Employee to contractor

We have an engineer who was originally hired as an employee and received an ISO grant. They're moving over to a contractor role, but we'd like to keep their vesting going without disrupting the schedule. Since ISOs require employee status, what's the cleanest way to handle this so the equity doesn't get messed up? Do we amend the original grant to convert to NSOs, or issue a new grant? And how do we reflect the change in Carta?

------------------------------
Rose Jian
------------------------------