Anthropic has added a Beta feature to the Claude API that allows effort levels to be adjusted within messages. Developers are no longer locked into a uniform setting—they can now change the model's response effort level mid-conversation, balancing answer thoroughness, response speed, and usage cost, while also influencing how much the model invests in reasoning, tool invocation, answer organization, and other stages. The method is simple: insert an empty-content system message into the message sequence and set the target level via output_config.effort—no changes to top-level configuration required, and no impact on prompt cache hits. This setting does not alter content that has already been generated; it takes effect for subsequent responses starting from the next new user input message. This makes it well suited for scenarios where the first half of a conversation involves simple Q&A and the second half shifts to complex analysis.