Mellum by JetBrains

What is Mellum?

Mellum is a family of fast, open-source language models developed by JetBrains, optimized for real-world development workflows where latency and performance matter most. The latest generation introduces a mixture-of-experts (MoE) architecture that delivers ultra-low-latency inference and high throughput, often twice as fast as similar-sized models. Mellum understands code, context, and intent, expanding beyond pure code completion to support both natural language and programming tasks.

Who it's for

• AI/ML engineers who need fast, cost-efficient inference for production workloads and real-time applications
• Developers building coding assistants or agent pipelines that require low-latency responses for specialized sub-tasks
• Teams moving from experimentation to production who want predictable costs, local deployment options, and full control over performance and privacy

Key features

Mixture-of-experts architecture

Mellum uses an MoE design with fewer active parameters per request, enabling strong coding quality while halving inference costs. This architecture brings MoE capabilities to a much smaller model class, making high-performance AI accessible without the overhead of larger models.

Ultra-low-latency inference

The model is built for real-time workflows, delivering responses in milliseconds rather than seconds. This makes it ideal for smart routing, pre-processing, and post-processing tasks where speed is critical.

Flexible deployment options

Mellum can be fine-tuned and deployed locally or on the cloud, giving you full control over performance, privacy, and infrastructure. Whether you need private, local AI usage or cloud-based scaling, the model adapts to your environment.

Transparent training and alignment

Trained on transparent data and aligned for consistency, Mellum ensures reliable outputs across both coding and natural language tasks. The model is pre-trained from scratch using a mix of natural language and code data, with a focus on coding and mathematical domains.

What stands out

"We built Mellum because not every task requires the largest or most complex models."

This philosophy drives Mellum's design: instead of forcing every use case through a massive, expensive model, Mellum provides a fast, efficient alternative for high-volume, latency-sensitive tasks. It excels at powering sub-agents in complex workflows, enabling low-latency RAG pipelines, and handling smart routing between models. By focusing on performance, latency, and cost, Mellum fills the gap between toy models and expensive frontier systems, making production-grade AI practical for teams of all sizes.

Worth checking out if…

You need a fast, open-source language model that balances strong coding and language capabilities with exceptional efficiency. Mellum is particularly valuable if you're building real-time AI workflows, handling high request volumes, or want to keep code and data fully under your control with local deployment. It's also a strong choice for teams looking to reduce inference costs without sacrificing quality, especially for tasks like code completion, smart routing, and specialized sub-agent processing.