A postmortem of three recent issues

What this post added

This post details three specific infrastructure bugs that intermittently degraded Claude's response quality between August and September. It explains the root causes, including misrouting to servers configured for a larger context window, a misconfiguration during token generation causing unexpected character outputs, and a latent bug in the XLA:TPU compiler triggered by a sampling code rewrite. The post also discusses the challenges in detection and diagnosis due to overlapping issues, inconsistent behavior, and privacy constraints, and outlines improvements to evaluation sensitivity, continuous quality checks, and debugging tooling.