Claude Opus 4.8: "a modest but tangible improvement"

Anthropic released Claude Opus 4.8 on May 28, 2026, describing it as a modest incremental improvement over its predecessor. A key advancement is improved honesty: the model is about four times less likely than the previous version to overlook flaws in code it writes, and it achieves lower factual hallucination rates (incorrect answers) primarily by declining to answer questions when uncertain rather than attempting to answer more questions.