cursor-principle-build-the-lever
Codex adaptation
Build the smallest rerunnable tool or check before repeating work. Required native capabilities: none; this is instruction-only. No external product dependency is required by the adapted path. No tool is required; a nondeterministic lever is unproven. This candidate is promoted for the bounded path described here; unrelated runtime parity remains unproven. This is a guide-only adaptation.
Build the Lever
When the work isn't trivial, build the tool that does it instead of doing it by hand.
A codemod, generator, or script does the work the same way every time and reruns for free. The tool is one artifact a reviewer can read and rerun to check the work. Hand-done changes can only be re-verified by redoing them. A deterministic script turns "trust me" into "run this".
Default to building the lever. Skip it only when the task is trivial, a couple of obvious edits you can see at a glance.
- Do the first unit by hand to learn the recipe, then build the tool. Prove it by rerunning it on that unit and diffing against your hand-done version. Make the lever safe to rerun.
- Codemod or script for edits, generator for repetitive files, a dump-to-sqlite query for analysis, a rerunnable check for verification.
- A deterministic lever beats fan-out. If the tool can process every unit in one pass, run it yourself. Don't fan out delegates to hand-apply what a script can do.
- When you fan work out to subagents, write the lever as a skill they all read: the recipe, the verification contract, and the do-not-touch fences in one artifact. Keep it outside the delegates' write scope so they can't quietly edit the contract.
- Applying this principle produces a file. If you cited it and there is no codemod, script, generator, or delegate skill in the diff, you didn't apply it.
- Commit the lever when the work outlives the session.
The bar is triviality, not repetition. A one-off still earns a lever when the lever is what makes the work checkable. Per the Laziness Protocol, build the smallest script that does or proves the job, never a framework.