Model comparison
Claude Opus 4.5 Thinking vs GPT-5.3 Codex
Head-to-head evidence from 14 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Opus 4.5 Thinking #69 (Estimated); GPT-5.3 Codex #26 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Opus 4.5 Thinking and GPT-5.3 Codex share 14 comparable benchmark results. 0 of 8 categories are comparable. 2 results are unique to Claude Opus 4.5 Thinking; 7 to GPT-5.3 Codex.
Updated July 23, 2026- Shared results
- 14
- Claude Opus 4.5 Thinking only
- 2
- GPT-5.3 Codex only
- 7
- Comparable categories
- 0 / 8
Benchmark data for Claude Opus 4.5 Thinking and GPT-5.3 Codex is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 14 shared benchmark results across 6 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
GPT-5.3 Codex has the larger context window at 400K, compared with 200K for Claude Opus 4.5 Thinking.
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 Opus 4.5 Thinking | Δ | GPT-5.3 Codex |
|---|---|---|---|
| Agentic | Claude Opus 4.5 ThinkingNot measured | MarginNo overlap | GPT-5.3 Codex71.4 |
| Coding | Claude Opus 4.5 ThinkingNot measured | MarginNo overlap | GPT-5.3 Codex67.2 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Opus 4.5 Thinking | GPT-5.3 Codex | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Opus 4.5 ThinkingNot available | GPT-5.3 Codex$1.75 input / $14 output | A complete price comparison is not available. |
| Generation speedtokens per second | Claude Opus 4.5 ThinkingNot available | GPT-5.3 Codex79 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Opus 4.5 ThinkingNot available | GPT-5.3 Codex88.26 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Opus 4.5 Thinking200K | GPT-5.3 Codex400K | GPT-5.3 Codex lists the larger context window. |
Benchmark Deep Dive
Agentic5 benchmarks
Coding5 benchmarks
Reasoning2 benchmarks
Knowledge7 benchmarks
| Benchmark | Claude Opus 4.5 Thinking | GPT-5.3 Codex | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 40.8% | 44.3% | GPT-5.3 Codex leads |
| AA-GPQA DiamondSource | 86.6% | 91.5% | GPT-5.3 Codex leads |
| AA-HLESource | 28.4% | 39.9% | GPT-5.3 Codex leads |
| AA-Omniscience IndexSource | 13.3% | 9.9% | Claude Opus 4.5 Thinking leads |
| AA-Omniscience AccuracySource | 45.7% | 51.8% | GPT-5.3 Codex leads |
| AA-Omniscience Hallucination RateSource | 59.8% | 86.9% | Claude Opus 4.5 Thinking leads |
| AA MMLU-ProSource | 89.5% | — | Not comparable |
Multilingual1 benchmarks
| Benchmark | Claude Opus 4.5 Thinking | GPT-5.3 Codex | Result |
|---|---|---|---|
| AA Global-MMLU-LiteSource | 91.3% | — | Not comparable |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | Claude Opus 4.5 Thinking | GPT-5.3 Codex | Result |
|---|---|---|---|
| AA-IFBenchSource | 58.0% | 75.4% | GPT-5.3 Codex leads |
Frequently Asked Questions (3)
Can I compare Claude Opus 4.5 Thinking and GPT-5.3 Codex on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for Claude Opus 4.5 Thinking and GPT-5.3 Codex today?
GPT-5.3 Codex: $1.75 input / $14.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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