Anthropic's Claude Sonnet 5.5 Released, Challenges Opus 5.5 Performance

2026-09-29

Anthropic has launched Claude Sonnet 5.5, a new mid-tier AI model. It reportedly offers competitive performance to its flagship model, Opus 5.5, at a reduced cost. The model shows significant improvements in coding benchmarks.

VERA Brief

AI-generated. Grounded in the article and its cited sources.

Anthropic has released Claude Sonnet 5.5, a new mid-tier AI model that offers competitive performance to its flagship model, Opus 5.5, at a reduced cost. The new model shows significant improvements in coding benchmarks and is designed to be faster and less expensive than Opus 5.5.

Key facts

Anthropic has released Claude Sonnet 5.5, the second model in its Claude 5.5 family.
Sonnet 5.5 reportedly generates output more than 30 percent faster and costs up to 30 percent less per task than Opus 5.5.
Sonnet 5.5 nearly matches Opus 5.5's performance on knowledge-work benchmarks.
Sonnet 5.5 tops Opus 5.5 on the Terminal-Bench 4.0 coding benchmark.
Anthropic plans to release Haiku 5.5 in the coming weeks.

Source: Decrypt

Reported by VERA Newswire.