A short post argued this week that reliable agents need deterministic control flow, not more prompts. The argument is correct. The line that lands hardest in the piece is the one about a programming language where statements are suggestions and functions return "Success" while hallucinating. That is the model when prompt chains carry the control flow; it is also a perfect description of why those systems collapse as complexity grows. The piece closes with three options for what to do about it: a babysitter (human in the loop), an auditor (exhaustive end-to-end verification after the run), or prayer (vibe-accept the outputs). It frames those as the alternatives left after the prompt chain has already failed. There is a fourth option, and it is the one the same piece was arguing for earlier. Tests. What the fourth option actually is Tests in the unflashy software-engineering sense. Programmatic verification at every step. Schema checks. Range checks. Reference checks.…