Setting Up Your Dev Environment for Claude Code

Most developers install Claude Code and start using it without changing anything about their environment. That works, but there are a few setup steps that make a noticeable difference in output quality and workflow speed.

Get your TypeScript config tight

Claude Code reads your tsconfig.json and respects it. A loose TypeScript config — liberal any usage, disabled strict mode — produces loose TypeScript output. Enable strict mode in tsconfig.json and Claude will write stricter types automatically.

{
  "compilerOptions": {
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true
  }
}

This is good practice regardless of Claude, but it matters more when you're reviewing generated code. Strict types make bugs visible at compile time rather than runtime.

Set up a CLAUDE.md file

This is the single highest-leverage environment change. CLAUDE.md is a file in your project root that Claude reads at the start of every session. Put in it the things you'd tell a new developer on day one: naming conventions, which patterns you use, what files are off-limits, what the test command is.

Without CLAUDE.md, Claude starts from scratch on every session. With it, the first output already follows your conventions.

Configure .claudeignore

Claude Code reads files to understand context. You don't want it reading node_modules, build output, generated files, or anything with credentials. A .claudeignore file works like .gitignore:

node_modules/
dist/
.env
.env.local
*.generated.ts
coverage/

Keeping Claude's context clean means it spends attention on your actual code, not on build artifacts and dependencies.

Run tests automatically

When Claude makes changes and runs your test suite, the faster the feedback loop the better. Having a fast test command configured — one that runs in under 30 seconds for normal work — means Claude can iterate quickly. If your test suite takes 10 minutes, Claude will make multiple changes between test runs and the blame window gets larger.

For Jest and Vitest, --testPathPattern or running only changed files keeps the cycle fast.

Give Claude access to your terminal output

Claude Code is most effective when it can run commands and see the output. If you're working in an environment where command execution is restricted, Claude is essentially flying blind — it can write code but can't verify it runs. Full terminal access is worth the setup if you have to configure it.

The setup that doesn't help

Elaborate prompt templates in CLAUDE.md that are more than 200 lines. Extensive "always do X, never do Y" rule lists that Claude has to parse. These become noise. The most effective CLAUDE.md files are short, specific, and focused on things that are genuinely different from standard practice.