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Adjacent typing undo coalescing: Coalescing loses the text preceding the first grouped edit · case 05

Coalescing loses the text preceding the first grouped edit.

Member previewVariant 5 · 3 implementations · 13 checks per implementation

Case contract

Only contiguous insertion edits without explicit boundary coalesce; preserve the first before-state and newest after-state; no-op input creates no history.

Why this case matters

A deterministic model of adjacent typing undo coalescing; 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
contiguous	`[["ab", "abc"]]`	`[["a", "abc"]]`	Failed

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