Help: Error 400 related to customfield

[Angel Salazar]

Hello, I am having error with my code and I can not find the solution, if you can help me or give me some recommendation I would appreciate it: The code basically what it does is to assign a “customer request type” by default depending on the type of issue selected when creating the issue when no customer request type is selected or the default value “No request type” is left. This is on the backend side not on the portal side.

Example: If I am creating an issue and I select Test incident as “issuetype” and in the customer request type field I select the default value “No request type” I want the customer request type field to be updated to “Testing-Test” when the issue is created.

The customField_10001 corresponds to the Customer Request Type field. It is a locked field that comes by default in Jira and is of type selection. I attach images for more clarity.

[Mercy]

The 400 error usually occurs because the Customer Request Type field (`customfield_10001`) cannot be set directly through the REST API or backend code—it’s a locked field managed internally by Jira Service Management. That field links issues to portal request types, and its value must correspond to a valid request type key (not the display name) that exists within the project’s service desk configuration. Jira only allows that field to be updated through the portal or by using the `serviceDeskId` and `requestTypeId` parameters in the [Create customer request API](