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Model comparison

Claude Mythos 5 vs Claude Opus 4.5

Data verified

Head-to-head evidence from 7 shared benchmark results across 4 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

83.93/100
Margin
19.7pts
← winning
64.22/100
5 category wins0 category wins

Public leaderboard positions: Claude Mythos 5 #1 (Supported); Claude Opus 4.5 #34 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Mythos 5 and Claude Opus 4.5 share 7 comparable benchmark results. 5 of 8 categories are comparable. 8 results are unique to Claude Mythos 5; 52 to Claude Opus 4.5.

Updated July 23, 2026
Shared results
7
Claude Mythos 5 only
8
Claude Opus 4.5 only
52
Comparable categories
5 / 8

Pick Claude Mythos 5 if you want the stronger benchmark profile. Claude Opus 4.5 only becomes the better choice if you want the cheaper token bill or you would rather avoid the extra latency and token burn of a reasoning model.

Confidence note. This is a partial-evidence comparison with 7 shared benchmark results across 4 evidence categories; 5 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 is clearly ahead on the BenchAlign aggregate, 83.93 to 64.22. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude Mythos 5's sharpest advantage is in mathematics, where it averages 97.6 against 57.5. The single biggest benchmark swing on the page is HLE, 64.5% to 30.8%.

Claude Mythos 5 is also the more expensive model on tokens at $10.00 input / $50.00 output per 1M tokens, versus $5.00 input / $25.00 output per 1M tokens for Claude Opus 4.5. That is roughly 2.0x on output cost alone. Claude Mythos 5 is the reasoning model in the pair, while Claude Opus 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 Mythos 5 gives you the larger context window at 1M+, compared with 200K for Claude Opus 4.5.

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 Claude Opus 4.5
CategoryClaude Mythos 5ΔClaude Opus 4.5
MathClaude Mythos 597.6Margin← 40.1Claude Opus 4.557.5
AgenticClaude Mythos 587.0Margin← 24.4Claude Opus 4.562.6
MultimodalClaude Mythos 593.5Margin← 23.6Claude Opus 4.569.9
CodingClaude Mythos 589.7Margin← 18.0Claude Opus 4.571.7
KnowledgeClaude Mythos 568.5Margin← 10.4Claude Opus 4.558.1
ReasoningClaude Mythos 5Not measuredMarginNo overlapClaude Opus 4.564.4
MultilingualClaude Mythos 5Not measuredMarginNo overlapClaude Opus 4.585.7
Inst. FollowingClaude Mythos 5Not measuredMarginNo overlapClaude Opus 4.569.5

Decisive benchmark drivers

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

More
A · Claude Mythos 5B · Claude Opus 4.5

  1. HLE

    Knowledge
    Source ↗
    A 64.5%B 30.8%
    Winner: Claude Mythos 5Δ 33.7
    HLE: Claude Mythos 5 scored 64.5%; Claude Opus 4.5 scored 30.8%. Claude Mythos 5 wins this benchmark.

  2. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 88%B 59.3%
    Winner: Claude Mythos 5Δ 28.7
    Terminal-Bench 2.0: Claude Mythos 5 scored 88%; Claude Opus 4.5 scored 59.3%. Claude Mythos 5 wins this benchmark.

  3. CharXiv

    Multimodal
    Source ↗
    A 93.5%B 68.5%
    Winner: Claude Mythos 5Δ 25
    CharXiv: Claude Mythos 5 scored 93.5%; Claude Opus 4.5 scored 68.5%. Claude Mythos 5 wins this benchmark.

  4. SWE-bench Pro

    Coding
    Source ↗
    A 80.3%B 57.1%
    Winner: Claude Mythos 5Δ 23.2
    SWE-bench Pro: Claude Mythos 5 scored 80.3%; Claude Opus 4.5 scored 57.1%. Claude Mythos 5 wins this benchmark.

  5. OSWorld-Verified

    Agentic
    Source ↗
    A 85%B 66.3%
    Winner: Claude Mythos 5Δ 18.7
    OSWorld-Verified: Claude Mythos 5 scored 85%; Claude Opus 4.5 scored 66.3%. 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 5Claude Opus 4.5Comparison
Input / output priceUSD per 1M tokensClaude Mythos 5$10 input / $50 outputClaude Opus 4.5$5 input / $25 outputClaude Opus 4.5 has the lower combined listed price.
Generation speedtokens per secondClaude Mythos 5Not availableClaude Opus 4.546 tok/sA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Mythos 5Not availableClaude Opus 4.51.01 sA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Mythos 51M+Claude Opus 4.5200KClaude Mythos 5 lists the larger context window.

Benchmark Deep Dive

AgenticClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Opus 4.5Result
Terminal-Bench 2.0Source 88%59.3%Claude Mythos 5 leads
OSWorld-VerifiedSource 85%66.3%Claude Mythos 5 leads
BrowseCompSource 88%—Not comparable
ExploitGymSource 17.5%—Not comparable
OSWorldSource —66.3%Not comparable
Claw-EvalSource —59.6%Not comparable
QwenClawBenchSource —52.3%Not comparable
τ³-bench resultsSource —70.2%Not comparable
VITA-BenchSource —23.3%Not comparable
DeepPlanningSource —26.4%Not comparable
ToolathlonSource —43.5%Not comparable
MCP AtlasSource —42.3%Not comparable
MCP-TasksSource —71.8%Not comparable
WideResearchSource —76.4%Not comparable
CyberGymSource —50.6%Not comparable
τ²-bench resultsSource —86.3%Not comparable
Gert LabsSource —64.23%Not comparable
JobBenchSource —32.3%Not comparable
CodingClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Opus 4.5Result
SWE-bench VerifiedSource 95.5%80.9%Claude Mythos 5 leads
SWE-bench ProSource 80.3%57.1%Claude Mythos 5 leads
Terminal-Bench 2.0Source 88.0%—Not comparable
LiveCodeBench v6Source —84.8%Not comparable
SWE MultilingualSource —77.5%Not comparable
NL2RepoSource —43.2%Not comparable
AA-SciCodeSource —47.0%Not comparable
Reasoning
BenchmarkClaude Mythos 5Claude Opus 4.5Result
LongBench v2Source —64.4%Not comparable
AI-NeedleSource —74%Not comparable
AA-LCRSource —65.3%Not comparable
CritPtSource —0.3%Not comparable
KnowledgeClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Opus 4.5Result
GPQASource 94.1%87%Claude Mythos 5 leads
HLESource 64.5%30.8%Claude Mythos 5 leads
HLE w/o toolsSource 59%—Not comparable
SuperGPQASource —70.6%Not comparable
MMLU-ProSource —89.5%Not comparable
MMLU-ReduxSource —96.6%Not comparable
C-EvalSource —92.2%Not comparable
Artificial Analysis Intelligence IndexSource —34.7%Not comparable
AA-GPQA DiamondSource —81.0%Not comparable
AA-HLESource —12.9%Not comparable
AA-Omniscience IndexSource —-3.9%Not comparable
AA-Omniscience AccuracySource —40.7%Not comparable
AA-Omniscience Hallucination RateSource —75.4%Not comparable
AA MMLU-ProSource —88.9%Not comparable
MathClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Opus 4.5Result
USAMO 2026Source 97.6%—Not comparable
AIME26Source —95.1%Not comparable
HMMT Feb 2025Source —92.9%Not comparable
HMMT Nov 2025Source —93.3%Not comparable
HMMT Feb 2026Source —85.3%Not comparable
MMAnswerBenchSource —84.0%Not comparable
FrontierMath v2 (Tiers 1-3)Source —20.690%Not comparable
FrontierMath v2 (Tier 4)Source —4.167%Not comparable
Multilingual
BenchmarkClaude Mythos 5Claude Opus 4.5Result
SWE MultilingualSource 92.2%—Not comparable
MMLU-ProXSource —85.7%Not comparable
NOVA-63Source —56.7%Not comparable
MultimodalClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Opus 4.5Result
SWE-bench MultimodalSource 54.9%—Not comparable
CharXivSource 93.5%68.5%Claude Mythos 5 leads
CharXiv w/o toolsSource 88.9%—Not comparable
MMMU-ProSource —70.6%Not comparable
MathVisionSource —74.3%Not comparable
VideoMMMUSource —84.4%Not comparable
ScreenSpot ProSource —45.7%Not comparable
V*Source —67.0%Not comparable
AA-MMMU-ProSource —71.2%Not comparable
Design Arena WebsiteSource —1277Not comparable
Inst. Following
BenchmarkClaude Mythos 5Claude Opus 4.5Result
IFEvalSource —90.9%Not comparable
IFBenchSource —58%Not comparable
AA-IFBenchSource —43.0%Not comparable
Frequently Asked Questions (6)

Which is better, Claude Mythos 5 or Claude Opus 4.5?

Claude Mythos 5 is ahead on BenchLM's BenchAlign leaderboard, 83.93 to 64.22. The biggest single separator in this matchup is HLE, where the scores are 64.5% and 30.8%.

Which is better for knowledge tasks, Claude Mythos 5 or Claude Opus 4.5?

Claude Mythos 5 has the edge for knowledge tasks in this comparison, averaging 68.5 versus 58.1. Inside this category, HLE is the benchmark that creates the most daylight between them.

Which is better for coding, Claude Mythos 5 or Claude Opus 4.5?

Claude Mythos 5 has the edge for coding in this comparison, averaging 89.7 versus 71.7. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.

Which is better for math, Claude Mythos 5 or Claude Opus 4.5?

Claude Mythos 5 has the edge for math in this comparison, averaging 97.6 versus 57.5. Claude Opus 4.5 stays close enough that the answer can still flip depending on your workload.

Which is better for agentic tasks, Claude Mythos 5 or Claude Opus 4.5?

Claude Mythos 5 has the edge for agentic tasks in this comparison, averaging 87 versus 62.6. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

Which is better for multimodal and grounded tasks, Claude Mythos 5 or Claude Opus 4.5?

Claude Mythos 5 has the edge for multimodal and grounded tasks in this comparison, averaging 93.5 versus 69.9. Inside this category, CharXiv is the benchmark that creates the most daylight between them.

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