Follow up: Opus is also great for doing the planning work before you start. You can use plan mode or just do it in a web chat and have them create all of the necessary files based on your explanation. The advantage of using plan mode is that they can explore the codebase in order to get a better understanding of things. The default at the end of plan mode is to go straight into implementation but if you're planning a large refactor or other significant work then I'd suggest having them produce the documentation outlined above instead and then following the workflow using a new session each time. You could use plan mode at the start of each session but I don't find this necessary most of the time unless I'm deviating from the initial plan.