Focus moves to reply textbox, but viewport does not scroll to reveal it in Notes

[karthick-murugan]

Description

When expanding a notes thread that contains a large number of replies (e.g., 25+), the list of replies extends beyond the visible viewport of the sidebar. After clicking "25 more replies", users can scroll down to view the full thread.

When the user clicks the tab action that reveals the "Add new reply" button, and then clicks "Add new reply", focus correctly moves to the reply textbox. However, the viewport does not scroll to the location of the focused input.

As a result:

• The reply textbox receives focus, but remains outside the visible area.
• The UI visually stays near the top of the thread.
• Users cannot see where focus has moved, leading to confusion.
• Users must manually scroll to locate the reply textbox.

Step-by-step reproduction instructions

1. Open a post with notes threads enabled.
2. Expand a notes thread with many replies (e.g., 25+).
3. Click "25 more replies" to reveal all replies.
4. Click the tab that reveals the "Add new reply" button.
5. Click "Add new reply".
6. Observe that focus goes to the reply textbox, but the viewport does not scroll to it.

Expected Behavior

• When focus moves to the reply textbox, the viewport should automatically scroll so the textbox is brought into view.
• The UI should clearly show the active input to maintain accessibility and user context.
• No manual scrolling should be required to locate the focused field.

Screenshots, screen recording, code snippet

REC-20251125130400.mp4

Environment info

• WordPress version (6.9-RC2)
• Gutenberg Version 22.1.2
• MacBook Pro
• Chrome Version 142.0.7444.176

Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes

Please confirm which theme type you used for testing.

• Block
• Classic
• Hybrid (e.g. classic with theme.json)
• Not sure