Introducing Mellum2: A 12B Mixture-of-Experts Model by JetBrains

What changed

• Mellum2 is a 12B-parameter Mixture-of-Experts model trained from scratch on natural language and code. - The model activates only 2.5B parameters per token, making it efficient for high-throughput, low-latency inference. - It is released under the Apache 2.0 license.

Why it matters

A concrete addition to Practical AI: Tools, Models & Frameworks: it changes what's available to builders today rather than being general commentary.

How it compares

Related prior coverage to compare against:

• Introducing Gemma 4 12B: a unified, encoder-free multimodal model
• Embedding AI into developer software
• Introducing the Model Spec

• Introducing Gemma 4 12B: a unified, encoder-free multimodal model similarity 0.25
• Embedding AI into developer software similarity 0.15
• Introducing the Model Spec similarity 0.11