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Brooklyn Nicholson
3b4dd68326
The composer's `cursorLayout` (in `ui-tui/src/lib/inputMetrics.ts`) used a hand-rolled word-wrap algorithm to decide where `useDeclaredCursor` should park the hardware cursor. But Ink's `<Text wrap="wrap">` renders the same text via `wrap-ansi`. The two algorithms disagreed on common real-world inputs — `"branch investigate"` at cols=20, `"hello world"` at cols=8, exact-fill strings like `"abcdefgh"` at cols=8 — so the hardware cursor parked several cells past where Ink actually rendered the last character. Users saw a multi-cell blank gap between their last-typed letter and the cursor block, especially on narrow terminals (the Cursor IDE built-in terminal was the worst offender). Three previous PRs (#26717, #25860, #22197) chased fast-echo displayCursor/cursorDeclaration drift and in-band-vs-native cursor heuristics. None of them touched the underlying wrap-algorithm mismatch, which is why the bug kept resurfacing. Fix: source cursorLayout's line breaks from wrap-ansi directly. Walk its emitted string char-by-char, tracking original-string offsets, push a VisualLine at each '\n'. Also drop the buggy `column >= w` overflow rule in cursorLayout — that's what pushed exact-fill text onto a phantom next row. canFastBackspaceShape now detects the wrap boundary in BOTH coordinate conventions (column === 0 OR column >= columns), since exact-fill now reports as (0, columns) instead of the previous (1, 0). The physical state is identical — the terminal auto-wraps at column N either way — but the layout function reports the position more honestly. Tests: - ui-tui/src/__tests__/textInputWrap.test.ts: 3 tests that pinned the BUGGY behavior were updated to assert wrap-ansi parity (the real invariant). Added a typing-prefix invariant: cursorLayout must agree with wrap-ansi at every character of a long input. - ui-tui/src/__tests__/cursorDriftRegression.test.ts: new file. Walks the user-reported bug message char-by-char at 7 widths and asserts agreement with wrap-ansi at every prefix. Verification: - 791/791 vitest tests pass. - 84/84 tui-gateway pytest tests pass via scripts/run_tests.sh. - PTY repro (typing into a real `hermes --tui` PTY at cols=50/55/60): cursor lands exactly 1 cell past the last typed char in every case the bug previously drifted.