Errno::ENOENT from Pathname#children says it plainly enough.

Assisted-by: GLM-5.3 via pi

diff --git a/lib/pro_tacts/contact.rb b/lib/pro_tacts/contact.rb
index 8b816f7..1998f3e 100644
--- a/lib/pro_tacts/contact.rb
+++ b/lib/pro_tacts/contact.rb
@@ -17,12 +17,10 @@ module ProTacts
     # directory is a valid empty address book, and dotfiles are skipped
     # (Finder drops .DS_Store into any directory it opens). Anything
     # else raises: a bad file 500s the request and lands in Sentry
-    # rather than quietly serving a partial address book.
+    # rather than quietly serving a partial address book. A missing
+    # directory surfaces as Errno::ENOENT from Pathname#children.
     def self.all(directory = ProTacts.config.contacts_dir)
-      directory = Pathname.new(directory)
-      raise ArgumentError, "contacts directory not found: #{directory}" unless directory.directory?
-
-      directory.children
+      Pathname.new(directory).children
         .reject { it.basename.to_s.start_with?(".") }
         .map { parse(it) }
     end
diff --git a/test/pro_tacts/test_contact.rb b/test/pro_tacts/test_contact.rb
index f9c10b2..bca93a5 100644
--- a/test/pro_tacts/test_contact.rb
+++ b/test/pro_tacts/test_contact.rb
@@ -48,11 +48,11 @@ class ContactTest < Minitest::Test
   end
 
   def test_a_missing_directory_raises
-    error = assert_raises(ArgumentError) do
+    error = assert_raises(Errno::ENOENT) do
       ProTacts::Contact.all(Pathname.new(Dir.mktmpdir) / "nonexistent")
     end
 
-    assert_match(/contacts directory not found/, error.message)
+    assert_match(/nonexistent/, error.message)
   end
 
   def test_non_kdl_files_raise