Add comprehensive support for Z-Image-Turbo (S3-DiT) models including:
Backend:
- New BaseModelType.ZImage in taxonomy
- Z-Image model config classes (ZImageTransformerConfig, Qwen3TextEncoderConfig)
- Model loader for Z-Image transformer and Qwen3 text encoder
- Z-Image conditioning data structures
- Step callback support for Z-Image with FLUX latent RGB factors
Invocations:
- z_image_model_loader: Load Z-Image transformer and Qwen3 encoder
- z_image_text_encoder: Encode prompts using Qwen3 with chat template
- z_image_denoise: Flow matching denoising with time-shifted sigmas
- z_image_image_to_latents: Encode images to 16-channel latents
- z_image_latents_to_image: Decode latents using FLUX VAE
Frontend:
- Z-Image graph builder for text-to-image generation
- Model picker and validation updates for z-image base type
- CFG scale now allows 0 (required for Z-Image-Turbo)
- Clip skip disabled for Z-Image (uses Qwen3, not CLIP)
- Optimal dimension settings for Z-Image (1024x1024)
Technical details:
- Uses Qwen3 text encoder (not CLIP/T5)
- 16 latent channels with FLUX-compatible VAE
- Flow matching scheduler with dynamic time shift
- 8 inference steps recommended for Turbo variant
- bfloat16 inference dtype
In `ObjectSerializerDisk`, we use `torch.load` to load serialized objects from disk. With torch 2.6.0, torch defaults to `weights_only=True`. As a result, torch will raise when attempting to deserialize anything with an unrecognized class.
For example, our `ConditioningFieldData` class is untrusted. When we load conditioning from disk, we will get a runtime error.
Torch provides a method to add trusted classes to an allowlist. This change adds an arg to `ObjectSerializerDisk` to add a list of safe globals to the allowlist and uses it for both `ObjectSerializerDisk` instances.
Note: My first attempt inferred the class from the generic type arg that `ObjectSerializerDisk` accepts, and added that to the allowlist. Unfortunately, this doesn't work.
For example, `ConditioningFieldData` has a `conditionings` attribute that may be one some other untrusted classes representing model-specific conditioning data. So, even if we allowlist `ConditioningFieldData`, loading will fail when torch deserializes the `conditionings` attribute.
Each of these was a bit off:
- The SD callback started at `-1` and ended at `i`. Combined w/ the weird math on the previous `calc_percentage` util, this caused the progress bar to never finish.
- The MultiDiffusion callback had the same problems as SD.
- The FLUX callback didn't emit a pre-denoising step 0 image. It also reported total_steps as 1 higher than the actual step count.
Each of these now emit the expected events to the frontend:
- The initial latents at 0%
- Progress at each step, ending at 100%
