Didn't see a response to
https://www.flyertalk.com/forum/29202871-post2261.html and then the thread got closed, so I'll post here and answer my own question:
I'm flying on AA PHL-MUC and then connecting on A3 MUC-HER. It's all on one ticket issued on AA stock (PHL-MUC-HER).
Since A3 is not OneWorld, I'm not sure if there's an interline agreement between them. Will bags checked in PHL go all the way to HER automatically, or do they need to be reclaimed in MUC and re-checked on A3 to HER? I don't think I've ever had to deal with this scenario. I almost never check bags, and I don't think I've ever had an international connection switching airlines. I'd be fine with carry-on but I'll be traveling with my mom and I'm sure she'll want to check her suitcase.
I checked with AA and they advised me that I would have to claim my bags in MUC and recheck them on A3. So just in case anyone else has this same question, here's the answer
