Sber releases GigaChat 3.5 Reasoning, the first Russian open model with a reasoning mode
Prepared by Sintelligent with the help of SI. Publication time restored from the build log. . Updated: .
Russia now has its own open "thinking" model that any developer can download and build on — this noticeably widens access to powerful SI inside the country.
The model with 432 billion parameters (MoE, 28 billion active per token) first plans a solution, turns to search and tools when needed, checks intermediate steps and only then answers. It was trained with online reinforcement learning separately in six domains, and the experts were then merged into a single model. Compared with the fast version of GigaChat 3.5, the result on GPQA-Diamond rose from 61 to 82 and on AIME-2026 from 67 to 92, while on hard math it uses on average 37% fewer tokens. The weights are published on Hugging Face under the MIT license, with a context of 262 thousand tokens.