Rather than having multiple agents running inside of one IDE window, I structure my codebase in a way that is somewhat siloed to facilitate development by multiple agents. This is an obvious and common pattern when you have a front-end and a back-end. Super easy to just open up those directories of the repository in separate environments and have them work in their own siloed space.

Then I take it a step further and create core libraries that are structured like standalone packages and are architected like third-party libraries with their own documentation and public API, which gives clear boundaries of responsibility.

Then the only somewhat manual step you have is to copy/paste the agent's notes of the changes that they made so that dependent systems can integrate them.

I find this to be way more sustainable than spawning multiple agents on a single codebase and then having to rectify merge conflicts between them as each task is completed; it's not unlike traditional software development where a branch that needs review contains some general functionality that would be beneficial to another branch and then you're left either cherry-picking a commit, sharing it between PRs, or lumping your PRs together.

Depending on the project I might have 6-10 IDE sessions. Each agent has its own history then and anything to do with running test harnesses or CLI interactions gets managed on that instance as well.