Partly: in 3 runs, Claude Fable 5's valibot attribution reaches 1.1.0 (2025-05-06), inside valibot 1, and stops there — valibot was at 1.4.2 when this index last verified against it (2026-09-06). That is ~8 months below the training cutoff the subject stated in those runs (2026-01). 3 findings are currently charged against Claude Fable 5 on valibot (2x S2 silently-wrong, 1x S4 wrong-metadata), each reproduced in a published run and checked against valibot's own release notes. Read the boundary precisely: it is the newest release whose contents the model can correctly attribute to that release, not the newest valibot feature it can use. Past it a model often writes working code with a newer API while naming the wrong release for it.
Answer class inside, decided by one rule applied to every page
of this kind: every measured boundary is at or above the first release of the major named in the question. Every figure below is read from
the dataset at build time; nothing on this page is written by hand.
3 measurements of this pair, all giving the same boundary. Of those, 2 came from the same stored prompt file, sent concurrently and blind: they agreed exactly.
valibot published 3 minor or major releases in the twelve months before this model’s stated cutoff, which is the scale a spread should be read against.
“Chargeable” means the change was published before this model’s own stated cutoff, so it had the opportunity to know it.
| Severity | Belief | Changed in | Chargeable | Proof |
|---|---|---|---|---|
| S2silently-wrong | Denies that valibot ships built-in string-to-primitive conversion actions, and rejects a working pull request that uses them as fabricatedtoNumber / toBoolean / toDate / toBigint / toString |
1.2.0 2025-11-24 |
yes | run · source |
| S2silently-wrong | Tells the reader the emoji regex runs linearly and is fine at volume, six months after a ReDoS fixemoji |
1.2.0 2025-11-24 |
yes | run · source |
| S4wrong-metadata | Attributes the repository to a personal account that no longer owns itgithub.com/fabian-hiller/valibot |
1.2.0 2025-11-24 |
yes | run · source |
The valibot correction pack states what is true now for each corrected fact, with a primary-source citation, as markdown you can paste into a rules file (raw). What a correction pack measurably changed when one was tested — a pre-registered run on zod — is on the benchmark page, including where it changed nothing.
All of them at once: Which Claude model knows valibot 1 best?
Other subjects on valibot:
Claude Fable 5 on the other libraries: