Overview
Mellum by JetBrains is a family of open-source language models designed for ultra-low-latency and high-performance inference. The latest model, Mellum2, uses a mixture-of-experts (MoE) architecture with 12B parameters, delivering strong coding and math capabilities while being cost-efficient. It is built for AI/ML engineers and researchers who need a fast, deployable LLM for real-world workflows.
Emdash is an open-source desktop application that serves as a "coding agent dashboard." It allows developers to run multiple coding agents in parallel, each in its own isolated Git worktree. Emdash integrates with 25+ coding agents (e.g., Codex, Cursor, Claude Code) and provides a unified interface to monitor sessions, review diffs, and turn issues into PRs.
Feature Comparison
| Feature | Mellum by JetBrains | Emdash |
|---|---|---|
| Primary Function | Family of fast, open-source language models optimized for low-latency inference and coding tasks | Open-source desktop app for running multiple coding agents in parallel, with session monitoring and Git integration |
| Target User | AI/ML engineers, researchers, and developers needing efficient, deployable LLMs | Developers who want to orchestrate coding agents and manage agentic workflows |
| Architecture | Mixture-of-experts (MoE) with 12B parameters (Mellum2); compact KV-cache for efficient GPU usage | Desktop application with ephemeral infrastructure; each agent runs in isolated Git worktree |
| Deployment | Local (Ollama, JetBrains AI Assistant) or cloud; Apache 2.0 license, open weights on Hugging Face | Desktop app (macOS, Windows, Linux); bring your own infrastructure (cloud or local) |
| Agent Support | Not an agent platform; provides the underlying LLM for agents to use | Works with 25+ coding agents (Codex, Cursor, Claude Code, etc.); auto-detects installed CLIs |
| Parallelism | High throughput via MoE; serves many concurrent requests on a single GPU | Run multiple agents in parallel, each in its own isolated workspace |
| Code Focus | Strong coding and math performance; supports multiple programming languages | Agentic development environment; focuses on orchestrating agents to write code |
| Customization | Fine-tunable; supports RLVR and SFT post-training | Connect to MCP servers; use any agent CLI; configurable via .emdashrc |
| License | Apache 2.0 (open source) | Open source (GitHub) |
Pricing
Mellum by JetBrains: Mellum is free and open-source under Apache 2.0. You can run it locally at no cost, or deploy on cloud infrastructure (costs depend on your chosen provider).
Emdash: Emdash is free and open-source. You pay only for the infrastructure you use (e.g., cloud compute for agent workspaces) and any agent API costs (e.g., Claude Code usage).
Pros and Cons
Mellum by JetBrains
Pros:
- Ultra-low latency and high throughput due to MoE architecture
- Strong coding and math performance in a compact 12B model
- Cost-efficient inference with fewer active parameters per request
- Flexible deployment: local, cloud, or on-premise
- Apache 2.0 license with open weights
Cons:
- Requires technical expertise to set up and fine-tune
- Not a standalone agent platform; needs integration with agent tools
- Limited to smaller model size compared to frontier models
Emdash
Pros:
- Parallel agent execution in isolated workspaces boosts productivity
- Works with 25+ coding agents out of the box
- Ephemeral infrastructure ensures clean, reproducible environments
- Built-in file editor and Git integration streamline workflows
- Open-source and free to use
Cons:
- Requires familiarity with Git and agent CLIs
- Desktop app only; no web or cloud version
- Dependent on external agent APIs and infrastructure costs
Verdict
Mellum is ideal for developers who need a fast, efficient, and customizable LLM for coding and language tasks, especially in production or latency-sensitive environments. Emdash is perfect for developers who want to orchestrate multiple coding agents in parallel, managing complex workflows from a single dashboard. Choose Mellum if you need the model itself; choose Emdash if you need a powerful agent orchestration platform.
Emdash
Mellum by JetBrains