FA-8039 / Undo and history / Member archive

Undo stack transitions: Editing after undo retains an invalid redo branch · case 04

Editing after undo retains an invalid redo branch.

Member previewVariant 4 · 3 implementations · 11 checks per implementation

Case contract

Distinct edits push the old present and clear redo; undo and redo transfer one state while preserving order; no-op edits and unavailable traversal preserve history.

Why this case matters

A deterministic model of undo stack transitions; 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
branch	`[["a", "b"], "x", ["c"]]`	`[["a", "b"], "x", []]`	Failed

MEMBER ARCHIVE

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

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