Migrating off Opus 4.8 is one line — swap the model ID. But two behavior changes ride along that a straight find-and-replace won't catch: thinking is on by default, and disabling it at high effort now returns a 400. Here's what breaks and the exact fix.
Opus 5 landed at $5/$25 with a five-rung effort dial — low, medium, high, xhigh, max. One field, output_config.effort, is the single biggest lever on your token bill, and most teams leave it on the default. Here's the copy-paste version, plus the two gotchas that bite.
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