Mellum2-12B-A2.5B-Instruct vs Mellum2-12B-A2.5B-Thinking

Mellum2-12B-A2.5B-Instruct makes more sense if you would rather avoid the extra latency and token burn of a reasoning model, while Mellum2-12B-A2.5B-Thinking is the cleaner fit if coding is the priority or you want the stronger reasoning-first profile.

Mellum2-12B-A2.5B-Instruct and Mellum2-12B-A2.5B-Thinking sit in the same Mellum2 12B-A2.5B family. This page is less about two unrelated model lineages and more about how the siblings trade off on benchmark shape, token costs, and practical limits like context window.

Mellum2-12B-A2.5B-Thinking is clearly ahead on the provisional aggregate, 59 to 27. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Mellum2-12B-A2.5B-Thinking's sharpest advantage is in coding, where it averages 69.9 against 37.2. The single biggest benchmark swing on the page is LiveCodeBench, 37.2% to 69.9%.

Mellum2-12B-A2.5B-Thinking is the reasoning model in the pair, while Mellum2-12B-A2.5B-Instruct is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use.