[BUG] Red screen / Assertion failed in Default Native BottomNavigationBar after Flutter 3.38.5 (since Feb 3, 2026)

[marcosskin]

Can we access your project?

• I give permission for members of the FlutterFlow team to access and test my project for the sole purpose of investigating this issue.

Current Behavior

Since the Flutter update to version 3.38.5 on February 3, 2026, the Test Mode crashes with a red screen (Assertion failed in bottom_navigation_bar.dart:1180) whenever the Default/Native Bottom Navigation Bar is enabled.

Important details:

• When running Test Mode while logged OUT of my account: The app opens the login screen normally.
• After logging in: The red screen (wall of bugs) appears immediately.
• When running Test Mode while already logged IN: It goes straight to the red screen.

The relevant error-causing widget is BottomNavigationBar.
Google and Floating navigation bars work perfectly, but I specifically want to keep the native one because the others break my entire app layout and design consistency.

Expected Behavior

The Default/Native Bottom Navigation Bar should work normally in Test Mode, exactly as it did before the Flutter 3.38.5 update.

Steps to Reproduce

1. Open any project that uses Bottom Navigation Bar set to "Flutter Default" / Native style.
2. Run Test Mode:
   • Option A (logged out): Login screen appears normally → after successful login → red screen.
   • Option B (logged in session): Red screen appears immediately.
3. The crash happens only with the native nav bar.

I have already tested:

• Disabling the nav bar → works
• Switching to Google or Floating → works.

Reproducible from Blank

• The steps to reproduce above start from a blank project.

Bug Report Code (Required)

ITFXzcmAsIxNxNhE0Lr9KsAxo2UwGUwbUOc7j9VEGAsjCePnE+0Mf+POZRNWYuqHSnNmIEyJjT4JptLVvYXPLcI5HxyaRoBJwZdxUxDvWjilVr2VEZDpQHBfN+RVGki41qawniJ7CLJfR3w87DuuDe6ub3qCf9qOYwx5e6fDbOY=

Visual documentation

Environment

- FlutterFlow version: v6.5.31
- Platform: Web and Windows
- Browser name and version: Chrome 145.0.7632.117 and Edge 145.0.3800.70
- Operating system and version affected: Windows 11 Home 25H2 26200.7840

Additional Information

This bug is completely blocking my ability to test and deploy the app. I am losing development time every day. The native nav bar is critical for my app's clean design – Google style looks bad and Floating takes unnecessary space. Please prioritize this as it's a regression from the recent Flutter update.
Important update: After submitting this issue, I pinned the FlutterFlow version back to v6.4 and the problem disappears completely. The Default/Native Bottom Navigation Bar works perfectly again in Test Mode (no red screen, no assertion failed).

This confirms it's a regression introduced after FlutterFlow v6.4 (with the forced Flutter 3.38.5 update on Feb 3, 2026). In the latest FlutterFlow version the bug happens every time, but pinning to v6.4 is a 100% reliable workaround for now.