diff --git a/vite_rails/lib/vite_rails/cli.rb b/vite_rails/lib/vite_rails/cli.rb
index 31418f6a..614fc6bf 100644
--- a/vite_rails/lib/vite_rails/cli.rb
+++ b/vite_rails/lib/vite_rails/cli.rb
@@ -31,7 +31,7 @@ def setup_app_files
       replace_first_line config.config_path, "app/frontend", %(    "sourceCodeDir": "#{dir}",)
     end
     setup_content_security_policy root.join("config/initializers/content_security_policy.rb")
-    append root.join("Procfile.dev"), "web: bin/rails s"
+    append_if_no_web_entry root.join("Procfile.dev"), "web: bin/rails s"
   end
 
   # Internal: Configure CSP rules that allow to load @vite/client correctly.
@@ -56,6 +56,18 @@ def setup_content_security_policy(csp_file)
     CSP
   end
 
+  # Internal: Append a line to a file only if no line starts with 'web:'
+  # @param path [Pathname] The path to the file
+  # @param contents [String] The line to append
+  def append_if_no_web_entry(path, contents)
+    content = read_lines(path)
+
+    # Check if any line starts with 'web:'
+    return if content.any? { |line| line.strip.start_with?("web:") }
+
+    append path, contents
+  end
+
   # Override: Create a sample JS file and attempt to inject it in an HTML template.
   def install_sample_files
     unless config.resolved_entrypoints_dir.join("application.js").exist?
diff --git a/vite_ruby/lib/vite_ruby/cli/install.rb b/vite_ruby/lib/vite_ruby/cli/install.rb
index e3f9c820..b3af00ad 100644
--- a/vite_ruby/lib/vite_ruby/cli/install.rb
+++ b/vite_ruby/lib/vite_ruby/cli/install.rb
@@ -61,7 +61,7 @@ def install_sample_files
 
   def_delegators "ViteRuby", :config
 
-  %i[append cp inject_line_after inject_line_after_last inject_line_before replace_first_line write].each do |util|
+  %i[append read_lines cp inject_line_after inject_line_after_last inject_line_before replace_first_line write].each do |util|
     define_method(util) { |*args|
       ViteRuby::CLI::FileUtils.send(util, *args) rescue nil
     }