Alibaba’s Qwen AI project has lost one of its most visible technical leaders just a day after the Chinese tech giant unveiled its new Qwen 3.5 open-weight small models.

Junyang Lin, a central technical leader on Alibaba’s Qwen team, said in a post on X on Tuesday that he was “stepping down” from the project, without elaborating. He joined Alibaba in July 2019 and became part of the Qwen team in April 2023, according to his LinkedIn profile.

The abrupt departure, which drew strong reactions from colleagues and industry partners, comes as global competition among AI developers intensifies and companies race to build models rivaling those from OpenAI, Google, and Anthropic.

Alibaba’s Qwen family of models has emerged as one of China’s most prominent open-weight AI efforts, with recent releases posting benchmark results that often rival systems from leading U.S. developers. The Chinese tech giant introduced the model in April 2023 and opened it to public use that September after receiving regulatory clearance.

Alibaba introduced its Qwen 3.5 Small Model series on Monday, with four models spanning 0.8B, 2B, 4B, and 9B parameters. The systems, the company said, are native multimodal models designed for uses ranging from on-device AI deployment to lightweight agents. The launch drew attention from figures in the AI community, including Elon Musk, who wrote on X that the models showed “impressive intelligence density.”

Lin’s departure came just as the Qwen team was pushing ahead with new releases, prompting unusually strong reactions from colleagues and partners who described his role in the project as central.

Wenting Zhao, a research scientist on the Qwen team, described Lin’s departure as “the end of an era,” thanking him in a post on X for helping drive the project’s advances in open source AI and engineering. Yuchen Jin, chief technology officer of AI infrastructure startup Hyperbolic, said Lin helped connect Qwen with the global developer community, recalling late-night collaboration with the team during model launches. Tiezhen Wang, head of APAC ecosystem at Hugging Face, also described Lin’s departure as “an immense loss” for the Qwen project.

The circumstances surrounding Lin’s departure remain unclear. Lin did not respond to a request for comment.

Chen Cheng, a contributor to the Qwen project, wrote that he was “heartbroken” by the news. In his post on X, Cheng appeared to be addressing Lin directly, writing, “I know leaving wasn’t your choice” and said the team had been working together on model launches only hours earlier.

Binyuan Hui, another member of the Qwen team, has updated his X profile to describe himself as “formerly MTS @Alibaba_Qwen.” However, it is not immediately clear whether he had left the company or when the change was made.

Alibaba did not respond to a request for comment on the reasons for the move or on the leadership structure of the Qwen team.