@Mint tile Minneapolis Scribe fitting, eh? Interesting. Sounds like a great solution. What do you mean by "while also meeting run"?

run, rise, nosing as well.

Hmm. You lost me. Initially I thought you meant to scribe a filler piece. Are you saying to scribe a whole new riser? @Mint tile Minneapolis

yes each tread and each riser gets custom scribed to fit . while that is being done one must also be accounting for run rise and nosing being in spec

Any reason why that gap cannot just be caulked?

No reason at all why it can't be caulked.

It looks like right now your riser is installed first and your tread butted up to it. When I did my stairs I tucked the tread under the riser during installation which meant a much smaller gap. It's been 3 years and there is little movement or need or need for caulking.

What about veneer strips to disguise the gap? The gap could be filled and sealed, and then matching wood strips applied on top.

To my knowledge, this has never been done (or atleast not advertised). Wouldn't that work? It would definitely look better than caulk or shoe molding...

When we did our stairs we installed the tread, followed by the riser so there were no gaps. Started at the bottom of the stairs and worked our way up. Start at bottom with first riser, then tread. Repeat x12-14!

is there any way to fasten the riser to the tread from the back side and pull the gap together?

@c_ z - no, we don't have access to the underside. I understand fastening the riser to the tread is the optimal solution, but we're too far in. So we're just looking for the most professional + sustainable option that keeps us moving fwd. Does anyone see an issue with using the 1/16" oak strips and fastening those to BOTH the tread and the riser as shown in the above pic?

I personally think it looks fine. If this is your own home and you like it, go for it. If not maybe you should ask the homeowner. If the riser is getting painted calking it would probably be fine too...

It's probably too late for this too, but you could maybe shim behind the riser to straighten it...