Desktop crash: Unable to load asset: "AssetManifest.json" on startup

[Dikshant005]

Describe the bug/problem

Launching the app crashes immediately with:
[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: Unable to load asset: "AssetManifest.json".
The asset does not exist or has empty data.

Steps to Reproduce the bug/problem

Clone repo
flutter pub get
Run on Windows desktop: flutter run -d windows
App throws the exception above and exits

Expected behavior

App launches normally.

Device Info (The device where you encountered this issue)

OS: Windows
Flutter channel/version: 3.38.5
Device: Windows (desktop)
Build mode: Debug (via flutter run)
Date: 2025-12-25

Flutter Doctor

Please run the flutter doctor -v command and provide the details below:

 flutter doctor -v
[✓] Flutter (Channel stable, 3.38.5, on Microsoft Windows [Version 10.0.26200.7462], locale en-IN) [698ms]
    • Flutter version 3.38.5 on channel stable at C:\Users\diksh\flutter projects\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision f6ff1529fd (2 weeks ago), 2025-12-11 11:50:07 -0500
    • Engine revision 1527ae0ec5
    • Dart version 3.10.4
    • DevTools version 2.51.1
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, cli-animations,
      enable-native-assets, omit-legacy-version-file, enable-lldb-debugging

[✓] Windows Version (11 Home Single Language 64-bit, 25H2, 2009) [1,859ms]

[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0) [4.5s]
    • Android SDK at C:\Users\diksh\AppData\Local\Android\Sdk
    • Emulator version 36.1.9.0 (build_id 13823996) (CL:N/A)
    • Platform android-36, build-tools 35.0.0
    • ANDROID_HOME = C:\Users\diksh\android-sdk
    • ANDROID_SDK_ROOT = C:\Users\diksh\android-sdk
    • Java binary at: C:\Program Files\Android\Android Studio\jbr\bin\java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 17.0.11+0--11852314)
    • All Android licenses accepted.

[✓] Chrome - develop for the web [263ms]
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[✓] Visual Studio - develop Windows apps (Visual Studio Build Tools 2019 16.11.52) [261ms]
    • Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools
    • Visual Studio Build Tools 2019 version 16.11.36602.28
    • Windows 10 SDK version 10.0.19041.0

[✓] Connected device (3 available) [366ms]
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.26200.7462]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 143.0.7499.109
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 143.0.3650.96

[✓] Network resources [1,881ms]
    • All expected network resources are available.

• No issues found!

[Dikshant005]

@animator
Here is my proposed fix
The crash happens because on newer Flutter desktop builds the asset bundle contains AssetManifest.bin (binary) but not AssetManifest.json. An older google_fonts code path was still trying to load AssetManifest.json, so rootBundle.loadString('AssetManifest.json') failed and the app crashed.
can i make a PR for this

[Aman071106]

@animator

Here is the complete issue analysis

I've investigated this crash and identified the root cause as a version incompatibility between the google_fonts package and newer versions of Flutter (specifically 3.25+ and the Master channel).

Findings

• Environment Difference:
  The crash occurs on Flutter 3.38.5 (Master channel) but is not reproducible on the current Stable channel (3.35.4) which we tested.

• Root Cause:
  Newer Flutter versions replaced AssetManifest.json with AssetManifest.bin for performance optimization.

• Dependency Issue:
  The project was using google_fonts: ^6.2.1, which still depends on AssetManifest.json.
  On the Master channel, this file is no longer generated, causing the runtime crash:
  Unable to load asset: "AssetManifest.json"

Evidence from google_fonts Changelog (pub.dev)

The google_fonts 6.3.0 changelog includes the line:

“Update AssetManifest to use the builtin Flutter API.”

• Link

This means:

• The package now uses Flutter’s official font loading APIs
• It relies on Flutter’s built-in asset manifest API instead of reading AssetManifest.json manually
• It fully supports the new AssetManifest.bin format introduced in Flutter 3.25+
• It follows the recommended, stable, future-proof way to load bundled fonts

Why this matters:
Flutter removed AssetManifest.json, and packages depending on it (like google_fonts < 6.3.0) started crashing.
The new APIs abstract this away so the package works across both old & new Flutter versions.

Resolution Applied

I have upgraded the dependency to google_fonts: ^6.3.3 in
packages/apidash_design_system/pubspec.yaml.
This ensures compatibility with future Flutter releases while remaining stable on current versions.

PR Status

A PR #990 with the fix is on the way.