Hi there,
And welcome Back…
Why This Happens
When someone flashes a custom sketch (like an Arduino “Blink” or serial test) over Meshtastic firmware, they’re wiping out Meshtastic entirely. It’s no different than installing your own bare-metal firmware. That’s why afterward:
- The device no longer shows up as
TinyUSBorMeshtasticover serial. - It won’t respond to Meshtastic apps or commands.
- It only boots your sketch — not the Meshtastic stack, not the radio, not the mesh.
So of course it looks “inaccessible” — you erased it.
So , you are overwriting the Meshtasic code on the xiao and it bombs?
What does the sketch look like ? Use the code tags and post it up “</>” paste it in there. Lets have a looksie 
what is the end goal, I bet there is a different way to do it.
HTH
GL 
PJ 