ARTICLE UPDATE ALERT: The day after we published Finding Miscompiles for Fun, Not Profit, Anthropic released Opus 4.8 an…

SemiAnalysis Twitter · SemiAnalysis (@SemiAnalysis_) · 2026-06-02

SemiAnalysis reports that Anthropic released Opus 4.8 and ultracode mode in Claude Code one day after their miscompile-finding article, with preliminary experiments showing the combination significantly better at filtering low-severity compiler bugs.

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Appears in

Claude Opus 4.8: Candid Model Launch with Mid-Conversation System Messages

Extraction

Topics: claude-codecompiler-bugsllm-coding-toolsanthropic

Claims

Anthropic released Opus 4.8 and ultracode mode in Claude Code on June 2, 2026.
Opus 4.8 combined with ultracode mode is significantly better at filtering out low-severity bugs than prior approaches.
The release coincided by one day with SemiAnalysis's article on using LLMs to find miscompiles.

Key quotes

Our preliminary experiments indicate that together these are significantly better at filtering out low-severity bugs