Remote Build does not work for Python 3.14 Apps on Flex

[hallvictoria]

Issue Summary:

Any deployment mechanism using remote build in the backend that targets a 3.14 Flex app will fail.

Examples include:

• VSCode Extension: deployments may timeout
• Core Tools (func azure functionapp publish): deployments fail with Platform 'python' version '3.14' is unsupported
• GitHub Actions

Mitigations / Workarounds:

Deployments to a 3.14 Flex app need to include pre-built dependencies.

You can build the correct package using

• func pack --build-native-deps: this requires Docker running (eg: Docker Desktop), and it builds function app locally using an image that matches the environment used in Azure. When enabled, Core Tools starts a Docker container, builds the app inside that container, and creates a ZIP file with all dependencies restored in .python_packages.
• Azure DevOps, with PythonVersion set to 3.14 and the pool set to ubuntu
• GitHub Actions
• Docker, targeting the image 4-python3.14-appservice

You can deploy the package with remote build disabled:

• az functionapp deployment source config-zip --src <zip> --build-remote false Ref
• func azure functionapp publish <app name> --no-build Ref
• GitHub Actions, setting remote build to false Ref

ETA for support

We are currently targeting December - January for this scenario to be supported.