Code Generation & Debugging with Claude Code
Claude Code in VS Code is a full coding partner. It reads your files, writes and edits code, runs tests, and reviews changes — all from the chat panel or with inline edits via Ctrl+K.
| Task | How to do it in Claude Code | Tip |
|---|---|---|
| Write a new function | Place cursor where you want it → Ctrl+K → describe what it should do | Mention the signature and edge cases you care about |
| Debug an error | Paste the error + stack trace in chat, or @ the file and say "line 42 is failing with…" | Ask Claude to explain why, not just fix — you'll learn faster |
| Code review | "Review @pr-changes.ts for security, performance, and readability. Rate each 1–10." | Use Opus for complex security reviews; Sonnet for routine checks |
| Refactor | "Refactor @orders.ts for readability. Do not change behaviour. Add JSDoc comments." | Review the diff before accepting — Claude is thorough but not always conservative |
| Write tests | "Write Jest tests for @cart.ts. Cover the happy path plus empty cart and invalid product ID." | Ask for tests before the implementation to drive TDD |
| Explain unfamiliar code | "Explain @legacy-auth.js line by line. I'm not familiar with this pattern." | Follow up with "what would you change and why?" for a free design review |
When Claude proposes an edit, VS Code shows a diff before you accept. Read it. Claude is accurate but not infallible — especially for niche library APIs or code paths it cannot fully see without being given all the relevant files.
Inline Editing with Ctrl+K
Select the Code
Highlight the lines you want Claude to change — or place your cursor at an insertion point for new code.
Press Ctrl+K
A small inline prompt bar appears. Type your instruction: "Add null check for userId" or "Rewrite this loop as a .map() call".
Review the Diff
Claude shows the proposed change highlighted in the editor. Green = added, red = removed.
Accept or Reject
Press Tab to accept the change, or Escape to discard it. You can also edit Claude's suggestion before accepting.
ThreadCo: Reviewing the Webhook Handler
You (in Claude Code chat): Review @webhook-handler.ts for security issues. Focus on: input validation, authentication, and anything that could be exploited by a malicious POST request. Rate each issue: Critical / High / Medium / Low. Claude responds: CRITICAL: Missing Stripe signature verification (line 14). Any HTTP client can send fake webhook events. Add: const sig = req.headers['stripe-signature']; stripe.webhooks.constructEvent(payload, sig, process.env.STRIPE_SECRET); HIGH: Raw body not preserved — signature verification will fail because body-parser is consuming the stream before verification. ...