Comment-only pass over the Python this PR touches: drop what the code already
says, collapse multi-line explanations that still read on one line, and keep
the reasoning that is not recoverable from the code. No code, docstring
semantics or behaviour changes; verified with an AST comparison against the
previous revision, and the backend suite is unchanged (same 37 environment
failures as before: the API integration tests that need a live keyed server,
the flash-attn install hooks, and the GPU memory fields).
A GGUF-quantized transformer's leading parameters are packed uint8 storage,
so reading next(parameters()).dtype handed nn.Module.to() an integer dtype
and every image-conditioned generation on a GGUF model (Qwen-Image-Edit)
failed with a 500. Probe the parameters for the first floating dtype, treat
an all-integer module as a no-op, and also catch TypeError so an unexpected
dtype can never break generation. Regression test included.
Addresses review findings on the SDXL family:
- Reject a GGUF load for single_file_is_pipeline families (SDXL) in validate_load_request,
before the route evicts the current model; SDXL has no transformer-only GGUF variant.
- Skip base-repo weight files when a whole-pipeline single file is loaded: from_single_file
(config=base) needs only the base config/tokenizer/scheduler, so a local .safetensors no
longer triggers a multi-GB base download.
- Remove the SDXL refiner from the non-GGUF trust allowlist: it is an img2img-only pipeline
but this backend loads every sdxl repo as the base txt2img pipeline.
- Normalize a blank/whitespace hf_token to None once in load_pipeline so every load branch
degrades to anonymous instead of erroring on a malformed token.
- Read the denoiser dtype from a parameter (compile-wrapped modules may lack .dtype) and
access state.family.denoiser_attr directly.
Adds/updates regression tests for the trust allowlist, GGUF rejection, and base-config filter.
A full-pipeline prefetch kept every repo file outside assets/, so an official
repo that ships multiple formats (SDXL Base: fp16 variants, ONNX, OpenVINO,
Flax, a top-level single-file twin) downloaded tens of GB from_pretrained never
loads. Skip non-torch exports and dtype-variant twins in
_pipeline_file_downloaded, and drop a component .bin when the same directory
carries a picked safetensors weight (diffusers' own preference).
SDXL is the first U-Net family in the diffusion backend: its denoiser is
pipe.unet (UNet2DConditionModel), not a DiT pipe.transformer, and a single-file
.safetensors is the whole pipeline rather than a transformer-only file. The
backend previously assumed a DiT transformer everywhere, so add the two hooks a
U-Net family needs and register SDXL.
DiffusionFamily gains denoiser_attr ("transformer" for DiT, "unet" for SDXL) and
single_file_is_pipeline (SDXL loads a single file via pipeline_class.from_single_file
with the base repo as config, instead of transformer_class.from_single_file plus a
companion assembly). _align_vae_dtype now reads the denoiser generically so img2img
and inpaint keep the VAE and U-Net dtypes aligned.
The non-GGUF trust gate is extended with a short, exact-match, safetensors-only
allowlist of official base repos (the SDXL base/refiner and sdxl-turbo), because
SDXL ships only as a full pipeline and has no unsloth-hosted GGUF. Local paths stay
trusted as before; a random repo, even one that detects as SDXL, is still rejected.
The image-conditioned and ControlNet workflows are the standard SDXL pipelines,
built around the resident modules via from_pipe like every other family, so SDXL
gets txt2img, img2img, inpaint, outpaint, upscale, LoRA and ControlNet. There is no
native sd.cpp mapping yet, so the no-GPU route falls back to diffusers.
Frontend catalog gains SDXL Base 1.0 and SDXL Turbo entries with SDXL step/guidance
defaults (Turbo: few steps, no CFG; base: ~30 steps, real CFG).
Tests: new test_diffusion_sdxl.py (family shape, detection, trust allowlist, model
kind, U-Net VAE-dtype alignment, LoRA gate) plus loader-branch tests in
test_diffusion_backend.py (pipeline-kind from_pretrained, single-file whole-pipeline
from_single_file, allowlist accept/reject). Verified live on GPU: sdxl-turbo loads
both as a pipeline and as a single file and generates coherent txt2img + img2img.
