Mellum2 Thinking — GGUF (BF16)

This repository contains a GGUF BF16 quantization of JetBrains/Mellum2-12B-A2.5B-Thinking, ready to run with llama.cpp, Ollama, LM Studio, and other GGUF-compatible runtimes.

This quantization (BF16): 16-bit, no quantization. The reference these quants are measured against; largest file.

Mellum 2 Thinking is a Mixture-of-Experts reasoning model (64 experts, 8 activated per token, 131,072-token context) that emits its chain of thought inside <think>...</think> blocks before the final answer. For the full model description, evaluation results, and architecture details, see the original model card: JetBrains/Mellum2-12B-A2.5B-Thinking.

Available quantizations

KL divergence and top-token agreement are measured against the BF16 logits on Wikitext-2 (n_ctx=512); lower KLD / higher agreement means closer to the unquantized model.

Download

hf download JetBrains/Mellum2-12B-A2.5B-Thinking-GGUF-BF16 Mellum2-12B-A2.5B-Thinking-BF16.gguf --local-dir .

Run with llama.cpp

# Pull and serve in one step (downloads the GGUF automatically)
llama-server -hf JetBrains/Mellum2-12B-A2.5B-Thinking-GGUF-BF16 \
  --ctx-size 131072 \
  --temp 0.6 --top-p 0.95 --top-k 20

# Or run a one-off prompt with a local file
llama-cli -m Mellum2-12B-A2.5B-Thinking-BF16.gguf \
  --ctx-size 131072 \
  --temp 0.6 --top-p 0.95 --top-k 20 \
  -p "Is 1024 a power of 2? Explain your reasoning."

The server exposes an OpenAI-compatible API on http://localhost:8080/v1:

from openai import OpenAI

client = OpenAI(base_url="http://localhost:8080/v1", api_key="llama.cpp")

chat_response = client.chat.completions.create(
    model="JetBrains/Mellum2-12B-A2.5B-Thinking-GGUF-BF16",
    messages=[
        {"role": "user", "content": "Is 1024 a power of 2? Explain your reasoning."},
    ],
    max_tokens=81920,
    temperature=0.6,
    top_p=0.95,
    extra_body={"top_k": 20},
)
print(chat_response.choices[0].message.content)

Run with Ollama

ollama run hf.co/JetBrains/Mellum2-12B-A2.5B-Thinking-GGUF-BF16

License

Released under the Apache 2.0 license.

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For the full model card, evaluation results, and architecture details, refer to the original model: JetBrains/Mellum2-12B-A2.5B-Thinking.