bitsandbytes 0.49.2's Params4bit.__new__ has no **kwargs and rejects the
_is_hf_initialized kwarg that transformers 5.12 passes during 4-bit weight
init, so every load_in_4bit model crashed with:
  Params4bit.__new__() got an unexpected keyword argument '_is_hf_initialized'
In production this turned a single default-model chat request (Qwen3.5-9B,
load_in_4bit) into a ~2h internal 60-retry storm. bnb 0.50.2 adds **kwargs to
Params4bit.__new__ (absorbs _is_hf_initialized); verified end-to-end: a
transformers load_in_4bit load now succeeds on cuda:0 (torch 2.11/cu130), and a
GPU 4-bit quantize/dequantize round-trips. Image rebuilt with bnb 0.50.2.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mw2KQiswmD69T45fTfjKwW