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Model comparison

Claude Fable 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.

83.68/100
Margin
30.1pts
← winning
53.61/100
2 category wins0 category wins

Public leaderboard positions: Claude Fable 5 #2 (Supported); Claude Sonnet 4.5 #96 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Fable 5 and Claude Sonnet 4.5 share 4 comparable benchmark results. 2 of 8 categories are comparable. 30 results are unique to Claude Fable 5; 8 to Claude Sonnet 4.5.

Updated July 23, 2026
Shared results
4
Claude Fable 5 only
30
Claude Sonnet 4.5 only
8
Comparable categories
2 / 8

Pick Claude Fable 5 if you want the stronger benchmark profile. Claude Sonnet 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 4 shared benchmark results across 3 evidence categories; 2 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.

Why this result

Claude Fable 5 is clearly ahead on the BenchAlign aggregate, 83.68 to 53.61. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude Fable 5's sharpest advantage is in agentic, where it averages 84.6 against 55.4. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 84.3% to 50%.

Claude Fable 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 Fable 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 Fable 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 Fable 5 and Claude Sonnet 4.5
CategoryClaude Fable 5ΔClaude Sonnet 4.5
AgenticClaude Fable 584.6Margin← 29.2Claude Sonnet 4.555.4
CodingClaude Fable 589.2Margin← 12.0Claude Sonnet 4.577.2
ReasoningClaude Fable 5Not measuredMarginNo overlapClaude Sonnet 4.513.6
KnowledgeClaude Fable 5Not measuredMarginNo overlapClaude Sonnet 4.583.4
MathClaude Fable 5Not measuredMarginNo overlapClaude Sonnet 4.511.2
MultimodalClaude Fable 557.9MarginNo overlapClaude Sonnet 4.5Not measured

Decisive benchmark drivers

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

More
A · Claude Fable 5B · Claude Sonnet 4.5

  1. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 84.3%B 50%
    Winner: Claude Fable 5Δ 34.3
    Terminal-Bench 2.0: Claude Fable 5 scored 84.3%; Claude Sonnet 4.5 scored 50%. Claude Fable 5 wins this benchmark.

  2. OSWorld-Verified

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

  3. SWE-bench Verified

    Coding
    Source ↗
    A 95%B 77.2%
    Winner: Claude Fable 5Δ 17.8
    SWE-bench Verified: Claude Fable 5 scored 95%; Claude Sonnet 4.5 scored 77.2%. Claude Fable 5 wins this benchmark.

Operational comparison

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

MetricClaude Fable 5Claude Sonnet 4.5Comparison
Input / output priceUSD per 1M tokensClaude Fable 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 Fable 5Not availableClaude Sonnet 4.5Not availableA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Fable 5Not availableClaude Sonnet 4.5Not availableA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Fable 51M+Claude Sonnet 4.5200KClaude Fable 5 lists the larger context window.

Benchmark Deep Dive

AgenticClaude Fable 5 wins
BenchmarkClaude Fable 5Claude Sonnet 4.5Result
Terminal-Bench 2.0Source 84.3%50%Claude Fable 5 leads
OSWorld-VerifiedSource 85%61.4%Claude Fable 5 leads
GDPval-AASource 1748—Not comparable
AA Agentic IndexSource 52.8%—Not comparable
τ²-bench resultsSource 98.5%—Not comparable
GDPval-AASource 62.4%—Not comparable
AA BriefcaseSource 1574—Not comparable
AA AutomationBenchSource 48.6%—Not comparable
AA EnterpriseOps-GymSource 51.1%—Not comparable
AA Harvey LABSource 93.6%—Not comparable
AA Tau3 BankingSource 26.8%—Not comparable
terminalBenchHardSource 62.9%—Not comparable
aaTerminalBench21Source 84.6%—Not comparable
VITA-BenchSource —17.0%Not comparable
Gert LabsSource —48.51%Not comparable
JobBenchSource —27.7%Not comparable
CodingClaude Fable 5 wins
BenchmarkClaude Fable 5Claude Sonnet 4.5Result
SWE-bench VerifiedSource 95%77.2%Claude Fable 5 leads
SWE-bench ProSource 80%—Not comparable
FrontierCode 1.1 MainSource 53.5%—Not comparable
Terminal-Bench 2.0Source 84.3%—Not comparable
cursorBench31Source 70.6%—Not comparable
cursorBench32Source 70.5%—Not comparable
VulcanBench v3Source 87.0%—Not comparable
AA Coding IndexSource 76.5%—Not comparable
AA-SciCodeSource 60.2%—Not comparable
Reasoning
BenchmarkClaude Fable 5Claude Sonnet 4.5Result
AA-LCRSource 70.0%—Not comparable
CritPtSource 28.6%—Not comparable
ARC-AGI-2Source —13.6%Not comparable
Knowledge
BenchmarkClaude Fable 5Claude Sonnet 4.5Result
Artificial Analysis Intelligence IndexSource 59.9%—Not comparable
AA-GPQA DiamondSource 92.6%—Not comparable
AA-HLESource 53.3%—Not comparable
AA-Omniscience IndexSource 40.2%—Not comparable
AA-Omniscience AccuracySource 61.4%—Not comparable
AA-Omniscience Hallucination RateSource 54.9%—Not comparable
GPQASource —83.4%Not comparable
Math
BenchmarkClaude Fable 5Claude Sonnet 4.5Result
AIME 2025Source —87%Not comparable
FrontierMath v2 (Tiers 1-3)Source —13.495%Not comparable
FrontierMath v2 (Tier 4)Source —4.167%Not comparable
Multimodal
BenchmarkClaude Fable 5Claude Sonnet 4.5Result
Blueprint-Bench 2Source 38.6%—Not comparable
OfficeQA ProSource 57.9%—Not comparable
Design Arena WebsiteSource 13321219Claude Fable 5 leads
Inst. Following
BenchmarkClaude Fable 5Claude Sonnet 4.5Result
AA-IFBenchSource 63.5%—Not comparable
Frequently Asked Questions (3)

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

Claude Fable 5 is ahead on BenchLM's BenchAlign leaderboard, 83.68 to 53.61. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 84.3% and 50%.

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

Claude Fable 5 has the edge for coding in this comparison, averaging 89.2 versus 77.2. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Claude Fable 5 or Claude Sonnet 4.5?

Claude Fable 5 has the edge for agentic tasks in this comparison, averaging 84.6 versus 55.4. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

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