Agents & InferenceSimon Willison

Introducing Claude Opus 5

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Summary A

Claude Opus 5 delivers near-frontier Claude Fable 5 performance at half the cost, maintaining Opus 4.8 pricing while taking the top spot on the Artificial Analysis leaderboard. For production agents, this enables highly proactive autonomous reasoning, such as a model independently writing its own computer vision pipeline to bypass data-access constraints. To deploy this successfully, you will need to immediately update your prompt designs to align with newly released context engineering rules for the Claude 5 generation.