Can I sand up to an edge containing lead paint without having to strip the entire staircase, hallway and landing?

[questionsquestions1]

Help - Can anyone explain how to avoid stripping a ridiculous amount of paint?

I'm aiming to have a stair runner with wooden sections along the edges of each step.

The paint on the steps is new enough to contain no lead. However the adjoining wall sections on either side do have lead paint in amongst the layers.

To remove the paint from the stairs I'll inevitably remove a little of the paint from the adjoining wall sections. Also when sanding down the steps I'll again come into contact with the adjoining wall sections. I'm assuming that means I'll have to safely strip at least some of the adjoining wall sections? e.g. a cm or two where the step meets the wall.

My concern is that once I remove a few cm of the section with lead paint, I'll then be left with a messy join that you'd normally sand down and repaint.... BUT I can't sand it down as that join will contain lead paint. In fact, where ever I strip up to I'll be left with a messy join.

Is there any way around this without having to strip the entire stair case, hallway and landing? e.g. cover the messy join with some kind of filler?

unless I'm misunderstanding....
I'd just sand the treads and risers up to the change in plane with the lead paint where the side pieces are, being careful where they join- i.e., not use a block on the edge, just the paper flat. If there are any bits on the lead-containing bit that you want to repaint that aren't flat (I assume you mean to repaint those bits?), use a filler that can be used thin, like the Mangers lightweight deep crack filler, to level the surface, then undercoat and topcoat.
Of course you do need to be careful about lead. But lead paint dried in oil is not going to kill you if you are careful not to make airborne dust out of it. Wear a mask when you are sanding close to the lead bits, and if you do just catch it a bit with the sandpaper wipe up any dust with a wet paper towel so it doesn't get airborne. You could try putting masking tape on the lead bits on the edge where you might 'catch it' with the sandpaper, though you may have to put a few layers on so as not to sand it off.
TBH I'd paint alongside the carpet runner too, just sanding enough to make it smooth, rather than stripping it back to wood, which is a big job. I'm thinking of doing that to our stairs when we replace the current edge-to-edge carpet. But that's a question of individual taste, of course.

Can't you leave the white paint on the stairs too and put the runner on top. It might look odd to have wood on the step and white on the rest of the bannister and skirting.