Migrating from Claude Sonnet 4.5 to Claude Sonnet 5.5
Claude Sonnet 4.5 stops answering on Nov 30, 2026 on the Claude API. Requests to a retired model fail. The provider’s replacement is Claude Sonnet 5.5.
- Shutdown
- Nov 30, 2026
- Time left
- 28 days left
- Replacement
- Claude Sonnet 5.5
What shuts down
claude-sonnet-4-5and its dated snapshots
Same date on Claude Platform on AWS and Microsoft Foundry. On Amazon Bedrock it runs until 2027-04-08.
Source: platform.claude.com. Check your provider’s deprecations page before you plan around a date.
Find every place you use it
The free scanner flags every reference in your repository and opens one issue with the deadline:
npx swapvera-scan .Or on every push, as a GitHub Action:
- uses: pixelric-spec/swapvera-scanner@v1
with:
fail-on: retiredWhat can change when you swap the ID
Prompts tuned for one model rarely transfer perfectly to the next. Check these before you merge:
- Structured output: JSON that stays valid and keeps the same field types.
- Tool calls: the same tools called with the same arguments, and no calls where there were none.
- Instructions in your system prompt that the new model follows differently, such as length limits or policies it must quote.
- Refusals and safety behavior on your edge cases.
- Parameters the new model rejects, such as a fixed temperature on reasoning models.
- Latency and cost per call at your real input sizes.
What broke for other teams
0of 5 teams
No team has shared results for Claude Sonnet 4.5 to Claude Sonnet 5.5 yet. Nothing about a migration is published until 5 different teams have shared it, so no single team’s results can be picked out.
Add yours when you run the verdict: swapvera run --share. Only categories are sent, never prompts or outputs. See exactly what is sent.
Check the switch on your own prompts
Swapvera runs your cases on Claude Sonnet 4.5 and Claude Sonnet 5.5 and comments a verdict on the pull request: safe to migrate, review these cases, or do not migrate.