Claude Opus 4.5

Claude Opus 4.5, released by Anthropic in November 2025, represents the company's most capable model in the 4.5 generation. Like Sonnet 4.5, it features a 200K token context window and 64K token output limit, but with enhanced reasoning and reliability capabilities that justify its premium positioning.

The model achieves 80.9% on SWE-bench and 59.3% on Terminal-bench, demonstrating superior performance on software engineering and command-line interface tasks. A key improvement is the 50-75% reduction in tool calling errors compared to previous models, along with up to 65% fewer tokens required to complete the same tasks, making it both more reliable and more efficient.

Claude Opus 4.5 excels at context management and multi-step reasoning, making it particularly well-suited for complex agentic workflows requiring reliable tool use and long-chain reasoning. Priced at $5 per million input tokens and $25 per million output tokens, it sits at the premium end of the market but offers commensurate capabilities for applications where accuracy, reliability, and reasoning depth are critical.