Why do you say it's not the installer? It looks to me as if he should have used a plumb line to be sure that it was straight. It because it is separate pieces that it doesn't go to the top?

Did you measure to have everything centered from the dimensions of the narrower treads? I think that would be the way to size the runner width for visual consistancy all the way up. If so, I’m not sure how this isn’t installer error.

I'm sorry, not a pro. It appears that the installer is installing crooked.... But why in the world did you take on the responsibility of measuring? When we've had flooring done, the measuring is free....

It looks like installer centered on bottom step and this is how it running. Maybe a narrower runner would work centered on top steps width 🤷🏻‍♀️

Because the steps “step in” only from the left side part-way up, this definitely isn’t the installer’s fault. I have no idea how to put a runner on those stairs since the stairs themselves will never be symmetrical. If you center at the top, it won’t be centered at the bottom. This site has it centered on the top and not centered at the bottom. You can take a look at see what you think. https://barclaystoneinteriors.com/design-101-stair-runners-need-know/

Thank you. I think maybe i need to have him center on the top? It's frustrating because I sent pictures and measurements to the flooring place. He should have come out to measure himself and make a recommendation. Here is the final product :(

Would it look better if narrower (this is 30") and centered at top?

You could do the runner in two sections, narrower centered up top and then a wider section centered on the lower, wider treads. Not sure why you had him finish the install rather than stop and get the carpet store people out to see it and come up with a plan.

Thanks, the carpet store guy said to have him finish since there were only 3 stairs left and they’d come out next week to find a solution. like the idea of doing in 2 sections.

Here is a similar stairway. They used a narrower runner and centered it above, ignoring the wider steps.

There is only one way to fix this and that is to fully carpet the upper stairs keeping to the left where my arrow is to show where you step juts out as well as to the right where again my arrow is where again your stair juts to the right. Follow these lines to the bottom which is centered between your posts. If the carpet store was out to measure this and do the layout they would have noticed this HOPEFULLY. If you did the measuring and ordering then you are stuck with a partial redo as this is the proper way to carpet these stairs. My image is crude but you get the idea.

Agree it is because your stairs vary in width. First they narrow on the right, then halfway up, they narrow at left. If you must have a runner, I would do narrower centered with top step.
If it were mine, I would mix the runner idea, it is going to look odd regardless, it will be a pain to vacuum, and you have beautiful stairs

that looks great! glad they sorted it out in a reasonable fashion.

Looks great! Beautiful staircase. Well done.

Looks great!!!!!!!!!!!

What color stain are those steps ? 
It makes sense on the second picture. Good fix.

Stain is provincial