In OXC, they always stop when they see a new enemy.
In OXCE:
1. when moving normally they stop (same as OXC)
2. when running (ctrl+move), they don't stop (different from OXC)... this was introduced as a balance improvement (trade speed for not being able to react to surprise quick enough)
3. when moving using shift+move, they also don't stop (new feature not available in OXC)
Point #2 is not configurable at the moment.
I'll add a config in the next version.
PS: in vanilla, running was not possible at all