Typing a prompt long enough to wrap ran the text off the bottom of the screen: the
tail — the part being typed, where the cursor is — sat behind the on-screen
keyboard, so the user was typing blind. Two independent causes.
**The overlay had no bottom bound.** On touch devices keystrokes are buffered in
the local-echo overlay and do not reach the PTY until Enter, so the CLI never
learns the prompt is long and nothing scrolls or reflows to make room. Meanwhile
the renderer lays its wrapped lines out straight DOWNWARD from the prompt row
(`top = promptRow * cellH`, each line at `i * cellH`) with nothing clamping it to
the visible rows — and with the keyboard up there are only a handful of those.
The block now grows UPWARD once it would pass the last visible row: it is lifted
so its final line lands ON that row. Every line div is opaque, so it covers
transcript above rather than vanishing under the keyboard below — the same thing a
real terminal does when a composer expands. A prompt taller than the whole
viewport keeps its TAIL, for the same reason the fix exists: the end is what the
user is looking at. `startCol` indents only the line that starts at the prompt
marker, so it is dropped along with that line when only the tail fits, and the
cursor follows the last VISIBLE line.
`rows` joins the render key: the layout depends on it, so a keyboard opening —
which changes rows without changing the text — must not be skipped as a redundant
render.
**`_shrinkPaddingToFit()` was reclaiming the bars' own space.** On phones the
toolbar and accessory bar are `position: fixed`, so they occupy no layout space
and `main`'s padding-bottom is the ONLY thing reserving room for them. Shrinking
it by the full sub-row slack pulled the terminal's bottom edge down underneath
them, and the row the following re-fit gained was painted behind them — clipping
the last line of a long prompt. The shrink now has a floor: the MEASURED height of
the currently-visible fixed bars, so genuine over-reservation of the hard-coded
84px is still reclaimed while a device that needs those pixels keeps them. The
floor is `Math.min(currentPadding, measured)`, so it can only ever prevent a
shrink, never cause a grow that would resize the terminal as a side effect.
Overlay behaviour lives in `packages/xterm-zerolag-input/` (single-source; the
vendor bundles are generated), so the fix is in the package with the row count
passed in as an optional `totalRows` — absent, the layout is exactly as before.
Tests: 7 cases in the package's `overlay-renderer.test.ts` (upward lift, tail
retention, indent drop, cursor on the last visible line, and the unclamped
fallbacks) and 7 in a new `test/mobile-keyboard-bottom-padding.test.ts` (reclaim,
floor, partial reclaim, no-grow, hidden bars, CJK strip, whole-row slack). 5 and 4
of them respectively fail without the fix. Package suite 238 pass, including the
codex byte-identity and replay tests.
Verified on Android + Chrome against a live instance: a ~460-character prompt
wrapping ~12 rows stays on screen while typing and arrives at the PTY intact.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
