Qwen3-4B · Multilingual Reasoning — thinks in 6 languages

A Qwen3-4B whose chain-of-thought is written in the target language — English, Chinese, Spanish, French, Arabic, Russian — not just the final answer. Standard reasoning models silently think in English and translate only the result; this model produces its <think>...</think> reasoning natively in each language, making multilingual math reasoning transparent and language-consistent.

Model details

  • Base model: Qwen/Qwen3-4B (official post-trained), not Qwen3-4B-Base.
  • Fine-tuning: SFT on a balanced 6-language long chain-of-thought math set (SFT-Math-45k-mling6, 43k problems, one language per problem, round-robin), 2 epochs. (Internal name: Qwen3-4B-mling6-SFT-ep2.)
  • Architecture: Qwen3ForCausalLM, 4B params, 36 layers, hidden 2560, vocab 151,936, context 40,960.
  • Languages: English, Chinese, Spanish, French, Arabic, Russian.
  • Format: thinking model — emits a <think>...</think> trace, then the answer.

Usage

from transformers import AutoModelForCausalLM, AutoTokenizer
name = "96kevinli29/Qwen3-4B-Multilingual-Reasoning"
tok = AutoTokenizer.from_pretrained(name)
model = AutoModelForCausalLM.from_pretrained(name, torch_dtype="bfloat16", device_map="auto")
msgs = [{"role": "user", "content": "Решите задачу шаг за шагом, рассуждая полностью на русском языке.\n\n..."}]
inputs = tok.apply_chat_template(msgs, add_generation_prompt=True, enable_thinking=True, return_tensors="pt").to(model.device)
out = model.generate(inputs, max_new_tokens=24576, temperature=0.7)
print(tok.decode(out[0][inputs.shape[1]:]))

To get in-language reasoning, prompt the model in the target language (input language drives the reasoning language).

Notes & limitations

  • On some scripts (notably Arabic and Russian) genuine in-language reasoning can exhibit generation-stability issues (looping / not terminating within the token budget). Read accuracy together with generation-completion rate.
  • Companion RL prompt set for improving stability: 96kevinli29/DAPO-Math-Multilingual-6Lang.

Training data & attribution

  • Base model: Qwen/Qwen3-4B (official post-trained).
  • SFT data source: built by translating English long chain-of-thought traces from OpenR1-Math (open-r1/OpenR1-Math-220k) (via a 45k English subset) into the five non-English languages with Qwen3-14B (faithful, paragraph-chunked; LaTeX / \boxed{} / <think> tags preserved). English traces pass through unchanged. Please cite Qwen3 and OpenR1-Math as upstream sources.
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