Anthropic has released the latest version of its largest Claude model, Opus. Claude Opus 4.5 is better at handling complex reasoning than previous Claude models and makes improvements across agentic tool use, computer use, novel problem solving, and more.
The company says early testers of the new model claim that it handles ambiguity better and reasons over tradeoffs without needing human intervention. “They told us that, when pointed at a complex, multi-system bug, Opus 4.5 figures out the fix. They said that tasks that were near-impossible for Sonnet 4.5 just a few weeks ago are now within reach. Overall, our testers told us that Opus 4.5 just ‘gets it,’” Anthropic wrote in a post.
This release also coincides with a new effort parameter being introduced in the Claude API, allowing developers to decide how much effort Claude should spend on a problem. According to Anthropic, Opus 4.5 uses significantly fewer tokens than its predecessors to solve problems, even at its highest effort level. For example, at a medium effort level, Opus 4.5 matches Sonnet 4.5’s score on SWE-bench Verified while using 76% fewer output tokens, while at the highest effort level it uses 48% fewer tokens while exceeding Sonnet 4.5’s performance by 4.3%.
In terms of safety, Anthropic claims that Opus 4.5 Thinking is less susceptible to prompt injection attacks than models like Sonnet 4.5 Thinking, GPT-5.1 Thinking, or Gemini 3 Pro Thinking.
Anthropic also announced updates to Claude Code that coincide with the new model’s release. First, Plan Mode can create more precise plans and execute them more thoroughly, with Claude asking clarifying questions upfront and building them into the plan before executing it. Second, Claude Code is now available in Anthropic’s desktop app, which allows multiple local and remote sessions to be run side-by-side.
Additionally, the Claude app will now automatically summarize earlier parts of a long conversation, and the Claude for Excel beta is expanding to Max, Team, and Enterprise users.
Opus 4.5 is available now across all of Anthropic’s apps and API and costs $5 per million input tokens and $25 per million output tokens.
“Opus 4.5 is a step forward in what AI systems can do, and a preview of larger changes to how work gets done,” the company wrote.