If you have a form in a
uib-tabset has its own scope, so the
forminside will be on the scope of the
uib-tabset. If you use the controller-as notation, it will find the correct scope (the one of the controller):
<uib-tab index="0" heading="Tab 1"> <form name="vm.forminside"> </form> </uib-tab>
See this edited plunker.