LLM Degraded Performance Outage: Multi-Model Postmortem Patterns & Resilience Guide
On September 4, 2026, OpenAI (ChatGPT and Codex), Anthropic (Claude), Google (Gemini), and xAI (Grok) all suffered degraded service within the same few hours — a simultaneous, multi-model outage that left companies with four redundant “independent” providers and zero working fallbacks at once. The root cause was not single-vendor failure but correlated infrastructure: shared cloud regions, shared network paths, and a shared accelerator supply chain. This guide breaks down what actually happened, the recurring postmortem fingerprints to recognize, and how to build a failover design that survives this class of correlated outage — including the documented non-AI path every organization needs before the next 3-hour window arrives. ...