Claude Opus 5.5 is a top-tier frontier AI model developed by Anthropic and released on September 22, 2026. It is a proprietary closed-weight model, available on the Claude Platform and on Amazon Web Services, Google Cloud and Microsoft Azure. The 1M-token context window is large enough to hold entire codebases, lengthy technical documents, or extended agentic sessions without truncation.
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Opus 5.5 is the first model in Anthropic’s Claude 5.5 family. Anthropic says it performs at the level of Claude Fable 5.1 on most work while costing less to run than Opus 5, and that it generates output noticeably faster. Testers highlighted large software tasks: one completed a 680,000-line code migration in under a day. Anthropic also says it writes more clearly than earlier models, puts the key information first, and is less likely to take hard-to-reverse actions or act outside its given boundaries. Because its biology and cybersecurity capabilities are comparable to Mythos 5.1, it ships with safeguards similar to Fable 5.1’s.
Anthropic reports strong results on agentic coding, including large code migrations and finding and fixing performance problems in existing software, which suits teams using AI on complex engineering work.
Agentic Coding & Computer Use
It is built for long agentic sessions in the terminal and on a computer, where it needs to act within given boundaries and avoid hard-to-reverse actions.
Knowledge Work & Writing
Anthropic says Opus 5.5 communicates more naturally than earlier models, with clearer writing and the most important information up front, which helps for reports, analysis and long collaboration sessions.
Large Codebase & Document Analysis
With a 1M-token context window, it can take in entire repositories, long contracts or extended conversation histories in a single prompt.
Strengths and limitations
Strengths
+Strong agentic coding and large-scale software changes
+Clearer, more natural writing than earlier Claude models
+Less likely to take hard-to-reverse actions or act outside given boundaries
+More resistant to prompt injection than Opus 5
+Very long documents and large codebases (1M context)
Limitations
−Closed-weight, so it cannot be self-hosted or fine-tuned on private data
−Biology and cybersecurity safeguards limit some dual-use tasks unless an organization is verified
−No thinking-off mode
Use it in FlowHunt
Use Claude Opus 5.5 in any flow, next to your own tools and knowledge sources.
About AnthropicSan Francisco, CA · Founded 2021 · anthropic.com
Anthropic is an AI safety company founded in 2021 by former OpenAI researchers Dario Amodei and Daniela Amodei, along with a group of colleagues who had led OpenAI's safety and policy teams. The company's stated mission is the responsible development of AI for the long-term benefit of humanity, and its research agenda is defined by that commitment: Constitutional AI (CAI), a technique for training models to be helpful, harmless, and honest through self-critique; mechanistic interpretability, which aims to reverse-engineer what individual neurons and circuits inside large networks actually compute; and scaling science, which tries to predict how model behaviour changes with compute and data. Anthropic publishes this research openly and has become one of the most cited AI safety labs in academic literature. Claude is Anthropic's public model family, named for Claude Shannon, the founder of information theory, and runs from Claude 1 to the Claude 5.5 generation and Claude Fable 5.1. Anthropic operates a commercial API and consumer-facing Claude.ai product, and maintains deep cloud partnerships with AWS (Amazon Bedrock) and Google Cloud (Vertex AI).
Claude Opus 5.5 is a top-tier frontier AI model developed by Anthropic and released in September 2026. It is the first model in the Claude 5.5 family.
Claude Opus 5.5 is a proprietary closed-weight model. Its weights are not publicly available. Access is through the Claude Platform and cloud platforms including Amazon Web Services, Google Cloud, and Microsoft Azure.
Claude Opus 5.5 supports a 1M-token context window, large enough to hold entire codebases, lengthy technical documents, or extended agentic sessions without truncation.
Yes — Claude Opus 5.5 is directly available in FlowHunt. You can use it to build AI agents, automated workflows, chatbots, and document processing pipelines without any additional setup.
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