Three Bugs Degraded Claude’s Response Quality

Since the start of August 2025, Claude’s response quality has degraded, with Anthropic later publishing a detailed postmortem explaining that the issues stemmed from bugs in the AI infrastructure rather than deliberate intervention. According to Anthropic, a context window routing error affected about 0.8% of Claude Sonnet 4 requests on 5 August, as load balancer changes by 29 August worsened the problem and by 31 August nearly 16% of requests were affected, due to sticky routing.

A misconfigured update deployed on 25 August disrupted token generation on Claude API TPU servers, producing characters in English responses and syntax errors in code generation, affecting Claude Opus 4/4.1 up to 28 August and Claude Sonnet 4 up to 2 September, with a rollback on 2 September and new deployment tests introduced to prevent recurrence.

A separate issue involved a XLA:TPU miscompilation after code improvements on 25 August, which was rolled back and later also reverted for Opus 3 and, as a precaution, for Sonnet 4. The investigation concluded these were bugs rather than deliberate actions, and the company implemented fixes to restore proper routing and output quality.