Claude Sonnet 4.5 vs o3
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for Claude Sonnet 4.5 and o3.
Claude Sonnet 4.5
Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows. It delivers state-of-the-art performance on coding benchmarks such as SWE-bench Verified, with...
o3
o3 is a well-rounded and powerful model across domains. It sets a new standard for math, science, coding, and visual reasoning tasks. It also excels at technical writing and instruction-following....
Technical Specifications
| Specification | Claude Sonnet 4.5 | o3 |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Context Window | 1,000,000 tokens | 200,000 tokens |
| Agent Suitability | 91/100 | N/A |
| Time to First Token (TTFT) | 380 ms | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | stable | stable |
| API Available | Yes | Yes |
| Released Date | 2025-09-29 | 2025-04-16 |
API Pricing Comparison
Input Price per Million Tokens
Claude Sonnet 4.5
$3.00
o3
$2.00
Output Price per Million Tokens
Claude Sonnet 4.5
$15.00
o3
$8.00
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Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
Claude Sonnet 4.5 Quirks & Gotchas
- ▸Excellent for long-form writing and nuanced document analysis
- ▸Slightly slower than Sonnet 4.6 — upgrade for production agentic use
o3 Quirks & Gotchas
No developer gotchas reported.