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System DesignVery Hard· System Design

How would you design an AI system a regulator could actually audit?

I’d start from the reconstruction test: months after the fact, can you show exactly why the system produced a specific output for a specific input? If the answer is no, the system isn’t auditable, however good its accuracy numbers look.

Passing that test requires recording the decision path, not just the final outcome:

  • The exact inputs.
  • Any retrieved context, with its sources — not just the final answer that used it.
  • The model and prompt versions in effect at that moment.
  • The confidence or score attached to the decision.
  • Which stages were deterministic rules versus model-driven judgment.
  • The human decision that followed, where a human was in the loop.

Two design principles fall out of that directly. First, make irreversible actions human-gated, so there’s always a named, accountable person behind anything that can’t be undone. Second, keep the deterministic parts of the system actually deterministic — every rule that gets moved into a model’s judgment instead of staying an explicit rule is a decision that can no longer be explained simply to an auditor, even if it performs better on average.

Code playground (Python)