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Claude Sonnet 4.5 vs GPT-5.3 Codex
A detailed comparison of Claude Sonnet 4.5 (Anthropic) and GPT-5.3 Codex (OpenAI) across pricing, performance, and features.
Pricing Comparison
| Metric | Claude Sonnet 4.5 | GPT-5.3 Codex | Difference |
|---|---|---|---|
| Input / 1M tokens | $3.00 | $2.00 | -33% |
| Output / 1M tokens | $15.00 | $16.00 | +7% |
| Context window | 200K | 200K | — |
| Max output | 16K | 65.536K | — |
Benchmark Comparison
| Benchmark | Claude Sonnet 4.5 | GPT-5.3 Codex |
|---|---|---|
| MMLU-Pro | 84.5% | 90% |
| HumanEval | 93% | 96.5% |
| GPQA | 68.2% | 78% |
Capabilities
| Capability | Claude Sonnet 4.5 | GPT-5.3 Codex |
|---|---|---|
| code | ✓ | ✓ |
| reasoning | ✓ | ✓ |
| text | ✓ | ✓ |
| tool-use | ✓ | ✓ |
| vision | ✓ | ✓ |
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- ✗Superseded by Sonnet 4.6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
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
Quick Verdict
Best value: GPT-5.3 Codex is the more affordable option at $2/$16 per 1M tokens.
Higher benchmarks: GPT-5.3 Codex scores higher on average across available benchmarks (88.2% avg).
Choose GPT-5.3 Codex if cost matters most. Choose Claude Sonnet 4.5 if you need the best possible quality for complex tasks.