escape parentheses and other special characters in tab completion

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

main.go

@@ -963,11 +963,13 @@ func currentWord(s string) (word string, start int, quote byte) {
 	return b.String(), start, quote
 }
 
-// escapeWord escapes characters that would otherwise be interpreted by shlex
+// escapeWord escapes characters that would otherwise be interpreted by the
+// shell. # and ~ are only special at the start of a word, so they are only
+// escaped at the start of s.
 func escapeWord(s string) string {
 	var b strings.Builder
-	for _, r := range s {
+	for i, r := range s {
-		if strings.ContainsRune(" \t\\'\";|&<>*?[${", r) {
+		if strings.ContainsRune(" \t\\'\"`;|&<>()*?[]{}$!", r) || (i == 0 && (r == '#' || r == '~')) {
 			b.WriteByte('\\')
 		}
 		b.WriteRune(r)

main_test.go

@@ -879,6 +879,43 @@ func TestShellCompleter_Do(t *testing.T) {
 	}
 }
 
+func TestEscapeWord(t *testing.T) {
+	tests := []struct{ in, want string }{
+		{"plain.txt", "plain.txt"},
+		{"my file (1).txt", `my\ file\ \(1\).txt`},
+		{"a`b`$c", "a\\`b\\`\\$c"},
+		{"a;b|c&d<e>f", `a\;b\|c\&d\<e\>f`},
+		{"*?[x]{y}!", `\*\?\[x\]\{y\}\!`},
+		{`it's "q"\`, `it\'s\ \"q\"\\`},
+		{"#a#b", `\#a#b`},
+		{"~a~b", `\~a~b`},
+	}
+	for _, tt := range tests {
+		if got := escapeWord(tt.in); got != tt.want {
+			t.Errorf("escapeWord(%q) = %q; want %q", tt.in, got, tt.want)
+		}
+	}
+}
+
+func TestShellCompleter_SpecialCharacters(t *testing.T) {
+	origDir, _ := os.Getwd()
+	defer os.Chdir(origDir)
+	os.Chdir(t.TempDir())
+	os.Create("song (live) & more.mp3")
+
+	got, length := completeLine("ls so")
+	want := []string{`ng\ \(live\)\ \&\ more.mp3`}
+	if !reflect.DeepEqual(got, want) || length != 2 {
+		t.Errorf("Do(%q) = %q, %d; want %q, 2", "ls so", got, length, want)
+	}
+	// Inside quotes nothing is escaped
+	got, _ = completeLine(`ls "so`)
+	want = []string{"ng (live) & more.mp3"}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Do(%q) = %q; want %q", `ls "so`, got, want)
+	}
+}
+
 // =============================================================================
 // Security fixes: history file, quoting/expansion, escape sequences, SIGINT
 // =============================================================================