Risk · 04
The new app still runs inside the tenant
On 25 September 2026 Microsoft put Copilot Managed Runtime into public preview. It hosts code inside the Microsoft 365 tenant boundary, on Microsoft-operated infrastructure, with identity, governed data access and lifecycle management. The point is not that building an app became casual. The point is where that code is allowed to live.
What the preview claims
Microsoft says the runtime powers apps built through Cowork, Code and Copilot Studio, and that an SDK route exists for other developers. Both the host and the SDK are previews. A preview is a place to learn the boundary, not a place to park a customer process you cannot explain to an auditor.
What an administrator can see
Hosted apps show up in a Microsoft 365 admin center Apps experience. Administrators can review policies and enable or disable an app. That is the practical question for a firm new to this: not whether a screen appeared quickly, but who can see the connections, the audience and the health, and who can turn the app off on a Tuesday.
Write access is a later decision
Microsoft's Studio example, an onboarding app or a field-service app that writes back to another system, is a product illustration, not a measured customer outcome. Start with a read. Agree the write, and the owner of that write, only after the data access has been checked.
Monday
Ask whoever runs Microsoft 365 whether the Apps experience for Managed Runtime is visible in your tenant, and who would be allowed to disable an app. Record the names.
If a preview app can write to a record, which team is allowed to say no?
Sources: Microsoft Copilot Blog, 25 September 2026, Copilot Managed Runtime (opens in a new tab). Microsoft, 10 September 2026, Build business apps with Copilot Cowork and Copilot Studio (opens in a new tab).
Where this note mentions FrontierOrg, that is a fictional method for rehearsing a decision. It is not a company, not a client, and not a case study.