Per-message effort changes beta expands to Claude on Google Cloud
BetaVerifiedAdded Sep 22, 2026
Per-message effort changes are now available in beta on Google Cloud for Claude Fable 5.1, Claude Mythos 5.1 and Claude Opus 5, using the same mid-conversation-output-config-2026-07-01 beta header.
Topics: LLMs
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More Claude Platform releases
Every Claude Platform release| Date | Release | Type |
|---|---|---|
| Sep 3 | ant CLI 1.30.0 adds ant apply to manage agents and resources as code Update | Update |
| Sep 1 | Claude Fable 5.1 launches alongside Claude Mythos 5.1 with 1M token context GA | GA |
| Sep 1 | Prompt cache reads on Claude Fable 5.1 and Mythos 5.1 drop to $0.25 per MTok Pricing | Pricing |
| Sep 1 | Claude Fable 5.1 and Mythos 5.1 reject tool_choice any and tool Update | Update |
| Sep 1 | Claude Fable 5.1 thinking blocks only replay to the same or newer models Update | Update |
| Sep 1 | Per-message effort changes enter beta on the Claude API Beta | Beta |
| Sep 1 | Claude API adds turn-scoped system messages in beta Beta | Beta |
| Sep 1 | Claude API thinking.display adds an updates mode in beta Beta | Beta |
