Regression: interactive dialog `textarea` elements render as single-line inputs

[iBrewerRoot]

Summary

Interactive dialog elements declared as "type": "textarea" are rendered as single-line text inputs in the mobile app. Pressing the return key submits the dialog instead of inserting a line break, so users cannot enter multi-line content in a field that is documented as multi-line.

Per the interactive dialogs documentation, textarea is "a multi-line plain text field" intended for input longer than 150 characters. The web and desktop clients render it correctly as a real multi-line field; only the mobile app is affected.

This is a regression: the same dialog, on the same server, still behaved correctly on mobile app 2.38.3 and is broken on 2.43.1.

It may belong to the same family as #9982 (date / datetime element types missing on mobile), where a legacy dialog element type is not rendered with the fidelity the documentation describes.

Steps to reproduce

1. Register a slash command (or plugin) that opens an interactive dialog containing a textarea element. Minimal payload:

{
  "trigger_id": "<trigger_id>",
  "url": "https://example.com/submit",
  "dialog": {
    "callback_id": "repro",
    "title": "Textarea repro",
    "elements": [
      {
        "display_name": "Multi-line field",
        "name": "notes",
        "type": "textarea",
        "optional": false,
        "max_length": 3000,
        "placeholder": "Type a line, press Enter, type a second line"
      }
    ],
    "submit_label": "Send"
  }
}

2. Open the dialog from the mobile app.
3. Tap the "Multi-line field" input, type a line of text, then press the return key on the on-screen keyboard.

Expected behavior

The field is rendered as a multi-line input (as on web/desktop). The return key inserts a line break, and the submitted value contains \n between lines. Submission happens only via the submit button.

Observed behavior

The field is rendered as a single-line input. The keyboard shows a submit/next affordance rather than a return key, and pressing it submits the whole dialog. There is no way to enter a line break, so the submitted value is always a single line.

Environment

• Affected mobile app version: 2.43.1
• Last version known to work: 2.38.3 — a user who had stayed on 2.38.3 kept the correct multi-line behavior and lost it upon updating, while colleagues on newer builds were already affected.
• Regression window: somewhere between 2.39.0 and 2.43.1. We had already observed the broken behavior on other devices by 2026-05-22, which points at 2.39.0 or 2.40.0.
• Reproduced on several Android devices and several Android OS versions — not device-specific or OS-version-specific. (iOS not tested.)
• Server version: 11.10.1, self-hosted, Team Edition.
• Web and desktop clients on the same server: not affected — textarea renders as a proper multi-line field.