Anthropic reverses its own advice on coding effort settings

Anthropic reversed its coding guidance, telling developers to start Claude effort at high instead of xhigh, per its documentation. The stakes: effort controls how much Claude thinks, not how much it says. Per the docs, changing effort doesn't reliably shorten responses.

The new guidance frames low and medium as the main dials for cost and latency, not as fallback settings for when high runs too slow.

Anyone dropping effort to cut verbosity is paying for less reasoning and getting the same response length back, per the documentation. The fix Anthropic recommends is prompting for length directly instead of treating effort as a verbosity dial.

Effort also changes how Claude uses tools. At lower levels it combines operations into fewer calls and skips preamble before acting. At higher levels it makes more calls and explains its plan first.

Anthropic's own instruction is to run a fresh effort sweep on your evals rather than reuse old ones. Any production prompt still pinned to xhigh from the Opus 4.7 or 4.8 era should be treated as unverified until it's rerun against current behavior. The reversal undoes advice tied to those two releases, so anyone who set defaults then is running on guidance Anthropic no longer stands behind.