STITCH: Simultaneous Thinking and Talking with Chunked Reasoning for
  Spoken Language Models
Authors: name: Cheng-Han Chiang; name: Xiaofei Wang; name: Linjie Li; name: Chung-Ching Lin; name: Kevin Lin; name: Shujie Liu; name: Zhendong Wang; name: Zhengyuan Yang; name: Hung-yi Lee; name: Lijuan Wang
Published: 2025-07-21 08:30:03

Abstract: Spoken Language Models (SLMs) are designed to take speech inputs and produce
spoken responses. However, current SLMs lack the ability to perform an
internal, unspoken thinking process before responding. In contrast, humans
typically engage in complex mental reasoning internally, enabling them to
communicate ideas clearly and concisely. Thus, integrating an unspoken thought
process into SLMs is highly desirable. While naively generating a complete
chain-of-thought (CoT) reasoning before starting to talk can enable thinking
for SLMs, this induces additional latency for the speech response, as the CoT
reasoning can be arbitrarily long. To solve this issue, we propose Stitch, a
novel generation method that alternates between the generation of unspoken
reasoning chunks and spoken response chunks. Since the audio duration of a
chunk of spoken response is much longer than the time to generate the tokens in
a chunk of spoken response, we use the remaining free time to generate the
unspoken reasoning tokens. When a chunk of audio is played to the user, the
model continues to generate the next unspoken reasoning chunk, achieving
simultaneous thinking and talking. Remarkably, Stitch matches the latency of
baselines that cannot generate unspoken CoT by design while outperforming those
baselines by 15% on math reasoning datasets; Stitch also performs equally well
on non-reasoning datasets as those baseline models. Some animations and
demonstrations are on the project page: https://d223302.github.io/STITCH.