<!-- PLEASE ENSURE YOU REVIEW THE CONTENT OF EACH ISSUE CAREFULLY, INCLUDING SUBSEQUENT COMMENTS BY YOURSELF OR OTHERS. --> <!-- IN PARTICULAR PLEASE ENSURE THAT SENSITIVE OR INAPPROPRIATE INFORMATION IS NOT UPLOADED --> #### Description: As seen below. Arc before, as provided to the method: <img width="1057" height="754" alt="Image" src="https://github.com/user-attachments/assets/ad347a0a-246f-4ccf-8ef4-be65552b1c74" /> After, with extend method causing failure: <img width="1057" height="751" alt="Image" src="https://github.com/user-attachments/assets/566f1378-795d-4479-b666-80ac213cb3be" /> #### Steps to reproduce: Run extend on an arc where the start angle is not 0, and the CS Z Vector is negative.