コンテキストエンジニアリング Context Engineering

I wrote CLAUDE.md in the current folder. Since the project is fictional, I couldn't check it against real files, so a few parts are guesses (listed below).

The rules file covers your three problems directly:

• Default exports: named exports only, with a short exception list for the files Next.js requires to be default.
• Invented helpers: the agent must search src/lib/ before writing any helper. If it thinks one is missing, it has to say what it searched and ask first.
• Prisma schema: it may not edit schema.prisma or run migrate or db push without approval. It must stop and describe the change instead.

It also tells the agent to ask rather than guess when requirements conflict or are missing.

Task context block to paste at the session start

TASK: Implement the "checkout" feature.

SCOPE (only touch these):
- src/checkout/        (new feature code: UI, server actions, types)
- src/lib/payments.ts  (payment logic)

READ FIRST, before writing anything:
- src/lib/payments.ts and `ls src/lib` (reuse existing helpers; list what you found)
- One existing feature folder in src/ as the pattern to follow: <PATH, e.g. src/cart/>
- The relevant Prisma models (read-only): <MODEL NAMES, e.g. Order, OrderItem, Payment>

CONSTRAINTS:
- Follow CLAUDE.md: named exports, reuse src/lib, no new deps.
- Do NOT modify prisma/schema.prisma. If checkout needs a schema change, stop and propose it.
- Never log or store raw card data; <PAYMENT PROVIDER, e.g. Stripe> handles it.

OPEN QUESTIONS (ask me, don't guess): <e.g. guest checkout? tax/shipping rules? failure and retry behavior?>

FIRST STEP: reply with a short plan (files to create or change, existing helpers you'll reuse), then wait for my go-ahead.

What you need to fill in

• Commands: I assumed standard npm scripts. Check them against your package.json.
• Pattern example: The example at the bottom is a placeholder. Swap in a real file from your repo, because one concrete example does more than any rule.
• Block placeholders: Fill the <...> spots in the pasted block (pattern folder, Prisma models, payment provider, open questions).
• Session length: Start a fresh session when checkout is done. If the session runs long, compact the history around 75% of the window and keep the task block and constraints intact.