Writing code with an agent does not cover the entirety of development work: the decisive part remains understanding precisely what was modified, whether the project still works, and what effect those changes produce in the application. GitHub dedicates a new introductory guide on the GitHub Copilot app to this step, focusing on three tools that make review more seamless: code diff visualization, the integrated terminal, and the browser used for previews.
The topic is not marginal, especially for those taking their first steps with assisted programming tools. When Copilot or an agent receives a task, it can alter multiple files and propose solutions much faster than manual editing. However, this very speed risks shifting the bottleneck to review: to verify the result, developers tend to open the repository or editor to read the code, the terminal to run commands, and a browser to check the interface. GitHub's guide presents the Copilot app as an environment where these three moments can be addressed within the same workflow.
From the agent's suggestion to reviewing changes
The first element is the diff, namely the view that compares the previous state of the files with the introduced changes. It is the starting point where every review should begin, because it allows developers to distinguish what was actually changed from the agent's interpretation of its own work.
In the case of a seemingly simple request, the diff can reveal broader changes than expected: a rewritten function, a touched configuration file, an affected dependency, or collateral changes to the interface. Reading these differences does not merely mean looking for syntax errors. It serves to evaluate whether the solution follows project conventions, whether it adds unnecessary complexity, and whether it respects the initial objective.
The distinction is important because generated code can be plausible without being appropriate for the context. An agent may produce a formally correct change, yet take an approach inconsistent with the application's architecture or the choices already established in the repository. Having the diff available directly in the app is therefore aimed at making the transition from automated proposal to human review more seamless, rather than treating the agent's output as an answer to be accepted wholesale.
For beginners, the diff view also offers educational value. Comparing before and after makes it possible to connect a natural-language prompt to the resulting lines of code. It provides a more concrete way to understand which files are involved in a feature and what impact a small change can have, provided the review does not simply become an automatic acceptance of the change.
The terminal as a verification step, not an incidental detail
The second piece of the puzzle is the terminal. In a software project, code is not verified simply because it looks clean in the review window: one must run commands, spin up the application, check for error messages, and, where available, execute tests or other tooling already configured for the project. The GitHub guide highlights this role of the terminal in the process of reviewing work performed by Copilot.
At least from a workflow perspective, the integration prevents constant context switching between windows. After reviewing the diff, developers can use the terminal to launch the local environment and observe the project's behavior. If a command returns an error, that feedback can be fed back to the agent to help correct the proposal; if execution succeeds without issues, it remains necessary to determine whether the result genuinely addresses the required use case.
This step highlights an often-overlooked limitation of using agents for coding. The absence of an immediate error does not equate to the correctness of the change. An application can boot up and still mishandle an edge case, alter existing behavior, or introduce a regression outside the tested path. The terminal therefore provides operational evidence, but it does not replace code review or a proper testing strategy.
GitHub targets the guide at beginners precisely because using the terminal can be perceived as an obstacle. Placing it alongside the diff and visual preview turns it into a natural part of verification, rather than a separate task reserved for more experienced developers. However, it remains essential to know which commands are being executed and what they entail, especially when an agent suggests operations that modify files, dependencies, or project configurations.
The in-browser preview closes the loop for web apps
The third tool described by GitHub is the built-in browser, designed to view the web app while it is being developed. This is where inspection shifts from the source code to the actual experience: a change to components, styles, routes, or content can be examined directly in the interface, without leaving the Copilot app environment.
For a web application, the preview is particularly useful because many issues cannot be spotted just by reading the code. An element may be present but end up off-screen, a navigation flow may open the wrong page, or content might not update as expected. Having the browser, terminal, and diff side by side makes it possible to follow a linear sequence: inspect the change, launch or update the project, verify the visual result, and, if necessary, return to the code to make adjustments.
However, not all checks can be reduced to a local preview. Performance, security, cross-device compatibility, integrations with external services, and production behavior require additional checks. The guide does not eliminate these validation layers; instead, it focuses on the most immediate cycle of assisted programming, where an agent's proposal must become an observable and controllable change before being considered complete.
A unified interface does not shift responsibility
The guide's most useful takeaway concerns methodology. Code-generation tools reduce the time needed to reach an initial implementation, but they make maintaining a readable review cycle even more critical. If reviewing requires too many steps across different applications, the temptation grows to rely on an agent's text description or to accept changes with only a superficial review.
Bringing diff, terminal, and browser together in the GitHub Copilot app attempts to reduce that friction. For teams and individual developers, the potential advantage is verification closer to the phase where code is written: not just asking Copilot to implement a feature, but inspecting modified files, running the project, and evaluating the result. It is a model that can make AI assistance more useful in learning activities as well, where seeing the relationship between instructions, code, and the final outcome matters just as much as getting a quick response.
However, the responsibility for the final decision remains with those working on the repository. The diff shows what changed, the terminal indicates how the environment reacts, and the browser makes the app's output visible; none of these tools alone certifies the quality, security, or adequacy of a change. The next step for those using Copilot is therefore to turn this sequence into a habit: every generated change must be read, executed, and observed, with checks proportionate to the project's complexity and risk.
