News
September 2026
Claude Opus 5.5 — September 22, 2026
Anthropic introduced Claude Opus 5.5, the first model in the Claude 5.5 family. It is designed for long-running agentic coding and knowledge work, with a 1M-token context window, 128K maximum output, adaptive thinking, and a lower $4/$20 per-million-token price than Opus 5.
Anthropic says Opus 5.5 performs at the level of Fable 5.1 on most work, uses fewer tokens on typical agent tasks, and improves communication, computer use, coding, and professional knowledge work. The release also changes several API behaviors, so existing Opus 5 integrations should follow the migration checklist before production rollout.
Claude Sonnet 5.5 — September 28, 2026
Anthropic subsequently announced Claude Sonnet 5.5 as a faster, cost-efficient model for everyday work. See the Anthropic newsroom for the latest release information while the detailed guide is being added to this site.