alt Hacker Newsgit worktree (or any COW snapshot like this) still leaves you reinstalling node_modules per tree and fighting over a dev server port. That's the actual cost, and none of these tools touch it. So I gave up on parallelizing inside one repo. I run agents across different projects — one repo each — and stay serial within a single project.
This! A hundred times over. It's hard enough having to review one serial set of changes managing parallel changes into a single code base has been a nightmare load on my brain so I avoid that unless I'm trying to prototype something quick and dirty.