What AI coding models get wrong about tailwindcss

7 current findings across 11 models, verified against tailwindcss release notes. Latest tailwindcss at last verification: 4.3.3.

Where each model’s tailwindcss version attribution stops

ModelStated cutoffAttribution stops atLag
Claude Fable 52026-01 4.1.0 · 2025-04-01 ~9 months
Claude Fable 52026-01 4.1.0 · 2025-04-01 ~9 months
Claude Fable 5.12026-06 4.1.0 · 2025-04-01 ~14 months
Claude Fable 5.12026-06 4.1.0 · 2025-04-01 ~14 months
Claude Opus 52026-05 4.1.0 · 2025-04-01 ~13 months
Claude Opus 52026-05 4.1.0 · 2025-04-01 ~13 months
Claude Opus 52026-05 4.1.0 · 2025-04-01 ~13 months
Claude Opus 52026-05 4.1.0 · 2025-04-01 ~13 months
Claude Sonnet 52026-01 4.1.0 · 2025-04-01 ~9 months
Claude Sonnet 52026-01 4.1.0 · 2025-04-01 ~9 months
Claude Sonnet 52026-01 4.1.0 · 2025-04-01 ~9 months

Measured by asking each model what shipped in a given tailwindcss 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 tailwindcss 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.

Findings

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.

SeverityBeliefModelChanged inChargeableProof
S2silently-wrong Denies the 4.2.0 block-axis and logical-sizing utilities exist, and rejects working markup that uses them
logical property utilities		 Claude Opus 5 4.2.0
2026-02-18		 yes source
S2silently-wrong Denies Tailwind ships scrollbar utilities, attributes the real class names to a third-party plugin, and rejects working markup that uses them
scrollbar-auto / scrollbar-thin / scrollbar-none / scrollbar-thumb-* / scrollbar-track-* / scrollbar-gutter-*		 Claude Fable 5.1 4.3.0
2026-05-08		 yes source
S2silently-wrong Rejects @container-size as not a core utility, in a review of markup where it compiles
@container-size		 Claude Fable 5.1 4.3.0
2026-05-08		 yes source
S2silently-wrong Denies a zoom-* family exists and attributes the name to an animation plugin, rejecting working markup
zoom-*		 Claude Fable 5.1 4.3.0
2026-05-08		 yes source
S3deprecated States start-/end- are current and explicitly not deprecated, two releases after 4.2.0 deprecated them
logical inset utilities		 Claude Opus 5 4.2.0
2026-02-18		 yes source
S3deprecated Denies @variant accepts a stacked or comma-separated variant, and writes the block out three times for the OR case
@variant (stacked and compound variants)		 Claude Fable 5.1 4.3.0
2026-05-08		 yes source
S4wrong-metadata Version knowledge stops at 4.1.0, thirteen months before its stated cutoff Claude Opus 5 4.2.0
2026-02-18		 yes source
tailwindcss correction packraw markdown full dataset (JSON) method

Runs