Claude Opus 4.5 is a frontier large language model developed by Anthropic, released in late 2025 as the flagship of the Claude 4 family. Designed for high-complexity tasks, the model is optimized for software engineering, autonomous agents, and multi-step enterprise workflows. It achieved a notable score of 80.9% on the SWE-bench Verified benchmark, demonstrating a significant advancement in solving real-world software engineering problems compared to its predecessors.
The model features a hybrid reasoning architecture that introduces an "effort" parameter for API users. This parameter allows the model to toggle between a standard, high-speed mode and an extended thinking mode. When operating in its base (non-reasoning) state, the model focuses on maximizing intelligence-per-token efficiency for tasks like deep research, data synthesis, and complex creative writing, while avoiding the additional latency and token costs associated with extended internal chains of thought.
Claude Opus 4.5 supports a 200,000-token context window and can generate up to 64,000 tokens in a single output. Anthropic has highlighted the model's improved alignment and safety profile, noting reduced rates of sycophancy and better resistance to prompt injection compared to earlier versions. It is frequently utilized in professional environments for long-horizon planning and autonomous computer interaction.