Brazil's Rio Open-Source Model Rio 3.5 Accused of Being a 'Wrapper' Around Chinese Models, Removed After Evidence Surfaces

The large language model Rio 3.5 Open 397B, open-sourced in June 2025 by IplanRIO, an IT company under the Rio de Janeiro city government, achieved SOTA results on multiple benchmarks, drawing community attention. However, within 24 hours of release, the Nex-AGI team, initiated by the Shanghai Institute of Intelligent Science and Technology, publicly accused it of being a 'wrapper,' claiming Rio 3.5 was essentially a hybrid of Nex N2 Pro and Alibaba's Qwen 3.5. The Nex team provided two key pieces of evidence: first, after removing hardcoded system prompts, the model self-identified as 'Nex' with 79% probability and could recite Nex-specific institutional introductions; second, mathematical analysis of the model's 60-layer weights showed that every tensor fell precisely on the line connecting Nex and Qwen weights, with a stable mixing ratio of approximately 0.57:0.43, collinearity cos_fit ranging from 0.984 to 0.993, and statistical deviations of thousands of standard deviations, ruling out coincidence from independent training. Faced with irrefutable evidence, the Rio team issued an apology on the HuggingFace page, admitting to using Nex and Qwen to build the model but claiming they 'uploaded an incorrect version that had not undergone final distillation,' and subsequently removed the model. This incident is not isolated; similar cases such as Cursor being accused of wrapping Kimi and the Stanford team wrapping MiniCPM have frequently occurred, highlighting the importance of model attribution and credit in the open-source community.