>You can't just run several tasks in parallel hoping for one of them to complete.

Not only can you, some providers recommend it and their tools provide it, like ChatGPT Codex (the web tool). Can’t find where I read it but I’m pretty sure Anthropic devs said early on that they kick off the same prompt to Claude Code in multiple simultaneous runs.

Personally, I’ve had decent success from this way of working.

Ok, maybe it helps somewhat. My experience is that when the agent fails or produce crappy code, it's not a matter of non-deterministic output of the LLM but rather that the task is just not suitable or the system prompt didn't provide enough information.