Pro Tools 12 on Mavericks.

Let's see what happens. I did it. Installed OK. Current session opened OK. Fingers crossed.

Good luck with PT12. Whenever you decide to upgrade OS X, go straight to Sierra. Don't bother with Yosemite or El Capitan. Yosemite introduced a few graphics slowdowns that most of us developers were eventually able to work around. But El Capitan caused some real issues--sluggish meters, slow GUIs--even on high-spec machines. Apple never admitted to change anything, but Sierra is back to the snappy performance you should be experiencing with Mavericks.

Interesting...I think I'm still on El Capitan...might have to move up.

Well, we started well, spent a full day tracking guitars without any issues, but I've run into issues now.

First off, my groups no longer have Solo locked. One mix I'm working on has like 15 different groups and solo no longer works in any of them. Easy enough fix, just go in and modify each group to include solo, but still a pain in the balls.

Then, last night I went to open PT and it immediately quit. When I relaunched, none of my "recent projects" were populated in the open recent projects menu. Then, when I open my project, the colors are no longer saturated on the mixer. Again, not a huge deal, but still inconvenient. Then I hooked up to my UH-7000/Svartbox combo and the I/O isn't showing up properly. Normally, for outputs, it shows 2 analog/2 digital, (7000 has 2 analog, Svart is 2 digital). Last night it was showing 4 analog outputs. The Tascam only has 2 analog outputs, not 4. Inputs were showing properly, 2 analog, 2 digital. Can't figure out any way to change how the output is showing. I spent an hour an a half restarting the machine, checking the audio/midi setup, the Tascam setup, reconnecting cables, power cycling the converters, creating an aggregate device (this had 3 analog outs and 1 digital, still screwey) etc, couldn't get it working right. Got frustrated and gave up for the night. Curious what other settings are boned now too. Total PITA.

I just set up Reaper on another laptop and will try testing the converter setup with that this weekend. Also, I have a second UH-7000 unit here at the office that I'll bring home and test with the PT setup.

Running 12.6 on Sierra Mac mini i7 ,motu16a with no problems.
Even loading some old Pro Tools 8 session no problems .

Running pt hd 12.5 on os 10.10.5. No problems if you don't use commit. I will hold of a bit longer to update.

This was my impression when I helped a local kid on a session. It worked but it looked like Greek! I have also had some issues with exported "sessions" from reaper. They were all user error, bit not a fan of a program that can't export an OMF file.