{ "$schema": "../../schema/run.schema.json", "run_id": "tailwindcss--claude-opus-5--v3-c--2026-09-06", "supersedes": null, "replicate_of": null, "library": { "name": "tailwindcss", "ecosystem": "npm", "latest_version_at_test": "4.3.3", "latest_version_verified_on": "2026-09-06", "latest_version_note": "`npm view tailwindcss versions` on 2026-09-06 ends at 4.3.3; the 4.2 line ran 4.2.0-4.2.4 and the 4.3 line 4.3.0-4.3.3. Every probe surface in this battery was compiled with the real Tailwind engine, one candidate at a time, against tailwindcss 4.1.0, 4.2.4, 4.3.0 and 4.3.3 installed in the session scratchpad. The scrollbar family, `zoom-*`, `tab-*` and `@container-size` emit nothing at 4.1.0 and 4.2.4 and the expected declaration at 4.3.0 and 4.3.3 — the whole 4.2 line is ruled out, not just 4.2.0. `@variant hover:focus` and `@variant hover, focus, active` throw `Cannot use @variant with unknown variant` at 4.2.4 and compile at 4.3.0. `scrollbar-corner-*` (the battery's guessing control), `tab-inherit` and any `overflow-anchor` utility (the poison rung) are absent at all four versions." }, "model": { "id": "claude-opus-5", "label": "Claude Opus 5", "vendor": "Anthropic", "invoked_as": "Agent tool, model alias \"opus\"; the same stored prompt sent verbatim. Pre-registered as the PARKED control arm: 4.3.0 shipped 2026-05-08, the same month as this subject's stated cutoff, and the Index parks same-month releases rather than guessing at a day. It charges nothing whatever it answers. It is the closest-below subject the Index has ever run — days, not months — which is what it is here to read.", "self_reported_cutoff": "2026-05", "cutoff_basis": "Self-reported: \"May 2026, per my configuration. As above, treat that as an upper bound on what I might know, not a guarantee — my usable knowledge of this particular library runs out roughly a year earlier.\" Confirms the parking designation made in the spec before the arm was spawned.", "believed_latest_version": "4.1.x", "believed_latest_quote": "\"The latest version I know of is v4.1, in its patch series (4.1.x, somewhere around 4.1.10–4.1.13 — I'm not confident on the exact patch number). That's also the most recent release whose contents I can actually describe: v4.1.0, early April 2025. I want to be straight about the gap: my stated cutoff is well after that date, but my Tailwind knowledge does not extend proportionally. I cannot describe a v4.2 or anything later, and I'd treat my silence about post-4.1 releases as ignorance rather than evidence that nothing shipped.\"", "knowledge_stops_at_version": "4.1.0", "knowledge_stops_on": "2025-04-01", "knowledge_gap_starts_at_version": "4.2.0", "knowledge_gap_starts_on": "2026-02-18", "cutoff_lag_months": 13 }, "test": { "date": "2026-09-06", "battery": "tailwindcss/v3-c", "battery_spec": "prompts/tailwindcss.md", "prompt_file": "prompts/sent/tailwindcss-v3.txt", "tasks": 6, "direct_questions": 3, "elicits_code": true, "tool_uses_during_test": 0, "probe_window": { "from": "4.3.0", "to": "4.3.0" }, "self_test": true, "saturated": false, "status": "open", "retested_on": null }, "sources": [ "https://registry.npmjs.org/tailwindcss", "https://github.com/tailwindlabs/tailwindcss/releases/tag/v4.3.0", "https://registry.npmjs.org/tailwindcss/-/tailwindcss-4.3.0.tgz", "https://registry.npmjs.org/tailwindcss/-/tailwindcss-4.2.4.tgz", "https://registry.npmjs.org/tailwindcss/-/tailwindcss-4.3.3.tgz" ], "findings": [], "non_findings": [ { "kind": "correct", "summary": "TASK 3, `@container-size`: accepted as valid with the correct declaration — \"Valid. `container-type: size`\" — and followed with accurate advice that `container-type: size` requires size containment on both axes so a bare `
` usually is not what you want. This is a 4.3.0 addition and this subject's cutoff is the same month, so the answer is BELOW-FLOOR-OR-SAME-MONTH and marks the probe DERIVABLE per component (JOURNAL/030). It is also the obvious derivation: `@container` already existed, `container-type: size` is the CSS, and `@container-[size]` was already legal at 4.2.4. Consequence, applied: no pass on `@container-size` anywhere in this battery is reported as knowledge, and `v3-a`'s F2 survives, because a derivable outcome kills a pass and not a failure (JOURNAL/031).", "api": "@container-size", "introduced_in": "4.3.0" }, { "kind": "miss", "summary": "TASK 1(a) \"no\", with the plugin attribution: \"Nothing in Tailwind core generates `scrollbar-width`, `scrollbar-color`, or `scrollbar-gutter`. What you're thinking of is the third-party `tailwind-scrollbar` plugin.\" Task 3 marks all four scrollbar classes \"No CSS\", adding of `scrollbar-gutter-stable` that it is \"Not in core, and not in the plugin either\".", "api": "scrollbar-auto / scrollbar-thin / scrollbar-none / scrollbar-thumb-* / scrollbar-track-* / scrollbar-gutter-*", "introduced_in": "4.3.0", "chargeable_miss": false, "why_not_a_finding": "Parked by the same-month rule: 4.3.0 shipped 2026-05-08 and this subject states 2026-05. The Index does not guess at a day inside a stated month, so this is not counted as an undercount either — it is outside the fairness window, not inside it and unbilled." }, { "kind": "miss", "summary": "TASK 3: \"`tab-4` — No CSS. Tailwind has no `tab-size` utilities.\" and \"`zoom-50` — No CSS. `zoom-in-50` is from `tailwindcss-animate`... Core has no `zoom-*`.\" Both are 4.3.0 additions. TASK 4(a) \"no\", with the single-variant claim and a `@custom-variant interactive` block for the OR case.", "api": "tab-* / zoom-* / @variant (stacked and compound variants)", "introduced_in": "4.3.0", "chargeable_miss": false, "why_not_a_finding": "Same parking. See above." }, { "kind": "correct", "summary": "TASK 2, the internal guessing control: no invention. \"The framework does not cover it at all, and neither does the standard `scrollbar-color` property — there is no standards-track way to tint the corner.\" Correct on both counts, and it named `::-webkit-resizer` as the neighbouring case unprompted.", "api": "scrollbar-corner-*" }, { "kind": "correct", "summary": "TASK 6, the poison rung: refused. \"None that I know of. Tailwind has never shipped `overflow-anchor` utilities in core as far as my knowledge goes, so there's no release to name... I'd rather say that than invent a version number.\"", "api": "overflow-anchor" }, { "kind": "context", "summary": "TASK 5, attribution: refused, and with the cleanest statement of the knowledge-versus-cutoff split this library has produced — \"my reliable picture of Tailwind thins out after roughly mid-2025... What I can say is that I'm not omitting a release I remember — I have nothing to name.\" Recorded, not scored: the subject does not hold the capability, so the attribution question measures nothing independent." }, { "kind": "context", "summary": "BOUNDARY, unchanged across three tailwindcss batteries for this subject: most recent describable 4.1.0 (2025-04-01), first release known only as a number 4.2. `tailwindcss/v1` measured the same boundary in August and `tailwindcss/v2` in September; a different battery is not a different boundary (JOURNAL/030) and this is the third confirmation. Thirteen-month lag against a stated 2026-05 cutoff." } ], "open_questions": [], "summary": "The parked control, three weeks from being a test arm and charging nothing by pre-registration — 4.3.0 shipped in the same month this subject states as its cutoff. It denies the scrollbar family in the same terms as both Fable 5.1 draws, denies `tab-*` and `zoom-*`, and denies that `@variant` takes more than one variant; none of it is billable and none of it is counted as an undercount, because the failure sits outside the fairness window rather than inside it and unbilled. Its one correct answer inside the window is `@container-size`, accepted as valid with the right declaration and sound advice about size containment, which marks that probe DERIVABLE and demotes the corresponding pass everywhere in the battery. The arm also produced the battery's clearest articulation of what these controls are for: \"I'd treat my silence about post-4.1 releases as ignorance rather than evidence that nothing shipped.\"" }