diff --git a/src/step4_cold_start.py b/src/step4_cold_start.py
index e69de29..bf15f70 100644
--- a/src/step4_cold_start.py
+++ b/src/step4_cold_start.py
@@ -0,0 +1,87 @@
+from transformers import AutoModelForCausalLM, AutoTokenizer
+from datasets import load_dataset
+from trl import SFTConfig, SFTTrainer, setup_chat_format
+import torch
+import os
+
+device = "cuda" if torch.cuda.is_available() else "mps" if torch.backends.mps.is_available() else "cpu"
+
+model_path = "./model"
+tokenizer_path = "./model" 
+
+model = AutoModelForCausalLM.from_pretrained(model_path).to(device)
+tokenizer = AutoTokenizer.from_pretrained(tokenizer_path)
+
+try:
+    model, tokenizer = setup_chat_format(model=model, tokenizer=tokenizer)
+except Exception as e:
+    print(f"Chat format setup failed: {e}, using default formatting")
+
+data_path = "./datas"
+train_data_files = [os.path.join(data_path, f) for f in os.listdir(data_path) if f.startswith("train")]
+valid_data_files = [os.path.join(data_path, f) for f in os.listdir(data_path) if f.startswith("valid")]
+
+file_ext = os.path.splitext(train_data_files[0])[1].lower() if train_data_files else '.json'
+data_type = {
+    '.json': 'json',
+    '.jsonl': 'json',
+    '.csv': 'csv',
+    '.txt': 'text'
+}.get(file_ext, 'json')
+
+ds = load_dataset(
+    data_type,
+    data_files={
+        'train': train_data_files,
+        'validation': valid_data_files
+    },
+    split=['train', 'validation']
+)
+
+finetune_name = "Dolly-SFT"
+sft_config = SFTConfig(
+    output_dir="./sft_output",
+    max_steps=1000000,
+    per_device_train_batch_size=4,
+    learning_rate=5e-5,
+    logging_steps=10,
+    save_steps=1000,
+    save_total_limit=2, 
+    evaluation_strategy="steps",
+    eval_steps=500,
+    load_best_model_at_end=True, 
+    resume_from_checkpoint=True,  
+    hub_model_id=finetune_name,
+)
+
+trainer = SFTTrainer(
+    model=model,
+    args=sft_config,
+    train_dataset=ds[0],
+    eval_dataset=ds[1],
+    tokenizer=tokenizer,
+)
+
+checkpoint_dir = None
+if os.path.exists(sft_config.output_dir):
+    checkpoints = [d for d in os.listdir(sft_config.output_dir) if d.startswith("checkpoint")]
+    if checkpoints:
+        latest_checkpoint = max(
+            [os.path.join(sft_config.output_dir, d) for d in checkpoints],
+            key=os.path.getctime
+        )
+        checkpoint_dir = latest_checkpoint
+        print(f"Resuming training from checkpoint: {latest_checkpoint}")
+
+trainer.train(resume_from_checkpoint=checkpoint_dir)
+
+trainer.save_model(f"./{finetune_name}")
+
+prompt = "Write a haiku about programming"
+messages = [{"role": "user", "content": prompt}]
+formatted_prompt = tokenizer.apply_chat_template(messages, tokenize=False)
+
+inputs = tokenizer(formatted_prompt, return_tensors="pt").to(device)
+outputs = model.generate(**inputs, max_new_tokens=100)
+print("\nAfter training:")
+print(tokenizer.decode(outputs[0], skip_special_tokens=True))
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