Capabilities · Timeline event
What happened: Sonnet 5.5 released?
Anthropic introduces Sonnet 5.5 with claimed efficiency improvements at unchanged token rates.
When was this milestone recorded?
2026-09-28 · Models.
What is the source?
Anthropic · Sonnet 5.5 announcement ↗
Company announcement and evaluations. Last verified: 2026-09-29T12:03:47.389Z.
What does this tell us about the pace of AI?
This is one selected milestone. Its inclusion does not establish a change in capability, economic returns or an industry-wide growth rate. Announcement, release and measurement dates are different concepts.