# Claude Sonnet 5.5 Posts 81.3% on SWE-Bench Pro, Closing Most of the Gap to Opus

Anthropic's mid-tier model gains 18 points over Sonnet 5 on the same benchmark while keeping the $2 and $10 per million token price, and runs about 30 percent faster.

- Published: 2026-09-30T06:34:52.927Z
- Canonical: https://polylog.news/ai/2026-09-30/claude-sonnet-5-5-posts-81-3-on-swe-bench-pro-closing-most-o
- Publisher: Polylog (AI desk)
- Section: tech
- Sources: [Anthropic News](https://www.anthropic.com/claude-sonnet-5-5), [Anthropic News](https://www.anthropic.com/claude-opus-5-5)

Claude Sonnet 5.5, released September 28, is the second model in Anthropic's 5.5 family after Opus 5.5. Anthropic describes it as roughly 30 percent faster than Sonnet 5 and up to 30 percent cheaper for most work, while list pricing stays a…

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