Regression introduced in #12296 (1e9837ae). The refactor replaced the original two-part guard:

// OLD — checked busy OR time
if (_lastTask is not null && (_busy || ShouldWait()))
    return _lastTask;

with a single condition that only checks the interval when the task is still running:

// NEW — only checks time when task is incomplete
if (_currentTask is not null &&
    !_currentTask.IsCompleted &&
    timeSinceLastExecution < _interval)
    return _currentTask;

Problem

When the action completes synchronously, IsCompleted is already true on the next call.
The completed task gets cleared and a new execution starts unconditionally, the time check is never reached.

Fix

Check the interval regardless of task completion state. Faulted tasks still allow immediate retry:

if (timeSinceLastExecution < _interval &&
    _currentTask is not null &&
    !_currentTask.IsFaulted)
{
    return _currentTask.IsCompleted
        ? Task.CompletedTask
        : _currentTask;
}

Why tests didn’t catch it

• slow async actions (Task.Delay) that keep the task running, or
• real delays between calls that exceed the interval.

No test covered the real MudColorPicker scenario: a synchronous action called rapidly within the interval.

Checklist:

• I've read the contribution guidelines
• My code follows the style of this project
• I've added or updated relevant unit tests