The "Act" operating mode has strict guardrails, and a card only moves into review if the agent explicitly asks for your review (via tool call) or has a question. It's less prone to unnecessary interruptions. For example agents often decide to pause during a multi-phase plan even though no human input is needed. If an agent decides to pause in this mode, the harness automatically nudges it forward.
The "Explore" operating mode works more like most other harnesses: if the agent decides it's done then it lands in review.
Most recent models (pretty much anything released within the past year) will automatically run tests before it thinks it's done, but you can define this for example by specifying a TDD approach in AGENTS.md. In practice when a task is sitting in review, the agent typically provides a summary about test status; and this is without any special guidance.
I also implemented a "Plan" operating mode, but nowadays models are good enough at following instructions that it might be a bit overkill. This mode mounts the workspace as read-only. I originally made this out of frustration when I used to use Cline (the agent would make changes even when their plan mode was enabled). Another reason why it's overkill is because each task in MIKE already has an isolated workspace. This mode still has some advantages though, especially if you have independent subtasks that can run in parallel.