Qwen3-8B-SW-Pivot-EN

Qwen3-8B-SW-Pivot-EN is an English-pivoted reasoning model fine-tuned from Qwen/Qwen3-8B-Base on Swahili questions and answers. This model receives questions in Swahili, produces its entire reasoning trace in English, then delivers the final answer in Swahili.

It is released alongside the paper Rethinking the Multilingual Reasoning Gap with Layer Swap.

Model details

  • Base model: Qwen/Qwen3-8B-Base
  • Language: Swahili (Q&A) with English CoT
  • Training: Full SFT, ~10B tokens, 2 epochs
  • Context length: 32,768 tokens
  • Dataset: lightonai/Dolci-Think-SFT-32B-Multilingual (Swahili Q&A with English CoT).

The model was trained on data derived from allenai/Dolci-Think-SFT-32B, released under the ODC-BY-1.0 license.

Related models

This model is part of a Swahili specialist trio designed to study the native reasoning gap:

Model CoT language Description
lightonai/Qwen3-8B-SW Swahili Native reasoning specialist
lightonai/Qwen3-8B-SW-Swap Swahili Layer Swap: middle layers (L13–L22) of Qwen3-8B-EN transplanted into Qwen3-8B-SW
lightonai/Qwen3-8B-SW-Pivot-EN English Same Swahili Q&A pairs, but CoT in English
lightonai/Qwen3-8B-EN English English specialist

Evaluation

All scores are mean accuracy (%) on the Swahili version of each benchmark, with sample standard deviation across runs. AIME 24/25 is averaged over 30 runs; the others over 10 runs, using the recommended generation parameters.

Model MGSM-Rev2 Global-MMLU-Lite GPQA-Diamond AIME 24/25 HumanEvalPlus Average
Qwen3-8B-SW 93.16 61.98 49.39 47.67 82.69 66.98
Qwen3-8B-SW-Swap 96.12 64.10 49.29 50.33 85.62 69.09
Qwen3-8B-SW-Pivot-EN 89.68 66.00 52.73 59.67 84.50 70.52
Qwen3-8B-EN 35.88 33.88 36.82 24.78 58.44 37.96

Benchmarks used:

Usage

from transformers import AutoModelForCausalLM, AutoTokenizer

model_name = "lightonai/Qwen3-8B-SW-Pivot-EN"
tokenizer = AutoTokenizer.from_pretrained(model_name)
model = AutoModelForCausalLM.from_pretrained(model_name, torch_dtype="auto", device_map="auto")

messages = [{"role": "user", "content": "Suluhisha: 24 × 17 = ?"}]
inputs = tokenizer.apply_chat_template(messages, return_tensors="pt", add_generation_prompt=True).to(model.device)

outputs = model.generate(inputs, max_new_tokens=32768, temperature=1.0, top_p=0.95, top_k=20)
print(tokenizer.decode(outputs[0][inputs.shape[-1]:], skip_special_tokens=True))

Recommended sampling: temperature=1.0, top_p=0.95, top_k=20, min_p=0.

Citation

If you find our work helpful, feel free to give us a cite.

@misc{lasbordes2026rethinking,
  title        = {Rethinking the Multilingual Reasoning Gap with Layer Swap},
  author       = {Lasbordes, Maxence and Chatelain, Amélie and Seddah, Djamé},
  year         = {2026},
  eprint       = {2605.26735},
  archivePrefix= {arXiv},
  primaryClass = {cs.CL}
}
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