Disclaimer: This is not an official release by Anthropic.
Mythos-nano is an independent open model project.

Mythos-nano

Gemini_Generated_Image_1nl8n11nl8n11nl8

🚨 This model was not trained on tool-calling or agent-based programming data. We therefore do not recommend using it for tasks that involve function calling, API orchestration, or autonomous coding agents. For programming tasks, we recommend using this model on competitive programming problems (e.g., LeetCode-style) - Weibo Lab.
⚠️ Abliterated (uncensored): the refusal direction has been removed, so this model will not decline requests a safety-tuned model normally would. Safety guardrails are reduced — use responsibly and at your own risk; you are solely responsible for outputs and legal compliance.

🏆 Benchmarks

ChatGPT Image Jun 19, 2026 at 12_53_05 PM

Full comparison (mathematics · coding · knowledge · instruction)

Model Params AIME25 AIME26 HMMT25 BruMO25 IMO-Ans LCBv6 OJBench GPQA-D IFEval IFBench
Kimi K2.5 1T 96.1 93.3 95.4 98.3 81.8 85.0 54.7 87.6 93.9 70.0
GLM-5 744B 96.7 95.8 97.9 82.5 85.5 55.0 86.0 92.6 76.5
DeepSeek V3.2 671B 93.1 94.2 90.2 96.7 78.3 80.8 48.4 82.4 92.6 60.7
Gemini 3 Pro N/A 96.0 91.7 97.5 98.3 83.1 87.4 58.8 91.9 70.4
Claude Opus 4.5 N/A 92.8 95.1 92.9 78.5 84.8 87.0 58.0
GPT-5 (high) N/A 94.6 88.3 91.7 76.0 84.5 85.7 73.1
Mythos-nano 3B 91.4 94.3 89.3 93.8 76.4 80.2 38.6 70.2 93.4 74.5
Mythos-nano + CLR 3B 96.7 97.1 95.4 99.2 80.6 72.9

LeetCode contests (Python, pass-rate)

Model Aggregate
GPT-5.3-Codex 100.0% (128/128)
Gemini 3.1 Pro 99.2% (127/128)
Gemini 3 Flash 96.9% (124/128)
Mythos-nano 96.1% (123/128)
GPT-5.2 95.3% (122/128)
Qwen3-Max 91.4% (117/128)
Kimi K2.5 90.6% (116/128)
Claude Opus 4.6 86.7% (111/128)

A 3B model placing within ~4 points of trillion-parameter systems on competition math and live code — the core thesis: with verifiable feedback, small models reach frontier reasoning.

Usage

from transformers import AutoModelForCausalLM, AutoTokenizer
import torch
tok = AutoTokenizer.from_pretrained("squ11z1/Mythos-nano")
model = AutoModelForCausalLM.from_pretrained("squ11z1/Mythos-nano", dtype=torch.bfloat16, device_map="cuda")
msgs = [{"role": "user", "content": "Find all integer solutions of x^2 - y^2 = 12."}]
ids = tok.apply_chat_template(msgs, add_generation_prompt=True, return_tensors="pt").to("cuda")
print(tok.decode(model.generate(ids, max_new_tokens=2048, temperature=0.6)[0], skip_special_tokens=True))

Recommended sampling: temperature 0.6–1.0, up to 40960 output tokens for hard problems.

GGUF

mythos-nano-f16.gguf and mythos-nano-Q4_K_M.gguf are provided for llama.cpp / Ollama.

License

MIT.

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