bug: Building APK leads to `'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte`

[datumbox]

Duplicate Check

• I have searched the opened issues and there are no duplicates

Describe the bug

Since earlier today, building an APK on Github Actions leads to 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte errors.

I am aware that no changes have happened on flet the last 3 days and I confirm that earlier in the morning the pipelines worked as expected. This is probably due to an upstream dependency from flet, but I thought to raise it here regardless to help investigate.

I confirmed two more things:

1. I restarted a GA run that was successful earlier today and it failed. This means it's not due a code-change on the downstream repo.
2. I've nuked all the caches, the problem persists.

Unfortunately I can't reproduce locally on my PC. I'm able to build without issues...

Here is the tail of the log from flet build apk --verbose on Github Actions:

(  ●   ) Installing JDK...
           JDK installed ✅                                                     
(  ●   ) Installing JDK...
           Android SDK installation found at /usr/local/lib/android/sdk         
(  ●   ) Installing Android SDK...
           Android SDK package "cmdline-tools;latest" is already installed      
(  ●   ) Installing Android SDK...
           Android SDK package "platform-tools" is already installed            
(  ●   ) Installing Android SDK...
           Android SDK package "platforms;android-35" is already installed      
(  ●   ) Installing Android SDK...
           Android SDK package "build-tools;34.0.0" is already installed        
(  ●   ) Installing Android SDK...
           Android SDK installed ✅                                             
(  ●   ) Installing Android SDK...
(●     ) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
(   ●  ) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
(    ● ) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
( ●    ) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
(  ●   ) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
(     ●) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
(  ●   ) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
( ●    ) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
(     ●) Creating app shell from gh:flet-dev/flet-build-template with ref 
"0.82.0"...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
( ●    ) Running Flutter doctor...
[18:19:26] Run subprocess: ['/home/runner/flutter/3.41.4/bin/flutter', 'doctor',
           '--no-version-check', '--suppress-analytics']                        
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
(   ●  ) Running Flutter doctor...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
(   ●  ) Running Flutter doctor...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
(●     ) Running Flutter doctor...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
(   ●  ) Running Flutter doctor...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
(    ● ) Running Flutter doctor...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
( ●    ) Running Flutter doctor...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
(   ●  ) Running Flutter doctor...
[18:19:46] Doctor summary (to see all details, run flutter doctor -v):          
           [✓] Flutter (Channel stable, 3.41.4, on Ubuntu 24.04.3 LTS           
           6.14.0-1017-azure, locale C.UTF-8)                                   
           [!] Android toolchain - develop for Android devices (Android SDK     
           version 36.1.0)                                                      
               ! Some Android licenses not accepted. To resolve this, run:      
           flutter doctor --android-licenses                                    
           [✓] Chrome - develop for the web                                     
           [✗] Linux toolchain - develop for Linux desktop                      
               ✗ GTK 3.0 development libraries are required for Linux           
           development.                                                         
                 They are likely available from your distribution (e.g.: apt    
           install libgtk-3-dev)                                                
               ! Unable to access driver information using 'eglinfo'.           
                 It is likely available from your distribution (e.g.: apt       
           install mesa-utils)                                                  
           [✓] Connected device (2 available)                                   
           [✓] Network resources                                                
                                                                                
           ! Doctor found issues in 2 categories.                               
                                                                                
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
(   ●  ) Running Flutter doctor...
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │
╰──────────────────────────────────────────────────────────────────────────────╯

Code sample

Sample Toml

[project]
name = "my_project"
version = "0.1.0"
description = ""
readme = "README.md"
requires-python = ">=3.13"
authors = [
    { name = "Anonymous", email = "anon@example.com" }
]
dependencies = [
    "flet>=0.82.0",
    "flet-audio>=0.82.0"
]

[build-system]
requires = ["setuptools>=61.0", "wheel"]
build-backend = "setuptools.build_meta"

[tool.flet]
org = "com.example"
product = "My Product"
company = "Example Corp"
copyright = ""

[tool.flet.app]
path = "src"
module = "main"

To reproduce

Build the APK using github actions

Expected behavior

No response

Screenshots / Videos

Captures

[Upload media here]

Operating System

Linux

Operating system details

ubuntu-latest

Flet version

0.82.0

Regression

Yes, it used to work in a previous Flet version (please specify the version in additional details)

Suggestions

No response

Logs

Logs

[Paste your logs here]

Additional details

No response

[zox47]

@ndonkoHenri same problem

[JogFeelingVI]

同样的问题

[23:59:41] Doctor summary (to see all details, run flutter doctor -v):          
           [✓] Flutter (Channel stable, 3.41.4, on Ubuntu 24.04.3 LTS           
           6.14.0-1017-azure, locale C.UTF-8)                                   
           [!] Android toolchain - develop for Android devices (Android SDK     
           version 36.1.0)                                                      
               ! Some Android licenses not accepted. To resolve this, run:      
           flutter doctor --android-licenses                                    
           [✓] Chrome - develop for the web                                     
           [✗] Linux toolchain - develop for Linux desktop                      
               ✗ GTK 3.0 development libraries are required for Linux           
           development.                                                         
                 They are likely available from your distribution (e.g.: apt    
           install libgtk-3-dev)                                                
               ! Unable to access driver information using 'eglinfo'.           
                 It is likely available from your distribution (e.g.: apt       
           install mesa-utils)                                                  
           [✓] Connected device (2 available)                                   
           [✓] Network resources                                                
                                                                                
           ! Doctor found issues in 2 categories.                               
                                                                                
╭──────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte       │

[ndonkoHenri]

Can confirm the issue. We will be looking into it.

[ndonkoHenri]

Its an upstream bug: binaryornot/binaryornot#642
Basically their recently released v0.5.0 misclassifies multiple .png files as text making cookiecutter (which we use for the flet-build-template) try utf-8 decode, hence fail. As fix, we need to pin to the version before 0.5.0, which is v0.4.4.

Please install it as temporary workaround: pip install "binaryornot<0.5"

Will open a PR so we constrain it in Flet deps directly.

[JogFeelingVI]

dependencies = [
  "flet>=0.82.0",
  "binaryornot==0.4.4",
  "requests",
]

The problem was solved by limiting it to 0.4.4. Thanks to ndonkoHenri

[hschneider]

The same error occurs when trying to build a macOS app:

$ flet build macos   
/usr/local/lib/python3.14/site-packages/watchdog/observers/__init__.py:68: UserWarning: Failed to import fsevents. Fall back to kqueue
  warnings.warn("Failed to import fsevents. Fall back to kqueue", stacklevel=1)
[20:29:43] Doctor summary (to see all details, run flutter doctor -v):                                        
           [!] Flutter (Channel stable, 3.41.4, on macOS 26.3.1 25D2128 darwin-arm64 (Rosetta), locale de-DE) 
               ! Warning: `flutter` on your path resolves to /Users/hschneider/flutter/bin/flutter, which is  
           not inside your current Flutter SDK checkout at /Users/hschneider/flutter/3.41.4. Consider adding  
           /Users/hschneider/flutter/3.41.4/bin to the front of your path.                                    
               ! Warning: `dart` on your path resolves to /Users/hschneider/flutter/bin/dart, which is not    
           inside your current Flutter SDK checkout at /Users/hschneider/flutter/3.41.4. Consider adding      
           /Users/hschneider/flutter/3.41.4/bin to the front of your path.                                    
           [!] Android toolchain - develop for Android devices (Android SDK version 36.1.0-rc1)               
               ! Some Android licenses not accepted. To resolve this, run: flutter doctor --android-licenses  
           [✓] Xcode - develop for iOS and macOS (Xcode 26.3)                                                 
           [✓] Chrome - develop for the web                                                                   
           [✓] Connected device (2 available)                                                                 
           [✓] Network resources                                                                              
                                                                                                              
           ! Doctor found issues in 2 categories.                                                             
                                                                                                              
╭────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ 'utf-8' codec can't decode byte 0x89 in position 0: invalid start byte                                     │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────╯