For about six months, my training partner worked late
We both got headlamps. The glare bothered me until I got a baseball cap and put the lamp over the brim, which eliminated the glare. You will wamt one with a short brim so it doesn't block too much light going down towards the trail right in front of you.
I was running trails, about half single track, on foggy nights with a cheao generic from china headlamp. Get an LED one wiht lime fifteen individual LEDs so that it is bright, but lasts like 200 miles of running on one set of batteries.
You probably won't be able to see well enough to hammer our five flat paced tempos on rough single track, at least in my experience, but solid paced runs should be fine.