The diff corrects a logical bug in `embed_youtube` within `src/snek/system/template.py` where the `and` operator had higher precedence than `or`, causing the condition to match links starting with "https://www.you" only when `v=` was present, but also matching any link with `si=` regardless of domain. By wrapping the two `or` conditions in parentheses, the fix ensures both `v=` and `si=` parameters are only checked against youtube links.