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GPT-5.3 Codex vs Claude Sonnet 4.5
A detailed comparison of GPT-5.3 Codex (OpenAI) and Claude Sonnet 4.5 (Anthropic) across pricing, performance, and features.
Pricing Comparison
| Metric | GPT-5.3 Codex | Claude Sonnet 4.5 | Difference |
|---|---|---|---|
| Input / 1M tokens | $2.00 | $3.00 | +50% |
| Output / 1M tokens | $16.00 | $15.00 | -6% |
| Context window | 200K | 200K | — |
| Max output | 65.536K | 16K | — |
Benchmark Comparison
| Benchmark | GPT-5.3 Codex | Claude Sonnet 4.5 |
|---|---|---|
| MMLU-Pro | 90% | 84.5% |
| HumanEval | 96.5% | 93% |
| GPQA | 78% | 68.2% |
Capabilities
| Capability | GPT-5.3 Codex | Claude Sonnet 4.5 |
|---|---|---|
| code | ✓ | ✓ |
| reasoning | ✓ | ✓ |
| text | ✓ | ✓ |
| tool-use | ✓ | ✓ |
| vision | ✓ | ✓ |
GPT-5.3 Codex Strengths
- ✓Best coding model from OpenAI
- ✓Large output window (65K tokens)
- ✓Strong reasoning for complex tasks
GPT-5.3 Codex Weaknesses
- ✗API access not yet available
- ✗Premium pricing
Claude Sonnet 4.5 Strengths
- ✓Well-tested and stable
- ✓Strong coding and analysis
Claude Sonnet 4.5 Weaknesses
- ✗Superseded by Sonnet 4.6
- ✗Same price as the newer model
Quick Verdict
Best value: Claude Sonnet 4.5 is the more affordable option at $3/$15 per 1M tokens.
Higher benchmarks: GPT-5.3 Codex scores higher on average across available benchmarks (88.2% avg).
Choose Claude Sonnet 4.5 if cost matters most. Choose GPT-5.3 Codex if you need the best possible quality for complex tasks.