Using the latest release (21.0.1), mesen labels for PCE fixed bank (bank0) symbols are offset by 0x2000 bytes.

Simple repro:

#include <pce.h> [[noreturn]] int main() { while(true) { } } 

mos-pce-clang++ main.cpp -o test.pce

Result:

PcePrgRom:2000:_init
PcePrgRom:2000:_start
PcePrgRom:2019:_fini
PcePrgRom:201a:nmi
PcePrgRom:201b-201c:main
PcePrgRom:201d-2021:exit
PcePrgRom:2022-2037:__pce_psg_init
PcePrgRom:2038-2070:__pce_vdc_init
PcePrgRom:2071:irq_timer
PcePrgRom:207b:irq_vdc
PcePrgRom:2085:irq_ext
PcePrgRom:3fd3:_early_start