[Feature]: Auto-grow the native mobile composer for long prompts

[fionn77]

Before submitting

• I searched existing issues and did not find a native-mobile request for an auto-growing long-prompt composer.
• I am describing a concrete mobile use case.

Area

apps/mobile on Android.

Thanks for continuing to improve the native mobile experience.

Problem or use case

When writing a longer prompt in the Android app, the composer shows only about three lines at a time and then scrolls internally. Reviewing or editing a multi-paragraph prompt becomes awkward because most of the draft is hidden inside a very small text area.

Proposed solution

Let the native composer grow vertically as the prompt wraps onto additional lines.

A practical behavior would be:

• start compact for short prompts;
• expand automatically while the draft grows;
• stop at a sensible maximum, such as a portion of the available viewport;
• only then use internal scrolling;
• keep the send/stop controls reachable above the keyboard;
• preserve the cursor position and draft while resizing.

A manual expand/full-screen drafting action could also be useful, but automatic growth would solve the common case with less friction.

Expected behavior

A longer prompt should expose substantially more than three lines while it is being edited, so the user can review the surrounding paragraphs without constantly scrolling inside the composer.

Environment

• Official T3 Code native Android app
• Google Pixel 7a
• Android OS and app/OTA versions not captured

Related issues

• [Feature]: Collapse chat input box on mobile when not focused #1262 requests collapsing the web composer when it is not focused.
• [Feature]: Collapsible composer so the thread is readable while a question or approval is pending #5120 requests a collapsible web composer around approvals, questions, and long drafts.

Those are compatible ideas but do not cover growing the focused native-mobile editor while composing a long prompt.

I am happy to test the resizing and keyboard behavior on Android.

[OffCrazyFreak]

Hi! Adding an Android +1 here, plus a few things I dug up in case they help whoever picks this up.

What I see

On the Android app the composer shows about three lines at a time, no matter how long the prompt gets, and then scrolls inside the box. With the keyboard open there is plenty of empty space above the composer that it could use, so longer prompts are hard to review before sending. (Android app, version not captured.)

Where the cap comes from

Looking at main at 5cc99e1c:

• apps/mobile/src/features/threads/ThreadComposer.tsx lines 854 to 862: the expanded style is a fixed minHeight: 72, maxHeight: 160 (collapsed is height: 36). Nothing reads the editor's content height, so the box never grows past that.
• For comparison, the web composer in apps/web/src/components/ComposerPromptEditorTiptap.tsx line 758 caps at max-h-52 (13rem).

Related threads

• fix(mobile): iOS composer sizes to its draft and can go full screen #14451 (open PR) does this for iOS: the composer grows to 8 lines or half the space above the keyboard, and gets a full-screen toggle. The same approach would fit Android nicely.
• [Feature]: Auto-grow the iOS mobile composer for long prompts #6915 is the iOS counterpart of this idea.
• [Feature]: Auto-grow the native mobile composer for long prompts #5343 was the Android issue for this; it was closed without a comment.
• [Bug]: iOS composer never grows with the prompt, and its controls ignore taps while the editor is focused #11987, fix(mobile): grow the composer with the typed prompt #11757, fix(mobile): auto-grow iOS composer for long prompts #5870 and fix(swift-ios): grow composer within available viewport #7299 are earlier iOS attempts and reports.
• [Bug]: Android composer and working pill cover the newest transcript lines during a running turn, and they cannot be scrolled into view #11992 (open) is a related Android bug where the composer covers the newest lines of the thread.

How other apps handle it

• ChatGPT: the iOS app added "a full-screen editor for longer prompts" in August 2026 (changelog mirror). On mobile web the box grows to roughly 30% of the screen before scrolling (DOM notes). People had been asking for this on the OpenAI forum since 2024.
• Google Messages: raised its limit from 4 to 14 visible lines in 2025 after user complaints (9to5Google).
• Telegram Android: grows up to 6 lines (setMaxLines(6)).
• Signal Android: grows up to 5 lines (styles.xml).
• Slack iOS: had a full-screen compose view (mentioned in its release notes).

The common pattern: grow with the text up to a cap, then scroll inside, and sometimes offer a full-screen mode for really long drafts.

What would help most

1. Auto-grow up to a share of the space above the keyboard (like the "half the available space" rule in fix(mobile): iOS composer sizes to its draft and can go full screen #14451). The box would then shrink when the keyboard opens and use more room when it is closed.
2. An optional expand button that opens a full-screen editor for long prompts.

Thanks for all the work on the mobile app!