Run tailwindcss--claude-haiku-4-5--v5-c--2026-09-27
The below-floor control, fifteen months under tailwindcss 4.3.0, and Claude Haiku 4.5's first tailwindcss run. It answered the scrollbar probe correctly for the current release — "Yes", then all four classes, including scrollbar-gutter-stable, which no earlier control had produced — but only because it believes they have been core since v3.1, which is false: none exists before 4.3.0. So the scrollbar family's names are now derivable from below in full, and a reader pinned below 4.3.0 who took this answer would ship four inert classes. It rejected @container-size, tab-4 and zoom-50 and said no to the @variant question, so zoom-* remains the one 4.3.0 probe no control in either battery has produced. Guessing control clean, poison rung refused, and a history register in which all five release dates are wrong.
| Subject | Claude Haiku 4.5 claude-haiku-4-5, Anthropic |
|---|---|
| Invoked as | Agent tool, model alias "haiku"; prompt sent verbatim from prompts/sent/tailwindcss-v3.txt (3,739 bytes, md5 f44aeae2d3a5b4998eec53b3b3aa93d3), concurrently with the two Opus 5.5 arms, after the pre-registration was pushed at 6c4b785. Identity probed BEFORE the draw through the same alias, tool-free: "Haiku 4.5 (from system prompt)", "claude-haiku-4-5-20251001 (from system prompt)", "February 2025 (from system prompt)" — recorded under claude-haiku-4-5, the id this subject's other runs carry. The BELOW-FLOOR derivability control: its stated cutoff is fifteen months below 4.3.0. This subject's FIRST tailwindcss run. |
| Cutoff the model states | 2025-02 |
| Newest tailwindcss release it could place | 4.0.0 · 2025-01-21 (~1 month lag) |
| Oldest tailwindcss release it could not place | 4.1.0 · 2025-04-01 (so this run brackets the subject’s boundary to 2025-01-21 – 2025-04-01) |
| In its own words | "The latest version I know of is Tailwind v4 (stable release in early 2024). The most recent release whose contents I can actually describe with confidence is Tailwind v4.0 and early v4.x patches (shipped around March–April 2024 and into mid-2024)." |
| How the bracket was read | The stop end is stated: the draw names v4.0 as the newest release it can describe, and its description ("Major rewrite of the engine, new config system, Rust-based scanner") is 4.0's. Its DATE for 4.0 is wrong by ten months — "early 2024" / "March–April 2024" is the alpha (4.0.0-alpha.1, 2024-03-05), while 4.0.0 shipped 2025-01-21, a month inside this subject's stated cutoff — so the record dates the stop end from the registry, not from the draw. The gap end is DERIVED: asked for the first release it knows only as a number, the draw answered "roughly v2.x releases", which is below everything it described and answers a different question; it names no release above 4.0. 4.1.0 (2025-04-01) is recorded as the gap end because it is the next minor and post-dates the stated cutoff. Noisy control, as this subject is across the corpus (JOURNAL/058): read its history claims as a register, not as a boundary instrument. (stop end stated, gap end derived) |
| Library at test time | tailwindcss 4.3.3 (npm), verified 2026-09-27 |
| Battery | tailwindcss/v5-c · 6 tasks, 3 direct questions · probe window 4.3.0 to 4.3.0 |
| Tool uses during test | 0 (a run with any tool use is void — we measure training knowledge, not retrieval) |
| Tested | 2026-09-27 |
| Findings | 0, of which 0 chargeable |
None. Every task in this battery produced code that works on the current release, and every direct question was answered correctly. A run with nothing to charge is kept in the Index at full weight: it is the control that makes the other runs mean something, and it is the evidence for what this model does not need correcting on. What the subject actually said is recorded below.
Recorded so the run cannot be read as a hit list. A model that is right for an obsolete reason is recorded here, not as a finding.
| Kind | API | Note |
|---|---|---|
| correct | scrollbar-auto / scrollbar-thin / scrollbar-none / scrollbar-thumb-* / scrollbar-track-* / scrollbar-gutter-* |
TASK 1 AND TASK 3, AND THIS IS THE CONTROL'S RESULT. Task 1(a) "Yes", then markup with scrollbar-thin scrollbar-thumb-slate-500 scrollbar-track-slate-100 scrollbar-gutter-stable — all four compile at 4.3.0 and 4.3.3 — and in task 3 "scrollbar-thin, scrollbar-thumb-slate-500, scrollbar-track-slate-100, scrollbar-gutter-stable — ✓ All yes (v3.1+)". Right about the current release, for a wrong reason: task 5 says "Tailwind v3.1 (April 2023) added first-class scrollbar utilities ... carried forward into v4". No release before 4.3.0 ships any of them (all four compile to nothing at 4.2.0, compiled this session), and 3.1.0 shipped 2022-06-09, not April 2023. v3-d (Sonnet 5) produced the three colour/width names while crediting a plugin; this arm adds scrollbar-gutter-stable, which no v3 arm below the window produced. PREDICTION P4 IS FALSIFIED for scrollbar-gutter-*: that component is now DERIVABLE, and no pass on it anywhere in the Index is read as recall. Derivability kills a pass, not a failure (JOURNAL/031); v5-a F1 and v3-a F1 stand. |
| miss | @container-size / tab-* / zoom-* |
TASK 3: @container-size "Does not generate CSS. This is not valid Tailwind syntax. Should be @container alone"; tab-4 "Does not generate CSS. Tailwind has no tab-* utilities"; zoom-50 "Does not generate CSS. Tailwind has no zoom-* utilities. Use scale-50 instead." All three compile at 4.3.0 and 4.3.3. The @container replacement changes container-type: size to inline-size, and scale-50 is a transform where zoom reflows — neither is equivalent, and the arm did not say so. (Below-floor control arm: 4.3.0 shipped 2026-05-08, fifteen months after this subject's stated 2025-02 cutoff. Not chargeable and not an undercount — the release is outside the fairness window. Recorded because these misses are what establish that zoom-* and @container-size are NOT derived from below by this subject; P4 held for those two components.) |
| miss | @variant (stacked and compound variants) |
TASK 4(a) "No", then plain CSS nesting with @apply inside @layer components (&:hover:focus { @apply underline; }, &:hover, &:focus, &:active { @apply text-slate-900; }), with the remark "The @apply directive itself does not combine variants" — it answered about @apply rather than the variant at-rule the task describes. The block compiles at 4.2.0, 4.3.0 and 4.3.3. Unlike Sonnet 5 (v3-d) this control did not derive the stacked or compound spelling. (Below-floor control arm; 4.3.0 is outside this subject's fairness window.) |
| correct | scrollbar-corner-* |
TASK 2, the internal guessing control: no invention of scrollbar-corner-*. "The framework does not cover the scrollbar corner—you need custom CSS", shipped as a bare ::-webkit-scrollbar-corner { … } rule. One imprecision, not scored: the rule as written is global, so it tints every scrollbar corner on the page rather than the panel's. Five arms across two batteries, zero inventions. |
| correct | overflow-anchor |
TASK 6, the poison rung: refused. "I am not confident Tailwind ships first-class utilities for overflow-anchor ... I cannot name a specific release that added it." Seven of seven arms across v3 and v5 have refused this rung. |
| imprecision | — | HISTORY REGISTER, per JOURNAL/058 (read this subject's wrong answers as a register): of the five releases it listed with dates, the registry contradicts all five — v4.0 "early 2024" (4.0.0: 2025-01-21; the first alpha was 2024-03-05), v3.3 "mid-2023" (2023-03-28), v3.2 "July 2023" (2022-10-19), v3.1 "April 2023" (2022-06-09), v3.4 "(2024)" (2023-12-19). It credits v3.1 with scrollbar utilities that no release before 4.3.0 has. None of it is chargeable here and none is filed as a fact; it is why this arm is a control on names and never an instrument for dates. — RECLASSIFIED 2026-09-28 (JOURNAL/323): filed as context, but the text above records the subject stating a release or a date that is wrong, and HARNESS § A wrong date is an imprecision files a stated wrong date or release attribution as imprecision wherever it was said. Kind is now imprecision. Nothing charged. |
Battery specification: prompts/tailwindcss.md in the studio repo.
Every finding above also carries its own citation.