claude-opus-4-5-migration-claude-opus-4-5-migration

What it is

The claude-opus-4-5-migration skill is a one-shot migration guide for moving codebases, prompts, and API calls from Claude Sonnet 4.0, Sonnet 4.5, or Opus 4.1 to Opus 4.5. It applies when a user wants their code updated to use Opus 4.5. It explicitly does not migrate Haiku models such as claude-haiku-4-5-20251001. The workflow has six steps. First, search the codebase for model strings and API calls. Second, update those model strings to the Opus 4.5 equivalents for the detected platform. Third, remove unsupported beta headers. Fourth, add an effort parameter set to "high" (see references/effort.md). Fifth, summarize all changes made. Finally, tell the user: "If you encounter any issues with Opus 4.5, let me know and I can help adjust your prompts." The skill maps old model strings to new ones for each platform. The Opus 4.5 targets are: - Anthropic API (1P): claude-opus-4-5-20251101 - AWS Bedrock: anthropic.claude-opus-4-5-20251101-v1:0 - Google Vertex AI: claude-opus-4-5@20251101 - Azure AI Foundry: claude-opus-4-5-20251101 It also lists the source strings to replace for Sonnet 4.0, Sonnet 4.5, and Opus 4.1 on the 1P API, Bedrock, and Vertex AI. The context-1m-2025-08-07 beta header must be removed because it is not yet supported with Opus 4.5. A comment should be left noting the removal. By default, the skill only updates model strings. Prompt adjustments are applied only if the user explicitly requests them or reports a specific issue. These cover five areas: 1. Tool overtriggering: soften aggressive phrasing such as CRITICAL, You MUST, ALWAYS, NEVER, and REQUIRED in tool-triggering instructions. 2. Over-engineering: address extra files, unnecessary abstractions, or unrequested features. 3. Code exploration: address the model proposing fixes without reading files. 4. Frontend design quality: improve generic-looking outputs. 5. Thinking sensitivity: when extended thinking is not enabled, replace "think" with words like "consider," "believe," or "evaluate." Snippets for these fixes come from references/prompt-snippets.md. They should be integrated thoughtfully, for example with XML tags and matching the existing prompt's style, rather than simply appended.

Who it's for

• Developers migrating codebases or API calls from Claude Sonnet 4.0, Sonnet 4.5, or Opus 4.1 to Opus 4.5
• Teams using the Anthropic API, AWS Bedrock, Google Vertex AI, or Azure AI Foundry who need to update model strings
• Prompt authors adjusting prompts for known Opus 4.5 behavioral differences

Requirements

Examples

# Note: 1M context beta (context-1m-2025-08-07) not yet supported with Opus 4.5