When the region's file is absent, libretro.c (7fea57a5) finds no name and no matching sha1, then maps its built-in OpenBIOS (libretro.c:3425-3511). The region runs show it: each region's disc reaches its game with only the other regions' BIOS staged, under the oracle's reference frames (records 2026-10-27-55dd1e4943c4, 13be0e68b799, 33780d47efdf). scph5500.bin, scph5501.bin and scph5502.bin are required: false, hle_fallback stays true. Written through campaign_profiles.
Beetle PSX, Beetle PSX HW and SwanStation rerun under the oracle with the Japanese BIOS menu as an error screen: a Japanese BIOS under a US disc is now a BIOS error.
Twelve runs on each of beetle_psx and beetle_saturn: each region's game with every regional BIOS, its own only, the others only and the region pack. One DuckStation check on the US disc with and without scph5501.bin.
Puzzle Bobble 2 (Japan) and Bust-A-Move 2 (Europe) on the PlayStation cores, and the three Saturn editions on Beetle Saturn, each frame reviewed on its PNG. Beetle Saturn's BIOS error lines, read from ss.c, are its error patterns.
Reference runs, then the full set, no BIOS and negative variants of Bust-A-Move 2 (USA) on Beetle PSX, Beetle PSX HW, SwanStation, PCSX-ReARMed and PCSX1, each judged by the boot oracle.
First real pass of campaign.py: the libretro PlayStation profiles with an hle_fallback claim (beetle_psx through mednafen_psx and mednafen_psx_hw, pcsx_rearmed and swanstation nightlies, pcsx1 built from its pinned commit), each run on Bust-A-Move 2 - Arcade Edition (USA) with and without scph5501.bin, under bubblewrap. Every core reached the game without the BIOS.