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MiniMax H3 INT8 ConvRot VAE produces black video with NaN/Inf output #15524

Description

@ZhuominLi

Bug report

Using minimax_h3_video_vae_int8_convrot.safetensors with the MiniMax H3 workflow produces an entirely black video. The same workflow works with minimax_h3_video_vae_fp16.safetensors.

Reproduction

  • ComfyUI: current local build
  • Model: MiniMax H3
  • VAE: minimax_h3_video_vae_int8_convrot.safetensors
  • GPU: RTX 2080 Ti, 22 GB
  • Resolution: 864×480
  • Length: 362 frames
  • Sampling: 4 steps
  • VAE path: native H3 spatial and temporal tiling

The output video is completely black. The log also reports:

RuntimeWarning: invalid value encountered in cast

This occurs while converting the decoded video tensor to 8-bit output, suggesting that the VAE output contains NaN or Inf values.

Relevant log information:

VAE load device: cuda:0, offload device: cpu, dtype: torch.float32
Requested to load MiniMaxH3VideoVAE
[VAEDecode] shape=(1, 24, 107, 30, 54)

The INT8 VAE file was loaded successfully, but the decoded output is invalid.

Could you please check whether this INT8 ConvRot VAE requires a specific ComfyUI, comfy-kitchen, dtype, attention backend, or loading configuration? Is this checkpoint compatible with the current MiniMax H3 VAE loader on RTX 2080 Ti/SM75?

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