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Rio 3.5 Open 397B is claimed to be developed by the IT company of Rio de…

2026-06-13 · 21:39 UTC ·@kimmonismus ·0 min read

Brief

A June 13, 2026 social post says Rio 3.5 Open 397B — built by Rio de Janeiro’s municipal IT company — has been open‑sourced and is being touted as state‑of‑the‑art, reportedly outperforming Alibaba’s proprietary Qwen 3.7. The thread positions Rio 3.5 alongside Minimax M3 as emerging frontier alternatives and links to a Hugging Face repo.

Why it matters

Rio 3.5 Open 397B is claimed to be developed by the IT company of Rio de Janeiro's city government (Prefeitura) and has been released as open source.

Key details

Poster and quoted account (@kimmonismus, quoting @ZenMagnets) claim Rio 3.5 397B is now SOTA and even outperforming Alibaba Qwen 3.7; alternatives called out are Minimax M3 and the Hugging Face repo linked (huggingface.co/prefeitura-ri…).

Source evidence

Wait what? Rio 3.5 Open 397B, developed by IT company of Rio de Janeiro's city government is now SOTA open source and even outperforming Qwen 3.7?

What is happening today.

Never heard of them before.

𝗭𝗲𝗻 𝗠𝗮𝗴𝗻𝗲𝘁𝘀 (@ZenMagnets)

Alibaba Qwen3.7 slowly fading into irrelevance at the frontier due to proprietary stance.
In it's place we have Minimax M3 and... checks notes Rio 3.5 397b, made by the municipal IT company of Rio de Janeiro's city government.

huggingface.co/prefeitura-ri…

— https://nitter.net/ZenMagnets/status/2065796012820848699#m