bug: Windows build fails silently in Flet 1.0.5 packaging stage and produces incomplete Python runtime (missing dependencies such as certifi) #7029

Duplicate Check

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

Describe the bug

Environment:

OS:
Windows 11 25H2
Build 10.0.26200.9711

Python:
3.14.7

Flet:
1.0.5

flet-cli:
1.0.5

Flutter:
3.44.8 (stable)

Dart:
3.12.2

Visual Studio:
2022 Community 17.14.33

Android SDK:
36.1.0

Note: flutter doctor reports: No issues found.

Summary

flet build windows --python-version 3.14 -v fails with:

Error building Flet app - see the log of failed command above.

However, no failed command, exception, or traceback is shown.

The generated Flutter project builds successfully with:

flutter build windows -v

...and exits successfully.

The generated executable launches, but fails immediately with:

ModuleNotFoundError: No module named 'certifi'

...indicating that Python dependencies were never installed into the packaged runtime.

Code sample

[Paste your code here]

To reproduce

Project

Python extension package:

TOML:

[project]
requires-python = ">=3.14,<3.15"

dependencies = [
"flet==1.0.5",
"httpx==0.28.1",
"certifi==2026.10.23",
]

Example application:

TOML:

dependencies = [
"test-extension-26",
"flet==1.0.5",
]

Flutter package:

YAML:

environment:
sdk: ">=3.12.2 <3.13.0"
flutter: ">=3.44.8 <3.45.0"

dependencies:
flutter:
sdk: flutter

flet: 1.0.5
image_painter: 0.7.1
fleather: 1.28.0
parchment: 1.27.0
display_metrics: 2.6.0

Build Command:

flet build windows --python-version 3.14 -v

Expected behavior

1. Build completes successfully, installing all declared Python dependencies into the bundled runtime.

...or:

2. Build fails with the underlying exception and full traceback.

Actual Behavior:

Build fails with a generic message:

Error building Flet app - see the log of failed command above.

...while:

1. No actual failing command is displayed,
2. No traceback is displayed,
3. Generated Flutter project builds successfully,
4. Bundled runtime is missing required dependencies.

Build output reaches:

_Running package command
Python 3.14 (CPython 3.14.7)

Compiling Python sources in a temp directory_

...and later:

flutter doctor
...
No issues found!

...but then ends with:

Error building Flet app - see the log of failed command above.

No actual failed command is shown.

Screenshots / Videos

Operating System

Windows

Operating system details

Windows 11

Flet version

1.0.5

Regression

No, it isn't

Suggestions

No response

Logs

build.log

[Paste your logs here]

Additional details

The generated Flutter project is fully created under:

build\flutter

...and can be built manually:

_cd build\flutter

flutter build windows -v_

Result:

Build succeeded.
0 Warning(s)
0 Error(s)

Packaged Runtime Missing Dependencies

Inside:

build\flutter\build\build_python_3.14.7\python

...the bundled runtime cannot import certifi:

python.exe -c "import certifi"

Output:

ModuleNotFoundError: No module named 'certifi'

Inspection of:

Lib\site-packages

...shows essentially only:

pip
pip-*.dist-info

...and none of the required runtime dependencies.

Expected packages such as:

certifi
httpx
oauthlib
repath
msgpack

...are absent.

Potentially Related Observation:

Verbose build output contains:

-r flet==1.0.5
-r test-extension-26 @ file:///C:/flutter/extension26
-r --no-cache-dir

The final entry appears suspicious:

-r --no-cache-dir

...as -r normally precedes a requirement specifier.

This may indicate malformed argument construction during the packaging step.