[hybrid_eg]

If you have access to under the stair case, you could remove drywall which will give you access to framing to feed the wires into corner of each step. But then the issue might be design of your actual tread.. i.e. you would need to have square edge cantilever type tread edge so that you can screw in the aluminum extrusion from the bottom (channel which holds led strip).. channel will be visible of course but they are relatively low profile and cantilever of tread should hide it pretty well.. most common treads (non custom job) are round nose, i.e. nosing comes as option from floor manufacturer.. If this is your case, depending on nosing that you have you may be able to router them.. its hard to tell as i dont know how much cantilever you have and you dont want to reduce too much material on the edge where people typically step on due to obvious safety reasons.

To make it seamless its best done when designing staircase from scratch..