Multiplex Thinking: Reasoning via Token-wise Branch-and-Merge

• URL: http://arxiv.org/abs/2601.08808v1
• Date: Tue, 13 Jan 2026 18:48:00 GMT
• Title: Multiplex Thinking: Reasoning via Token-wise Branch-and-Merge
• Authors: Yao Tang, Li Dong, Yaru Hao, Qingxiu Dong, Furu Wei, Jiatao Gu,
• Abstract summary: Large language models often solve complex reasoning tasks more effectively with Chain-of-Thought (CoT)<n>Humans, by contrast, often reason softly by maintaining a tractable probability distribution over plausible next steps.<n>We propose Multiplex Thinking, a soft reasoning mechanism that samples K candidate tokens and aggregates their embeddings into a single continuous multiplex token.<n>Multiplex Thinking is self-adaptive: when the model is confident, the multiplex token is nearly discrete and behaves like standard CoT.
• Score: 87.51901436392427
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Large language models often solve complex reasoning tasks more effectively with Chain-of-Thought (CoT), but at the cost of long, low-bandwidth token sequences. Humans, by contrast, often reason softly by maintaining a distribution over plausible next steps. Motivated by this, we propose Multiplex Thinking, a stochastic soft reasoning mechanism that, at each thinking step, samples K candidate tokens and aggregates their embeddings into a single continuous multiplex token. This preserves the vocabulary embedding prior and the sampling dynamics of standard discrete generation, while inducing a tractable probability distribution over multiplex rollouts. Consequently, multiplex trajectories can be directly optimized with on-policy reinforcement learning (RL). Importantly, Multiplex Thinking is self-adaptive: when the model is confident, the multiplex token is nearly discrete and behaves like standard CoT; when it is uncertain, it compactly represents multiple plausible next steps without increasing sequence length. Across challenging math reasoning benchmarks, Multiplex Thinking consistently outperforms strong discrete CoT and RL baselines from Pass@1 through Pass@1024, while producing shorter sequences. The code and checkpoints are available at https://github.com/GMLR-Penn/Multiplex-Thinking.

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