This guide covers migrating Messages API code. If you use Claude Managed Agents, no changes beyond updating the model name are required.
Automate your migration with the Claude API skill. In Claude Code, run /claude-api migrate to invoke the bundled Claude API skill. It works for any current Claude model as the target:
/claude-api migrate this project to claude-opus-5The skill applies the model ID swap and, as needed, breaking parameter changes, prefill replacement, and effort calibration for your target model across your code base, then produces a checklist of items to verify manually. It asks you to confirm the migration scope (entire working directory, a subdirectory, or a specific file list) before editing any files. The skill also detects Amazon Bedrock and Claude Platform on AWS clients and adjusts model ID formats and feature changes for those platforms.
Claude Opus 5 is a step-change improvement over Claude Opus 4.8, strong on deep reasoning, agentic and long-horizon tasks, and test-time compute scaling. For behavioral differences and model-specific prompting patterns, see Prompting Claude Opus 5.
Claude Opus 5 is a drop-in upgrade for Claude Opus 4.8 at the same pricing of $5 USD per million input tokens and $25 USD per million output tokens; see Claude pricing. There are two breaking changes for code already running on Claude Opus 4.8, covered under Breaking changes. Claude Opus 5 supports the same set of features as Claude Opus 4.8, including the 1M token context window (the default, with no beta header), 128k max output tokens, adaptive thinking, prompt caching, batch processing, the Files API, PDF support, vision, and server-side and client-side tools, with two exceptions: web fetch is not available on Claude Opus 5, and Priority Tier is not supported on Claude Opus 5. See each tool page for model availability.