Claude Opus 4.8: "a modest but tangible improvement"
Claude Opus 4.8 has been released, offering modest improvements over its predecessor. The update emphasizes honesty in AI responses, reducing unsupported claims and factual inaccuracies. Key features include a lower minimum prompt cache and the ability to update system messages mid-conversation.
- ▪Claude Opus 4.8 is priced the same as previous models at $5 per million input and $25 per million output.
- ▪The model is reported to be four times less likely to allow flaws in code to pass unremarked compared to its predecessor.
- ▪One of the main improvements is its ability to flag uncertainties and avoid unsupported claims.
Opening excerpt (first ~120 words) tap to expand
Claude Opus 4.8: “a modest but tangible improvement” 28th May 2026 Anthropic shipped Claude Opus 4.8 today. My favourite thing about it is this note in the release announcement: Users will find Opus 4.8 to be a modest but tangible improvement on its predecessor. There’s still more to be done: we’re working on developing and releasing models that provide many of the same capabilities as Opus at a lower cost. It’s so refreshing to see an AI lab honestly describe a release as a minor incremental improvement over the previous model! Honesty seems to be a theme. Here’s my other favorite note from that announcement: One of the most prominent improvements in Opus 4.8 is its honesty. We train all our models to be honest---for instance, to avoid making claims that they can’t support.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Simon Willison’s Weblog.