extraction preserves existing files and adds .perch/rules/perch-guide-express.yaml. Review each where selector before running a check on your application.
Configure your coding agent
perch setup claude-code
perch setup codex
perch setup cursor
perch setup piChoose the setup command for the agent you use.
Check the edit, fix the finding, check again
perch check reserve.cjs --rules stock-never-negative --json
perch check transaction.cjs --rules transaction-releases-client --json
perch check server.cjs --rules discount-limit --jsonRun the check after an agent edit. Read the finding and affected code, repair the implementation, and repeat the identical command. Keep the application regression tests as separate gates.
Exit 3 means a finding. Exit 1 or 2 means the check did not complete. A pass does not prove application correctness. Fresh judgments can vary; unchanged requests reuse cached answers. Relevant source is sent to the configured model service.