Qwen-Image 2.1

1. Model introduction

Qwen-Image 2.1 is the unified text-to-image and image-to-image successor of Qwen-Image. Conditioning is Qwen3-VL (pre-final-norm hidden states); the DiT is a single-stream block-causal transformer with an RGBA VAE. CFG is distilled into the checkpoint, so the official default is no guidance. miles-diffusion trains the T2I path. Image-conditioned editing is served by the rollout engine but is not a recipe yet. Day-0 references:

diffusers #14804
sglang-diffusion #39983

2. Supported variants

Model	HF ID	Notes
Qwen-Image 2.1	`Qwen/Qwen-Image-2.1`	Family key `qwen_image21`

A name containing qwen-image-2.1, qwen-image-21, qwenimage21, or qwen_image21 resolves to this family. Matching keeps the longest pattern, so Qwen/Qwen-Image-2.1 resolves to qwen_image21.

3. Family config

Registered in miles/backends/fsdp_utils/configs/qwen_image21.py:

Property	Value	Why
Timestep scaling	Trajectory timesteps ÷ 1000	Matches diffusers’ `t / 1000`; sglang-d divides inside the DiT
CFG combine	`uncond + scale·(cond − uncond)`, no cond-norm rescale	Mirrors `pipeline_qwenimage21`
Cond collation	Pad `encoder_hidden_states`, rebuild `img_mask` = text zeros + target slots, `img_shapes` from `--diffusion-height/width`	Rollout sends Qwen3-VL text; the train DiT wants the joint mask
Noise pred	Slice `[:, -target_tokens:]`	Single-stream forward emits the joint sequence
RoPE caches	Rebuilt on CUDA after materialize	Same CPU/CUDA `torch.pow` trap as 1.0
LoRA targets	`to_q/k/v`, `to_out.0`, `img_mlp.{proj,out,gate_layer}`	Single-stream block; no text-branch add-proj

4. Launch

Canonical recipe: scripts/run_diffusion_grpo_qwenimage21_pickscore_1gpu.py — 1 colocated GPU, train + sglang + PickScore, 512×512, 16×16 group, lr 1e-4. Real-weight GRPO needs ≥80GB; 32GB only finished generate. Status: 📈 V — Verified — 200 rollouts on one H200. Smoothed rollout/reward/raw_mean rises from about 0.82 to about 0.87.

# alignment diagnostic: freeze weights so log_prob_mean_abs_diff is train-vs-rollout
python3 scripts/run_diffusion_grpo_qwenimage21_pickscore_1gpu.py \
  --num-rollout 2 --extra-args "--debug-skip-optimizer-step"

# local checkpoint
python3 scripts/run_diffusion_grpo_qwenimage21_pickscore_1gpu.py \
  --hf-checkpoint /path/to/qwen-image-2.1

5. Recipe notes

Official sampling is 40 steps / CFG 1. This recipe uses 10 steps and the same SDE window as Qwen-Image 1.0 (--diffusion-sde-window-range 3,5, 2 SDE steps). Default is 16 prompts × 16 samples, lr 1e-4, 200 rollouts.
--rollout-patch-group qwen_image21 turns off the engine’s prefix KV cache so every SDE step recomputes the full joint sequence, matching the trainer, and keeps the RoPE layouts out of the rollout response.
--sglang-lora-merge-mode dynamic keeps PEFT unmerged on the engine, same as 1.0.
A 32 GB card will not hold the full 2.1 DiT + Qwen3-VL + VAE + PickScore at 1024² without offload. Raise batch/resolution only after adding GPUs or component offload.

6. Reference results

The canonical 1-GPU recipe over 200 rollouts (512², 16×16, lr 1e-4) on one H200:

Smoothed rollout/reward/raw_mean moves from about 0.82 to about 0.87. train/log_prob_mean_abs_diff stays near 2e-5 on the same run:

7. Pairs well with

Qwen-Image 1.0 — the flow_grpo-aligned 5-GPU reference recipe.
LoRA weight sync — --lora-ipc-weight-sync is on.
Deterministic Training — --deterministic-mode is on.

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Qwen-Image 2.1

1. Model introduction

2. Supported variants

3. Family config

4. Launch

5. Recipe notes

6. Reference results

7. Pairs well with

​1. Model introduction

​2. Supported variants

​3. Family config

​4. Launch

​5. Recipe notes

​6. Reference results

​7. Pairs well with

1. Model introduction

2. Supported variants

3. Family config

4. Launch

5. Recipe notes

6. Reference results

7. Pairs well with