What is this hose?

bottom line: I can't figure out what hose connects to this, and where the other end is. I think it's either the low side of the AC compressor, or a heater hose.

Rest of the story: my 2013 V-5 started throwing P261B errors and overheating. I replaced the IC water pump and thermostat, and it starts and runs no problem (no leaks). I'm not letting it run very long, however (like 5 mins at a time), since I can't figure out what this one pipe connects to, and I don't want it to start dumping coolant, or worse, killing the AC compressor (AC is currently OFF).

Yes, I'm an idiot. I took pictures of some of it during disassembly, but not this part (it was towards the end of pulling the water pump and tstat, and I was getting frustrated, and pulling whatever to be able to get to it). I've looked at various shop manuals (alldataDIY), but can't quite determine what it is using those.

Any help more than welcome.