Claude Opus 4.5 is Anthropic’s top-end Claude 4.5 model, designed for hard reasoning, coding, and long-horizon agent workflows. Compared to earlier Opus versions, it brings three headline improvements: higher raw capability (especially for coding and analysis), much better token efficiency, and lower pricing. Anthropic’s announcement highlights that Opus 4.5 delivers state-of-the-art results on internal reasoning and coding benchmarks while using significantly fewer tokens than previous Opus variants. This matters in practice because you can get more work done per request without having to constantly clamp down on model verbosity.
Technically, Opus 4.5 also benefits from improved long-context handling and context management. While Sonnet 4.5 is the one explicitly documented with a 200K (and optional 1M) token window, Opus 4.5 inherits similar long-context behavior and adds automatic context summarization when conversations get large. Independent evaluations note that when context fills up, Opus 4.5 can compact earlier parts into summaries so agents can keep running without hard resets. That makes it attractive for multi-day coding sessions, long document reviews, or agent loops that need to maintain state across many tool calls.
Finally, Opus 4.5 introduces a tunable effort parameter that controls how much “thinking” the model does per request. At lower effort, it aims for faster, cheaper answers; at higher effort, it spends more compute to improve solution quality, especially on hard coding or reasoning tasks. Anthropic’s own data shows that at matched quality levels, Opus 4.5 uses fewer tokens than Sonnet 4.5, and at maximum effort it surpasses Sonnet’s performance on coding benchmarks. For teams already using retrieval-augmented generation with a vector database such as Milvus or Zilliz Cloud, that efficiency means you can push more retrieved context plus more thoughtful reasoning into each request while still keeping costs under control.