| 1 | --- |
| 2 | name: principle-build-the-lever |
| 3 | description: "Apply to any non-trivial work, not just bulk work: edits, migrations, analyses, checks. Build the tool that does it or proves it (codemod, script, generator, or a skill your subagents follow) instead of working by hand. The tool is the artifact a reviewer can rerun." |
| 4 | disable-model-invocation: true |
| 5 | --- |
| 6 | # Build the Lever |
| 7 | |
| 8 | When the work isn't trivial, build the tool that does it instead of doing it by hand. |
| 9 | |
| 10 | **Why:** Two payoffs. Throughput: a codemod, generator, or script does the work the same way every time and reruns for free. Confidence: 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". |
| 11 | |
| 12 | **Pattern:** Default to building the lever. Skip it only when the task is trivial, a couple of obvious edits you can see at a glance. |
| 13 | |
| 14 | - 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. |
| 15 | - Codemod or script for edits, generator for repetitive files, a dump-to-sqlite query for analysis, a rerunnable check for verification. |
| 16 | - 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. |
| 17 | - 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. |
| 18 | - 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. |
| 19 | - Commit the lever when the work outlives the session. |
| 20 | |
| 21 | **Balance:** The bar is triviality, not repetition. A one-off still earns a lever when the lever is what makes the work checkable. Per the [ |
| 22 | |
| 23 | Distinct from [Encode Lessons in Structure](../principle-encode-lessons-in-structure/SKILL.md |