Anthropic launches Claude Opus 4.8

Anthropic is launching ‌an upgraded Claude Opus 4.8 model even ⁠as it works to release its powerful, market-moving Mythos model to ‌all customers in the coming weeks. The company said Opus 4.8 will be available ⁠for the same price as its predecessor and shows ‌improvements across benchmarks. Users on claude.ai now have control over the amount of effort Claude puts into a task.

Claude Opus 4.8 is Anthropic's current flagship large language model. It sits at the top of the Claude model family above Sonnet and Haiku. Opus 4.8 is designed for the most demanding tasks: agentic workflows, complex reasoning, and multi-step coding runs that require sustained performance.

In addition to improvements pretty much across the board in benchmark tests, which we will get to next, there are also some other new characteristics:

·         Honesty and self-calibration: A persistent problem with frontier AI models in general, not just with Claude models, is overconfidence. We all see it: when a model confidently reports it has completed a task when the evidence is thin, or when it writes code and fails to flag obvious issues.

Anthropic's internal evaluations show that Opus 4.8 has better honesty and self-calibration. In particular, it is four times less likely than Opus 4.7 to fail to report flawed code, so honesty shows up largely as a win for developers in particular.

·         Alignment: Anthropic ran a detailed alignment assessment before release, and a few findings are worth flagging.

Opus 4.8 is substantially better at being honest about its own work. In a test where the model summarizes a coding session that secretly contained failures, it glosses over those failures only 3.7% of the time. It's also the first Claude model to score zero on a test where it must catch flawed data before reporting a result.

·         Fast mode for Opus 4.8 — where the model operates at 2.5× the speed — is now three times cheaper than it was for previous Opus models.