Claude Code documentation describes a diff panel for reviewing working-tree changes without leaving the session. In fullscreen rendering, the /diff command opens the panel beside the conversation; it lists changed files with added and removed line counts, shows each file's diff, and refreshes whenever Claude edits a file or runs a shell command. The panel needs a git repository, a terminal at least 110 columns wide, and Claude Code v2.1.260 or later.
The practical change is that review moves into the agent loop: selected lines can be attached to the next prompt, so a developer can point Claude at a specific hunk instead of describing it. The documentation covers behavior and requirements only; it does not measure whether in-session review reduces missed defects compared with reviewing changes in an editor or pull request.