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Model comparison

Claude Mythos 5 vs Claude Sonnet 4.5

Data verified

Head-to-head evidence from 4 shared benchmark results across 3 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

83.93/100
Margin
30.3pts
← winning
53.61/100
3 category wins1 category wins

Public leaderboard positions: Claude Mythos 5 #1 (Supported); Claude Sonnet 4.5 #96 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Mythos 5 and Claude Sonnet 4.5 share 4 comparable benchmark results. 4 of 8 categories are comparable. 11 results are unique to Claude Mythos 5; 8 to Claude Sonnet 4.5.

Updated July 23, 2026
Shared results
4
Claude Mythos 5 only
11
Claude Sonnet 4.5 only
8
Comparable categories
4 / 8

Pick Claude Mythos 5 if you want the stronger benchmark profile. Claude Sonnet 4.5 only becomes the better choice if knowledge is the priority or you want the cheaper token bill.

Confidence note. This is a partial-evidence comparison with 4 shared benchmark results across 3 evidence categories; 4 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 53.61. 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 11.2. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 88% to 50%. Claude Sonnet 4.5 does hit back in knowledge, so the answer changes if that is the part of the workload you care about most.

Claude Mythos 5 is also the more expensive model on tokens at $10.00 input / $50.00 output per 1M tokens, versus $3.00 input / $15.00 output per 1M tokens for Claude Sonnet 4.5. That is roughly 3.3x on output cost alone. Claude Mythos 5 is the reasoning model in the pair, while Claude Sonnet 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 Sonnet 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 Sonnet 4.5
CategoryClaude Mythos 5ΔClaude Sonnet 4.5
MathClaude Mythos 597.6Margin← 86.4Claude Sonnet 4.511.2
AgenticClaude Mythos 587.0Margin← 31.6Claude Sonnet 4.555.4
KnowledgeClaude Mythos 568.5Margin→ 14.9Claude Sonnet 4.583.4
CodingClaude Mythos 589.7Margin← 12.5Claude Sonnet 4.577.2
ReasoningClaude Mythos 5Not measuredMarginNo overlapClaude Sonnet 4.513.6
MultimodalClaude Mythos 593.5MarginNo overlapClaude Sonnet 4.5Not measured

Decisive benchmark drivers

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

More
A · Claude Mythos 5B · Claude Sonnet 4.5

  1. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 88%B 50%
    Winner: Claude Mythos 5Δ 38
    Terminal-Bench 2.0: Claude Mythos 5 scored 88%; Claude Sonnet 4.5 scored 50%. Claude Mythos 5 wins this benchmark.

  2. OSWorld-Verified

    Agentic
    Source ↗
    A 85%B 61.4%
    Winner: Claude Mythos 5Δ 23.6
    OSWorld-Verified: Claude Mythos 5 scored 85%; Claude Sonnet 4.5 scored 61.4%. Claude Mythos 5 wins this benchmark.

  3. SWE-bench Verified

    Coding
    Source ↗
    A 95.5%B 77.2%
    Winner: Claude Mythos 5Δ 18.3
    SWE-bench Verified: Claude Mythos 5 scored 95.5%; Claude Sonnet 4.5 scored 77.2%. Claude Mythos 5 wins this benchmark.

  4. GPQA

    Knowledge
    Source ↗
    A 94.1%B 83.4%
    Winner: Claude Mythos 5Δ 10.7
    GPQA: Claude Mythos 5 scored 94.1%; Claude Sonnet 4.5 scored 83.4%. 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 Sonnet 4.5Comparison
Input / output priceUSD per 1M tokensClaude Mythos 5$10 input / $50 outputClaude Sonnet 4.5$3 input / $15 outputClaude Sonnet 4.5 has the lower combined listed price.
Generation speedtokens per secondClaude Mythos 5Not availableClaude Sonnet 4.5Not availableA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Mythos 5Not availableClaude Sonnet 4.5Not availableA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Mythos 51M+Claude Sonnet 4.5200KClaude Mythos 5 lists the larger context window.

Benchmark Deep Dive

AgenticClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Sonnet 4.5Result
Terminal-Bench 2.0Source 88%50%Claude Mythos 5 leads
OSWorld-VerifiedSource 85%61.4%Claude Mythos 5 leads
BrowseCompSource 88%—Not comparable
ExploitGymSource 17.5%—Not comparable
VITA-BenchSource —17.0%Not comparable
Gert LabsSource —48.51%Not comparable
JobBenchSource —27.7%Not comparable
CodingClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Sonnet 4.5Result
SWE-bench VerifiedSource 95.5%77.2%Claude Mythos 5 leads
SWE-bench ProSource 80.3%—Not comparable
Terminal-Bench 2.0Source 88.0%—Not comparable
Reasoning
BenchmarkClaude Mythos 5Claude Sonnet 4.5Result
ARC-AGI-2Source —13.6%Not comparable
KnowledgeClaude Sonnet 4.5 wins
BenchmarkClaude Mythos 5Claude Sonnet 4.5Result
GPQASource 94.1%83.4%Claude Mythos 5 leads
HLESource 64.5%—Not comparable
HLE w/o toolsSource 59%—Not comparable
MathClaude Mythos 5 wins
BenchmarkClaude Mythos 5Claude Sonnet 4.5Result
USAMO 2026Source 97.6%—Not comparable
AIME 2025Source —87%Not comparable
FrontierMath v2 (Tiers 1-3)Source —13.495%Not comparable
FrontierMath v2 (Tier 4)Source —4.167%Not comparable
Multilingual
BenchmarkClaude Mythos 5Claude Sonnet 4.5Result
SWE MultilingualSource 92.2%—Not comparable
Multimodal
BenchmarkClaude Mythos 5Claude Sonnet 4.5Result
SWE-bench MultimodalSource 54.9%—Not comparable
CharXivSource 93.5%—Not comparable
CharXiv w/o toolsSource 88.9%—Not comparable
Design Arena WebsiteSource —1219Not comparable
Frequently Asked Questions (5)

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

Claude Mythos 5 is ahead on BenchLM's BenchAlign leaderboard, 83.93 to 53.61. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 88% and 50%.

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

Claude Sonnet 4.5 has the edge for knowledge tasks in this comparison, averaging 83.4 versus 68.5. Inside this category, GPQA is the benchmark that creates the most daylight between them.

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

Claude Mythos 5 has the edge for coding in this comparison, averaging 89.7 versus 77.2. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

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

Claude Mythos 5 has the edge for math in this comparison, averaging 97.6 versus 11.2. Claude Sonnet 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 Sonnet 4.5?

Claude Mythos 5 has the edge for agentic tasks in this comparison, averaging 87 versus 55.4. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

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