Anthropic's Sonnet 5.5 nearly matches Opus 5.5 while costing 30% less per task
The Decoder · rss · 2026-09-29
Anthropic has released Claude Sonnet 5.5, the second model in its Claude 5.5 family: over 30% faster output, up to 30% cheaper per task, and nearly matching Opus 5.5 on knowledge-work benchmarks.
- Terminal-Bench coding score jumps from 10.3% to 70.6%
- Haiku 5.5 is announced for the coming weeks
- That will give Anthropic a direct counterpart to each of OpenAI's three GPT-6 models
The Decoder reports the full numbers.
More from Models
- Early Sonnet 5.5 impressions: ~5x faster bug fixes at high effort — burkov · 2026-09-29
- Why 4o feels different: thread argues native omni training, not capability, shapes model personality — RileyRalmuto · 2026-09-29
- Sonnet 5.5 effort settings make no difference in 15-task coding test: 9/15 at low, medium and high — every · 2026-09-29
- PrunaAI claims its text-to-video modes sit on DesignArena Pareto frontiers — guennemann · 2026-09-29
- Reddit user: Opus 5.5 silently falls back to Opus 5 on nearly every prompt — fishcat_catfish · 2026-09-29
- Sonnet 5.5 clones open-source editor Proof at low effort, joining elite group of just four models — every · 2026-09-29