Anthropic
Claude Opus 5.5 Releases
Release log
All changesOfficial changelog
Claude Platform release notes - Claude Platform Docs (covers all Anthropic models)
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Questions
When was Claude Opus 5.5 released
Sep 22, 2026, per platform.claude.com.
Where is the official Claude Opus 5.5 changelog
Claude Platform release notes - Claude Platform Docs, at https://platform.claude.com/docs/en/release-notes/overview.
Source: claude.com, read Nov 9, 2026.