FA-8587 / Tab interfaces / Member archive

Tab selection and activation mode: Removing the focused tab selects the wrong fallback · case 02

Removing the focused tab selects the wrong fallback.

Member previewVariant 2 · 3 implementations · 10 checks per implementation

Case contract

Focus traverses enabled tabs; automatic mode activates on focus, manual mode requires Enter or Space; removed focus or selection falls back to first enabled tab.

Why this case matters

A deterministic model of tab selection and activation mode; this isolates one interface invariant without requiring a browser.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
removed focus	`["c", "a"]`	`["a", "a"]`	Failed

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