In this tutorial, we work directly with Qwen3.5 models distilled with Claude-style reasoning and set up a Colab pipeline that lets us switch between a 27B GGUF variant and a lightweight 2B 4-bit version with a single flag. We start by validating GPU availability, then conditionally install either llama.cpp or transformers with bitsandbytes, depending on the selected path. Both branches are unified through shared generate_fn and stream_fn interfaces, ensuring consistent inference across backends. We also implement a ChatSession class for multi-turn interaction and build utilities to parse <think> traces, allowing us to explicitly separate reasoning from final outputs during execution.
MODEL_PATH = "2B_HF"
import torch
if not torch.cuda.is_available():
raise RuntimeError(
"❌ No GPU! Go to Runtime → Change runtime type → T4 GPU."
)
gpu_name = torch.cuda.get_device_name(0)
vram_gb = torch.cuda.get_device_properties(0).total_memory / 1e9
print(f"✅ GPU: {gpu_name} — {vram_gb:.1f} GB VRAM")
import subprocess, sys, os, re, time
generate_fn = None
stream_fn = NoneWe initialize the execution by setting the model path flag and checking whether a GPU is available on the system. We retrieve and print the GPU name along with available VRAM to ensure the environment meets the requirements. We also import all required base libraries and define placeholders for the unified generation functions that will be assigned later.
if MODEL_PATH == "27B_GGUF":
print("\n📦 Installing llama-cpp-python with CUDA (takes 3-5 min)...")
env = os.environ.copy()
env["CMAKE_ARGS"] = "-DGGML_CUDA=on"
subprocess.check_call(
[sys.executable, "-m", "pip", "install", "-q", "llama-cpp-python", "huggingface_hub"],
env=env,
)
print("✅ Installed.\n")
from huggingface_hub import hf_hub_download
from llama_cpp import Llama
GGUF_REPO = "Jackrong/Qwen3.5-27B-Claude-4.6-Opus-Reasoning-Distilled-GGUF"
GGUF_FILE = "Qwen3.5-27B-Claude-4.6-Opus-Reasoning-Distilled-Q4_K_M.gguf"
print(f"⏳ Downloading {GGUF_FILE} (~16.5 GB)... grab a coffee ☕")
model_path = hf_hub_download(repo_id=GGUF_REPO, filename=GGUF_FILE)
print(f"✅ Downloaded: {model_path}\n")
print("⏳ Loading into llama.cpp (GPU offload)...")
llm = Llama(
model_path=model_path,
n_ctx=8192,
n_gpu_layers=40,
n_threads=4,
verbose=False,
)
print("✅ 27B GGUF model loaded!\n")
def generate_fn(
prompt, system_prompt="You are a helpful assistant. Think step by step.",
max_new_tokens=2048, temperature=0.6, top_p=0.95, **kwargs
):
output = llm.create_chat_completion(
messages=[
{"role": "system", "content": system_prompt},
{"role": "user", "content": prompt},
],
max_tokens=max_new_tokens,
temperature=temperature,
top_p=top_p,
)
return output["choices"][0]["message"]["content"]
def stream_fn(
prompt, system_prompt="You are a helpful assistant. Think step by step.",
max_new_tokens=2048, temperature=0.6, top_p=0.95,
):
print("⏳ Streaming output:\n")
for chunk in llm.create_chat_completion(
messages=[
{"role": "system", "content": system_prompt},
{"role": "user", "content": prompt},
],
max_tokens=max_new_tokens,
temperature=temperature,
top_p=top_p,
stream=True,
):
delta = chunk["choices"][0].get("delta", {})
text = delta.get("content", "")
if text:
print(text, end="", flush=True)
print()
class ChatSession:
def __init__(self, system_prompt="You are a helpful assistant. Think step by step."):
self.messages = [{"role": "system", "content": system_prompt}]
def chat(self, user_message, temperature=0.6):
self.messages.append({"role": "user", "content": user_message})
output = llm.create_chat_completion(
messages=self.messages, max_tokens=2048,
temperature=temperature, top_p=0.95,
)
resp = output["choices"][0]["message"]["content"]
self.messages.append({"role": "assistant", "content": resp})
return respWe handle the 27B GGUF path by installing llama.cpp with CUDA support and downloading the Qwen3.5 27B distilled model from Hugging Face. We load the model with GPU offloading and define a standardized generate_fn and stream_fn for inference and streaming outputs. We also implement a ChatSession class to maintain conversation history for multi-turn interactions.
elif MODEL_PATH == "2B_HF":
print("\n📦 Installing transformers + bitsandbytes...")
subprocess.check_call([
sys.executable, "-m", "pip", "install", "-q",
"transformers @ git+https://github.com/huggingface/transformers.git@main",
"accelerate", "bitsandbytes", "sentencepiece", "protobuf",
])
print("✅ Installed.\n")
from transformers import AutoModelForCausalLM, AutoTokenizer, BitsAndBytesConfig, TextStreamer
HF_MODEL_ID = "Jackrong/Qwen3.5-2B-Claude-4.6-Opus-Reasoning-Distilled"
bnb_config = BitsAndBytesConfig(
load_in_4bit=True,
bnb_4bit_quant_type="nf4",
bnb_4bit_compute_dtype=torch.bfloat16,
bnb_4bit_use_double_quant=True,
)
print(f"⏳ Loading {HF_MODEL_ID} in 4-bit...")
tokenizer = AutoTokenizer.from_pretrained(HF_MODEL_ID, trust_remote_code=True)
model = AutoModelForCausalLM.from_pretrained(
HF_MODEL_ID,
quantization_config=bnb_config,
device_map="auto",
trust_remote_code=True,
torch_dtype=torch.bfloat16,
)
print(f"✅ Model loaded! Memory: {model.get_memory_footprint() / 1e9:.2f} GB\n")
def generate_fn(
prompt, system_prompt="You are a helpful assistant. Think step by step.",
max_new_tokens=2048, temperature=0.6, top_p=0.95,
repetition_penalty=1.05, do_sample=True, **kwargs
):
messages = [
{"role": "system", "content": system_prompt},
{"role": "user", "content": prompt},
]
text = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(text, return_tensors="pt").to(model.device)
with torch.no_grad():
output_ids = model.generate(
**inputs, max_new_tokens=max_new_tokens, temperature=temperature,
top_p=top_p, repetition_penalty=repetition_penalty, do_sample=do_sample,
)
generated = output_ids[0][inputs["input_ids"].shape[1]:]
return tokenizer.decode(generated, skip_special_tokens=True)
def stream_fn(
prompt, system_prompt="You are a helpful assistant. Think step by step.",
max_new_tokens=2048, temperature=0.6, top_p=0.95,
):
messages = [
{"role": "system", "content": system_prompt},
{"role": "user", "content": prompt},
]
text = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(text, return_tensors="pt").to(model.device)
streamer = TextStreamer(tokenizer, skip_prompt=True, skip_special_tokens=True)
print("⏳ Streaming output:\n")
with torch.no_grad():
model.generate(
**inputs, max_new_tokens=max_new_tokens, temperature=temperature,
top_p=top_p, do_sample=True, streamer=streamer,
)
class ChatSession:
def __init__(self, system_prompt="You are a helpful assistant. Think step by step."):
self.messages = [{"role": "system", "content": system_prompt}]
def chat(self, user_message, temperature=0.6):
self.messages.append({"role": "user", "content": user_message})
text = tokenizer.apply_chat_template(self.messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(text, return_tensors="pt").to(model.device)
with torch.no_grad():
output_ids = model.generate(
**inputs, max_new_tokens=2048, temperature=temperature, top_p=0.95, do_sample=True,
)
generated = output_ids[0][inputs["input_ids"].shape[1]:]
resp = tokenizer.decode(generated, skip_special_tokens=True)
self.messages.append({"role": "assistant", "content": resp})
return resp
else:
raise ValueError("MODEL_PATH must be '27B_GGUF' or '2B_HF'")We implement the lightweight 2B path using transformers with 4-bit quantization through bitsandbytes. We load the Qwen3.5 2B distilled model efficiently onto the GPU and configure generation parameters for controlled sampling. We again define unified generation, streaming, and chat session logic so that both model paths behave identically during execution.
def parse_thinking(response: str) -> tuple:
m = re.search(r"<think>(.*?)</think>", response, re.DOTALL)
if m:
return m.group(1).strip(), response[m.end():].strip()
return "", response.strip()
def display_response(response: str):
thinking, answer = parse_thinking(response)
if thinking:
print("🧠 THINKING:")
print("-" * 60)
print(thinking[:1500] + ("\n... [truncated]" if len(thinking) > 1500 else ""))
print("-" * 60)
print("\n💬 ANSWER:")
print(answer)
print("✅ All helpers ready. Running tests...\n")We define helper functions to extract reasoning traces enclosed within <think> tags and separate them from final answers. We create a display utility that formats and prints both the thinking process and the response in a structured way. This allows us to inspect how the Qwen-based model reasons internally during generation.
print("=" * 70)
print("📝 TEST 1: Basic reasoning")
print("=" * 70)
response = generate_fn(
"If I have 3 apples and give away half, then buy 5 more, how many do I have? "
"Explain your reasoning."
)
display_response(response)
print("\n" + "=" * 70)
print("📝 TEST 2: Streaming output")
print("=" * 70)
stream_fn(
"Explain the difference between concurrency and parallelism. "
"Give a real-world analogy for each."
)
print("\n" + "=" * 70)
print("📝 TEST 3: Thinking ON vs OFF")
print("=" * 70)
question = "What is the capital of France?"
print("\n--- Thinking ON (default) ---")
resp = generate_fn(question)
display_response(resp)
print("\n--- Thinking OFF (concise) ---")
resp = generate_fn(
question,
system_prompt="Answer directly and concisely. Do not use <think> tags.",
max_new_tokens=256,
)
display_response(resp)
print("\n" + "=" * 70)
print("📝 TEST 4: Bat & ball trick question")
print("=" * 70)
response = generate_fn(
"A bat and a ball cost $1.10 in total. "
"How much does the ball cost? Show complete reasoning and verify.",
system_prompt="You are a precise mathematical reasoner. Set up equations and verify.",
temperature=0.3,
)
display_response(response)
print("\n" + "=" * 70)
print("📝 TEST 5: Train meeting problem")
print("=" * 70)
response = generate_fn(
"A train leaves Station A at 9:00 AM at 60 mph toward Station B. "
"Another leaves Station B at 10:00 AM at 80 mph toward Station A. "
"Stations are 280 miles apart. When and where do they meet?",
temperature=0.3,
)
display_response(response)
print("\n" + "=" * 70)
print("📝 TEST 6: Logic puzzle (five houses)")
print("=" * 70)
response = generate_fn(
"Five houses in a row are painted different colors. "
"The red house is left of the blue house. "
"The green house is in the middle. "
"The yellow house is not next to the blue house. "
"The white house is at one end. "
"What is the order from left to right?",
temperature=0.3,
max_new_tokens=3000,
)
display_response(response)
print("\n" + "=" * 70)
print("📝 TEST 7: Code generation — longest palindromic substring")
print("=" * 70)
response = generate_fn(
"Write a Python function to find the longest palindromic substring "
"using Manacher's algorithm. Include docstring, type hints, and tests.",
system_prompt="You are an expert Python programmer. Think through the algorithm carefully.",
max_new_tokens=3000,
temperature=0.3,
)
display_response(response)
print("\n" + "=" * 70)
print("📝 TEST 8: Multi-turn conversation (physics tutor)")
print("=" * 70)
session = ChatSession(
system_prompt="You are a knowledgeable physics tutor. Explain clearly with examples."
)
turns = [
"What is the Heisenberg uncertainty principle?",
"Can you give me a concrete example with actual numbers?",
"How does this relate to quantum tunneling?",
]
for i, q in enumerate(turns, 1):
print(f"\n{'─'*60}")
print(f"👤 Turn {i}: {q}")
print(f"{'─'*60}")
resp = session.chat(q, temperature=0.5)
_, answer = parse_thinking(resp)
print(f"🤖 {answer[:1000]}{'...' if len(answer) > 1000 else ''}")
print("\n" + "=" * 70)
print("📝 TEST 9: Temperature comparison — creative writing")
print("=" * 70)
creative_prompt = "Write a one-paragraph opening for a sci-fi story about AI consciousness."
configs = [
{"label": "Low temp (0.1)", "temperature": 0.1, "top_p": 0.9},
{"label": "Med temp (0.6)", "temperature": 0.6, "top_p": 0.95},
{"label": "High temp (1.0)", "temperature": 1.0, "top_p": 0.98},
]
for cfg in configs:
print(f"\n🎛️ {cfg['label']}")
print("-" * 60)
start = time.time()
resp = generate_fn(
creative_prompt,
system_prompt="You are a creative fiction writer.",
max_new_tokens=512,
temperature=cfg["temperature"],
top_p=cfg["top_p"],
)
elapsed = time.time() - start
_, answer = parse_thinking(resp)
print(answer[:600])
print(f"⏱️ {elapsed:.1f}s")
print("\n" + "=" * 70)
print("📝 TEST 10: Speed benchmark")
print("=" * 70)
start = time.time()
resp = generate_fn(
"Explain how a neural network learns, step by step, for a beginner.",
system_prompt="You are a patient, clear teacher.",
max_new_tokens=1024,
)
elapsed = time.time() - start
approx_tokens = int(len(resp.split()) * 1.3)
print(f"~{approx_tokens} tokens in {elapsed:.1f}s")
print(f"~{approx_tokens / elapsed:.1f} tokens/sec")
print(f"GPU: {torch.cuda.get_device_name(0)}")
print(f"Peak VRAM: {torch.cuda.max_memory_allocated() / 1e9:.2f} GB")
import gc
for name in ["model", "llm"]:
if name in globals():
del globals()[name]
gc.collect()
torch.cuda.empty_cache()
print(f"\n✅ Memory freed. VRAM: {torch.cuda.memory_allocated() / 1e9:.2f} GB")
print("\n" + "=" * 70)
print("🎉 Tutorial complete!")
print("=" * 70)We run a comprehensive test suite that evaluates the model across reasoning, streaming, logic puzzles, code generation, and multi-turn conversations. We compare outputs under different temperature settings and measure performance in terms of speed and token throughput. Finally, we clean up memory and free GPU resources, ensuring the notebook remains reusable for further experiments.
In conclusion, we have a compact but flexible setup for running Qwen3.5-based reasoning models enhanced with Claude-style distillation across different hardware constraints. The script abstracts backend differences while exposing consistent generation, streaming, and conversational interfaces, making it easy to experiment with reasoning behavior. Through the test suite, we probe how the model handles structured reasoning, edge-case questions, and longer multi-step tasks, while also measuring speed and memory usage. What we end up with is not just a demo, but a reusable scaffold for evaluating and extending Qwen-based reasoning systems in Colab without changing the core code.
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