Horizon Application Manager identifies managed ThinApp packages using Horizon-specific GUIDs built in to the package (these GUIDs are separate from the MSI-file GUIDs mentioned earlier). You generate these GUIDs when you activate Horizon Manager for a package. In order for Horizon Application Manager to identify a package as an update to an existing package, the AppID of the two packages must be the same. Horizon will also use another Package.ini parameter called VersionID to understand which of the packages are the latest. You can manually find the AppID of a package using the ThinApp SDK but it's not a very user-friendly method. Your best option is therefore to run Setup Capture specifying that you are creating an update package during the Horizon activation part of the wizard. This method will extract all the necessary information and inject them into the new package's Package.ini file.
Let's have a look at a Horizon implementation...