Rio 3.5 Open 397B – from Rio de Janeiro's city government (huggingface.co) AI

A Hugging Face model card describes Rio 3.5 Open 397B, an open, multimodal “frontier-class” AI model from Rio de Janeiro’s municipal IT company IplanRIO, post-trained from Qwen 3.5 397B and released under the MIT license. The card highlights its SwiReasoning framework for dynamically switching between latent and explicit reasoning to improve the accuracy/efficiency trade-off, lists key model specs (Mixture-of-Experts with ~397B total/~17B active parameters and a ~1M token context window), and provides benchmark results plus implementation examples for Transformers, vLLM, and SGLang.