Head-to-head comparison across 1benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Haiku 4.5
56
Mellum2-12B-A2.5B-Thinking
59
Pick Mellum2-12B-A2.5B-Thinking if you want the stronger benchmark profile. Claude Haiku 4.5 only becomes the better choice if coding is the priority or you need the larger 200K context window.
Coding
+3.4 difference
Claude Haiku 4.5
Mellum2-12B-A2.5B-Thinking
$1 / $5
N/A
N/A
N/A
N/A
N/A
200K
128K
Pick Mellum2-12B-A2.5B-Thinking if you want the stronger benchmark profile. Claude Haiku 4.5 only becomes the better choice if coding is the priority or you need the larger 200K context window.
Mellum2-12B-A2.5B-Thinking has the cleaner provisional overall profile here, landing at 59 versus 56. It is a real lead, but still close enough that category-level strengths matter more than the headline number.
Mellum2-12B-A2.5B-Thinking is the reasoning model in the pair, while Claude Haiku 4.5 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 Haiku 4.5 gives you the larger context window at 200K, compared with 128K for Mellum2-12B-A2.5B-Thinking.
Mellum2-12B-A2.5B-Thinking is ahead on BenchLM's provisional leaderboard, 59 to 56.
Claude Haiku 4.5 has the edge for coding in this comparison, averaging 73.3 versus 69.9. Mellum2-12B-A2.5B-Thinking stays close enough that the answer can still flip depending on your workload.
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