feat(models): add LoRA support for Qwen-Image-2.1

[Pfannkuchensack]

Summary

Adds LoRA support to Qwen-Image-2.1.

Stacked on #9787. This PR's own change is the last commit; the one before it is #9787 (#9784 is merged).

Layouts. The published LoRAs target the diffusers module names under a diffusion_model. (ComfyUI), transformer. / base_model.model. (diffusers/PEFT) or lora_unet_ (Kohya) prefix. One exception: ComfyUI fuses each block's gated MLP input into img_mlp.gate_up. It is split by its output rows into gate_layer (first half) and proj (second half), as the base checkpoint converter does. The split covers low-rank layers, PEFT/ai-toolkit DoRA (output-dim magnitude) and full (diff) layers. Full diffs on the RMSNorm weights (attn.norm_q/norm_k, txt_in.text_norm), which ComfyUI's official Turbo LoRA carries, are merged into those weights on every format, since no sidecar can patch a norm.

All or nothing. Identification and conversion share one key table. A LoRA with a layer this transformer lacks, or with a gate_up layer that cannot be split, is not installed as a Qwen-Image-2.1 LoRA. That covers LoKR, LoHA and LyCORIS DoRA, which mix both halves. Applying only the part that fits would pass a partial LoRA off as a whole one.

Backend

• New LoRA_LyCORIS_QwenImage21_Config: the gated MLP's names (gate_up, gate_layer, proj, out) or the 4096 width of the block attention (to_q/k/v, to_out.0, low-rank or LoKR), excluding FLUX.2 LoRAs and anything with unsupported keys. Qwen-Image LoRA configs no longer claim such files, attention-only 2.1 LoKr included.
• FLUX's Kohya detector now accepts only FLUX's own block names (double_blocks, single_blocks); a Kohya Qwen LoRA whose every key is on the MLP no longer reads as FLUX.
• New qwen_image_2_1_lora_loader and qwen_image_2_1_lora_collection_loader nodes. They refuse non-LoRAs and LoRAs of other bases by name, with a hint that Qwen Image LoRAs do not fit 2.1, and skip LoRAs already applied.
• qwen_image_2_1_denoise patches the transformer for the whole sampling run, before the prefix KV cache is built:
  • plain weights are patched in place and restored afterwards;
  • GGUF/int8 weights get sidecars, and fp8 ones per layer;
  • working memory is reserved only for sidecars: the LoRA sizes plus one MLP-wide update per forward.

webv2: qwen-image-2-1 joins the LoRA-supported bases. The graph routes the transformer through the collection loader.

Docs: a LoRA section on the Qwen-Image-2.1 page, plus the generate-panel and model-families rows.

Related Issues / Discussions

Part of #9594. Depends on #9787.

QA Instructions

• Python: the affected suites pass locally, ruff clean; the full suite runs in CI.
• webv2: pnpm lint passes; the generation suites pass.
• Docs: the build passes, internal links are valid.
• Covered on CPU:
  • comfy and Kohya layouts across every block and top-level module, against a meta-device transformer;
  • the exact gate_up split, including DoRA magnitudes and full layers;
  • all prefixes, and alpha;
  • refusals: LoKR/LyCORIS DoRA on gate_up, foreign layers;
  • identification against every other LoRA config, the FLUX.2 Klein 9B cases, and a stripped real LoRA fixture;
  • the denoise path with a real Linear, merged and as a sidecar: the update is applied from the first step and the weight is unchanged afterwards;
  • collection dedupe and refusal messages; the webv2 graph.
• GPU (RTX 4090):
  • ComfyUI's Turbo LoRA (avg. rank 178, with norm diffs) on the Base model at 8 steps turns the unfinished image into a sharp one on bf16 (merged), GGUF and int8 (sidecars); the sidecar runs land within bf16 rounding of the merged one.
  • A Manga-to-Photo LoRA changes GGUF txt2img and Diffusers edits; the Diffusers weights are bit-identical before and after a LoRA run.
  • Three community 2.1 LoRAs and the Turbo LoRA install as qwen-image-2-1.

Review

All material findings were resolved, with regression tests:

• LoRAs with foreign or unsplittable layers were applied partially; they are now refused at install time and at conversion;
• the gate_up split now splits every row-indexed value (low-rank up, DoRA magnitude, full diff), not just the low-rank pair;
• working memory was reserved for direct patching too; it is now sized only for sidecars;
• the collection loader could apply a LoRA twice;
• from GPU testing: the official Turbo LoRA installed as unknown (norm diffs);
• from the PR1 review: 2.1 LoRAs on only to_out.0 or the MLP halves, and attention-only LoKr, were filed as Qwen-Image LoRAs.

Remaining limitation: a LoRA on only to_q/to_k/to_v of FLUX.2 Klein 9B's first blocks has exactly the keys and shapes of a Qwen-Image-2.1 one and is identified as the latter. This is pinned in a test and noted in the docs.

Compatibility / Rollout

• Generated API files: openapi.json and schema.ts are regenerated; the changes are additive: two new nodes and a new LoRA config. qwen_image_2_1_denoise moves to 1.2.0 without new fields.
• Model identification: the new config only claims LoRAs that no other config claimed before.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Meaningful regression coverage added / updated where needed; obsolete tests/code removed
• Persisted-state and API changes include required migrations / compatibility validation
• Relevant performance/efficiency opportunities considered; material claims have evidence
• Material review findings resolved and relevant checks rerun
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)