Claude Opus 5.5
Anthropic’s flagship for demanding reasoning, coding and long-horizon agents.
Claude Opus 5.5 is Anthropic’s flagship model for demanding reasoning, coding, and long-horizon agentic work, succeeding Claude Opus 5. It is particularly strong at multi-step changes in large codebases and sustained autonomous tasks.
- Provider
- Anthropic
- Type
- Language model
- Released
- Sep 22, 2026
- Context window
- 1M tokens
- Max output
- 128K tokens
- Price
- $4.00 input / $20.00 output per 1M tokens
- Input
- text, image, file
- Output
- text
- Open weights
- No
- Knowledge cutoff
- Jun 1, 2026
Best for
- Coding
- Agents
- Reasoning
- Research
- Long context
- Enterprise
Strengths
- Top Intelligence Index score
- Large-codebase refactors
- Long-running agents
- 1M-token context
More from Anthropic
- Claude Sonnet 5.5 — Anthropic. Near-flagship intelligence at a mid-tier price; the everyday workhorse for builders.
- Claude Haiku 5.5 — Anthropic. Small, fast and inexpensive — built for subagents, summarization and browser use.
- Claude Fable 5.1 — Anthropic. Premium model for long-running agentic workflows, refactors and visual front-end work.
- Claude Opus 5 — Anthropic. Previous-generation Opus; still a strong reasoning and coding model.
Tools that use it
- Claude Code — Anthropic. Agentic coding in your terminal, IDE and browser.
- Cursor — Anysphere. The AI-native code editor.
- Claude Agent SDK — Anthropic. The agent harness behind Claude Code, as a library.
- Vertex AI — Google Cloud. Google Cloud’s AI platform.
- Claude — Anthropic. Anthropic’s AI assistant for thinking and making.