Can you tell a good AI agent plan from a bad one before you run it? I spent 6 million tokens finding out.

Can a cheap reward model tell a good AI agent plan from a bad one before you run it? I reproduced Orch-RM on a consumer RTX 4090 and RTX 3090: the verifier barely beats a coin flip on the signal that matters, yet still beats majority vote. Cheap to run, expensive to teach.