[bug]: Date sorting in Table Layout isn't working for sub-tasks

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

When sorting the work items list by Start date or Due date, the main tasks are ordered correctly, but the sub-tasks nested underneath them do not follow the chronological order.

As seen in the screenshots:

• First screenshot (ascending order): Sub-task 2.2 (May 13, 2026) appears before Sub-task 2.1 (May 12, 2026)
• Second screenshot (descending order): Sub-task 1.1 (May 5, 2026) appears before Sub-task 1.2 (May 6, 2026)

Expected behavior

Sub-tasks should also be sorted chronologically by their "Start date" or by their "Due date" within their respective parent task group when a date sort is applied.

Steps to reproduce

Go to the Work Items view.

1. Create a main task with multiple sub-tasks (same as the screenshots)
2. Assign different "Start dates" to the sub-tasks
3. Click on the Start date column header to apply an ascending sort.
4. Observe that the sub-tasks do not re-order themselves chronologically

Environment

Production

Browser

Google Chrome

Variant

Self-hosted

Version

Up-to-date docker images (makeplane/plane-*) pulled today (no version number shown anywhere)

Start in the Work Items view and trace how Start date and Due date sorting handles nested sub-tasks. Reproduce the issue with a parent task and dated sub-tasks, then verify that ascending and descending sorts place each child chronologically within its parent.