containerapp update removes existing scale rules

[epDugas]

Describe the bug

Containerapp with kind = functionapp.
Scale triggers are automatically handled by the function host.
When issuing command:

 az containerapp update \
            --name somename \
            --resource-group somerg \
            --image someimageregistry:commithash

all existing scale rules are removed. This causes an issue, as the azure function host checks a hash on blob storage, and if the hash is the same, it doesn't perform a synctriggers, to re-create the rules.
I effectively end up with a non-functioning containerapp every time I deploy.
The only workaround I have found it to go and manually delete the blob that contains the hash, and restart the containerapp.

Related command

 az containerapp update \
            --name somename \
            --resource-group somerg \
            --image someimageregistry:commithash

Errors

No errors, output shows rules removed.

Issue script & Debug output

"scale": ***
"cooldownPeriod": 300,
"maxReplicas": 3,
"minReplicas": 0,
"pollingInterval": 30,
"rules": null
***,

Expected behavior

Expect existing scale rules to not be deleted on az containerapp update.

Environment Summary

azure-cli available on github runner (ubuntu-latest)

Additional context

No response

[yonzhan]

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

[microsoft-github-policy-service]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @howang-ms, @Greedygre.

[Greedygre]

Hi, What is the version you are using? @epDugas
You can get the version information with az version command.

And can you show the --debug logs? Thanks

[Greedygre]

From CLI side, for update command:
az containerapp update -n {} -g client.env_rg_eastus --image mcr.microsoft.com/azuredocs/containerapps-helloworld:latest --debug
it will send PATCH request payload like this:

cli.azure.cli.core.util: Request URL: 'https://management.azure.com/subscriptions/xxxx/resourceGroups/client.env_rg_eastus/providers/Microsoft.App/containerApps/test-app?api-version=2025-10-02-preview'
cli.azure.cli.core.util: Request method: 'PATCH'
cli.azure.cli.core.util: Request body:
cli.azure.cli.core.util: {"properties": {"template": {"containers": [{"image": "mcr.microsoft.com/azuredocs/containerapps-helloworld:latest", "imageType": "ContainerImage", "name": "nginx", "command": ["npm", "start"], "env": [{"name": "HTTP_PORT", "value": "80"}], "resources": {"cpu": 0.5, "memory": "1Gi", "ephemeralStorage": "2Gi"}}], "revisionSuffix": null}}}

It will not touch template.scale part. So if it remove all scale rules, it might be backend issue or logic.

[khushishah513]

Hi @epDugas, we were not able to reproduce this issue on our end. To investigate further, we’ll need additional details from you. Please open a support ticket for Azure Container Apps and include all the required information. Thank you. This will help the engineering team analyze the backend behavior and provide a resolution. Thanks!