An update is held only by a module that cannot load on it

Until now an update could be held for two reasons that had nothing to do with whether it would work. A module could declare a platform version the new build's version string did not rank above — fixed earlier this week. And a course or package could lack a prebuilt bake for the new build: the update waited until every one had been rebuilt for it, although the installation compiles such content itself when it starts, exactly as it does on every pull request that ships it. On 7 September both rules together kept every production installation on its morning build for the whole day while every candidate would have run fine.

What holds an update now is measured, not declared. For every module you have installed, the platform asks the new build one question: would the bytes you are running load there? Each build publishes the list of types it carries; the platform links your module's actual bytes against that list before it rolls. A module that references a type the new build does not have — the only way an update can take away something that works today — holds the update, and the hold names the module and the missing type. A module the new build ships a fresh version of is adopted at the roll and needs no check.

A missing bake is a cost, not a hold. If a course or package has no prebuilt bake for the new build, the update proceeds and the content compiles when the new build starts. The Updates tab tells you in advance which ones will ("would recompile at boot: AgenticPrimer, Crm"), so a slower first start is never a surprise. Installations that must never compile content at start (Modules:RequirePrebuilt) keep the previous behaviour: for them a missing bake still holds.

When the platform cannot tell, it says so and does not guess. A build published before this change carries no type list, so a landed module cannot be checked against it. That is reported on the Updates tab as "could not be determined" — it neither clears the update nor holds it. The platform then decides at start-up, on the same measurement, and keeps the previous version of a module whose new one cannot load.

See The Module Platform Link Gate for how the measurement works and Release Availability Gates for what the gate reports.