Extends diffusion LoRA training beyond SDXL to the three popular DiT families
via a single shared flow-matching loop parameterised by small per-family specs
(loading, prompt/latent encoding, transformer forward, save). Verified against
diffusers 0.38.0:
- FLUX.1-dev: 2x2 latent packing + image ids, guidance-embed forward, on-the-fly
nf4 QLoRA of the 12B transformer (the dev repo is gated, so training needs the
user's HF token).
- Qwen-Image: 5D VAE latents normalised by the per-channel latents_mean/std,
img_shapes forward, prequant nf4 base by default (on-the-fly nf4 for the bf16
base).
- Z-Image: list I/O with the reversed timestep convention and a negated
prediction, bf16 only.
The registry (get_trainer) and DiffusionFamily.trainable / train_base_repos now
route these families to the DiT trainer; the SDXL blocklist guard is replaced by
a positive family resolution that also rejects GGUF repos (inference-only) and
still-unsupported families. Per-family defaults + labels + VRAM notes are exposed
via family_train_infos for the Train UI.
Memory: caption embeddings are precomputed once and the text encoders freed
before the loop; gradient checkpointing (non-reentrant, required for bnb 4-bit)
and 8-bit AdamW are on by default.
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