I will preface this by stating that I am new at installing hardwood floors. I am currently installing bamboo hardwood floors using nail installation on two second floor bedrooms separated by a hallway. A set of stairs from the first floor joins the hallway at approximately the midpoint. I understand how to backfill the adjacent bedroom, but how do I backfill to the stairs? On the stairs, I am installing planks with stair nosing. I can provide pictures if needed. Thanks for any help in advance.

On your 1st run down the hall, have you taken into your layout figuring, a full plank at the top step , where it meets the nosing ?
Usually I will square the top step to the hall, start at that location , and run down the hall, (when possible). Sounds like that's not the way it's going in.

Ditto.I would also start in the hallway off the stairnose. then the bedrooms. Otherwise you migt end up with a small sliver at the noseing.

Thanks for the replies. You're right that I haven't squared a full plank at the top of the step. In retrospect, I would have started at the step and fill the bedrooms. I think i'm going to end up with a small sliver somewhere. I don't know if I should do it in one of the doorways or at the stair nosing. Any thoughts?

Avoid doing that in a doorway, total eyesore.
IMO there's no option but to head on toward the step, and find out where you stand at the nosing. Then we take it from there, ( there's a few tricks ).

Some times ya just gotta have some small cuts on the outside walls. Better that than one right in front of a stairway. Might be able to get away with a half a plank. Sometines I spend hours measuring to lay out a house.

Depending on the width of the narrow rip at the nosing, you may be able to get away with ripping some of the overhang off, ( on the bottom side of the nosing ). If this is a possibility, you can elimate a narrow rip of plank by pulling the nosing in toward the floor.