ComfyUI 0.34 (commit ff6c8a8a) hands MiniMax H3 a per-token denoise mask: the DiT derives per-row timesteps from it, presenting preserved rows at the video cond timestep (0.999) and the audio stream rescaled. LanPaint implements the 0.33 single-schedule contract in its own replace step and inner dynamics, so on 0.34 the mask-driven row timesteps contradicted the injected latents and both streams came out wrong.
Detect the contract from the ComfyUI version (>= 0.34) and hide the mask from the model's extra_conds for the paint loop, so the DiT keeps the uniform row timesteps LanPaint's math expects. Image models and ComfyUI <= 0.33 are unaffected.