Default scheduler: plain static shift 5.0 instead of dynamic shifting (sdxs-micro schedule)

Verified bit-identical to the approved A/B frame; --scheduler-test now compares the shipped static
shift against Qwen-Image-2.1's original dynamic schedule. Also fixed a silent config trap: a loaded
scheduler config carries _use_default_values, which makes from_config drop every key set afterwards.

NOTICE

@@ -14,7 +14,8 @@ Modified files, as required by section 2.b of the agreement:
   transformer/*.safetensors  re-saved in fp16, plus the 66 `text_fusion.*` tensors of the
                              adapter from the image21-08b-text-encoder-adapter project (adapter_v11)
   vae/                       copied unchanged (fp32)
-  scheduler/                 copied unchanged
+  scheduler/                 modified: dynamic shifting off, plain static `shift` 5.0, `shift_terminal`
+                             removed (was 0.02) — the sdxs-micro schedule
   text_encoder/              different model: Qwen3.5-0.8B instead of Qwen3-VL-8B. Upstream files are
                              re-saved in fp16 (bf16 -> fp16, single `model.safetensors` instead of
                              the sharded bf16 file); `config.json` is unchanged. Modified under the

README.md

@@ -30,7 +30,7 @@ Text-to-image, character and scene editing, and transparent (RGBA) generation in
 | text encoder | **Qwen3.5-0.8B**, 1.7 GB fp16 — upstream checkpoint re-saved to fp16, tokenizer/processor files unchanged (native: Qwen3-VL-8B, 17.5 GB) |
 | conditioning | cosine **0.94** against the native Qwen3-VL-8B encoder (text positions) |
 | VAE | Qwen-Image-2.1, 16× spatial, fp32 |
-| scheduler | `FlowMatchEulerDiscreteScheduler` |
+| scheduler | `FlowMatchEulerDiscreteScheduler`, plain static shift 5.0 (dynamic shifting off) |
 | resolution | `output_resolution`, 1024 by default; follows the condition image aspect ratio |
 | precision | fp16 everywhere except the VAE |
 | peak VRAM | ~17.5 GB resident, less with `enable_model_cpu_offload()` |
@@ -40,7 +40,8 @@ Text-to-image, character and scene editing, and transparent (RGBA) generation in
 The text encoder is replaced by **Qwen3.5-0.8B** plus a 158M adapter, fine-tuned to reproduce what
 the native encoder produced — both from plain text and from text read together with the reference
 images (**Improved using Qwen**). The adapter lives *inside* the DiT as its text-fusion block, so the
-whole model is one self-contained diffusers folder and no 17.5 GB encoder is needed anywhere.
+whole model is one self-contained diffusers folder and no 17.5 GB encoder is needed anywhere. The
+sampler runs a plain static shift of 5.0 instead of the original dynamic shifting.
 
 ### Examples
 
@@ -112,8 +113,8 @@ python example.py --prompt "..." --negative "low quality, blurry, watermark" --c
 python example.py --prompt "..." --scheduler-test --shift 5 --out ab.png
 ```
 
-`--scheduler-test` renders every prompt twice with the same seed — the default dynamic-shift schedule
-and a plain static `--shift` (sdxs-micro uses 5.0) — and glues the pair with labels, so a schedule
+`--scheduler-test` renders every prompt twice with the same seed — the shipped static `--shift` (5.0)
+and Qwen-Image-2.1's original dynamic-shift schedule — and glues the pair with labels, so a schedule
 change can be judged without rerunning anything by hand.
 
 `--size` sets a square frame (or the frame *area* when `--image` supplies the aspect ratio);

example.py

@@ -19,8 +19,8 @@ clothing and background unchanged." --out swap.png
   python example.py --prompt "..." --width 1280 --height 768 --out wide.png
   python example.py --prompt "..." --negative "low quality, blurry, watermark" --cfg 3 --out cfg.png
 
-  # scheduler A/B: the same seed and prompt rendered twice, default dynamic shift vs a static shift,
-  # glued side by side with labels (sdxs-micro uses a plain static shift of 5.0)
+  # scheduler A/B: the same seed and prompt rendered twice — the shipped static shift versus
+  # Qwen-Image-2.1's original dynamic-shift schedule — glued side by side with labels
   python example.py --prompt "..." --scheduler-test --shift 5 --out ab.png
 
 The pipeline is loaded once, so a batch pays the ~17 GB load a single time; every prompt uses the
@@ -47,19 +47,40 @@ def read_prompts(path):
     return [line for line in lines if line and not line.startswith("#")]
 
 
-def build_shift_scheduler(pipe, shift):
-    """Copy of the pipeline scheduler with a plain static shift instead of dynamic shifting.
+def _scheduler_config(pipe):
+    """Scheduler config as plain values, with the service key dropped.
+
+    A loaded config carries `_use_default_values`, and `ConfigMixin.extract_init_dict` *removes* those
+    keys from a dict passed to `from_config`. Left in, every field we set afterwards (base_shift,
+    max_shift, shift_terminal, ...) would be silently dropped and replaced by library defaults.
+    """
+    return {k: v for k, v in dict(pipe.scheduler.config).items() if k != "_use_default_values"}
+
+
+def static_scheduler(pipe, shift):
+    """Pipeline scheduler with a plain static shift — the shipped default (sdxs-micro uses 5.0).
 
     sdxs-micro's config is exactly `{shift: 5.0, use_dynamic_shifting: false}`, so `shift_terminal`
-    (which stretches the schedule to end at a fixed sigma) is switched off here as well.
+    (which stretches the schedule to end at a fixed sigma) is switched off as well.
     """
     from diffusers import FlowMatchEulerDiscreteScheduler
 
-    config = dict(pipe.scheduler.config)
+    config = _scheduler_config(pipe)
     config.update(use_dynamic_shifting=False, shift=shift, shift_terminal=None)
     return FlowMatchEulerDiscreteScheduler.from_config(config)
 
 
+def dynamic_scheduler(pipe):
+    """Qwen-Image-2.1's original schedule (dynamic shifting), kept for the `--scheduler-test` A/B."""
+    from diffusers import FlowMatchEulerDiscreteScheduler
+
+    config = _scheduler_config(pipe)
+    config.update(use_dynamic_shifting=True, shift=1.0, shift_terminal=0.02, base_shift=0.5,
+                  max_shift=0.9, base_image_seq_len=256, max_image_seq_len=8192,
+                  time_shift_type="exponential")
+    return FlowMatchEulerDiscreteScheduler.from_config(config)
+
+
 def run(pipe, scheduler, args, prompt, call):
     """One generation on a fresh generator with the same seed; the scheduler is swapped for the call."""
     previous = pipe.scheduler
@@ -108,9 +129,9 @@ def main():
     ap.add_argument("--cfg", type=float, default=1.0,
                     help="true_cfg_scale: 1.0 = no guidance, which is how this model is meant to run")
     ap.add_argument("--scheduler-test", action="store_true",
-                    help="render two frames per prompt (default dynamic shift vs static shift) and glue them")
+                    help="also render Qwen-Image-2.1's original dynamic-shift schedule and glue the pair")
     ap.add_argument("--shift", type=float, default=5.0,
-                    help="static shift for the second frame of --scheduler-test; sdxs-micro uses 5.0")
+                    help="static shift of the shipped scheduler; sdxs-micro uses 5.0")
     ap.add_argument("--steps", type=int, default=30)
     ap.add_argument("--seed", type=int, default=1234)
     ap.add_argument("--device", default="cuda")
@@ -144,17 +165,17 @@ def main():
     else:
         pipe.to(args.device)
 
-    shift_scheduler = build_shift_scheduler(pipe, args.shift) if args.scheduler_test else None
+    static = static_scheduler(pipe, args.shift)
+    dynamic = dynamic_scheduler(pipe) if args.scheduler_test else None
     call = dict(image=condition, negative_prompt=args.negative, output_resolution=args.size,
                 height=args.height, width=args.width, num_inference_steps=args.steps,
                 true_cfg_scale=args.cfg, output_type="pil")
 
     for index, prompt in enumerate(prompts, start=1):
-        image = run(pipe, pipe.scheduler, args, prompt, call)
-        if shift_scheduler is not None:
-            shifted = run(pipe, shift_scheduler, args, prompt, call)
-            image = side_by_side(image, shifted, "default scheduler",
-                                 f"static shift {args.shift:g} (sdxs-micro style)")
+        image = run(pipe, static, args, prompt, call)
+        if dynamic is not None:
+            image = side_by_side(image, run(pipe, dynamic, args, prompt, call),
+                                 f"static shift {args.shift:g} (default)", "dynamic shift (Qwen 2.1)")
         path = os.path.join(out, f"{index:04d}.png") if batch else out
         image.save(path)
         print(f"[{index}/{len(prompts)}] {path} -> {image.size}  {prompt[:70]}", flush=True)

scheduler/scheduler_config.json

@@ -1,18 +1,7 @@
 {
   "_class_name": "FlowMatchEulerDiscreteScheduler",
   "_diffusers_version": "0.37.0.dev0",
-  "base_image_seq_len": 256,
-  "base_shift": 0.5,
-  "invert_sigmas": false,
-  "max_image_seq_len": 8192,
-  "max_shift": 0.9,
   "num_train_timesteps": 1000,
-  "shift": 1.0,
-  "shift_terminal": 0.02,
-  "stochastic_sampling": false,
-  "time_shift_type": "exponential",
-  "use_beta_sigmas": false,
-  "use_dynamic_shifting": true,
-  "use_exponential_sigmas": false,
-  "use_karras_sigmas": false
+  "shift": 5.0,
+  "use_dynamic_shifting": false
 }