Mellum2 12B-A2.5B
Mellum2 12B-A2.5B is JetBrains' from-scratch SWE-focused MoE (12.15B total, 2.5B active), released June 2026 under Apache-2.0. Purpose-built for code completion and agentic SWE tasks rather than general chat; the Q4_K_M GGUF build is ~8GB.
Overview
Mellum2 12B-A2.5B is JetBrains' from-scratch SWE-focused MoE (12.15B total, 2.5B active), released June 2026 under Apache-2.0. Purpose-built for code completion and agentic SWE tasks rather than general chat; the Q4_K_M GGUF build is ~8GB.
Strengths
- Apache-2.0 license with commercial use allowed
- MoE efficiency (2.5B active of 12.15B total) at a small footprint
- Purpose-trained on software-engineering tasks, not general chat
Weaknesses
- Narrow training focus — general chat/knowledge quality unverified
- New vendor entrant to open weights; little independent track record
- GGUF ships from a community-mirror HF repo, not a first-party Ollama library tag
Reviewed quality benchmarks
First-party rows were run by RunLocalAI; reviewed community rows are labeled in the data. Every row links to the raw test-run log.
| Benchmark | Quant | Runtime / Hardware | Score | Raw log |
|---|---|---|---|---|
HumanEval+ tested 2026-07-20 | Q4_K_M | ollama-0.32.1-vast5090 rtx-5090 | 76.8/100 | Gist → |
Q4_K_M note:First-party HumanEval+ on a rented Vast.ai RTX 5090 32GB instance via Ollama 0.32.1. Generation via evalplus_openai_generate.py, scoring via evalplus.evaluate (native Linux, no Windows shim needed). No DB credentials were placed on the rented host — results were pulled back and ingested from the operator's machine.
Want to verify? Every row links to its Gist with full stdout and stderr of the run. The runner script is in the public repo (scripts/run-humaneval-plus.ts) — reproducible end-to-end. Browse all coding scores at /benchmarks/coding.
Quantization variants
Each quantization trades model quality for file size and VRAM. Q4_K_M is the most popular starting point.
| Quantization | File size | VRAM required |
|---|---|---|
| Q4_K_M | 8.0 GB | 10 GB |
Get the model
Ollama
One-line install
ollama run hf.co/JetBrains/Mellum2-12B-A2.5B-Thinking-GGUF-Q4_K_MRead our Ollama review →HuggingFace
Original weights
Source repository — direct quantization required.
Hardware that runs this
Cards with enough VRAM for at least one quantization of Mellum2 12B-A2.5B.
Models worth comparing
Same parameter band, plus what's one tier above and below — so you can decide what actually fits your hardware.
Frequently asked
What's the minimum VRAM to run Mellum2 12B-A2.5B?
Can I use Mellum2 12B-A2.5B commercially?
What's the context length of Mellum2 12B-A2.5B?
How do I install Mellum2 12B-A2.5B with Ollama?
Source: huggingface.co/JetBrains/Mellum2-12B-A2.5B-Thinking-GGUF-Q4_K_M
Reviewed by RunLocalAI Editorial. See our editorial policy for how we research and verify model claims.
Related — keep moving
Verify Mellum2 12B-A2.5B runs on your specific hardware before committing money.