Microsoft's CEO argues the durable moat isn't the frontier model — commoditizing input — but the firm-owned 'learning loop': private evals on outcomes, models on internal traces, queryable memory. Test: swap the model without losing 'company veteran' expertise. This describes Microsoft's exact position: platform layer, not model race. The claim carries a pre-registered verifier: learning loop becomes moat only when switching cost measures — retention through swap, durable revenue line, usage depth surviving migration. Vendor essays don't count. Filings will.