OP here.

I didn't want to complain about OpenCode too much because it's open-source and kind of the scrappy underdog to Claude/Codex, but I do find its multitasking support pretty limited. I have to specifically remind it to spin up subagents, and when it does, it'll do 2-3 tasks in parallel and then wait until all of them finish. It can't seem to inspect tasks in progress, and if a subagent dies or hangs, the main agent can't seem to retrieve any information from it, even though I as the human can look at the session and see what happened.

Are you doing anything special to make OpenCode multitask well?

If you want it to do things in parallel ... have you tried the superpowers skill?