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Model comparison

Claude Sonnet 4.5 vs GPT-5.3 Codex

Data verified

Head-to-head evidence from 6 shared benchmark results across 3 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

53.61/100
Margin
13.1pts
winning →
66.69/100
1 category wins1 category wins

Public leaderboard positions: Claude Sonnet 4.5 #96 (Estimated); GPT-5.3 Codex #26 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Sonnet 4.5 and GPT-5.3 Codex share 6 comparable benchmark results. 2 of 8 categories are comparable. 6 results are unique to Claude Sonnet 4.5; 15 to GPT-5.3 Codex.

Updated July 20, 2026
Shared results
6
Claude Sonnet 4.5 only
6
GPT-5.3 Codex only
15
Comparable categories
2 / 8

Pick GPT-5.3 Codex if you want the stronger benchmark profile. Claude Sonnet 4.5 only becomes the better choice if coding is the priority or you would rather avoid the extra latency and token burn of a reasoning model.

Confidence note. This is a partial-evidence comparison with 6 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

GPT-5.3 Codex is clearly ahead on the BenchAlign aggregate, 66.69 to 53.61. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

GPT-5.3 Codex's sharpest advantage is in agentic, where it averages 71.4 against 55.4. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 50% to 77.3%. Claude Sonnet 4.5 does hit back in coding, so the answer changes if that is the part of the workload you care about most.

Claude Sonnet 4.5 is also the more expensive model on tokens at $3.00 input / $15.00 output per 1M tokens, versus $1.75 input / $14.00 output per 1M tokens for GPT-5.3 Codex. GPT-5.3 Codex 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. GPT-5.3 Codex gives you the larger context window at 400K, 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 Sonnet 4.5 and GPT-5.3 Codex
CategoryClaude Sonnet 4.5ΔGPT-5.3 Codex
AgenticClaude Sonnet 4.555.4Margin→ 16.0GPT-5.3 Codex71.4
CodingClaude Sonnet 4.577.2Margin← 10.0GPT-5.3 Codex67.2
ReasoningClaude Sonnet 4.513.6MarginNo overlapGPT-5.3 CodexNot measured
KnowledgeClaude Sonnet 4.583.4MarginNo overlapGPT-5.3 CodexNot measured
MathClaude Sonnet 4.511.2MarginNo overlapGPT-5.3 CodexNot measured

Decisive benchmark drivers

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

More
A · Claude Sonnet 4.5B · GPT-5.3 Codex

  1. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 50%B 77.3%
    Winner: GPT-5.3 CodexΔ 27.3
    Terminal-Bench 2.0: Claude Sonnet 4.5 scored 50%; GPT-5.3 Codex scored 77.3%. GPT-5.3 Codex wins this benchmark.

  2. SWE-bench Verified

    Coding
    Source ↗
    A 77.2%B 85%
    Winner: GPT-5.3 CodexΔ 7.8
    SWE-bench Verified: Claude Sonnet 4.5 scored 77.2%; GPT-5.3 Codex scored 85%. GPT-5.3 Codex wins this benchmark.

  3. OSWorld-Verified

    Agentic
    Source ↗
    A 61.4%B 64.7%
    Winner: GPT-5.3 CodexΔ 3.3
    OSWorld-Verified: Claude Sonnet 4.5 scored 61.4%; GPT-5.3 Codex scored 64.7%. GPT-5.3 Codex wins this benchmark.

Operational comparison

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

MetricClaude Sonnet 4.5GPT-5.3 CodexComparison
Input / output priceUSD per 1M tokensClaude Sonnet 4.5$3 input / $15 outputGPT-5.3 Codex$1.75 input / $14 outputGPT-5.3 Codex has the lower combined listed price.
Generation speedtokens per secondClaude Sonnet 4.5Not availableGPT-5.3 Codex79 tok/sA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Sonnet 4.5Not availableGPT-5.3 Codex88.26 sA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Sonnet 4.5200KGPT-5.3 Codex400KGPT-5.3 Codex lists the larger context window.

Benchmark Deep Dive

AgenticGPT-5.3 Codex wins
BenchmarkClaude Sonnet 4.5GPT-5.3 CodexResult
Terminal-Bench 2.0Source 50%77.3%GPT-5.3 Codex leads
OSWorld-VerifiedSource 61.4%64.7%GPT-5.3 Codex leads
VITA-BenchSource 17.0%—Not comparable
Gert LabsSource 48.51%57.47%GPT-5.3 Codex leads
JobBenchSource 27.7%33.7%GPT-5.3 Codex leads
τ²-bench resultsSource —86%Not comparable
CodingClaude Sonnet 4.5 wins
BenchmarkClaude Sonnet 4.5GPT-5.3 CodexResult
SWE-bench VerifiedSource 77.2%85%GPT-5.3 Codex leads
SWE-bench ProSource —56.8%Not comparable
SWE-RebenchSource —58.2%Not comparable
Vibe Code BenchSource —61.77%Not comparable
AA-SciCodeSource —53.2%Not comparable
Reasoning
BenchmarkClaude Sonnet 4.5GPT-5.3 CodexResult
ARC-AGI-2Source 13.6%—Not comparable
AA-LCRSource —74.0%Not comparable
CritPtSource —16.9%Not comparable
Knowledge
BenchmarkClaude Sonnet 4.5GPT-5.3 CodexResult
GPQASource 83.4%—Not comparable
Artificial Analysis Intelligence IndexSource —44.3%Not comparable
AA-GPQA DiamondSource —91.5%Not comparable
AA-HLESource —39.9%Not comparable
AA-Omniscience IndexSource —9.9%Not comparable
AA-Omniscience AccuracySource —51.8%Not comparable
AA-Omniscience Hallucination RateSource —86.9%Not comparable
Math
BenchmarkClaude Sonnet 4.5GPT-5.3 CodexResult
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 Sonnet 4.5GPT-5.3 CodexResult
Design Arena WebsiteSource 12221195Claude Sonnet 4.5 leads
AA-MMMU-ProSource —78.5%Not comparable
Inst. Following
BenchmarkClaude Sonnet 4.5GPT-5.3 CodexResult
AA-IFBenchSource —75.4%Not comparable
Frequently Asked Questions (3)

Which is better, Claude Sonnet 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex is ahead on BenchLM's BenchAlign leaderboard, 66.69 to 53.61. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 50% and 77.3%.

Which is better for coding, Claude Sonnet 4.5 or GPT-5.3 Codex?

Claude Sonnet 4.5 has the edge for coding in this comparison, averaging 77.2 versus 67.2. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Claude Sonnet 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex has the edge for agentic tasks in this comparison, averaging 71.4 versus 55.4. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

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