diff --git a/unsloth/models/rl.py b/unsloth/models/rl.py index 9ec4d76ed3..14a07e193a 100644 --- a/unsloth/models/rl.py +++ b/unsloth/models/rl.py @@ -1168,6 +1168,41 @@ def patch_functions(RLTrainer, trainer_file, RLTrainer_name, all_imports, import "model = self._prepare_peft_model(model, peft_config, args)\n", "pass\n" ) + # Skip add_adapter("ref") for reference model computation + # Unsloth: We comment out the "ref" adapter creation because: + # 1. We want to use the original BASE MODEL as the reference model, not the SFT/LoRA model + # 2. PEFT doesn't allow multiple adapters when target_parameters is used (MoE models) + # When "ref" is not in peft_config, GRPO/RLOO fallback uses disable_adapter() + # which gives the base model logits - exactly what we want + add_adapter_block_pattern = ( + r"([ \t]*)" # Capture leading indentation + r"if\s+is_peft_available\(\)\s+and\s+is_peft_model\(model\)\s+and\s+args\.beta\s*!=\s*0\.0\s*:" + r"(.*?)" # Match the entire block until ref_param.data.copy_ + r"ref_param\.data\.copy_\(param\.data\)" + ) + + def comment_out_block(match): + """Comment out each line in the matched block, preserving indentation.""" + full_match = match.group(0) + indent = match.group(1) + lines = full_match.split("\n") + commented_lines = [] + # Add explanation comment first + commented_lines.append( + f"{indent}# Unsloth: Commented out - use base model as reference, not SFT/LoRA model" + ) + # Comment out each line - insert # after leading whitespace to preserve indentation + for line in lines: + if line.strip(): + stripped = line.lstrip() + leading_ws = line[: len(line) - len(stripped)] + commented_lines.append(f"{leading_ws}# {stripped}") + else: + commented_lines.append(line) + return "\n".join(commented_lines) + + init = re.sub(add_adapter_block_pattern, comment_out_block, init, flags = re.DOTALL) + # Set use_vllm if not set if "args.use_vllm" in init and "model" in init and "args" in init: # .*? matches first match. .+? matches final match.