Model comparison
Claude 3.5 Sonnet vs GPT-5.3 Codex
Head-to-head evidence from 1 shared benchmark result across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude 3.5 Sonnet #132 (Estimated); GPT-5.3 Codex #26 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude 3.5 Sonnet and GPT-5.3 Codex share 1 comparable benchmark result. 1 of 8 categories are comparable. 3 results are unique to Claude 3.5 Sonnet; 20 to GPT-5.3 Codex.
Updated July 20, 2026- Shared results
- 1
- Claude 3.5 Sonnet only
- 3
- GPT-5.3 Codex only
- 20
- Comparable categories
- 1 / 8
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Claude 3.5 Sonnet only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.
Confidence note. This is a partial-evidence comparison with 1 shared benchmark result across 1 evidence category; 1 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 47.74. 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 coding, where it averages 67.2 against 49. The single biggest benchmark swing on the page is SWE-bench Verified, 49% to 85%.
Claude 3.5 Sonnet 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 3.5 Sonnet 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 3.5 Sonnet.
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 | Claude 3.5 Sonnet | Δ | GPT-5.3 Codex |
|---|---|---|---|
| Coding | Claude 3.5 Sonnet49.0 | Margin→ 18.2 | GPT-5.3 Codex67.2 |
| Agentic | Claude 3.5 SonnetNot measured | MarginNo overlap | GPT-5.3 Codex71.4 |
| Knowledge | Claude 3.5 Sonnet59.4 | MarginNo overlap | GPT-5.3 CodexNot measured |
| Math | Claude 3.5 Sonnet1.6 | MarginNo overlap | GPT-5.3 CodexNot measured |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
SWE-bench Verified
CodingA 49%B 85%Winner: GPT-5.3 CodexΔ 36SWE-bench Verified: Claude 3.5 Sonnet scored 49%; GPT-5.3 Codex scored 85%. GPT-5.3 Codex wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude 3.5 Sonnet | GPT-5.3 Codex | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude 3.5 Sonnet$3 input / $15 output | GPT-5.3 Codex$1.75 input / $14 output | GPT-5.3 Codex has the lower combined listed price. |
| Generation speedtokens per second | Claude 3.5 SonnetNot available | GPT-5.3 Codex79 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude 3.5 SonnetNot available | GPT-5.3 Codex88.26 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude 3.5 Sonnet200K | GPT-5.3 Codex400K | GPT-5.3 Codex lists the larger context window. |
Benchmark Deep Dive
Agentic5 benchmarks
CodingGPT-5.3 Codex wins5 benchmarks
Reasoning2 benchmarks
Knowledge7 benchmarks
| Benchmark | Claude 3.5 Sonnet | GPT-5.3 Codex | Result |
|---|---|---|---|
| GPQASource | 59.4% | — | 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 |
Math2 benchmarks
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | Claude 3.5 Sonnet | GPT-5.3 Codex | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 75.4% | Not comparable |
Frequently Asked Questions (2)
Which is better, Claude 3.5 Sonnet or GPT-5.3 Codex?
GPT-5.3 Codex is ahead on BenchLM's BenchAlign leaderboard, 66.69 to 47.74. The biggest single separator in this matchup is SWE-bench Verified, where the scores are 49% and 85%.
Which is better for coding, Claude 3.5 Sonnet or GPT-5.3 Codex?
GPT-5.3 Codex has the edge for coding in this comparison, averaging 67.2 versus 49. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.
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