| Feature | Sonnet 4.5 | Opus 4.5 |
|---|---|---|
| API Price | $3 input / $15 output per million tokens | $5 input / $25 output per million tokens |
| Token Efficiency | Less efficient than Opus | More efficient, uses fewer tokens for comparable results |
| Best Use Case | High-throughput applications where speed matters | Complex tasks that require deeper reasoning |
| Cost Considerations | Lower base price, ideal for high volume when efficiency is less critical | Higher base price, but can be more cost-effective due to token efficiency and the "effort" parameter |
Opus 4.5 solves problems with dramatically fewer steps—less backtracking, less redundant exploration, less verbose reasoning. At medium effort level, Opus 4.5 matches Sonnet 4.5's best SWE-bench score while using 76% fewer output tokens. At high effort, it exceeds Sonnet 4.5 by 4.3 percentage points while still using 48% fewer tokens.
