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Model comparison

Claude Mythos 5 vs Mellum2-12B-A2.5B-Thinking

Data verified

Head-to-head evidence from 1 shared benchmark result across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.

83.93/100
No comparison
N/A
1 category wins0 category wins

Public leaderboard positions: Claude Mythos 5 #1 (Supported); Mellum2-12B-A2.5B-Thinking unranked (Not scored). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Mythos 5 and Mellum2-12B-A2.5B-Thinking share 1 comparable benchmark result. 1 of 8 categories are comparable. 14 results are unique to Claude Mythos 5; 4 to Mellum2-12B-A2.5B-Thinking.

Updated July 23, 2026
Shared results
1
Claude Mythos 5 only
14
Mellum2-12B-A2.5B-Thinking only
4
Comparable categories
1 / 8

Treat this as a split decision. Claude Mythos 5 makes more sense if knowledge is the priority or you need the larger 1M+ context window; Mellum2-12B-A2.5B-Thinking is the better fit if its strengths line up with your actual workload.

Confidence note. This is a partial-evidence comparison with 1 shared benchmark result across 1 evidence category; 1 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.

Why this result

Claude Mythos 5 and Mellum2-12B-A2.5B-Thinking finish on the same BenchAlign overall score, so this is less about a single winner and more about where the edge shows up. The BenchAlign headline says tie; the benchmark table is where the real choice happens.

Claude Mythos 5 gives you the larger context window at 1M+, compared with 128K for Mellum2-12B-A2.5B-Thinking.

Category breakdown

Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.

Category scores and score margins for Claude Mythos 5 and Mellum2-12B-A2.5B-Thinking
CategoryClaude Mythos 5ΔMellum2-12B-A2.5B-Thinking
KnowledgeClaude Mythos 568.5Margin← 10.9Mellum2-12B-A2.5B-Thinking57.6
AgenticClaude Mythos 587.0MarginNo overlapMellum2-12B-A2.5B-ThinkingNot measured
CodingClaude Mythos 589.7MarginNo overlapMellum2-12B-A2.5B-ThinkingNot measured
MathClaude Mythos 597.6MarginNo overlapMellum2-12B-A2.5B-ThinkingNot measured
MultimodalClaude Mythos 593.5MarginNo overlapMellum2-12B-A2.5B-ThinkingNot measured
Inst. FollowingClaude Mythos 5Not measuredMarginNo overlapMellum2-12B-A2.5B-Thinking76.5

Decisive benchmark drivers

The largest measured benchmark gaps in this matchup, with exact reported values.

More
A · Claude Mythos 5B · Mellum2-12B-A2.5B-Thinking

  1. GPQA

    Knowledge
    Source ↗
    A 94.1%B 57.6%
    Winner: Claude Mythos 5Δ 36.5
    GPQA: Claude Mythos 5 scored 94.1%; Mellum2-12B-A2.5B-Thinking scored 57.6%. Claude Mythos 5 wins this benchmark.

Operational comparison

Runtime and commercial metrics are compared only when both models have a complete sourced value.

MetricClaude Mythos 5Mellum2-12B-A2.5B-ThinkingComparison
Input / output priceUSD per 1M tokensClaude Mythos 5$10 input / $50 outputMellum2-12B-A2.5B-ThinkingNot availableA complete price comparison is not available.
Generation speedtokens per secondClaude Mythos 5Not availableMellum2-12B-A2.5B-ThinkingNot availableA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Mythos 5Not availableMellum2-12B-A2.5B-ThinkingNot availableA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Mythos 51M+Mellum2-12B-A2.5B-Thinking128KClaude Mythos 5 lists the larger context window.

Benchmark Deep Dive

Agentic
BenchmarkClaude Mythos 5Mellum2-12B-A2.5B-ThinkingResult
Terminal-Bench 2.0Source 88%—Not comparable
OSWorld-VerifiedSource 85%—Not comparable
BrowseCompSource 88%—Not comparable
ExploitGymSource 17.5%—Not comparable
BFCL v4Source —45.6%Not comparable
Coding
BenchmarkClaude Mythos 5Mellum2-12B-A2.5B-ThinkingResult
SWE-bench VerifiedSource 95.5%—Not comparable
SWE-bench ProSource 80.3%—Not comparable
Terminal-Bench 2.0Source 88.0%—Not comparable
KnowledgeClaude Mythos 5 wins
BenchmarkClaude Mythos 5Mellum2-12B-A2.5B-ThinkingResult
GPQASource 94.1%57.6%Claude Mythos 5 leads
HLESource 64.5%—Not comparable
HLE w/o toolsSource 59%—Not comparable
MMLU-ReduxSource —86.2%Not comparable
GPQA-DSource —57.6%Not comparable
Math
BenchmarkClaude Mythos 5Mellum2-12B-A2.5B-ThinkingResult
USAMO 2026Source 97.6%—Not comparable
Multilingual
BenchmarkClaude Mythos 5Mellum2-12B-A2.5B-ThinkingResult
SWE MultilingualSource 92.2%—Not comparable
Multimodal
BenchmarkClaude Mythos 5Mellum2-12B-A2.5B-ThinkingResult
SWE-bench MultimodalSource 54.9%—Not comparable
CharXivSource 93.5%—Not comparable
CharXiv w/o toolsSource 88.9%—Not comparable
Inst. Following
BenchmarkClaude Mythos 5Mellum2-12B-A2.5B-ThinkingResult
IFEvalSource —76.5%Not comparable
Frequently Asked Questions (2)

Which is better, Claude Mythos 5 or Mellum2-12B-A2.5B-Thinking?

Claude Mythos 5 and Mellum2-12B-A2.5B-Thinking are tied on the BenchAlign overall score, so the right pick depends on which category matters most for your use case.

Which is better for knowledge tasks, Claude Mythos 5 or Mellum2-12B-A2.5B-Thinking?

Claude Mythos 5 has the edge for knowledge tasks in this comparison, averaging 68.5 versus 57.6. Inside this category, GPQA is the benchmark that creates the most daylight between them.

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