Construct validity of Claude Opus 4.8's System Card – A commentary

TL;DR: A read of the Claude Opus 4.8 system card with a focus on alignment assessment and construct validity of evaluation methods. Three main concerns: 1) chain-of-thought monitoring misses reasoning that never surfaces in the text; 2) evaluation awareness is under-estimated; 3) the evaluators come largely from the same model family, so agreement may reflect shared assumptions. None of this shows Opus 4.8 is unsafe but only that some verdicts are more confident than the methods warrant.Introduc...