13 current findings across 20 models, verified against valibot release notes. Latest valibot at last verification: 1.4.2.
| 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 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 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 |
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.
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 |
| 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 |