Issue Summary

When a workflow transition is configured with a native Jira validator (e.g., "Field Required" or "Validate a field") targeting the Parent field (or potentially others), the validator fails to block the transition if the field is updated/cleared directly on the Transition Screen.

The validator appears to evaluate the issue's state before the transition screen updates are applied, rather than validating the new values provided during the transition.

Note: This is reproducible in the New/Modern Transition Experience (this is not reproducible in the Old Transition Screen experience - https://community.atlassian.com/t5/Jira-articles/Now-GA-try-the-new-issue-transition-experience-in-Jira/ba-p/2734436 

Steps to Reproduce

1. Ensure the New Modern Transition Screen experience is enabled for the site
2. Configure a workflow transition with a validator (e.g., Field Required) for the Parent field.
3. Take a work item that currently has a Parent value.
4. Trigger the transition to open the transition screen.
5. On the transition screen, clear the Parent field.
6. Click the transition button (e.g., "Update" or "Done").

Expected Results

The validator should identify that the Parent field is now empty and block the transition with an error message.

Actual Results

The transition succeeds. The validator treats the field as if it still contains the pre-transition value.

Workaround

Currently there is no known workaround for this behaviour. A workaround will be added here when available