There have been a number of changes in the locations of Lync client registry settings in Lync 2013. One change that seems to be causing confusion is the new location for the registry setting that controls UI suppression.
As a quick review, when UI suppression is enabled (through this registry setting), the Lync client does not display its user interface when the Lync client process starts. Instead, you can use the Lync client SDK to create your own user interface elements from scratch. For instance, you could show contacts and presence and/or control calls from within your existing line of business application.
In Lync 2010, the registry setting controlling UI suppression on 32-bit machines was:
On 64-bit machines, it was:
When this key had a value of 1, UI suppression would be enabled.
In Lync 2013, the setting is now located in a completely different part of the registry:
If you try to use the key at the old location, it won’t actually enable UI suppression for the Lync 2013 client.