The company that ships the best coding model on the planet just published a postmortem worth sitting with: three innocent-looking config changes quietly degraded Claude's output — and it took weeks to track down.
If the team that knows AI best can fail to notice their own model getting worse, what makes a business think it can eyeball an agent's output and catch the rot?
Speed isn't in question. Whether the quality holds — and whether you'd even notice if it didn't — is the whole game.
Two signals: speed is settled, "is it still good?" is not
Anthropic's own postmortem. Their internal investigation confirmed that three independent changes in March–April 2026 — lowering Claude Code's default reasoning effort, a cache bug that wiped session data every turn, and a system-prompt revision aimed at reducing verbosity — collectively degraded output quality. Note: not model rot — config-layer drift, with no single alarm, found only weeks later via user feel and investigation.
