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Model comparison

Claude Mythos 5 vs Grok 4.20

Data verified

Head-to-head evidence from 5 shared benchmark results across 4 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

83.93/100
Margin
29.3pts
← winning
54.68/100
3 category wins0 category wins

Public leaderboard positions: Claude Mythos 5 #1 (Supported); Grok 4.20 #88 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Mythos 5 and Grok 4.20 share 5 comparable benchmark results. 3 of 8 categories are comparable. 10 results are unique to Claude Mythos 5; 13 to Grok 4.20.

Updated July 23, 2026
Shared results
5
Claude Mythos 5 only
10
Grok 4.20 only
13
Comparable categories
3 / 8

Pick Claude Mythos 5 if you want the stronger benchmark profile. Grok 4.20 only becomes the better choice if you want the cheaper token bill or you need the larger 2M context window.

Confidence note. This is a partial-evidence comparison with 5 shared benchmark results across 4 evidence categories; 3 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 54.68. 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 agentic, where it averages 87 against 47.1. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 88% to 47.1%.

Claude Mythos 5 is also the more expensive model on tokens at $10.00 input / $50.00 output per 1M tokens, versus $2.00 input / $6.00 output per 1M tokens for Grok 4.20. That is roughly 8.3x on output cost alone. Grok 4.20 gives you the larger context window at 2M, compared with 1M+ for Claude Mythos 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 Grok 4.20
CategoryClaude Mythos 5ΔGrok 4.20
AgenticClaude Mythos 587.0Margin← 39.9Grok 4.2047.1
MultimodalClaude Mythos 593.5Margin← 23.4Grok 4.2070.1
CodingClaude Mythos 589.7Margin← 22.6Grok 4.2067.1
ReasoningClaude Mythos 5Not measuredMarginNo overlapGrok 4.2053.3
KnowledgeClaude Mythos 568.5MarginNo overlapGrok 4.20Not measured
MathClaude Mythos 597.6MarginNo overlapGrok 4.20Not measured

Decisive benchmark drivers

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

More
A · Claude Mythos 5B · Grok 4.20

  1. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 88%B 47.1%
    Winner: Claude Mythos 5Δ 40.9
    Terminal-Bench 2.0: Claude Mythos 5 scored 88%; Grok 4.20 scored 47.1%. Claude Mythos 5 wins this benchmark.

  2. CharXiv

    Multimodal
    Source ↗
    A 93.5%B 60.9%
    Winner: Claude Mythos 5Δ 32.6
    CharXiv: Claude Mythos 5 scored 93.5%; Grok 4.20 scored 60.9%. Claude Mythos 5 wins this benchmark.

  3. SWE-bench Pro

    Coding
    Source ↗
    A 80.3%B 51.8%
    Winner: Claude Mythos 5Δ 28.5
    SWE-bench Pro: Claude Mythos 5 scored 80.3%; Grok 4.20 scored 51.8%. Claude Mythos 5 wins this benchmark.

  4. SWE-bench Verified

    Coding
    Source ↗
    A 95.5%B 76.7%
    Winner: Claude Mythos 5Δ 18.8
    SWE-bench Verified: Claude Mythos 5 scored 95.5%; Grok 4.20 scored 76.7%. 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 5Grok 4.20Comparison
Input / output priceUSD per 1M tokensClaude Mythos 5$10 input / $50 outputGrok 4.20$2 input / $6 outputGrok 4.20 has the lower combined listed price.
Generation speedtokens per secondClaude Mythos 5Not availableGrok 4.20233 tok/sA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Mythos 5Not availableGrok 4.2010.33 sA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Mythos 51M+Grok 4.202MGrok 4.20 lists the larger context window.

Benchmark Deep Dive

AgenticClaude Mythos 5 wins
BenchmarkClaude Mythos 5Grok 4.20Result
Terminal-Bench 2.0Source 88%47.1%Claude Mythos 5 leads
OSWorld-VerifiedSource 85%—Not comparable
BrowseCompSource 88%—Not comparable
ExploitGymSource 17.5%—Not comparable
DeepSearchQASource —62.8%Not comparable
Gert LabsSource —38.36%Not comparable
CodingClaude Mythos 5 wins
BenchmarkClaude Mythos 5Grok 4.20Result
SWE-bench VerifiedSource 95.5%76.7%Claude Mythos 5 leads
SWE-bench ProSource 80.3%51.8%Claude Mythos 5 leads
Terminal-Bench 2.0Source 88.0%—Not comparable
LiveCodeBench ProSource —74.2%Not comparable
Vibe Code BenchSource —4.06%Not comparable
Reasoning
BenchmarkClaude Mythos 5Grok 4.20Result
ARC-AGI-2Source —53.3%Not comparable
Knowledge
BenchmarkClaude Mythos 5Grok 4.20Result
GPQASource 94.1%—Not comparable
HLESource 64.5%—Not comparable
HLE w/o toolsSource 59%31.6%Claude Mythos 5 leads
GPQA-DSource —88.5%Not comparable
HealthBench HardSource —20.3%Not comparable
MedXpertQA (Text)Source —50.2%Not comparable
Math
BenchmarkClaude Mythos 5Grok 4.20Result
USAMO 2026Source 97.6%—Not comparable
Multilingual
BenchmarkClaude Mythos 5Grok 4.20Result
SWE MultilingualSource 92.2%—Not comparable
MultimodalClaude Mythos 5 wins
BenchmarkClaude Mythos 5Grok 4.20Result
SWE-bench MultimodalSource 54.9%—Not comparable
CharXivSource 93.5%60.9%Claude Mythos 5 leads
CharXiv w/o toolsSource 88.9%—Not comparable
MMMU-ProSource —75.2%Not comparable
ERQASource —54.1%Not comparable
SimpleVQASource —57.4%Not comparable
MedXpertQA (MM)Source —65.8%Not comparable
Design Arena WebsiteSource —1257Not comparable
Frequently Asked Questions (4)

Which is better, Claude Mythos 5 or Grok 4.20?

Claude Mythos 5 is ahead on BenchLM's BenchAlign leaderboard, 83.93 to 54.68. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 88% and 47.1%.

Which is better for coding, Claude Mythos 5 or Grok 4.20?

Claude Mythos 5 has the edge for coding in this comparison, averaging 89.7 versus 67.1. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Claude Mythos 5 or Grok 4.20?

Claude Mythos 5 has the edge for agentic tasks in this comparison, averaging 87 versus 47.1. 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 Grok 4.20?

Claude Mythos 5 has the edge for multimodal and grounded tasks in this comparison, averaging 93.5 versus 70.1. Inside this category, CharXiv is the benchmark that creates the most daylight between them.

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