Anthropic · Model release
Claude Opus 5.5 released
Anthropic's new flagship. Input and output cost 20% less than Opus 5, and cache reads, most of the cost of agentic coding, 60% less.
- Occurrence
- Occurrence date basis
- Provider publication date
- Status recorded with this event
- available
- Event checked
Original sources
- Introducing Claude Opus 5.5 (opens in a new tab) ↗
First-party source · Source checked
Input and output tokens are $4 and $20 per million, 20% less than Opus 5. Cache reads (which make up the majority of agentic and coding work costs) are $0.20 per million tokens, 60% less than Opus 5.
- Claude API Release Notes (opens in a new tab) ↗
First-party source · Source checked
September 22, 2026 ... On Claude Opus 5.5, thinking can't be disabled: thinking: {"type": "disabled"} and thinking: {"type": "enabled", ...} return a 400 error.
Recording provenance
First recorded by StackReplay . This is a discovery date, not the occurrence date.
Event ID: claude-opus-5-5-released