ClickableSlider previously accepted the mouse press without forwarding to QSlider, so the drag mechanism never started. Now setSliderPosition is called first (jumping the handle to the click point) and the event is always forwarded so Qt enters normal drag mode. mouseMoveEvent is also overridden to keep snapping to the cursor during a drag. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>