The most expensive AI architecture mistake of 2026 has a name. Almost nobody is using it. Two papers from late 2025 ended a debate that the LinkedIn AI thought-leader class hasn't caught up to yet: → Multi-agent LLM systems fail in production at rates between 41% and 86.7% → The MAST failure taxonomy maps 14 distinct failure modes into 3 root causes → 79% of multi-agent production breakdowns come from just two categories: specification ambiguity and coordination gaps

