CLAUDE.md, diffs, and safe commits

Every session starts knowing nothing about your project's conventions. A CLAUDE.md at the project root is where you stop re-explaining them: the commands that actually work, the conventions that aren't visible in a single file, and the boundaries that matter.

# Project notes

- Package manager is pnpm. `npm install` will produce a
  second lockfile and break CI.
- `pnpm test` runs unit tests; `pnpm test:e2e` needs a
  running database and is not part of the normal loop.
- `src/generated/` is code-generated. Edit the schema in
  `schema.prisma` instead.

Notice what those lines have in common: each one prevents a specific, plausible mistake, and each is verifiably true today. That's the bar. A guidance file full of aspirations — "write clean, well-tested code" — costs context and prevents nothing. And it contains no secrets: this file is read by every session and usually committed to the repository.

The other habit worth building is asking Claude to explain a diff. Make a small change yourself, then ask what it does and what might break. You're using it as a reviewer rather than an author, and it's a good one — it will mention the caller you forgot. Check the explanation against the actual diff, the same as always.

Publishing stays yours. Running the checks and drafting a commit message is work worth delegating; git push is not. The distinction isn't about capability, it's about reversibility — a local commit is a thing you can amend, and a pushed commit is a thing other people have. Keep the irreversible step behind a human.

Which leads to the last skill of this level: recovering. Ask for a harmless bad edit on purpose, stop, look at what changed, and restore just that. Doing it once deliberately, in a folder where it doesn't matter, is how you learn that the answer is a narrow targeted revert and never a broad destructive command typed in a hurry.

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