Working with Claude Code as your agent IDE partner

Give a clear task, review the diff, redirect early

After this, you'll be able to use Claude Code or Cursor's agent mode to make a targeted file change by writing a precise task description and reviewing the diff before accepting.

Before you start

Complete Tab Complete first; this lesson builds on using AI to generate and review code changes.

The idea

Agent IDE tools like Claude Code and Cursor don't just complete lines of code; they read your entire project and make actual file changes based on a task you describe in plain English. Your job in this workflow is three things: write a precise task description, review the diff the agent produces, and redirect it early if it goes wrong.

Here is the before and after: 'Fix the auth bug' is too vague; the agent changes multiple files, introduces a new issue, and you spend an hour tracking it down. 'In auth.ts, the isTokenValid function always returns false because the expiry check compares a string to a number; fix the comparison so it correctly returns true for a valid, non-expired token' gives the agent a file name, a function name, and a specific problem; the diff it produces is one targeted line.

Now try it: pick a single function in a project you are working on and write a task description that names the file, the function, and the exact behavior you want changed. Review every line of the diff before accepting; reading diffs is the core skill of agent IDE use.

Try it (12 min)

Watch out for

Accepting a large diff without reading every line; agents can confidently introduce subtle bugs across multiple files
Writing a task that says 'clean up' or 'refactor' without specifying which wrong behavior to fix
Skipping the scope boundary; 'do not change other files without telling me' prevents scope creep
Treating a failed first attempt as a dead end; describe what went wrong specifically and the agent can usually fix it

Paste this into Claude

I am working in [describe your project: what it is and what language it uses]. I need to make a change to [specific file name and function or section]. Right now it [describe the current behavior: what it does that is wrong or missing, one sentence]. I want it to [describe the desired behavior: what it should do instead, one sentence]. The change should not affect [describe any behavior that must stay the same]. When you are done, explain what you changed and why in one sentence. Do not change any other files without telling me why you need to.

What good looks like

The diff contains changes only to the file you named, or the agent explains why it touched others
The behavior you listed as 'must stay the same' still works after the change
You can read every line of the diff and understand exactly what it does
The agent's one-sentence explanation matches what you see in the diff

When this breaks

Breaks when the task description has no file or function scope because the agent interprets the request broadly and changes things you did not intend
Breaks when you accept without reviewing because bugs introduced by agents are often subtle and do not appear until much later in testing
Breaks when you let the agent run multiple iterations without reviewing between them because each iteration compounds the previous mistake and the final state can be far from what you originally intended

You can now

Read every line of the diff, confirm the change does exactly what you described, and run the affected feature to verify nothing else broke.

Key takeaways

The agent IDE handles the editing; your job is the task description and the diff review. Vague tasks produce large diffs that touch files you didn't intend. Specific tasks produce small, targeted ones.

Claude Code and Cursor's agent mode make actual file changes; your task description determines the scope
A precise task names the file, the function, and the specific behavior to change; not a general goal
Reading the diff before accepting is the core skill; it keeps you in control of what lands in your codebase
One specific change at a time is faster than asking the agent to fix multiple things at once

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I am working in [describe your project: what it is and what language it uses]. I need to make a change to [specific file name and function or section]. Right now it [describe the current behavior: what it does that is wrong or missing, one sentence]. I want it to [describe the desired behavior: what it should do instead, one sentence]. The change should not affect [describe any behavior that must stay the same]. When you are done, explain what you changed and why in one sentence. Do not change any other files without telling me why you need to.