On March 26, 2026, Anthropic shipped a bug that caused Claude to clear its thinking buffer every turn instead of only after idle sessions. Claude Code quality degraded significantly for weeks before the company identified and fixed the root cause.
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Expert: Anthropic Engineering, Official Postmortem On March 26, 2026, Anthropic shipped a bug that caused Claude to clear its thinking buffer every turn instead of only after idle sessions. This meant Claude effectively had no mid-session memory for reasoning, causing significantly degraded code quality for weeks. Users reported Claude "could not be trusted to perform complex engineering." Anthropic's own postmortem confirmed: "The bug caused thinking to be cleared every turn — essentially Claude had no memory mid-session." The fix was deployed after the root cause was identified. Source: https://www.anthropic.com/engineering/april-23-postmortem
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