[fipar]

I have a 2021 one and it never hit the breaks with nothing standing in the way. I don't have the manual in front of me but IIRC, it should only activate without an actual obstacle if the circumstances are such that something may be confused for an obstacle (e.g., driving down a steep enough hill that the end of it may be detected as a wall, never happened to me but I've never done more than 25 deg slopes).

I know you're not asking for advise but I'd recommend to have that checked, my recollection is that the manual spends far more pages listing the circumstances under which the system may fail to apply the brakes than those in which it may break when it didn't have to, so it seems odd enough for me that I'd get that checked if it happened to me.

[sobjornstad]

I've never had this happen on my 2017 Forester either in ~30,000 miles of highway driving with the adaptive cruise (the Subaru system is fully vision-based with no radar).

The one issue I've noticed is that it sometimes hits the brakes for cars that are obviously exiting the highway because a tiny sliver of the car is still technically in the driving lane, so I've learned to keep my foot over the gas pedal to override it in that case. The amount of braking isn't scary though, it's just annoying because there's no need to slow down at all.

[PyWoody]

I have a 2021 Subaru Legacy and I've never had the phantom breaking as well. I've put about 10k miles on the car with at least 7k of it being on adaptive cruise. All of the miles have been on country roads with hills, sharp turns, traffic, inclement weather, etc.

I second the suggestion to get it checked.