I'm not the expert here, but AOS only applies when you're currently in the US. Has this person been in the US for over a decade without a valid status?

Currently in the US. Reentered US again after visa overstay and maintained valid status since then. Current employee is planning to apply for H-1B next year. Although prior overstay length is < 180 days - the worry is still there.

There are a lot of "forgiveness rules" but they are tricky. I think you need to consult a lawyer to assess the exact situation. I hope this works out!

The facts matter so it's tough to advise without knowing them all but as general rule, as long as the overstay was for less than 6 months, you should be able to adjust status in the U.S.