How high can you go with OS X and still use Final Cut Pro 7?

Any OS after 10.8 is not supported. So FCP may work, it may not. Some people have no problems, others have nothing but. Know that running older software on newer OS versions that don't support it will be problematic. Not all of the features will work the way they should.

I know that Motion and Compressor stop working under Mavericks and Yosemite. Oh, sure, a couple people say they work, but they don't work for me, and there are many many others who are like me...the apps don't work. If you need them, you'll have to get the updated versions of those...and you can't do a SEND TO from FCP on those.

My opinion? If you use this machine to earn a living...or if you rely on FCP 7...don't upgrade the OS. It doesn't buy you any more functionality with that software. If you need the new OS for other software to work...then you might consider making your computer Dual-boot. Meaning two partitions with different OS versions on both.

I am using Yosemite 10.10.3 and FCP7 works on my MBP2014. I intended to stay on 10.6.8 but my computer died (MBP17) and needed ~1000 repair so decided to upgrade...

I am trying to install/learn FCPX as well and have had trouble running both on the same machine. If you do upgrade that must be done carefully...

Paul

I've just begun a project on FCP 7 running on Yosemite. It's a right pain in the backside. It keeps crashing. Log & Transfer doesn't seem to work for Canon video camera's. And right now, I hold my breath every time I do something different on the project in case it crashes before I can save!

May consider going over to FCP X as it is supported on latter OSs.