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Claude Sonnet 4.5 vs GPT-5.3-Codex

GPT-5.3-Codex leads Claude Sonnet 4.5 on coding, 60.0 to 39.5 on the Vibe Coding Index, at about the same output price ($14.00 vs $15.00 per million). Updated October 21, 2026; 23 benchmarks have a result for both.

Replace Claude Sonnet 4.5 Replace GPT-5.3-Codex
Claude Sonnet 4.5Anthropic
Coding
39.5
Overall
49.5
Output $/M
$15.00
10
GPT-5.3-CodexOpenAI
Coding
60.0
Overall
No data
Output $/M
$14.00
13
vs boards won of 23 shared

Claude Sonnet 4.5 or GPT-5.3-Codex: which to pick

Pick GPT-5.3-Codex for coding: it scores 60.0 on the Vibe Coding Index against 39.5 for Claude Sonnet 4.5.

Pick Claude Sonnet 4.5 for a larger context window (1M against 400K tokens) and work measured by Design Arena: agents building web apps or Design Arena: agents building full-stack apps, where it leads.

Model AClaude Sonnet 4.5Anthropic39.5/1003 independent benchmarks$1.16 per solved taskModel BGPT-5.3-CodexOpenAI60.0/1003 independent benchmarks$0.59 per solved task
Shared results
23
Claude Sonnet 4.5 only
72
GPT-5.3-Codex only
11
Like-for-like categories
4 of 9

Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
Claude Sonnet 4.5 39.5 from 3 benchmarks, GPT-5.3-Codex 60.0 from 3 benchmarks.
Widest category
Coding, 16.5 points apart on average over 8 shared benchmarks.
Widest single gap
Vibe Code Bench (Vals AI): Claude Sonnet 4.5 22.6% against GPT-5.3-Codex 61.8%, 39.2 points apart on a 0 to 100 scale.
Output price
Claude Sonnet 4.5 $15.00 against GPT-5.3-Codex $14.00 per million output tokens, 1.1x apart.
Context window
Claude Sonnet 4.5 takes 1M tokens, GPT-5.3-Codex 400K.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryClaude Sonnet 4.5BarsGPT-5.3-CodexTies
Coding08
Intelligence02
Agentic work32
Web design71
All shared boards1013
CodingLike-for-likeSix of these boards feed the Vibe Coding Index08
Coding benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
SWE-bench Verified74.8%Not measuredOnly Claude Sonnet 4.5 measured
SWE-bench Multilingual67.0%Not measuredOnly Claude Sonnet 4.5 measured
LMArena WebDev13941407GPT-5.3-Codex
AA Coding Index52.1Not measuredOnly Claude Sonnet 4.5 measured
LiveCodeBench (Vals AI)73.0%87.3%GPT-5.3-Codex
SWE-bench Verified (Vals AI)70.0%78.0%GPT-5.3-Codex
Vibe Code Bench (Vals AI)22.6%61.8%GPT-5.3-Codex
IOI (Vals AI)Not measured53.8%Only GPT-5.3-Codex measured
Terminal-Bench Hard (Artificial Analysis run)Not measured53.0%Only GPT-5.3-Codex measured
Terminal-Bench46.5%78.4%GPT-5.3-Codex
GSO-Bench14.7%Not measuredOnly Claude Sonnet 4.5 measured
WeirdML47.7%79.3%GPT-5.3-Codex
Cybench60.0%Not measuredOnly Claude Sonnet 4.5 measured
ALE-BenchNot measured1655.2Only GPT-5.3-Codex measured
LMArena Text: coding1488Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: software and IT1473Not measuredOnly Claude Sonnet 4.5 measured
LMArena WebDev: React13861395GPT-5.3-Codex
LMArena WebDev: HTML13991422GPT-5.3-Codex
LMArena WebDev: from an imageNot measured1443Only GPT-5.3-Codex measured
Neither model has a result on the other 20 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index02
Intelligence benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
AA Intelligence Index20.732.5GPT-5.3-Codex
Epoch Capabilities Index146.7157.1GPT-5.3-Codex
Agentic workLike-for-likePublic boards, shown as published, kept out of the index32
Agentic work benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
AA Agentic Index15.8Not measuredOnly Claude Sonnet 4.5 measured
Design Arena: agents building web apps10591032Claude Sonnet 4.5
Design Arena: agents building full-stack apps1050983Claude Sonnet 4.5
Design Arena: agents building mobile apps11371054Claude Sonnet 4.5
Design Arena: agents building Android appsNot measured1084Only GPT-5.3-Codex measured
Design Arena: agents building Godot gamesNot measured1124Only GPT-5.3-Codex measured
τ²-Bench TelecomNot measured86.0%Only GPT-5.3-Codex measured
METR time horizons67.4%74.5%GPT-5.3-Codex
Remote Labor Index2.1%Not measuredOnly Claude Sonnet 4.5 measured
GDPval42.5%Not measuredOnly Claude Sonnet 4.5 measured
DeepResearch Bench52.6%Not measuredOnly Claude Sonnet 4.5 measured
OSWorld62.9%Not measuredOnly Claude Sonnet 4.5 measured
Vending-Bench 2$3,839$5,940GPT-5.3-Codex
Berkeley Function Calling Leaderboard (BFCL)73.2%Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 27 boards here
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index16 boards, none shared
Reasoning benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
GPQA Diamond81.6%Not measuredOnly Claude Sonnet 4.5 measured
MMMU Pro (Vals AI)79.3%Not measuredOnly Claude Sonnet 4.5 measured
GPQA Diamond (Artificial Analysis run)Not measured91.5%Only GPT-5.3-Codex measured
Humanity's Last Exam (Artificial Analysis run)Not measured42.5%Only GPT-5.3-Codex measured
GPQA Diamond (Epoch AI run)82.3%Not measuredOnly Claude Sonnet 4.5 measured
ARC-AGI63.7%Not measuredOnly Claude Sonnet 4.5 measured
ARC-AGI-213.6%Not measuredOnly Claude Sonnet 4.5 measured
SimpleBench54.3%Not measuredOnly Claude Sonnet 4.5 measured
Chess puzzles10.0%Not measuredOnly Claude Sonnet 4.5 measured
Mystery game puzzles17.0%Not measuredOnly Claude Sonnet 4.5 measured
EBR-bench2.4%Not measuredOnly Claude Sonnet 4.5 measured
VPCT39.8%Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: hard prompts1462Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: expert1483Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: hard prompts in English1471Not measuredOnly Claude Sonnet 4.5 measured
Kagi LLM Benchmark57.9%Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 6 boards here
MathDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
Math benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
AIME88.2%Not measuredOnly Claude Sonnet 4.5 measured
MGSM (Vals AI)94.3%Not measuredOnly Claude Sonnet 4.5 measured
OTIS Mock AIME77.8%Not measuredOnly Claude Sonnet 4.5 measured
FrontierMath, tiers 1 to 323.9%Not measuredOnly Claude Sonnet 4.5 measured
FrontierMath, tier 42.4%Not measuredOnly Claude Sonnet 4.5 measured
ProofBench19.0%Not measuredOnly Claude Sonnet 4.5 measured
MATH level 597.7%Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: math1449Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: mathematical work1462Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 4 boards here
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index14 boards, none shared
Knowledge benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
MMLU Pro87.4%Not measuredOnly Claude Sonnet 4.5 measured
LegalBench (Vals AI)84.1%Not measuredOnly Claude Sonnet 4.5 measured
CaseLaw (Vals AI)62.2%Not measuredOnly Claude Sonnet 4.5 measured
CorpFin (Vals AI)62.0%Not measuredOnly Claude Sonnet 4.5 measured
TaxEval (Vals AI)73.3%Not measuredOnly Claude Sonnet 4.5 measured
MortgageTax (Vals AI)64.0%Not measuredOnly Claude Sonnet 4.5 measured
MedQA (Vals AI)94.7%Not measuredOnly Claude Sonnet 4.5 measured
MedCode (Vals AI)44.1%Not measuredOnly Claude Sonnet 4.5 measured
SimpleQA Verified30.7%Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: science1448Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: medicine and healthcare1444Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: legal and government1451Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: business and finance1440Not measuredOnly Claude Sonnet 4.5 measured
FACTS Benchmark Suite40.6%Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 4 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index71
Web design benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
Design Arena: websites11901163Claude Sonnet 4.5
Design Arena: UI components11731137Claude Sonnet 4.5
Design Arena: game dev11661161Claude Sonnet 4.5
Design Arena: data viz11671164Claude Sonnet 4.5
Design Arena: 3D11581008Claude Sonnet 4.5
Design Arena: all code categories11831145Claude Sonnet 4.5
Design Arena: SVG11151129GPT-5.3-Codex
Design Arena: ASCII art12051152Claude Sonnet 4.5
Neither model has a result on the other 1 board here
GeneralDirectional onlyPublic boards, shown as published, kept out of the index24 boards, none shared
General benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
SAGE (Vals AI)36.1%Not measuredOnly Claude Sonnet 4.5 measured
MedScribe (Vals AI)84.5%Not measuredOnly Claude Sonnet 4.5 measured
IFBenchNot measured75.4%Only GPT-5.3-Codex measured
Long context reasoning (AA-LCR)Not measured83.3%Only GPT-5.3-Codex measured
DTBench83.2%Not measuredOnly Claude Sonnet 4.5 measured
LMCA38.8%Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text1438Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: instruction following1459Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: creative writing1442Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: English1450Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: non-English1425Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: Chinese1460Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: German1427Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: Japanese1390Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: Korean1402Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: French1459Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: Spanish1458Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: Russian1437Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: Polish1423Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: multi-turn1465Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: longer queries1475Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: writing and language1442Not measuredOnly Claude Sonnet 4.5 measured
LMArena Text: entertainment and media1428Not measuredOnly Claude Sonnet 4.5 measured
LMArena Document1450Not measuredOnly Claude Sonnet 4.5 measured
Neither model has a result on the other 22 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Claude Sonnet 4.5 and GPT-5.3-Codex
BenchmarkClaude Sonnet 4.5GPT-5.3-CodexLeader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

Claude Sonnet 4.5$0.011Fits in one request
GPT-5.3-Codex$0.0088Fits in one request

GPT-5.3-Codex costs less

Repository review

50K input + 3K output tokens

Claude Sonnet 4.5$0.195Fits in one request
GPT-5.3-Codex$0.130Fits in one request

GPT-5.3-Codex costs less

Agent loop

200K input + 10K output tokens

Claude Sonnet 4.5$0.750Fits in one request
GPT-5.3-Codex$0.490Fits in one request

GPT-5.3-Codex costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of Claude Sonnet 4.5 and GPT-5.3-Codex
SpecificationAnthropic Claude Sonnet 4.5OpenAI GPT-5.3-Codex
MakerAnthropicOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 29, 2025February 24, 2026
Context window1M400K
Input $/Mtok$3.00$1.75
Output $/Mtok$15.00$14.00
Coding index39.560.0
Independent measurements behind it33
Cost per solved task$1.16$0.59
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Sonnet 4.5 better than GPT-5.3-Codex for coding?

Pick GPT-5.3-Codex for coding: it scores 60.0 on the Vibe Coding Index against 39.5 for Claude Sonnet 4.5. Pick Claude Sonnet 4.5 for a larger context window (1M against 400K tokens) and work measured by Design Arena: agents building web apps or Design Arena: agents building full-stack apps, where it leads.

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

Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; GPT-5.3-Codex costs $1.75 and $14.00. Per solved SWE-bench Verified task, Claude Sonnet 4.5 costs $1.16 and GPT-5.3-Codex $0.59.

Which has the bigger context window, Claude Sonnet 4.5 or GPT-5.3-Codex?

Claude Sonnet 4.5, with 1M tokens against 400K.

How many benchmarks is the Claude Sonnet 4.5 vs GPT-5.3-Codex comparison based on?

23 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 4.5's coding index rests on 3 independent benchmarks and GPT-5.3-Codex's on 3. Where only one model has a result, the page says so instead of naming a winner.

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<p style="font:13px/1.4 sans-serif;margin:6px 0 0">Source: <a href="https://llmbenchmark.ai/compare/claude-sonnet-4-5-vs-gpt-5-3-codex">LLMBenchmark.ai, Claude Sonnet 4.5 vs GPT-5.3-Codex</a></p>