Hmm...  Looks like a unified diff to me...
The text leading up to this was:
--------------------------
|diff -up a/st.c b/st.c
|--- a/st.c	2026-02-12 14:56:55.248311919 -0300
|+++ b/st.c	2026-02-12 14:36:36.827197795 -0300
--------------------------
Patching file st.c using Plan A...
Hunk #1 failed at 2513.
1 out of 1 hunks failed
done