Reproduction

• Install the forgecode harness
• Set up the OpenAICompatible provider to point at a local oMLX endpoint
• I don't know if this is model-dependent, but I was using https://huggingface.co/deepsweet/Qwen3.6-35B-A3B-MLX-VL-oQ8-FP16
• Send any prompt (I just started with "hi")
• Error output:

 ERROR: POST http://127.0.0.1:8000/v1/chat/completions                                                                        
                                                                                                                                          
 Caused by:                                                                                                                               
     0: Failed to create completion message: {"error": {"message": "Cache corruption not recoverable after retries: 'NoneType' object is  
 not iterable", "type": "server_error"}}                                                                                                  
     1: {"message":"Cache corruption not recoverable after retries: 'NoneType' object is not iterable","type":"server_error"}             

• The "Cache corruption" error message seems to be spurious, I cleared the in-memory and ssd caches and it didn't resolve.

Diagnosis

When logits_processors is None (no repetition/presence/frequency penalties configured), mlx-lm's GenerationBatch._step crashes with:

TypeError: 'NoneType' object is not iterable

This is caught by omlx's cache corruption recovery, but since the root cause persists, requests fail after 3 retries with:

Cache corruption not recoverable after retries: 'NoneType' object is not iterable

Fix

Three layers of defense to normalise None → []:

1. _create_batch_generator — pass [] instead of None to BatchGenerator constructor
2. _patched_generation_batch_step — normalise None → [] before calling mlx-lm's _step (which crashes at any(None))
3. _patched_ppb_split — normalise None → [] when splitting batches

Consistent with the existing fix at line 6528 where per_row_lps = list(logits_processors) if logits_processors else [] was already applied.