az functionapp deployment source config-zip to flex consumption function apps inconsistenly fails

[tekking]

Describe the bug

Please let me know (or remove/move this issue) if this is not the correct spot for this issue (I'm not sure if the behavior comes from az cli itself, or the kudu function host).
We're currently moving from (linux) consumption apps to using flex consumption apps. While deploying our app source (C#) to our function apps with az cli, we're seeing inconsistent failures, reporting deployment was partially succesful, but with no clear failure in the included logs in command line.

Function app itself (in Azure) shows the deployment in a failed state in deployment center with Message like '[KuduSpecializer] Kudu has been restarted after package deployed for deployment 034b9835-723a-4c45-a879-a921f13df306. Kudu Restart Count: 1.'. While I couldn't find much information on this, the single resource I found (at https://learn.microsoft.com/en-us/answers/questions/5818081/azure-function-deployment) implies that the message is a transient restart state, and polling proces should wait longer before polling again.

Is it possible the cli is getting back this reply and ending/cancelling the deployment process at that point, or is the failure intended behavior (and possibly unrelated to above message)?

Related command

az functionapp deployment source config-zip -g $ResourceGroupName
-n $FunctionAppName --src $PackagePath
--debug

Errors

In CLI:
ERROR: Deployment was partially successful. These are the deployment logs:
[{"log_time": "2026-04-14T13:48:01.034239Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "Starting deployment pipeline.", "type": 0}, {"log_time": "2026-04-14T13:48:01.0345968Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-SourcePackageUriDownloadStep] Skipping download. Zip package is present at /tmp/zipdeploy/034b9835-723a-4c45-a879-a921f13df306.zip", "type": 0}, {"log_time": "2026-04-14T13:48:01.0347716Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ValidationStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.0477203Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ValidationStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.0480149Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ExtractZipStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1456618Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ExtractZipStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1459906Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ContentValidationStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1462036Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ContentValidationStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1463926Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PreBuildValidationStep] Skipping pre-build validation (remotebuild = false).", "type": 0}, {"log_time": "2026-04-14T13:48:01.1465806Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-OryxBuildStep] Skipping oryx build (remotebuild = false).", "type": 0}, {"log_time": "2026-04-14T13:48:01.1467617Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PostBuildValidationStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1469602Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PostBuildValidationStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1471881Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PackageZipStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.677484Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PackageZipStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.6780361Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-UploadPackageStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.9159076Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-UploadPackageStep] completed. Uploaded package to storage successfully.", "type": 0}, {"log_time": "2026-04-14T13:48:02.0999034Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-RemoveWorkersStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:02.1552036Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-RemoveWorkersStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:02.1555245Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-SyncTriggerStep] starting.", "type": 0}]

In Function deployment center:

[KuduSpecializer] Kudu has been restarted after package deployed for deployment 034b9835-723a-4c45-a879-a921f13df306. Kudu Restart Count: 1.

Issue script & Debug output

Logs from azure task with debug flag passed to command

WARNING: Getting scm site credentials for zip deployment
WARNING: Starting zip deployment. This operation can take a while to complete ...
WARNING: Deployment endpoint responded with status code 202 for deployment id "034b9835-723a-4c45-a879-a921f13df306"
ERROR: Deployment was partially successful. These are the deployment logs:
[{"log_time": "2026-04-14T13:48:01.034239Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "Starting deployment pipeline.", "type": 0}, {"log_time": "2026-04-14T13:48:01.0345968Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-SourcePackageUriDownloadStep] Skipping download. Zip package is present at /tmp/zipdeploy/034b9835-723a-4c45-a879-a921f13df306.zip", "type": 0}, {"log_time": "2026-04-14T13:48:01.0347716Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ValidationStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.0477203Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ValidationStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.0480149Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ExtractZipStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1456618Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ExtractZipStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1459906Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ContentValidationStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1462036Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-ContentValidationStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1463926Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PreBuildValidationStep] Skipping pre-build validation (remotebuild = false).", "type": 0}, {"log_time": "2026-04-14T13:48:01.1465806Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-OryxBuildStep] Skipping oryx build (remotebuild = false).", "type": 0}, {"log_time": "2026-04-14T13:48:01.1467617Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PostBuildValidationStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1469602Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PostBuildValidationStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.1471881Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PackageZipStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.677484Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-PackageZipStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:01.6780361Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-UploadPackageStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:01.9159076Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-UploadPackageStep] completed. Uploaded package to storage successfully.", "type": 0}, {"log_time": "2026-04-14T13:48:02.0999034Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-RemoveWorkersStep] starting.", "type": 0}, {"log_time": "2026-04-14T13:48:02.1552036Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-RemoveWorkersStep] completed.", "type": 0}, {"log_time": "2026-04-14T13:48:02.1555245Z", "id": "034b9835-723a-4c45-a879-a921f13df306", "message": "[Kudu-SyncTriggerStep] starting.", "type": 0}]

Expected behavior

From the earlier linked QA I think the az cli might have to wait for the restart to finish before polling status again (instead of failing deployment).

Environment Summary

{
"azure-cli": "2.85.0",
"azure-cli-core": "2.85.0",
"azure-cli-telemetry": "1.1.0",
"extensions": {
"azure-devops": "1.0.2"
}
}

(Run from AzureCli@2 task in Azure DevOps)

Additional context

No response

[microsoft-github-policy-service]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @kamperiadis, @amamounelsayed, @khkh-ms, @act-observability-squad.

[yonzhan]

Thank you for opening this issue, we will look into it.

[microsoft-github-policy-service]

🔔 Routing this issue to @act-observability-squad.

[microsoft-github-policy-service]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @kamperiadis, @amamounelsayed, @khkh-ms, @act-observability-squad.