I received stock options on Decemebr 2015, vesting started June 2015 (before grant date) - Company was sold in a merger in November 2016 (more than one year after vesting started but less than a year after grant date) -My 1099b said “stocks non covered”. Do I have a long or a shor term gain?
I don't understand the time line and I think you're using terms incorrectly. The "grant date" for options is usually when the options are bestowed upon you. You can't necessarily exercise them at that moment, frequently because the options themselves have to "vest"due to the passage of time, i.e, after vesting the options become options you can't possibly lose and you have the right to "exercise" the options. Having the options vest then typically means you can "exercise" them, i.e., pay the per share strike price and receive the actual stock.
So the usual time line is "grant", "vest", "exercise", not "vest", grant" and then "exercise". You don't mention actually exercising the stock option and receiving the stock. It's the "exercise" that starts the clock ticking on the holding period.
If you actually received the stock, ("exercised"), in December 2015 - did you? - and then sold the stock November 2016 you have a less than one year holding period.