GitHub Copilot app for Beginners: Using the diff, terminal, and browser

Reviewing an agent's change usually means three separate stops: a diff view, a terminal, and a browser. The GitHub Copilot app folds all three into panels that sit alongside the session, so an agent's work can be inspected, executed, and previewed without leaving the app.

Reviewing changes in the diff panel

A diff is a before-and-after comparison. The diff panel renders exactly which lines were added, removed, or changed, with additions in green and deletions in red.

From there you decide what happens next: accept the changes, leave comments, or ask Copilot to revise. The final call stays with you.

Executing commands in the terminal panel

Commands run inside the session through the terminal panel, either by hand or as a configured script exposed via the Run button. For the most part you are running the project's own commands and reading the output.

For a website, a dev server script that opens the client folder and then runs npm run dev can be added and started by clicking Run. Multiple terminal windows can be open at once, so you can switch between them and keep issuing commands.

Previewing and iterating in the browser panel

Anything with a user interface closes its loop in the browser panel, which lets you open the project and exercise a new feature as a user would. To keep iterating, the Pick & Polish tool selects an element and adjusts it with the agent. Re-running the dev server script after those changes shows what was fixed.

One loop, from diff to pull request

Review the diff, start the project in the terminal, check it in the browser, iterate until the feature works. At that point the change can be accepted directly in the Copilot app and a pull request created. Keeping review, run, and preview side by side is what makes agent-authored changes feel verifiable rather than risky, because the merged result is something you have actually seen work.

Before accepting an agent's work, ask: What's changed? Does it run? Does it actually work?

Working through that list first keeps you in control of what an agent produces.