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Hierarchical sibling sort and stable identity: Sibling label comparison ignores stipulated casefold equivalence · case 05

Sibling label comparison ignores stipulated casefold equivalence produces the wrong hierarchical widget state in a regression fixture.

Member previewVariant 5 · 3 implementations · 6 checks per implementation

Case contract

Only direct children of the target parent are sorted by casefolded display label, with original order retained on ties; each child subtree moves as one block. Missing labels sort last in ascending order; descending reverses the complete comparison order. Focus, selection and expansion remain ID-based; sibling positions are recomputed from sorted roots.

Why this case matters

Offline executable model of a hierarchical accessibility interaction; inputs are bounded and valid as stipulated. No browser, assistive technology, or normative ARIA conformance is claimed.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
stable tie	`[["outside", "r", "z", "zz", "zzz", "b", "a", "q"], {"a": 3, "b": 2, "z": 1}, "z", ["zzz"], ["r", "z"]]`	`[["outside", "r", "b", "z", "zz", "zzz", "a", "q"], {"a": 3, "b": 1, "z": 2}, "z", ["zzz"], ["r", "z"]]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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