Oracle

An independent source of truth that can say whether an output is correct without a human reading it: a reference implementation, a differential comparison against a known-good tool, a property test, a type checker. The presence or absence of an oracle predicts more about how well agents do on a task than any topology or prompt does. Where one exists, verification is cheap and parallelism is safe. Where none exists, every gate on this page degrades into a model arguing that it is finished.