Using Claude Code for a full project: what you need to set up first

Using Claude Code for individual tasks is different from using it across an entire project over weeks. The setup that's optional for a quick task becomes mandatory when Claude is working in the same codebase repeatedly.

Here's what I've found makes the difference between a project that goes smoothly and one that accumulates technical debt from session to session.

CLAUDE.md before you write any code

Start with a CLAUDE.md in the root of the project. Put in it: the stack and versions, the file structure conventions, the naming patterns, the error handling approach, the testing strategy. This is the document Claude reads to understand how to work in this codebase.

Don't write it all upfront — you don't know all the conventions yet. Start with the basics and add to it as you make decisions. The rule: if you've told Claude the same thing twice, put it in CLAUDE.md.

A test suite from the start

Projects where tests exist from day one are easier for Claude to work in long-term. Tests give Claude a way to verify its own work. Without them, each session relies on Claude's ability to reason about correctness, which degrades as the codebase gets more complex.

You don't need complete coverage — you need enough that "run the tests" is a meaningful check. Integration tests that cover the main user flows are worth more than unit tests for individual functions.

Git discipline

Commit after every meaningful unit of work. Not "at the end of the session" — after each feature, each bug fix, each refactor. This keeps the git history clean and gives you rollback points that are meaningful rather than arbitrary.

Tell Claude to commit in its task prompts. It will do it if you ask. If you don't ask, it builds up changes and commits everything at once, which makes the history hard to read.

A task file for each session

Before each session: write a brief file with the goal, the files in scope, and what done looks like. Update it during the session. At the end, mark what's complete and what's left.

This sounds like overhead. It's not — it takes two minutes and it prevents the session drift where you started trying to fix authentication and ended up refactoring the component structure because Claude noticed something.

Regular CLAUDE.md updates

After any decision you might need to explain to Claude again — update CLAUDE.md. After any session where Claude made a wrong assumption — update CLAUDE.md to prevent it next time. Treat it as a living document, not a one-time setup.

Over a month of development, a well-maintained CLAUDE.md becomes the primary reason Claude's output stays consistent with how the project is built.