principle-build-the-lever

1# Build the Lever
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3When the work isn't trivial, build the tool that does it instead of doing it by hand.
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5A 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".
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7Default to building the lever. Skip it only when the task is trivial, a couple of obvious edits you can see at a glance.
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9- 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.
10- For a comparison tool, seed one known-bad change for each output it claims to compare, and confirm the tool reports each mismatch. For example, change a total, then separately swap item assignments while keeping the totals. If required input is missing, the tool must refuse or report the result as inconclusive, never as a match. Keep these controls with the experiment and rerun them before you trust its results.
11- Codemod or script for edits, generator for repetitive files, a dump-to-sqlite query for analysis, a rerunnable check for verification.
12- 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.
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