Observed arrival · 2026-09-07
The Stale Priors Index
An empirical index tracking which versions of fast-moving software libraries AI coding models can correctly identify.
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Field notes
The index measures version attribution rather than only whether generated code runs: it asks models to identify when a library feature entered its release history, then records the last release they can date correctly. The homepage currently spans seven named libraries and reports 140 code runs, including 14 runs used to measure the instrument itself. Its disclosures also label self-tests, where the AI producing the index evaluates a model from its own family.
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