Claude Opus 4.5

• 🏢 Anthropic frontier reasoning model, released December 2025.
• 🧠 Built for complex software engineering and long-horizon agentic work.
• 👁️ Multimodal: handles text and image inputs.
• 📏 Roughly 200K-token context window for extended sessions.
• 🔧 Supports function calling, tool use, and extended thinking.
• 🔒 Anthropic reports improved robustness to prompt injection.
• 🌐 Includes web search and computer-use capabilities.
• ⚡ Sustains performance through long autonomous coding runs.

Anthropic

Anthropic is an American artificial intelligence company headquartered in San Francisco, focused on developing large language models under the Claude family. Founded with a strong emphasis on AI safety research, the company has become one of the most…

Claude Opus 4.5 is Anthropic's frontier reasoning model in the Opus line, positioned for complex software engineering, agentic workflows, and long-horizon computer use across browsers, desktops, and spreadsheets. It accepts text and image inputs, supports tool calling and extended thinking, and works with roughly a 200K-token context window, with new tooling for longer-running agents and integrations for Excel, Chrome, and desktop use.

Against earlier Opus generations, Anthropic's system card reports its best internal results on software coding and agentic tasks among its own evaluated frontier models, alongside substantial improvements in reasoning and mathematics. Anthropic also describes measurable gains on its hardest internal evaluations and consistent behavior through roughly 30-minute autonomous coding sessions, framing it as a clear step beyond Claude Sonnet 4.5 for sustained, multi-step execution.

The model is the foundation for several later releases. Anthropic's Claude Opus 4.6 system card characterizes that successor as an upgrade—sometimes substantial—on Opus 4.5, citing improvements in long-context reasoning, knowledge work, research, and some areas of agentic coding and tool use. The lineage continues through to Claude Opus 4.8, which Anthropic's docs describe as its most capable generally available model with a 1M-token context window.

In short, Opus 4.5 marked a step toward more reliable, lower-overhead long-horizon autonomy, emphasizing structured planning, tool orchestration, and execution reliability over prior Opus models, while remaining a strong general-purpose reasoning and coding option.