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Remote Build does not work for Python 3.14 Apps on Flex #1801
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on Nov 18, 2025 Is there any update on this? I saw the initial timeline was January / February?
The fix has been deployed to all regions, so remote build for Python 3.14 is now fully supported.
Still getting this message:
[2026-07-08T23:36:08.337Z] Starting the function app deployment... Remote build for Python 3.14 is not yet supported for Flex. Please refer to aka.ms/py314-remote-build-flex for more details. [2026-07-08T23:36:08.340Z] Creating archive for current directory...Just drop the runtime stack of the Function app to Python 3.13, that seems to fix it
EDIT: My suggestion was only intended as a temporary workaround, not a long-term solution. It was aimed for those who needed deployments working immediately and whose specifications did not depend on Python 3.14-specific features. I appreciate that this thread is specifically about Python 3.14 support, and I apologise for presenting the downgrade as a fix rather than a temporary workaround.Reacted by J Rob GantStill getting this message:
[2026-07-08T23:36:08.337Z] Starting the function app deployment... Remote build for Python 3.14 is not yet supported for Flex. Please refer to aka.ms/py314-remote-build-flex for more details. [2026-07-08T23:36:08.340Z] Creating archive for current directory...I can confirm that the last time I deployed that I also am continuing to receive this error. Maybe it didn't make it through? For now, we just have instructions in our deployment to run the following (we use uv for package management):
uv sync uv pip install pip uv run func azure functionapp publish "<FUNCTION_APP_NAME>" --build local
I don't agree that downgrading to 3.13 is an acceptable solution at this point - this runtime has been released since last October and I'm sure there's a chance you have dependencies or implementations that depend on 3.14.
Anyone else here continuing to see the "unsupported" behavior? Any chance that J Rob Gant (@rgant) or myself just need to update something on our side?
Reacted by J Rob GantI forgot to mention that despite the warning message build was successful and my Azure Functions are all running python 3.14 successfully after deploys last night.
Hey all, this is a non-blocking warning from Core Tools. Your deployments will work successfully.
Apologies for any confusion - this warning has been removed in Azure/azure-functions-core-tools#5375 and will be released in the next version of Core Tools (4.13.0)
Reacted by Oliver Winhammar and J Rob Gant
Issue Summary:
Any deployment mechanism using remote build in the backend that targets a 3.14 Flex app will fail.
Examples include:
func azure functionapp publish): deployments fail withPlatform 'python' version '3.14' is unsupportedaz functionapp deployment source config-zip): deployments fail withPlatform 'python' version '3.14' is unsupportedMitigations / 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.4-python3.14-appserviceYou can deploy the package with remote build disabled:
az functionapp deployment source config-zip --src <zip> --build-remote falseReffunc azure functionapp publish <app name> --no-buildRefETA for support
We are currently targeting January - February for this scenario to be supported.
Example Error Messages: