WinBuzzer: Microsoft routing selected Excel/Outlook AI prompts to MAI to cut Copilot inference costs. Microsoft declined comment. Framing: directional cost strategy, not OpenAI divorce. Commodity tasks (summaries, formulas, short replies) to MAI; harder reasoning stays on OpenAI/Anthropic. Foreshadows cheaper-default / premium third-party Copilot pricing as OpenAI partnership discounts fade.