Stop showing scrollbar unless we are in terminalBuffer mode

[jacob314]

This works around rendering artifcats in alternate buffer mode while not in
terminalBuffer mode.

Summary

Fixes #25316

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses rendering artifacts that occur in alternate buffer mode by refining the conditions under which the scrollbar is displayed. By tying the visibility of the scrollable component to the terminal buffer configuration, the UI ensures a more consistent and stable rendering experience.

Highlights

• Conditional Scrollbar Rendering: Updated the rendering logic for the scrollbar to depend on the terminal buffer configuration rather than the alternate buffer state.

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[gemini-cli]

Hi @jacob314, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[jacob314]

ScrollableList was causing the render artifacts seen in the bug when rendering when rendering with a background color in alternate buffer mode but not terminalBuffer mode.

We'll eventually make getUserTerminalBuffer() the default so no harm in restricting showing the scrollbars in the input prompt to this case.

[github-actions]

Size Change: +8 B (0%)

Total Size: 34.1 MB

Filename	Size	Change
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./bundle/interactiveCli-BMTIFCV4.js	1.29 MB	+1.29 MB (new file)	🆕
./bundle/oauth2-provider-4P5ATSTI.js	9.16 kB	+9.16 kB (new file)	🆕

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Filename	Size	Change
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./bundle/cleanup-XMDNMCN4.js	0 B	-932 B (removed)	🏆
./bundle/devtools-36NN55EP.js	696 kB	0 B
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_{compressed-size-action}

[gemini-code-assist]

Code Review

This pull request attempts to modify the rendering condition for the ScrollableList component in InputPrompt.tsx. However, the change introduces regressions in auto-scrolling functionality and incorrect UI behavior in the main buffer. It is recommended to revert the condition to use isAlternateBuffer and instead pass the configuration via a prop to the ScrollableList component to maintain consistent behavior.

[gemini-code-assist]

Replacing isAlternateBuffer with config.getUseTerminalBuffer() as the condition for rendering ScrollableList introduces a regression in scrolling functionality and incorrect behavior in the main buffer:

1. Broken Auto-scrolling: The useEffect at line 1668 (which ensures the cursor remains visible by scrolling the list) depends on listRef.current. When config.getUseTerminalBuffer() is false, ScrollableList is not rendered, listRef.current remains null, and the input prompt will no longer automatically scroll to follow the cursor. Manual scrolling keys (PageUp/PageDown) provided by ScrollableList are also lost.
2. Main Buffer Behavior: If a user has terminalBuffer enabled in their config but is currently in the terminal's main scrollback (isAlternateBuffer is false), the prompt will now incorrectly render a ScrollableList with a scrollbar.

To achieve the goal of hiding the scrollbar while maintaining functionality, you should keep the isAlternateBuffer check and instead pass the configuration to the scrollbar prop of ScrollableList (e.g., <ScrollableList ... scrollbar={config.getUseTerminalBuffer()} />).

Suggested change

	{config.getUseTerminalBuffer() ? (
	{isAlternateBuffer ? (

References

1. Maintain consistency with existing UI behavior across components. Defer non-standard UX pattern improvements to be addressed holistically rather than in a single component.