JetBrains Open-Sources Mellum2: 12B MoE Coding Model for Multi-Model Pipelines
JetBrains
JetBrains released Mellum2 under Apache 2.0: a 12B Mixture-of-Experts model (2.5B active parameters, 64 experts activating 8 per token) trained on approximately 10.6T tokens for software engineering. Designed as a fast focal model for routing, RAG, subagents, and high-throughput coding features, it delivers 2x faster inference versus comparably-sized dense models.
Why it matters
First open-source coding MoE from a major IDE vendor, designed to slot into multi-model pipelines rather than replace frontier models.
Importance: 3/5
Official JetBrains blog, HuggingFace blog, and Neowin; notable as the first open-source coding MoE from a major IDE company.