Whetstone tells you whether a new agent version actually improved — without letting the agent train on its own test. The exam evolves, stays private, and every promotion decision is an auditable artifact.
Whatever the team fine-tunes or prompts on. Whetstone reads it; it never reads Whetstone.
A new adapter, agent build, or prompt stack proposed for release.
An evolving exam bank graded by checker specs — there is no answer key to leak. Items the candidate trained on are quarantined before they can flatter it.
Gains vs. regressions on items that discriminate, written to an append-only ledger.
Repair items carry a checker spec: any verified strict refinement that survives the stress pool passes. You cannot memorize what was never written down.
Every candidate exam item is tested for row identity against the actual training buffers before promotion into the bank.
Discrimination is learned from grading history; saturated items retire; the bank refreshes at the frontier the last grading exposed.