Hi,
It seems that your solution is not fully cross-platform since on Windows the function Pm_CreateVirtualInput() you use to create virtual Midi-In port is not supported:

Virtual devices are not supported by Windows (Multimedia API). Calls on Windows do nothing except return pmNotImplemented

https://portmidi.github.io/portmidi_docs/group__grp__device.html#gaf262cf560e105c9a44f7b30eb868951e

So it seems the latest Midi-In port related commit from Nukeykt should work better overall:
1130e05

True, my PR is mostly Mac focused, maybe i can keep the two and make it a flat during compilation with Claire cmake?

True, my PR is mostly Mac focused, maybe i can keep the two and make it a flat during compilation with Claire cmake?

It seems portMidi also supports opening existing Midi In ports the same way as RtMidi does so a run-time check for failing Pm_CreateVirtualInput() call should be enough. In case of a failing call it should open an existing Midi In port (port number can be read from the command line as in latest main branch or from a config file).