Anthropic Claude Opus 5.5, released in September 2026, is the new-generation flagship and the first model in the Claude 5.5 family, built for long-running agentic coding and knowledge work. It performs at the level of the top-tier Fable 5.1 on most work, costs less to run than Opus 5, and generates output more than 30 percent faster. Against Opus 5 it raises agentic coding on Terminal-Bench from 52 to 66 percent, catches 72 percent of known bugs in code review versus 56 percent, and leads on business workflow automation, computer use, and chart reading; its replies put the most important information up front. Its knowledge cutoff is June 2026, and it supports very long context. The interface offers a reasoning-effort dropdown (five levels, default high), an option to show the thinking process, web search, and image and document upload; extended thinking is always on and cannot be switched off. Use it for large refactors, code review, and deep cross-document research; use Sonnet 5 or Haiku 5.5 for light everyday chat. If you need to search the web for information, please turn on the "Web Search" switch. Maximum context window (input and output combined): about 1,000,000 tokens. Maximum output per reply: about 64,000 tokens (model reasoning, if any, counts toward this limit). Maximum total upload size per request: 512MB (all files and message content combined). Accepted document formats: pdf, docx, xlsx, pptx, txt, csv (file content is provided to the model as extracted text). Accepted image formats: gif, jpeg, jpg, png, webp. Animated GIF images are analyzed using only the first frame. Maximum number of images: 600. When uploading more than 20 images, each side must be at most 2,000 pixels. Maximum size per image: 10MB (base64-encoded). Maximum total image size per message: 20MB (text and history share the same request size limit; uploads close to the limit may still be rejected). Image dimensions: 200 to 8,000 pixels per side. Output content formats: Text/Image Pricing: High This module supports continuous conversations. AI can make mistakes. Please verify important information.