Mid-conversation system messages available on Claude Fable 5, Mythos 5 and Opus 4.8
Tech · Releases · Wed, July 15, 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.
Every year
Also on Jul 15, 2026
| Date | Event | When |
|---|---|---|
| Wed, Jul 15, 2026 | Bank of Canada rate announcement, July 15, 2026 | 2 mo ago |
Source, method and history
- Source
- anthropic
- How we know
- From the Releases API (releases.fru.dev), which reads each vendor's changelog.
- Who
- anthropic
- Recurs
- one-off
- More on fru.dev
- releases.fru.dev
- Feed
- Subscribe to Releases
- Changes
- 2026-09-25: added to 2026-07-15