ParaThinker: Native Parallel Reasoning for Scaling LLM Test-Time Compute

Hao Wen, Yifan Su, Feifei Zhang, Xinrui Wu, Yi Sun, Yunxin Liu, Yunhao Liu, Ya-Qin Zhang, Yuanchun Li


Abstract
Test-time scaling improves the reasoning capability of large language models by generating longer sequential chains of thought. While effective, this approach reaches a bottleneck as computation increases, resulting in a “test-time scaling plateau” where further computation provides only marginal gains. We argue that this ceiling reflects a limitation of the scaling strategy rather than model capability, a phenomenon we term Tunnel Vision, where imperfect early steps can lock the model into a suboptimal reasoning path. Motivated by this observation, we propose ParaThinker, an end-to-end parallel reasoning framework that trains LLMs to generate multiple reasoning paths in parallel and aggregate them into a final answer within a single architecture. By exploring different lines of thought, ParaThinker sidesteps the Tunnel Vision issue and unlocks the model’s reasoning potential. On challenging reasoning benchmarks, ParaThinker achieves accuracy improvements (e.g., 6.5%–20.7% on AIME-24 with a 1.5B model) over sequential-reasoning LLMs under the same budget of decoding tokens. Under matched decoding token budgets and with KV-cache reuse, ParaThinker achieves 38.7%–66.8% lower inference latency than sequential decoding via batched parallel generation. The code is available at https://github.com/MobileLLM/ParaThinker.
Anthology ID:
2026.findings-emnlp.1469
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
31265–31285
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1469/
DOI:
Bibkey:
Cite (ACL):
Hao Wen, Yifan Su, Feifei Zhang, Xinrui Wu, Yi Sun, Yunxin Liu, Yunhao Liu, Ya-Qin Zhang, and Yuanchun Li. 2026. ParaThinker: Native Parallel Reasoning for Scaling LLM Test-Time Compute. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 31265–31285, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
ParaThinker: Native Parallel Reasoning for Scaling LLM Test-Time Compute (Wen et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1469.pdf