Claude Sonnet 5.5 Launches With Lower Task Costs and Cursor Support

Anthropic introduced Claude Sonnet 5.5 on September 28 as the second model in its Claude 5.5 family. The model keeps Sonnet 5's API prices at $2 per million input tokens and $10 per million output tokens; Anthropic says its output generation is more than 30% faster and that it costs up to 30% less per task in its testing (Anthropic).

Sonnet 5.5 is positioned for well-scoped coding and knowledge-work tasks where the result can be checked. Anthropic describes Opus 5.5 as the better fit for complex, open-ended work requiring sustained judgment (Anthropic's model announcement; Claude's model-selection guide).

Key Takeaways

• Model ID: claude-sonnet-5-5 on Anthropic's developer platform (Anthropic).
• Token price: $2 per million input tokens and $10 per million output tokens, the same as Sonnet 5 (Anthropic).
• Task efficiency: Anthropic reports output generation more than 30% faster and up to 30% lower cost per task than Sonnet 5 in its testing (Anthropic).
• Cursor: Cursor lists Sonnet 5.5 in its model picker. Add it from Cursor Settings > Models (Cursor model documentation).
• Claude Code settings: Claude Code and Claude apps default to Medium effort; the Claude Platform defaults to High (Anthropic).

What Sonnet 5.5 Is For

Anthropic recommends Sonnet 5.5 for well-scoped everyday coding, bug fixes, feature iteration, and polished documents, slides, and spreadsheets. Its developer guide says the model fits best when a task has a clear specification and a way to check the result. For the hardest long-horizon work, Anthropic recommends considering Opus 5.5 instead (Anthropic; Claude's model-selection guide).

The speed and cost claims refer to work completed, not a lower per-token price. Sonnet 5.5 keeps the same listed input and output rates as Sonnet 5, while Anthropic says it typically uses fewer tokens to do the same work. Its announcement reports output generation more than 30% faster and up to 30% less cost per task in Anthropic's testing (Anthropic).

Where to Use It

Anthropic lists claude-sonnet-5-5 as the model identifier for developers starting on the Claude Platform. Its announcement also says Sonnet 5.5 is available on Amazon Web Services, Google Cloud, and Microsoft Azure (Anthropic; Anthropic's migration guide).

Cursor's model documentation lists Claude Sonnet 5.5 as an available model and directs users to Cursor Settings > Models to add it to the model picker. The page says Sonnet 5.5 supports thinking mode and context windows up to 1M tokens (Cursor model documentation). Sonnet 5.5 draws from Cursor's third-party Other Models usage pool. Cursor lists global-endpoint prices of $2 per million input tokens and $10 per million output tokens (Cursor model documentation).

Effort Settings and API Migration

Effort defaults differ by surface: Anthropic lists Medium for Claude Code and the Claude apps, and High for the Claude Platform. Anthropic's developer guide recommends starting at High for general API use, Medium for well-specified agentic coding tasks, and Medium or Low for latency-sensitive chat. Effort levels are recalibrated, so the same label does not necessarily produce the same amount of thinking as it did on Sonnet 5 (Anthropic; Claude's model-selection guide).

If an API integration used thinking: {"type": "disabled"} on Sonnet 5, Anthropic says that setting is not supported on Sonnet 5.5. The migration guide says to use thinking: {"type": "between_tools"} to turn off up-front thinking; this setting is accepted at Low, Medium, and High effort, but not at Xhigh or Max. Anthropic also recommends rerunning effort tests and re-baselining cost after a migration (Anthropic's migration guide).

Sources

• Anthropic, “Introducing Claude Sonnet 5.5,” September 28, 2026: https://www.anthropic.com/claude-sonnet-5-5
• Anthropic, “Migrating to Claude Sonnet 5.5”: https://platform.claude.com/docs/en/models/sonnet-5-5/migration-guide
• Claude Devs, “Building with Claude Sonnet 5.5,” September 28, 2026: https://claude.dev/blog/building-with-claude-sonnet-5-5/
• Cursor Docs, “Claude Sonnet 5.5”: https://cursor.com/docs/models/claude-sonnet-5-5