Bug: input prompt clips the last character of a line whose width exactly matches the prompt width

[pmenic]

Summary

When the input line fills the prompt width exactly and the user keeps typing, the new character + cursor become invisible. The buffer is correct — pressing Enter submits the full text including the invisible suffix — so this is a pure rendering issue.

Environment

• Gemini CLI: 0.39.1
• OS: Windows 11
• Shell: PowerShell (Windows Terminal)
• Terminal size: 50 columns × 5 rows
• Plan mode active
• ui.terminalBuffer: true in ~/.gemini/settings.json

Reproduction

1. Resize the terminal to ~50 columns (the exact width is not critical, only that the test string ends up matching inputWidth).
2. At the input prompt type parola repeatedly until the line is full, then continue with pa. The cursor sits at the right edge.
3. Type one more character (e.g. r).

Expected

The prompt grows to a second visual line and shows par plus the cursor on it.

Observed

The new character and cursor disappear; the visible line still ends with pa. The text is in the buffer — Enter submits the full string parola parola parola parola parola parola parola par.

Root cause

VirtualizedList (used by ScrollableList to render the input lines when ui.terminalBuffer: true) applies paddingRight: 1 for its scroll gutter (packages/cli/src/ui/components/shared/VirtualizedList.tsx:738). The input prompt was passing width={inputWidth} to ScrollableList (packages/cli/src/ui/components/InputPrompt.tsx:1865), so the inner content area was inputWidth - 1. A visual line exactly inputWidth chars wide had its last char clipped.

Fix

Compensate for the gutter by passing width={inputWidth + 1} to ScrollableList, so the inner content area equals inputWidth. The fix is staged on branch fix/inputprompt-wrap-truncates-last-char on my fork (commit e9f20f206) with a regression test; I'll open the PR once one of my existing open PRs is reviewed/merged.

Notes

• Only the ui.terminalBuffer: true render path is affected. The fallback render path (InputPrompt.tsx:1875-1891) does not go through VirtualizedList and renders correctly.

[gemini-cli]

This is a professional-quality UI bug where the input prompt clips characters when matching terminal width.

Effort Analysis:
The root cause is localized to packages/cli/src/ui/components/InputPrompt.tsx where the width passed to the scrollable list fails to account for the internal gutter padding of VirtualizedList.tsx:738. This is a straightforward off-by-one logic error in a single UI component, fitting the 'Localized Bug Fixes' and 'UI/Aesthetic Adjustments' Small effort guidelines.