If you implement a project, keep the specs and tests and re-implement it, it should not matter the exact way it was coded as long as it was well tested. So you don't need deterministic LLMs.

I think work with LLMs should be centered on testing, since it is how the agent is fenced off in a safe space where it can move without risk. Tests are the skin, specs are the bones, and the agent is the muscle.

I think reading the code as the sole defense against errors is a grave mistake, it is "vibe testing". LGTM is something you cannot reproduce. Reading all the code is like walking the motorcycle.