Microsoft used its July 29 fiscal fourth-quarter earnings call to outline a strategy of keeping the enterprise agent layer under its control while allowing the underlying AI model to change. CEO Satya Nadella presented model substitutability as a way to improve cost, resilience and business continuity. Microsoft closed its fiscal year on June 30 with $331.8 billion in revenue and $133.7 billion in net income, according to the company’s Q4 earnings release, which also disclosed a $3.2 billion gain from Microsoft’s Anthropic investment. Nadella argued enterprises should keep the model separate from the harness containing their memory, context and action space, making any given model swappable. Microsoft said its cloud catalogue now includes more than 11,000 models from providers including OpenAI, Anthropic, Mistral and xAI, alongside Microsoft’s own MAI family, and reported a fivefold increase since the start of 2026 in customers building with models from multiple providers. Nadella used the recent Hugging Face security incident to illustrate the operational case for model diversity, noting that Hugging Face’s responders initially tried to analyse the attack using frontier models supplied through commercial APIs, but the providers’ safety controls blocked requests containing real attack commands and exploit material, leading the company to instead use the open-weight GLM 5.2 model on its own infrastructure.