What must chimney flashing do at the exterior openings of windows and doors?

Chimney flashing is essential for preventing water intrusion around the junctions where a chimney meets the roof. At the exterior openings of windows and doors, the flashing must extend to the surface of the exterior wall finish. This ensures that any water running down the wall or chimney is directed away from the vulnerable areas where moisture can enter the structure. Properly installed flashing forms a barrier that channels water away, thereby protecting the integrity of the building envelope and minimizing the risk of water damage inside.

The other choices do not align with the primary function of chimney flashing at openings. While extending to the roof edge may be relevant for roof installations, it does not address the key requirement at windows and doors. Similarly, being covered with paint or being flexible and movable does not pertain to the essential goal of ensuring effective water management around those critical junctions.