Move bnb Params4bit.shape fix to a runtime shim in app.py; restore pristine bundled diffusers

app.py

@@ -19,6 +19,24 @@ from huggingface_hub import hf_hub_download
 
 from diffusers import Ideogram4Pipeline
 
+# Runtime shim (keeps the bundled diffusers pristine): cu130-era bitsandbytes returns Params4bit.shape as a
+# plain tuple, but diffusers' check_quantized_param_shape calls .numel() on it. math.prod handles both, so
+# this is a no-op once diffusers/bnb fix it upstream.
+import math  # noqa: E402
+
+from diffusers.quantizers.bitsandbytes.bnb_quantizer import BnB4BitDiffusersQuantizer  # noqa: E402
+
+
+def _check_quantized_param_shape(self, param_name, current_param, loaded_param):
+    n = math.prod(tuple(current_param.shape))
+    inferred_shape = (n,) if "bias" in param_name else ((n + 1) // 2, 1)
+    if tuple(loaded_param.shape) != tuple(inferred_shape):
+        raise ValueError(f"Expected flattened shape of {param_name} to be {inferred_shape}, got {tuple(loaded_param.shape)}.")
+    return True
+
+
+BnB4BitDiffusersQuantizer.check_quantized_param_shape = _check_quantized_param_shape
+
 MODEL_ID = "diffusers-internal-dev/ideogram-4-nf4-v2"
 LM_HEAD_REPO = "multimodalart/qwen3-vl-8b-instruct-lm-head"
 AOTI_REPO = "multimodalart/i4-block-aoti"

diffusers_src/src/diffusers/quantizers/bitsandbytes/bnb_quantizer.py

@@ -16,7 +16,6 @@ Adapted from
 https://github.com/huggingface/transformers/blob/c409cd81777fb27aadc043ed3d8339dbc020fb3b/src/transformers/quantizers/quantizer_bnb_4bit.py
 """
 
-import math
 from typing import TYPE_CHECKING, Any
 
 from ...utils import get_module_from_name
@@ -210,8 +209,7 @@ class BnB4BitDiffusersQuantizer(DiffusersQuantizer):
         current_param_shape = current_param.shape
         loaded_param_shape = loaded_param.shape
 
-        # newer bitsandbytes returns Params4bit.shape as a plain tuple (no .numel()); math.prod handles both.
-        n = math.prod(current_param_shape)
+        n = current_param_shape.numel()
         inferred_shape = (n,) if "bias" in param_name else ((n + 1) // 2, 1)
         if loaded_param_shape != inferred_shape:
             raise ValueError(