Claude Sonnet 5.5 is Anthropic's faster, cheaper partner to Claude Opus 5.5, aimed at everyday tasks such as fixing bugs and making documents, slides and spreadsheets.
In plain words
Sonnet 5.5 is the second model in Anthropic's Claude 5.5 family. Anthropic says it writes output more than 30% faster than Sonnet 5 and that, in its tests, a typical task costs as much as 30% less. API prices are $2 for each million input tokens and $10 for each million output tokens. For complex, open-ended work that needs sustained judgment, Anthropic says Opus 5.5 is still clearly stronger.
A quick example
Imagine a developer who asks Sonnet 5.5 to find out why a sign-up form keeps rejecting valid email addresses. It traces the bug, proposes a small fix and writes a short summary of the change.
Where you'll meet it
- Everyday coding, such as fixing bugs, and making documents, slides and spreadsheets.
- Chat in the Claude apps, or building through the Claude Platform, AWS, Google Cloud and Microsoft Foundry.
Related
Sources
- DocsIntroducing Claude Sonnet 5.5, Anthropic · read 3 Oct 2026
- DocsClaude Sonnet, Anthropic · read 3 Oct 2026
Checked by WhatIsAI against the sources above · 3 Oct 2026. A full five-minute explainer with a diagram may follow. Spotted an error? Report it.