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Model comparison

Claude Fable 5 vs GPT-5.3 Codex

Data verified

Head-to-head evidence from 16 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

83.68/100
Margin
17.0pts
← winning
66.69/100
2 category wins0 category wins

Public leaderboard positions: Claude Fable 5 #2 (Supported); GPT-5.3 Codex #26 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Fable 5 and GPT-5.3 Codex share 16 comparable benchmark results. 2 of 8 categories are comparable. 18 results are unique to Claude Fable 5; 5 to GPT-5.3 Codex.

Updated July 23, 2026
Shared results
16
Claude Fable 5 only
18
GPT-5.3 Codex only
5
Comparable categories
2 / 8

Pick Claude Fable 5 if you want the stronger benchmark profile. GPT-5.3 Codex only becomes the better choice if you want the cheaper token bill.

Confidence note. This is a partial-evidence comparison with 16 shared benchmark results across 6 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 66.69. 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 coding, where it averages 89.2 against 67.2. The single biggest benchmark swing on the page is SWE-bench Pro, 80% to 56.8%.

Claude Fable 5 is also the more expensive model on tokens at $10.00 input / $50.00 output per 1M tokens, versus $1.75 input / $14.00 output per 1M tokens for GPT-5.3 Codex. That is roughly 3.6x on output cost alone. Claude Fable 5 gives you the larger context window at 1M+, compared with 400K for GPT-5.3 Codex.

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 GPT-5.3 Codex
CategoryClaude Fable 5ΔGPT-5.3 Codex
CodingClaude Fable 589.2Margin← 22.0GPT-5.3 Codex67.2
AgenticClaude Fable 584.6Margin← 13.2GPT-5.3 Codex71.4
MultimodalClaude Fable 557.9MarginNo overlapGPT-5.3 CodexNot measured

Decisive benchmark drivers

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

More
A · Claude Fable 5B · GPT-5.3 Codex

  1. SWE-bench Pro

    Coding
    Source ↗
    A 80%B 56.8%
    Winner: Claude Fable 5Δ 23.2
    SWE-bench Pro: Claude Fable 5 scored 80%; GPT-5.3 Codex scored 56.8%. Claude Fable 5 wins this benchmark.

  2. OSWorld-Verified

    Agentic
    Source ↗
    A 85%B 64.7%
    Winner: Claude Fable 5Δ 20.3
    OSWorld-Verified: Claude Fable 5 scored 85%; GPT-5.3 Codex scored 64.7%. Claude Fable 5 wins this benchmark.

  3. SWE-bench Verified

    Coding
    Source ↗
    A 95%B 85%
    Winner: Claude Fable 5Δ 10
    SWE-bench Verified: Claude Fable 5 scored 95%; GPT-5.3 Codex scored 85%. Claude Fable 5 wins this benchmark.

  4. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 84.3%B 77.3%
    Winner: Claude Fable 5Δ 7
    Terminal-Bench 2.0: Claude Fable 5 scored 84.3%; GPT-5.3 Codex scored 77.3%. 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 5GPT-5.3 CodexComparison
Input / output priceUSD per 1M tokensClaude Fable 5$10 input / $50 outputGPT-5.3 Codex$1.75 input / $14 outputGPT-5.3 Codex has the lower combined listed price.
Generation speedtokens per secondClaude Fable 5Not availableGPT-5.3 Codex79 tok/sA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Fable 5Not availableGPT-5.3 Codex88.26 sA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Fable 51M+GPT-5.3 Codex400KClaude Fable 5 lists the larger context window.

Benchmark Deep Dive

AgenticClaude Fable 5 wins
BenchmarkClaude Fable 5GPT-5.3 CodexResult
Terminal-Bench 2.0Source 84.3%77.3%Claude Fable 5 leads
OSWorld-VerifiedSource 85%64.7%Claude Fable 5 leads
GDPval-AASource 1748—Not comparable
AA Agentic IndexSource 52.8%—Not comparable
τ²-bench resultsSource 98.5%86%Claude Fable 5 leads
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
Gert LabsSource —57.47%Not comparable
JobBenchSource —33.7%Not comparable
CodingClaude Fable 5 wins
BenchmarkClaude Fable 5GPT-5.3 CodexResult
SWE-bench VerifiedSource 95%85%Claude Fable 5 leads
SWE-bench ProSource 80%56.8%Claude Fable 5 leads
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%53.2%Claude Fable 5 leads
SWE-RebenchSource —58.2%Not comparable
Vibe Code BenchSource —61.77%Not comparable
Reasoning
BenchmarkClaude Fable 5GPT-5.3 CodexResult
AA-LCRSource 70.0%74.0%GPT-5.3 Codex leads
CritPtSource 28.6%16.9%Claude Fable 5 leads
Knowledge
BenchmarkClaude Fable 5GPT-5.3 CodexResult
Artificial Analysis Intelligence IndexSource 59.9%44.3%Claude Fable 5 leads
AA-GPQA DiamondSource 92.6%91.5%Claude Fable 5 leads
AA-HLESource 53.3%39.9%Claude Fable 5 leads
AA-Omniscience IndexSource 40.2%9.9%Claude Fable 5 leads
AA-Omniscience AccuracySource 61.4%51.8%Claude Fable 5 leads
AA-Omniscience Hallucination RateSource 54.9%86.9%Claude Fable 5 leads
Multimodal
BenchmarkClaude Fable 5GPT-5.3 CodexResult
Blueprint-Bench 2Source 38.6%—Not comparable
OfficeQA ProSource 57.9%—Not comparable
Design Arena WebsiteSource 13321193Claude Fable 5 leads
AA-MMMU-ProSource —78.5%Not comparable
Inst. Following
BenchmarkClaude Fable 5GPT-5.3 CodexResult
AA-IFBenchSource 63.5%75.4%GPT-5.3 Codex leads
Frequently Asked Questions (3)

Which is better, Claude Fable 5 or GPT-5.3 Codex?

Claude Fable 5 is ahead on BenchLM's BenchAlign leaderboard, 83.68 to 66.69. The biggest single separator in this matchup is SWE-bench Pro, where the scores are 80% and 56.8%.

Which is better for coding, Claude Fable 5 or GPT-5.3 Codex?

Claude Fable 5 has the edge for coding in this comparison, averaging 89.2 versus 67.2. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Claude Fable 5 or GPT-5.3 Codex?

Claude Fable 5 has the edge for agentic tasks in this comparison, averaging 84.6 versus 71.4. Inside this category, OSWorld-Verified is the benchmark that creates the most daylight between them.

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