diff --git a/lua/settings.lua b/lua/settings.lua
index c416555..4999b45 100644
--- a/lua/settings.lua
+++ b/lua/settings.lua
@@ -23,6 +23,16 @@ end
 -- Set background based on system theme on startup
 set_background_from_system()
 
+-- Handle SIGUSR1 signal to update theme when system theme changes
+-- External watcher script (scripts/theme-watcher.sh) sends this signal
+vim.api.nvim_create_autocmd('Signal', {
+  pattern = 'SIGUSR1',
+  callback = function()
+    set_background_from_system()
+  end,
+  desc = 'Update colorscheme when system theme changes',
+})
+
 -- Store initial working directory as project root
 -- Used by netrw navigation to return to project root after following symlinks
 vim.g.project_root = vim.fn.getcwd()