Anthropic

claude-sonnet-4-5-20250929: retirement date, replacement, how to migrate

claude-sonnet-4-5-20250929 retires on 2026-11-30 on the Anthropic API; the vendor's named replacement is claude-sonnet-5-5.

This date is the one in the Anthropic notice for the Anthropic API. Other platforms that host the same model publish their own dates.

Facts

Retirement date: 2026-11-30
Status: Scheduled, in 47 days
Replacement: claude-sonnet-5-5
Official notice: https://platform.claude.com/docs/en/about-claude/model-deprecations#2026-09-30-claude-sonnet-4-5-model
Notice date: 2026-09-30

Find it in your code

npx @upseam/cli inspect anthropic

grep -rnF 'claude-sonnet-4-5-20250929' .

The first command reads your repository and the change data bundled in the package; nothing leaves your machine. The second is a plain text search.

Migrate

claude-sonnet-4-5-20250929 claude-sonnet-5-5

Change the id in your code and config to the vendor's named replacement. The record does not say whether outputs, parameters or prices stay the same, so read the vendor's notice before you switch. Open the vendor's notice.

Get warned automatically

Upseam is Dependabot for APIs: it watches vendor changelogs and opens a checked pull request when a change affects your code. See how it works.

Last updated 2026-09-30 · Markdown copy