FA-22158 / Autocomplete interactions / Member archive

Completion replacement spans: caret uses replaced token length instead of inserted length · case 03

The caret completion transition produces an incorrect observable state.

Member previewVariant 3 · 3 implementations · 22 checks per implementation

Case contract

Suggestion insertion replaces the half-open token span [start,end), preserving surrounding text. Caret moves after inserted text, explicit selection takes precedence over token fallback, and a stale text epoch rejects replacement. These spans count Python code points, not browser UTF-16 units.

Why this case matters

Autocomplete couples draft text, suggestion identity and asynchronous presentation; this bounded lifecycle model isolates one observable interaction defect.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
normal caret	`7`	`8`	Failed

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