Anthropic has rolled out Claude Opus 4.8, replacing Opus 4.7 with improved performance and new controls for consumers and developers.

The update delivers stronger results across a range of evaluations. For example, it aims to address a general problem with AI models: “They sometimes jump to conclusions.”

Opus 4.8 flags uncertainties about its work and is less likely to make unsupported claims, the company claims.

Alongside the update, Claude users now get an "effort" setting that trades speed for deeper processing, while Claude Code adds a research preview feature called dynamic workflows for handling larger tasks.

Early testers saw improvements in reliability and decision-making for agent-style work. They emphasized efforts to reduce overconfident outputs without supporting evidence.

For developers, the Messages API now supports system entries within the messages list. It allows teams to adjust instructions mid-run without disrupting prompt caching or routing changes through a user turn.

The company also said Opus 4.8's fast mode runs 2.5x faster and is priced below earlier fast options, while the model now defaults to higher-effort processing. Claude Code rate limits have also been increased to support heavier token usage at "extra" and "max" effort levels.

Anthropic added that it is working on future models that match Opus-level capability at lower cost, as well as a new class of models designed to exceed Opus in intelligence.

As part of Project Glasswing, certain organizations are testing Claude Mythos Preview for cybersecurity work. Models of this capability level require stronger cyber safeguards before they can be released more broadly, the company added.

“We're making swift progress on developing these safeguards and expect to be able to bring Mythos-class models to all our customers in the coming weeks," the company noted.

Last week, Anthropic shared a sweeping update on Project Glasswing, saying its artificial intelligence-assisted security testing effort has already uncovered “more than 10,000 high-or critical-severity vulnerabilities” across widely used software systems.

Anthropic has been working with roughly 50 partner organizations in a security-focused collaboration. The bottleneck is no longer finding vulnerabilities. Instead, it handles the human workload required to verify issues, coordinate disclosures with maintainers and deploy patches, the company noted.

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