Patching ComfyUI-MPS-INT8 to fix MiniMax H3 VAE crashes on Mac
Kris_RenderBob · reddit · 2026-10-03
A developer traced a MiniMax H3 VAE decoding crash on Mac to the custom ComfyUI-MPS-INT8 backend lagging behind the current Comfy Kitchen interface: int8linear() didn't accept the newer inputactweight, inputacteps, residual and residualscale arguments.
With Codex's help, they patched backend.py (line 318) to:
- apply RMS normalization via applyinputact() before the accelerated INT8 op, passing inputact=None internally to avoid double activation
- apply residual + residualscale × result via applyresidual() before returning
All four existing MPS GPU tests passed, normalization/residual math was checked against an independent reference, and video generation works after a restart. The author notes the backend loads fine at startup — it only breaks when the decoder passes the newer arguments — and reports an unrelated colored-patches issue separately.
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