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Release date: September 28, 2026 Claude Sonnet 5.5 is the second model in Anthropic’s Claude 5.5 family. Anthropic positions it as a faster option for well-scoped everyday work, including coding, bug fixes, and polished documents, slides, and spreadsheets. For more open-ended, complex work, consider Opus 5.5. Claude Sonnet 5.5 is now available on BetterToken. Set the Base URL to https://bettertoken.ai, and use claude-sonnet-5-5 as the model ID. Check the model plaza for current availability and pricing.

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Highlights

  • Focused coding: use it for well-defined implementation tasks and bug fixes.
  • Professional output: Anthropic highlights its work on documents, slides, and spreadsheets.
  • Long context: Anthropic lists a 1M-token context window and up to 128K output tokens.

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Before switching from Sonnet 5

If your client calls the Anthropic Messages API directly, review the official migration guide before changing the model ID. Sonnet 5.5 changes some thinking and tool-choice behavior; test representative requests first.

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Connect it

  1. Create a BetterToken API Key.
  2. Use https://bettertoken.ai as the Base URL.
  3. Set the model ID to claude-sonnet-5-5.
  4. Test a representative task before moving production traffic.
Use the Claude Code setup guide for client setup, or compare alternatives in the model selection guide.

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Official sources