MiniMax Unveils 'Space Bunny' Identity: Open Weights Released for 428B Parameter MoE Model M3.1 Flash
MiniMax has released open weights for its previously anonymous 'Space Bunny' model, confirmed as a 428B parameter MoE architecture. Focused on coding and agents, it is free for non-commercial use but requires written permission for enterprises exceeding $20M in annual revenue.
Chinese AI company MiniMax released the open weights for its coding and agent-specialized large language model, "MiniMax M3.1 Flash," on Hugging Face and ModelScope on October 23. Previously, the model operated anonymously via API under the name "Space Bunny," processing over 200 trillion tokens cumulatively. The release reveals its true architecture: approximately 428 billion total parameters using a Mixture-of-Experts (MoE) design, activating 23 billion parameters per token, with a context window of 1 million tokens.
Technically, MiniMax states that M3.1 Flash builds upon the MiniMax M3 architecture released in June, with three key modifications: replacing the remaining three full-attention layers with a proprietary sparse attention mechanism to make the entire model sparse; incorporating quantization-aware training; and utilizing DSpark for speculative decoding. SGLang, vLLM, and TokenSpeed are recommended for local inference frameworks.
Performance metrics are self-reported by the vendor. MiniMax claims the model scores 76.2 on BankerToolBench (investment banking task automation), matching Claude Opus 5. On DeepSWE v1.1 (code repair accuracy), it scores 73.7%, surpassing Kimi K3 and GLM-5.3 but trailing the DeepSeek V4.1 Flash series and Opus 5. In Automation-Bench v1.0.6, it scored 62.2, ranking first among the seven compared models.
The license is the MiniMax Community License. Non-commercial use is free. Commercial use requires prominent attribution stating "Built with MiniMax M3.1-Flash." If the product's annual revenue is below $20 million, a one-time email notification is required; if it exceeds $20 million, prior written permission from MiniMax must be obtained.