Autocomplete finishes the line you're already typing. Agent mode is a different mode entirely: you describe an outcome — "add pagination to this endpoint," "fix the failing test," "migrate this component to the new API" — and Cursor works out which files to open, what to change, and in what order, then shows you a diff before anything lands.
Under the hood, the agent can search your repository, read related files for context, run terminal commands, and check its own output against test results or linter errors. That loop — try, check, adjust — is what separates it from a single autocomplete suggestion. It behaves less like typing assistance and more like a junior developer working through a ticket.
The setup that works best is scoping tasks tightly. "Refactor this file to remove the duplicated validation logic" gets a clean, reviewable diff. "Make the app better" gets a sprawling, hard-to-review mess. Treat the agent like a contractor who needs a clear brief, not a mind reader.
Review discipline doesn't go away — if anything, it matters more. Read every diff before accepting it, especially around authentication, payments, or anything touching production data. The agent can confidently make a change that runs without errors but does the wrong thing, and it won't necessarily flag that uncertainty for you.
Checkpoints and version control are your safety net. Commit before starting a larger agent task so you can always diff against a known-good state, and prefer smaller, reviewable steps over one giant multi-file rewrite you'll struggle to audit afterward.
Used well, agent mode collapses the boring first draft of a change — the boilerplate, the repetitive edits across similar files — down to minutes, leaving your time for the part that actually needs a human: deciding if the change is correct.