When required to replace seething?

[Tom Crews]

I had this show up in an inspection. The roof seething appears black due to a roof leak. At what point does the seething required to be replaced?

[Jerry Peck]

Did you poke at it with your finger, screw driver, or a probe? If so, what did you find?

[Jack Feldmann]

What Jerry said!
I would be seething too if I forgot to probe the sheathing for damage.

[Jerry Peck]

Curious as to what is on the roof at that spot, to the left of the vent stack - a chimney structure or similar?

If so, the side of it may also be affected, as well as that truss top chord.