Migrating from Claude Sonnet 4 and Claude Opus 4 to Claude Sonnet 5.5
Claude Sonnet 4 and Claude Opus 4 stopped answering on Jun 15, 2026 on the Claude API. Requests to a retired model fail. The provider’s replacement is Claude Sonnet 5.5.
- Shutdown
- Jun 15, 2026
- Retired
- 140 days ago
- Replacement
- Claude Sonnet 5.5
What shuts down
claude-sonnet-4and its dated snapshotsclaude-sonnet-4-0and its dated snapshotsclaude-opus-4and its dated snapshotsclaude-opus-4-0and its dated snapshots
On Amazon Bedrock, Claude Sonnet 4 ran until 2026-10-14.
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 and Claude Opus 4 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 and Claude Opus 4 and Claude Sonnet 5.5 and comments a verdict on the pull request: safe to migrate, review these cases, or do not migrate.