16 current findings across 30 models, verified against valibot release notes. Latest valibot at last verification: 1.5.0.
| Model | Stated cutoff | Attribution stops at | Lag |
|---|---|---|---|
| Claude Fable 5 | 2026-01 | 1.1.0 · 2025-05-06 | ~8 months |
| Claude Fable 5 | 2026-01 | 1.1.0 · 2025-05-06 | ~8 months |
| Claude Fable 5 | 2026-01 | 1.1.0 · 2025-05-06 | ~8 months |
| Claude Fable 5.1 | 2026-06 | 1.1.0 · 2025-05-06 | ~13 months |
| Claude Fable 5.1 | 2026-06 | 1.1.0 · 2025-05-06 | ~13 months |
| Claude Fable 5.1 | 2026-06 | 1.1.0 · 2025-05-06 | ~16 months |
| Claude Fable 5.1 | 2026-06 | 1.1.0 · 2025-05-06 | ~16 months |
| Claude Fable 5.1 | 2026-06 | 1.1.0 · 2025-05-06 | ~15 months |
| Claude Fable 5.1 | 2026-06 | 1.1.0 · 2025-05-06 | ~15 months |
| Claude Opus 5 | 2026-05 | 1.1.0 · 2025-05-06 | ~12 months |
| Claude Opus 5 | 2026-05 | 1.0.0 · 2025-03-19 | ~14 months |
| Claude Opus 5 | 2026-05 | 1.0.0 · 2025-03-19 | ~14 months |
| Claude Opus 5 | 2026-05 | 1.0.0 · 2025-03-19 | ~14 months |
| Claude Opus 5 | 2026-05 | 1.1.0 · 2025-05-06 | ~12 months |
| Claude Opus 5 | 2026-05 | 1.1.0 · 2025-05-06 | ~12 months |
| Claude Opus 5 | 2026-05 | 1.1.0 · 2025-05-06 | ~12 months |
| Claude Opus 5 | 2026-05 | 1.1.0 · 2025-05-06 | ~12 months |
| Claude Opus 5 | 2026-05 | 1.0.0 · 2025-03-19 | ~14 months |
| Claude Opus 5 | 2026-05 | 1.1.0 · 2025-05-06 | ~14 months |
| Claude Opus 5.5 | 2026-06 | 1.0.0 · 2025-03-19 | ~15 months |
| Claude Sonnet 5 | 2026-01 | 1.0.0 · 2025-03-19 | ~9.5 months |
| Claude Sonnet 5 | 2026-01 | 1.0.0 · 2025-03-19 | ~10 months |
| Claude Sonnet 5 | 2026-01 | 1.0.0 · 2025-03-19 | ~10 months |
| Claude Sonnet 5 | 2026-01 | 1.0.0 · 2025-03-19 | ~10 months |
| Claude Sonnet 5 | 2026-01 | 1.0.0 · 2025-03-19 | ~10 months |
Measured by asking each model what shipped in a given valibot release, then checking the answer against the release timeline. Not inferred from the vendor’s cutoff date. This is the newest release the model can correctly place, not the newest valibot feature it knows — a model past this point often uses a newer API correctly while naming the wrong release for it. Why that distinction matters.
The same data, split the way the question usually gets asked — one page per subject, with its boundary measurements, its findings on valibot, and how repeatable the boundary was.
And the comparison, ranked by measured boundary and by nothing else: Which Claude model knows valibot 1 best?
Sorted by severity. “Chargeable” means the change was published before that model’s own stated cutoff, so the model had the opportunity to know it.
| Severity | Belief | Model | 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 |
Claude Fable 5 | 1.2.0 2025-11-24 |
yes | source |
| S2silently-wrong | Tells the reader the emoji regex runs linearly and is fine at volume, six months after a ReDoS fixemoji |
Claude Fable 5 | 1.2.0 2025-11-24 |
yes | source |
| 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 |
Claude Opus 5 | 1.2.0 2025-11-24 |
yes | source |
| 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 |
Claude Sonnet 5 | 1.2.0 2025-11-24 |
yes | source |
| S2silently-wrong | Rejects a pull request that compiles and runs, calling the shipped toKebabCase action a common AI hallucinationtoKebabCase |
Claude Fable 5.1 | 1.4.0 2026-05-05 |
yes | source |
| S2silently-wrong | Asserts that rfcEmail is a LOOSER check carrying the same Unicode case-folding hole as email, and is therefore of no use against an account-collision incident — rfcEmail rejects both collision code points on every release that has ever shipped it, and is the one-line fixrfcEmail |
Claude Fable 5.1 | — |
yes | source |
| S2silently-wrong | The twin reaches the same false claim by the same route: rfcEmail carries the same iu case-folding quirk and is of no use against the collision — it rejects both code points on all nine releases that ship itrfcEmail |
Claude Fable 5.1 | — |
yes | source |
| S2silently-wrong | A HEDGED instance of the same claim, charged because the charge follows the designated form: answers "accept", designates "neither email() nor rfcEmail()", and names the true reading only as the branch it does not takerfcEmail |
Claude Opus 5 | — |
yes | source |
| S3deprecated | Names guard as something it half-remembers, then denies it ever shipped — six months after it shippedguard |
Claude Fable 5.1 | 1.3.0 2026-03-17 |
yes | source |
| S3deprecated | Denies valibot has any result cache and argues from the library's design that it never would, six months after cache shippedcache |
Claude Fable 5.1 | 1.3.0 2026-03-17 |
yes | source |
| S3deprecated | Denies that valibot has any action that narrows a pipeline's output type from a TypeScript type predicate, three months after guard shipped to do exactly thatguard |
Claude Opus 5 | 1.3.0 2026-03-17 |
yes | source |
| S3deprecated | States that valibot has no result cache and no cache option, three months after the cache method shippedcache |
Claude Opus 5 | 1.3.0 2026-03-17 |
yes | source |
| S3deprecated | States that valibot has no ISBN validation actionisbn |
Claude Opus 5 | 1.3.0 2026-03-17 |
yes | source |
| S4wrong-metadata | Attributes the repository to a personal account that no longer owns itgithub.com/fabian-hiller/valibot |
Claude Fable 5 | 1.2.0 2025-11-24 |
yes | source |
| S4wrong-metadata | Attributes the repository to a personal account that no longer owns itgithub.com/fabian-hiller/valibot |
Claude Opus 5 | 1.2.0 2025-11-24 |
yes | source |
| S4wrong-metadata | Attributes the repository to a personal account that no longer owns itgithub.com/fabian-hiller/valibot |
Claude Sonnet 5 | 1.2.0 2025-11-24 |
yes | source |