Anthropic publicly documented stop_details on refusal responses, with category and explanation fields for routing.

Refusals now carry machine-readable class and human-readable reason, letting apps choose the right next step.

For builders handling refusals, this moves refusal routing into documented response fields without a beta header.

• Jun 12, 2026Claude Opus 4.8 defaults the effort parameter to high across all surfaces.
• Jun 12, 2026Claude Opus 4.8 lowers prompt caching’s minimum cacheable prompt length to 1,024 tokens versus Opus 4.7.
• Jun 12, 2026Claude Opus 4.8 with adaptive thinking triggers reasoning only when a turn needs it.

This is the world we build in. It moves this fast. We move with it.