Overview
The first model in the Claude 5.5 family for long-running agentic coding and knowledge work, with adaptive thinking, a 1M context window, and 128K output.
Claude Opus 5.5
The first model in the Claude 5.5 family for long-running agentic coding and knowledge work, with adaptive thinking, a 1M context window, and 128K output.
Anthropic launched Claude Opus 5.5 on 2026-09-22 with API model ID `claude-opus-5-5`, available through the Claude API, AWS, Google Cloud, and Microsoft Foundry.
MODEL NUMBER073
- First public date
- 2026-09-22
- Organization
- Anthropic
- Family
- Claude
01
Specifications
Only published specifications are shown.
02
Overview
Why it mattered
Opus 5.5 advances the Opus line toward more efficient long-running agent work, with lower typical workload cost and faster output than Opus 5.
PreviousClaude Opus 5— · 1M ctx
CurrentClaude Opus 5.5— · 1M ctx
04
Architecture & capabilities
Model capabilities
Adaptive reasoningLong-horizon agentCodingTool use
Product features
Professional work
05
Release history
Anthropic launched Claude Opus 5.5 as the first model in the Claude 5.5 family for long-running agentic coding and knowledge work, available through the API, AWS, Google Cloud, and Microsoft Foundry.
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07
Sources
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