`az deployment group create` sends invalid JSON as deployment payload

[kamil-mrzyglod]

Describe the bug

When using the az deployment group command I expect, that the API called under the hood (https://learn.microsoft.com/en-us/rest/api/resources/deployments/create-or-update?view=rest-resources-2025-04-01&tabs=HTTP) will receive a proper payload as described in the documentation, for instance:

PUT https://management.azure.com/subscriptions/00000000-0000-0000-0000-000000000001/resourcegroups/my-resource-group/providers/Microsoft.Resources/deployments/my-deployment?api-version=2025-04-01

{
  "properties": {
    "template": {
      "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
      "contentVersion": "1.0.0.0",
      "parameters": {
        "inputObj": {
          "type": "object"
        }
      },
      "resources": [],
      "outputs": {
        "inputObj": {
          "type": "object",
          "value": "[parameters('inputObj')]"
        }
      }
    },
    "parameters": {
      "inputObj": {
        "expression": "[createObject('foo', externalInputs('fooValue'))]"
      }
    },
    "externalInputDefinitions": {
      "fooValue": {
        "kind": "sys.envVar",
        "config": "FOO_VALUE"
      }
    },
    "externalInputs": {
      "fooValue": {
        "value": "baz"
      }
    },
    "mode": "Incremental"
  }
}

However, instead, it gets an invalid JSON as the template property isn't correctly serialized:

{"properties": {"parameters": {}, "mode": "Incremental", template:{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": []
}}}

Note that it happens only for a custom cloud environment created.

Related command

az deployment group create -n test-deployment --template-file templates/empty-deployment.json -g rg-test

Errors

The command failed with an unexpected error. Here is the traceback:
The content for this response was already consumed
Traceback (most recent call last):
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/init.py", line 703, in _run_job
result = cmd_copy(params)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/init.py", line 336, in call
return self.handler(*args, **kwargs)
~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/command_operation.py", line 120, in handler
return op(**command_args)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/command_modules/resource/custom.py", line 602, in deploy_arm_template_at_resource_group
return _deploy_arm_template_at_resource_group(cmd=cmd,
resource_group_name=resource_group_name,
...<4 lines>...
no_prompt=no_prompt, template_spec=template_spec, query_string=query_string,
validation_level=validation_level)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/command_modules/resource/custom.py", line 661, in _deploy_arm_template_at_resource_group
return sdk_no_wait(no_wait, mgmt_client.begin_create_or_update, resource_group_name, deployment_name, deployment)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/util.py", line 759, in sdk_no_wait
return func(*args, **kwargs)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/core/tracing/decorator.py", line 119, in wrapper_use_tracer
return func(*args, **kwargs)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/mgmt/resource/deployments/operations/_deployments_operations.py", line 5411, in begin_create_or_update
raw_result = self._create_or_update_initial(
resource_group_name=resource_group_name,
...<7 lines>...
**kwargs
)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/mgmt/resource/deployments/operations/_deployments_operations.py", line 5304, in _create_or_update_initial
raise HttpResponseError(response=response, error_format=ARMErrorFormat)
azure.core.exceptions.HttpResponseError: (InternalError) Internal error: 't' is an invalid start of a property name. Expected a '"'. Path: $.properties | LineNumber: 0 | BytePositionInLine: 57.
Code: InternalError
Message: Internal error: 't' is an invalid start of a property name. Expected a '"'. Path: $.properties | LineNumber: 0 | BytePositionInLine: 57.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/arm.py", line 109, in handle_template_based_exception
raise CLIError(ex.inner_exception.error.message)
^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'error'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/knack/cli.py", line 233, in invoke
cmd_result = self.invocation.execute(args)
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/init.py", line 666, in execute
raise ex
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/init.py", line 734, in _run_jobs_serially
results.append(self._run_job(expanded_arg, cmd_copy))
~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/init.py", line 726, in _run_job
return cmd_copy.exception_handler(ex)
~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/azure/cli/core/commands/arm.py", line 112, in handle_template_based_exception
raise_subdivision_deployment_error(ex.response.internal_response.text, ex.error.code if ex.error else None)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/requests/models.py", line 926, in text
if not self.content:
^^^^^^^^^^^^
File "/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/lib/python3.13/site-packages/requests/models.py", line 897, in content
raise RuntimeError("The content for this response was already consumed")
RuntimeError: The content for this response was already consumed

Issue script & Debug output

debug.log

Expected behavior

The provided template is correctly serialized and the command does not fail.

Environment Summary

azure-cli 2.78.0

core 2.78.0
telemetry 1.1.0

Extensions:
application-insights 1.2.3

Dependencies:
msal 1.34.0b1
azure-mgmt-resource 23.3.0

Python location '/opt/homebrew/Cellar/azure-cli/2.78.0/libexec/bin/python'
Config directory '/Users/kamilmrzyglod/.azure'
Extensions directory '/Users/kamilmrzyglod/.azure/cliextensions'

Python (Darwin) 3.13.9 (main, Oct 14 2025, 13:52:31) [Clang 17.0.0 (clang-1700.3.19.1)]

Legal docs and information: aka.ms/AzureCliLegal

Your CLI is up-to-date.

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 @Azure/deployments-owners.