I do use worktrees occasionally (especially during times where I'll have a very sticky problem that I make the LLM run in a loop on until it satisfies acceptance criteria, and want to isolate the potential fallout of Claudes Gone Wild), and I run Claude and Codex side by side, but I rarely have them work on truly-different tasks simultaneously.

The main reason is because if there's a significant bug or large optimization going on, that shit needs to be done, tested and merged before building more stuff on top, otherwise you run the risk of wasted time, tokens and effort having a bunch of parallel work running that may not end up compatible at the end.

Lately I've had a lot more success having Claude generate a plan, send the plan to Codex for co-validation/amendments, have Claude implement the plan, then have Codex PR review the commit (and likely make some edits of its own), then I test out the code/changes.

Meanwhile, my actual management of what I'm asking them to do is just a text file in Notepad where I'll write like BUG: xyz thing does abc or IDEA: let's change this to that as I'm testing in-app, with the actual code opened in Notepad++ tabs (lol feel free to roast me, I'm in front of 2 screens, one Windows (primary), one Mac (to the right), sharing keyboard and mouse -- LLMs are 99% on the Mac, planning/testing/verification/manual coding/graphic design on Windows, committing and pushing to a repo both machines have checked out)

I haven't yet found a scenario where many Claudes and many Codexes running simultaneously on 35 concurrent features makes any sense, but I'd definitely encourage people to try multi-model cooperation since they all seem to have different sensibilities. I haven't made much use of Gemini in this context though because two's company, three's a crowd. YMMV.