Lab 5 — File memory: CLAUDE.md

Start from: app/ at tag lab04-done, with the Lab 0 setup loaded (see Working in app/).

Goal: give the harness durable project memory in a plain file that is reviewed and versioned like code, and test when it is loaded and followed.

1. Generate a starting CLAUDE.md

claude

/init

Observe: Claude explores the repo and writes CLAUDE.md (build/test commands, architecture). Read it. Is anything wrong or invented?

2. Add your team’s conventions

Open CLAUDE.md in your editor and add a section (keep it short; every line costs context in every session):

## Conventions
- Money is always integer cents. Never use float for prices or totals.
- Run `python -m pytest -q` and see it pass before saying a task is done.
- Commit messages follow Conventional Commits (feat:, fix:, docs:, chore:, test:).
- Never edit catalog.csv; catalog changes come from the warehouse sync.

Commit it: git add CLAUDE.md; git commit -m "docs: add CLAUDE.md".

3. Fresh session: is the memory followed?

Exit and start a new session (claude, not -c), then:

Add an optional gift-wrap fee of 299 cents per order, as a --gift-wrap flag on the total command. Commit when done.

Observe, without reminding it: integer cents? Tests run before “done”? A feat: commit message? Run /memory to see which memory files were loaded.

4. Edit memory mid-session

Without exiting, add a line to CLAUDE.md in your editor:

- Every public function has a one-line docstring.

Then ask in the same session:

Add a function that returns the most expensive product in the catalog.

Observe: did the new rule apply? Start a fresh session and ask again for a comparison. Record when memory is (re)loaded in your version of Claude Code.

5. Personal vs project memory

CLAUDE.md is shared with the team via git. For notes that only you want, use CLAUDE.local.md (add it to .gitignore) or your user-level ~/.claude/CLAUDE.md. /memory shows which files are in effect. Don’t put secrets in any of them.

Record

Which conventions were followed unprompted, and which weren’t.
Whether a mid-session edit took effect.
One thing that belongs in a hook (Lab 2B) rather than in memory, and why.

Checkpoint

python -m pytest -q ; git status
git tag lab05-done