In version 1.52 the behavior of ImGuiWindowFlags_AlwaysAutoResize has changed when using columns to arrange widgets - it looks like the auto resize doesn't account for the columns. This was working in version 1.50:

ImGui::Begin("foo", 0, ImGuiWindowFlags_AlwaysAutoResize);
   ImGui::Columns(4);
       // blah blah
   ImGui::Columns(1);
ImGui::End();

But in 1.52 looks like this: