(Wix 4) Remember Property Pattern - Admin/System privileges

[back2root]

I'm trying to get the Remember Property Pattern implemented on a Registry key, that is only accessible to Administrators & LocalSystem.

Initially, the RegistryKey is set by the installer like:

<Component Id="ConfVal" Directory="INSTALLFOLDER">
    <RegistryKey Root="HKLM" Key="SOFTWARE\foo\bar">
        <RegistryValue Name="baz-token" Value="[BAZ_TOKEN]" Type="string">
            <Permission User="[WIX_ACCOUNT_LOCALSYSTEM]" GenericAll="yes" />
            <Permission User="[WIX_ACCOUNT_ADMINISTRATORS]" GenericAll="yes" />
        </RegistryValue>
    </RegistryKey>
</Component>

Reading the key during Major upgrade will not succeed, as RegistrySearch is performed during the first stage and thus performed before the installer elevated the privileges from user context.

<Property Id="BAZ_TOKEN" Secure="yes">
    <RegistrySearch Id="DetermineToken" Type="raw" Root="HKLM" Key="SOFTWARE\foo\bar" Name="baz-token" />
</Property>

I see, that you can use <SetProperty Sequence="execute" ... to postpone a SetProperty from client into server mode (where it should run elevated. How ever this is neither working for <Property ... nor can <SetProperty... retreive it's value using <RegistrySearch ....

What is the way of preserving the configuration of a system service across upgrades?