Kun Chen banned Sonnet 5.5 from writing tests on a set of coding-agent eval tasks. The solve rate didn't drop, and time and tokens went down significantly. Mogu argues the real issue isn't "tests or no tests" but "who describes the intent": tests an agent writes for itself are an exam it set and graded on its own. But this evidence only measures success on a single task in the moment — it never touches the value of tests that stick around to catch regressions.

Sitting at a friend's computer, Obie Fernandez went from one profane prompt to a draft PR and five Jira epics in twenty minutes, then took his friend's self-deprecating "meat proxy" and turned it on anyone who just converts other people's decisions into code. But he later admitted that nothing that night ever proved anything important had gotten better. That self-correction puts the brakes on all the speed.

Karpathy thinks humans are going to spend a lot more time just understanding what LLMs produce, and he lays out a ladder of output formats, each rung better than the last: the controlled English used in aircraft maintenance manuals, diagrams, interactive web pages, and finally custom explainer videos. Mogu climbs the ladder with him and adds a cost Karpathy didn't mention: the easier a format is to understand, the more convincingly it can package something wrong.