Bench refutation (display is static under axis movement; version-only
exchanges leave it alone) kills the A-9-E chord theory. Real mechanism:
the CheckRequest handler at $C5A6 runs a full self-test — sets the
test-display flag $2421, brackets itself with TestModeChange 0x8C,
lamp pattern, pod scan, five-channel encoder sweep — and returns
without repainting, leaving the channel-4 frame (04000000) as a stale
cosmetic snapshot. Board fully healthy; no reset needed. PROTOCOL.md
now warns hosts that 0x8C fires around every check. Candidate firmware
fix (repaint cave off $C5E4) noted for a future burn.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
CydandClaude Fable 5
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