Claude Opus 5.5 brings significant improvements in output speed and efficiency, generating output tokens more than 30 percent faster than its predecessor, Claude Opus 5. This means it can finish tasks with fewer tokens, making it more cost-effective.
One of the key differences is the effort calibration. Claude Opus 5.5 defaults to a medium effort level, unlike Claude Opus 5, which defaults to high. This change allows for better control over the trade-off between intelligence, latency, and cost. For instance, at its default medium effort, Claude Opus 5.5 matches or exceeds the performance of Claude Opus 5 at high effort on coding and knowledge-work evaluations. This makes it more efficient for tasks like code review and financial modeling.
For those migrating from Claude Opus 5, it’s important to note that existing prompts should perform well without changes. However, there are specific patterns and adjustments to consider. For example, if your integration ran with thinking disabled on Claude Opus 5, you’ll need to start at a low effort level and measure the performance. Claude Opus 5.5 doesn’t accept thinking: {"type": "disabled"} at high effort or below, so adjustments are necessary.
Another significant improvement is in handling complex visual inputs. Claude Opus 5.5 reads visual material more accurately, even at its lowest effort setting. This is particularly useful for tasks involving dense charts, diagrams, and screenshots. It can read values off dense charts more accurately than Claude Opus 5 did at its highest effort setting, using a small fraction of the output tokens.
For unattended agentic runs, Claude Opus 5.5 provides better progress updates. This is crucial for long tasks where you need to monitor progress without constant intervention. The model also handles multi-agent workflows more efficiently, finishing tasks sooner and providing clearer updates on its progress.
In terms of API changes, there are four breaking changes when migrating from Claude Opus 5. These include adjustments to effort levels, thinking behavior, and handling of complex visual inputs. For detailed migration steps, refer to the migration guide provided by Anthropic.
Overall, Claude Opus 5.5 offers a more efficient and accurate model for a variety of tasks, from code review to financial modeling. Its improved handling of visual inputs and better progress updates make it a robust choice for both attended and unattended tasks.
