Thousand Arms (SLUS-00845) soft-locks at first in-engine cutscene: script waits for SPU IRQ that never fires

[mxvisor]

Describe the bug

The game loads the first in-engine scripted scene (night village, main character going on a road).

Expected behavior

The scripted scene starts: dialogue window opens with voiced text
("Be quiet, already." etc.), scene proceeds.

Steps to reproduce the bug

1. Start new game.
2. The game loads the first in-engine scripted scene
3. Wait.

Operating System

Windows 11

PCSX-Redux version

Version: 24734.20260713.10.x64
Build: 345
Changeset: f22e4c1
Date & time: 2026-07-13 22:49:36

CPU model

Core I7-860

GPU model & Drivers

Nvidia RTX 5070 TI, version 610.74

BIOS version

retail BIOS (SCPH-101, sha-known 171bdcec) and bundled OpenBIOS

Options

• Dynarec CPU
• 8MB
• OpenGL GPU
• Fastboot
• Debugger

Iso checks

No response

Logs

No response

Additional information

• The scene loads fine (the overlay with dialogue text is present in RAM at
  0x8009F000, character idle animation plays), but the dialogue window never
  appears and the scene never advances.
• In the debugger the game is spinning in a loop waiting for an SPU IRQ that
  is never delivered.
• If "Always enable SPU IRQ" is toggled ON while the game is stuck: exactly
  one dialogue window is displayed (with voice), after which the game freezes
  completely.
• If "Always enable SPU IRQ" is enabled from boot: the game hangs right at the
  start of gameplay, before the scene.

This matches the game's known reliance on SPU IRQ for streaming dialogue voice
data: Thousand Arms is listed among SPU-IRQ-dependent titles in Mednafen's
SPU-IRQ notes (https://github.com/libretro/beetle-psx-libretro/blob/master/mednafen/psx/notes/SPU-IRQ),
and TODO.md in this repo mentions pending work on IRQ integration.