Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Opus 4.8
95
Mellum2-12B-A2.5B-Instruct
27
Verified leaderboard positions: Claude Opus 4.8 #4 · Mellum2-12B-A2.5B-Instruct unranked
Pick Claude Opus 4.8 if you want the stronger benchmark profile. Mellum2-12B-A2.5B-Instruct only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Coding
+39.2 difference
Knowledge
+29.2 difference
Claude Opus 4.8
Mellum2-12B-A2.5B-Instruct
$5 / $25
N/A
N/A
N/A
N/A
N/A
1M
128K
Pick Claude Opus 4.8 if you want the stronger benchmark profile. Mellum2-12B-A2.5B-Instruct only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Claude Opus 4.8 is clearly ahead on the provisional aggregate, 95 to 27. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Opus 4.8's sharpest advantage is in coding, where it averages 76.4 against 37.2. The single biggest benchmark swing on the page is GPQA, 93.6% to 40.9%.
Claude Opus 4.8 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. Claude Opus 4.8 gives you the larger context window at 1M, compared with 128K for Mellum2-12B-A2.5B-Instruct.
Claude Opus 4.8 is ahead on BenchLM's provisional leaderboard, 95 to 27. The biggest single separator in this matchup is GPQA, where the scores are 93.6% and 40.9%.
Claude Opus 4.8 has the edge for knowledge tasks in this comparison, averaging 70.1 versus 40.9. Inside this category, GPQA is the benchmark that creates the most daylight between them.
Claude Opus 4.8 has the edge for coding in this comparison, averaging 76.4 versus 37.2. Mellum2-12B-A2.5B-Instruct stays close enough that the answer can still flip depending on your workload.
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