Migrating from Opus 4.1 to Claude Opus 4.5 generally involves updating the model ID, simplifying prompts, and adopting new features such as the effort parameter and advanced tool use. Opus 4.5 handles reasoning more effectively, so many prompt patterns written for Opus 4.1’s limitations can be cleaned up. Start by swapping the model identifier in your API or SDK calls, then evaluate how Opus 4.5 responds with your existing instructions. Many prompts become shorter because Opus 4.5 understands intent without detailed step instructions.
Anthropic provides a migration plugin and upgrade guidance that automatically adjusts prompts, expectations, and patterns from Sonnet 4.x and Opus 4.1 to the newer model. This plugin highlights areas where Opus 4.5 behaves differently—particularly around tool use, reasoning depth, and output verbosity. Even if you migrate manually, these guidelines help simplify prompts, adjust system messages, and ensure you’re using effort appropriately. For fragile chains of thought or multi-step flows, Opus 4.5 typically produces more reliable behavior with fewer hacks.
If you use retrieval, no changes are needed for your vector database setup. Systems that use Milvus or Zilliz Cloud can continue retrieving documents and injecting them into prompts or tool calls exactly as before. After enabling Claude Opus 4.5 in staging, run A/B tests against Opus 4.1 under real workloads—coding tasks, document analysis, or agent runs. Once outputs and costs look stable, you can migrate traffic gradually or switch your “latest” model alias in production. Over time, you can adopt Opus 4.5’s advanced tools, long-running agent patterns, and memory capabilities to fully benefit from the upgrade.