Claude Opus 4.6 is a frontier language model developed by Anthropic, released in February 2026 as an upgrade to the Opus 4.5 model. It serves as the flagship of the Claude 4 series, optimized for high-complexity reasoning, agentic planning, and large-scale knowledge work. The model introduces Adaptive Reasoning (also referred to as Adaptive Thinking), a feature that allows the system to dynamically determine the depth of reasoning required for a given prompt, replacing static thinking budgets with a more flexible resource allocation system.
The model features a 1 million token context window in beta, a fivefold increase over its predecessor, designed to mitigate performance degradation in long-running conversations. To support these massive inputs, Anthropic introduced Context Compaction, a server-side summarization technology that automatically condenses conversation history to maintain performance in extended agentic sessions. Additionally, the model supports an expanded output capacity of up to 128,000 tokens, facilitating the generation of multi-file codebases and extensive technical documentation.
Performance benchmarks indicate significant improvements in professional domains. Claude Opus 4.6 achieved record scores on Terminal-Bench 2.0 for agentic coding and Humanity's Last Exam for multidisciplinary reasoning. In economic evaluations, the model demonstrated state-of-the-art results on the GDPval-AA benchmark, measuring performance in finance, legal, and other professional tasks. Developers can influence the model's behavior through four distinct effort levels—low, medium, high, and max—which balance latency and cost against reasoning depth.
Safety and reliability are central to the architecture. According to Anthropic's internal evaluations, Opus 4.6 maintains low rates of misaligned behaviors, such as deception or sycophancy, while showing improved accuracy in identifying its own coding and debugging errors. The model is also designed with a specialized focus on enterprise productivity, including improved capabilities for research and structured data analysis across professional document formats.