This week did not ship a new closed flagship that resets the application stack. It shipped the buying surface around the stack that already exists. OpenAI cut GPT-5.6 Luna 80% and Terra 20% while holding Sol steady; Microsoft disclosed M365 Copilot paid seats above 30 million, GitHub Copilot at 50 million users, and Purview audits of more than 15 billion Copilot interactions; Snowflake put a Cortex AI Gateway in front of models, tools, and MCP servers; Moonshot released Kimi K3's full weights under a revenue-tiered commercial license. The CIO question that follows is not "which model?" It is "which tier, which gateway, which license, which audit trail?" The AI Stack Weekly owns the cross-domain synthesis and the house measurement on GPT-5.6 tier spreads; this issue stays on the procurement mechanics those moves create.
Seats are not value. Microsoft's FY26 Q4 print is grade-5 commercial evidence of distribution — Cloud revenue $59.3B (+27%), Azure annual revenue past $100B, Copilot net adds more than doubling quarter over quarter — but it is not workflow proof of value. "Copilot revenue accelerated over 60% QoQ" is vendor-characterized on the earnings call, not a breakout line item. Purview's >15B audited interactions show that the observability pipe exists; they do not show average revenue per user (ARPU), weekly active use, or workflow attach. Procurement should demand those three numbers before treating seat scale as ROI.
The same honesty applies to product instrumentation. Microsoft's MAI hill-climbing claims — up to 84% lower GPU cost for PowerPoint image generation versus GPT-Image-2, +26% OneDrive save rates, 96% CyberGym with roughly half the cost of a prior GPT-5.4 stack by routing about 90% of tasks to MAI-Cyber-1-Flash — are all vendor-reported. Harvey's statement that it just posted its "first quarter with over $100M ARR added" is a commercial metric, not a matter-level outcome study. No audited or independent customer-measured workflow ROI with a named baseline and method cleared the bar inside Jul 27–Aug 2. Label the numbers; do not launder them into evidence.
Where the week is most actionable is dated enterprise readiness. GitHub will turn new generally available Copilot models on by default on Aug 26 unless Business/Enterprise orgs opt out. EU AI Act Article 50 transparency obligations become enforceable Aug 2, with administrative fines up to EUR 15 million or 3% of worldwide annual turnover, whichever is higher. The MCP 2026-07-28 specification deprecates Dynamic Client Registration (DCR) toward Client ID Metadata Documents (CIMD) and pushes enterprise-managed authorization. Snowflake's Cortex AI Gateway is the right shortlist entry for MCP sprawl, but many of its cost, routing, and partner-identity features remain private preview — treat them as not production-ready until GA dates are contractual. Buy the control plane you can audit, not the seat count you can celebrate.