Mid-conversation system messages available on Claude Fable 5, Mythos 5 and Opus 4.8
GAVerifiedAdded Sep 22, 2026
Mid-conversation system messages work on Claude Fable 5, Mythos 5 and Opus 4.8 on the Claude API, Amazon Bedrock and Google Cloud with no beta header required, correcting earlier availability notes.
Topics: LLMs, Developer tools
Summaries of vendors' own notes. Product names and logos belong to their owners; logos via logo.dev.
More Claude Platform releases
Every Claude Platform release| Date | Release | Type |
|---|---|---|
| Jul 14 | Admin API adds Claude Enterprise user management in beta Beta | Beta |
| Jul 14 | Self-serve HIPAA configuration for Claude Enterprise and the Claude API Update | Update |
| Jul 17 | Legacy Claude Console Workbench sunsets on August 17, 2026 Deprecation | Deprecation |
| Jul 17 | Claude experimental prompt tools APIs retire with the Workbench on August 17, 2026 Deprecation | Deprecation |
| Jul 10 | Dreams research preview adds Claude Fable 5 and Claude Sonnet 5 Preview | Preview |
| Jul 10 | Claude Access Transparency docs expand coverage of cmek_preserve events Update | Update |
| Jul 22 | Claude Managed Agents agents accept an effort level in model configuration Update | Update |
| Jul 22 | Claude Managed Agents webhooks cover environment and memory store lifecycle Update | Update |
