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[ARTICLE · art-27045] src=github.com ↗ pub= topic=large-language-models verified=true sentiment=↓ negative

Rio de Janeiro's "homegrown" LLM appears to be a merge of an existing model

Rio de Janeiro's city government released a large language model called Rio-3.5-Open-397B, claiming it was originally trained by IplanRIO. However, an investigation reveals the model is a direct element-wise merge of Nex-AGI's Nex-N2 model and Qwen's Qwen3.5-397B-A17B, with no evidence of independent training. The model identifies itself as Nex 79% of the time and recites Nex-AGI's backstory word-for-word.

read1 min publishedJun 14, 2026
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[ prefeitura-rio/Rio-3.5-Open-397B](https://huggingface.co/prefeitura-rio/Rio-3.5-Open-397B) is presented as an original 397B model trained by

[IplanRIO](https://iplanrio.rio.rj.gov.br/). It is not. Its weights are a

direct element-wise merge of our model, Nex, with the official— about

baseQwen3.5-397B-A17B 0.6 Nex / 0.4 Qwen— and we find

no evidence of any training of their own. We can show this

two completely independent ways:

With Rio's hard-coded "You are Rio" system prompt removed, its own deployed model identifies itself as "Nex, from Nex-AGI" 79% of the time — and as "Rio" 0% of the time.It even recites our organization's bespoke backstory word-for-word. Every weight tensor in Rio is, to thousands of standard deviations, the same 0.6/0.4 blend of Nex and Qwen— across all 60 layers and every component of the network. Other finetunes cannot be explained as interpolations.

Below is the evidence. Judge for yourself.

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