10 results for Opus 5.5 model fallback

Why Claude switched models in your conversation with Opus 5 or Opus 5.5Most requests sent to Opus 5 or Opus 5.5 won’t encounter fallback safety interventions… You can switch back to Opus 5 or Opus 5.5 anytime from the model picker… Automatic model switching works the same way everywhere you can use Claude Opus 5 or Opus 5.5:
Claude Code model configuration5.5: claude --model claude-sonnet-5-5 For Opus 5.5: claude --model claude-opus-5-5 For Fable… Sonnet 5.5, claude-sonnet-5-5 Opus 5.5, claude-opus-5-5 Fable 5.1, claude-fable-5-1… ="claude-sonnet-5-5"' >> ~/.zshrc Opus 5.5: echo 'export ANTHROPIC_MODEL="claude-opus-5-5"' >>
Why Claude switched models in your conversation with Sonnet 5.5Opus 5 or Opus 5.5… Fallback requests: If you're opted into automatic model switching and the chat switches to Sonnet 5 after… For how safeguards work on Claude Opus 5.5, see Why Claude switched models in your conversation with
Change the model, effort, and thinking settingsThe effort selector is available for Claude Sonnet 5.5, Opus 5.5, Fable 5.1, Opus 5, Sonnet 5, Fable… Thinking cannot be turned off in Claude when using Claude Sonnet 5.5, Claude Opus 5.5, Claude Fable 5.1… On Opus 5.5 and Fable 5.1, thinking is always on at every effort level, including on the Claude API
How large is the context window on paid Claude plans?Claude Opus 5.5 1M tokens Claude Opus 5 1M tokens Claude Opus 4.8… Claude Opus 5.5 1M tokens Claude Opus 5 1M tokens Claude Opus 4.8… 5.5 1M tokens Claude Opus 5 1M tokens Claude Opus 4.8 1M tokens
How up-to-date is Claude's training data?Claude Opus 5.5 was trained on data up until June 2026… 5.5 was trained on data up until June 2026… If you ask about more recent events, the model may not have accurate information
Why Claude switched models in your conversation with Fable 5 or Fable 5.1After the switch, the model picker stays on Opus for the rest of the conversation… Fallback requests: If you are opted into automatic model switching, and the conversation switches to… What happens after a fallback
Real-time cyber safeguards on Claude Opus and SonnetNote: This article applies only to Opus and Sonnet class models, but doesn’t apply to Claude Opus 5.5… We'll soon be expanding the Cyber Verification Program to include Opus 5.5, Sonnet 5.5, and Mythos class… or Sonnet 5.5
Release notesSeptember 22, 2026 Claude Opus 5.5 launch We just launched Claude Opus 5.5, the first model in our… September 28, 2026 Claude Sonnet 5.5 launch We just launched Claude Sonnet 5.5, the second model… Sonnet 5.5 is a faster, lower-cost complement to Claude Opus 5.5
Preserved thinking: changing how the Messages API handles thinking blocks to protect against distillationOn Claude Fable 5.1, Claude Opus 5.5, and Claude Sonnet 5.5, new API accounts can no longer edit the… 5.5 Applies Doesn't apply Claude Sonnet 5.5 Applies Doesn't apply This… Accounts created before then Claude Fable 5.1 Applies Doesn't apply Claude Opus