diff --git a/lua/LspUI/lightbulb/util.lua b/lua/LspUI/lightbulb/util.lua
index 1195cc1..df24dd4 100644
--- a/lua/LspUI/lightbulb/util.lua
+++ b/lua/LspUI/lightbulb/util.lua
@@ -64,6 +64,7 @@ end
 --- @param buffer_id integer buffer's id
 --- @param callback function callback is a function, has a param boolean
 M.request = function(buffer_id, callback)
+    -- this buffer id maybe invalid
     if not api.nvim_buf_is_valid(buffer_id) then
         return
     end
diff --git a/lua/LspUI/pos_abstract.lua b/lua/LspUI/pos_abstract.lua
index b3d20f6..48b9d66 100644
--- a/lua/LspUI/pos_abstract.lua
+++ b/lua/LspUI/pos_abstract.lua
@@ -868,7 +868,8 @@ M.secondary_view_render = function()
         M.secondary_view_window(lib_windows.display_window(second_window_wrap))
     end
     -- prevent extra shadows
-    vim.schedule(function()
+    -- vim.schedule(function()
+    api.nvim_win_call(M.secondary_view_window(), function()
         api.nvim_set_option_value("winhighlight", "Normal:Normal", {
             win = M.secondary_view_window(),
         })
@@ -881,6 +882,8 @@ M.secondary_view_render = function()
         )
     end)
 
+    -- end)
+
     api.nvim_win_set_config(M.secondary_view_window(), {
         title_pos = "center",
         title = method.name,
diff --git a/lua/LspUI/signature/init.lua b/lua/LspUI/signature/init.lua
index e69de29..f3aada6 100644
--- a/lua/LspUI/signature/init.lua
+++ b/lua/LspUI/signature/init.lua
@@ -0,0 +1 @@
+-- TODO: complete this