@MaxonL16591286 To customize the error message when a case fails to open due to an ABAC policy in Pega, you can’t directly modify the Open activity since it’s marked as Final and can’t be overridden. However, you can create a custom activity to wrap around the Open activity, where you can check for specific error conditions like the ABAC policy failure and set a custom error message. Alternatively, you can adjust the Param.ErrorMessage in the activity by adding a condition to check for an ABAC policy failure and then setting your custom message instead of the default one. Another option is to handle the error in a flow action by checking if the case failed to open and displaying a custom error message. You could also create a post-processing activity that runs after the Open activity to check for failure and update the error message accordingly. Finally, if the ABAC policy itself is causing the issue, you might consider customizing the error messages within the policy configuration.