I just use git worktrees in a single container. Albeit I don’t have more than 3 agents going at a time generally due to my own context switching limitations.
It's a different level of isolation, worktrees help agent work on different code repository in parallel but things get wonky once you consider processes and environments variables
The way I do it is each worktree gets its own .env, with dev credentials to whatever it needs access to, and my coworkers have theirs set up to have an isolated Postgres database per worktree, but I didn’t bother with that in my setup— maybe I will, though. It’s a simple script to create a worktree and properly prepare it.