diff --git a/pkg/lipsdk/auth/sanitize_test.go b/pkg/lipsdk/auth/sanitize_test.go
index f1ce873b..ecfc5811 100644
--- a/pkg/lipsdk/auth/sanitize_test.go
+++ b/pkg/lipsdk/auth/sanitize_test.go
@@ -9,25 +9,28 @@ func TestSanitizePublicChallengeSummary(t *testing.T) {
 	t.Parallel()
 	fb := "fallback-msg"
 	cases := []struct {
-		name string
-		in   string
-		want string
+		name     string
+		in       string
+		maxRunes int
+		want     string
 	}{
-		{"empty uses fallback", "", fb},
-		{"whitespace uses fallback", "   \t  ", fb},
-		{"plain short unchanged", "Sign in to continue.", "Sign in to continue."},
-		{"collapses internal space", "a  \tb", "a b"},
-		{"strips controls", "line1\x00line2", "line1 line2"},
-		{"bearer triggers fallback", "Please use Bearer sk-abc", fb},
-		{"access_token triggers fallback", "Open https://x?access_token=secret", fb},
-		{"long truncates", strings.Repeat("x", 400), strings.Repeat("x", 254) + "…"},
+		{"empty uses fallback", "", 255, fb},
+		{"whitespace uses fallback", "   \t  ", 255, fb},
+		{"plain short unchanged", "Sign in to continue.", 255, "Sign in to continue."},
+		{"collapses internal space", "a  \tb", 255, "a b"},
+		{"strips controls", "line1\x00line2", 255, "line1 line2"},
+		{"bearer triggers fallback", "Please use Bearer sk-abc", 255, fb},
+		{"access_token triggers fallback", "Open https://x?access_token=secret", 255, fb},
+		{"long truncates", strings.Repeat("x", 400), 255, strings.Repeat("x", 254) + "…"},
+		{"zero maxRunes defaults to 256", strings.Repeat("x", 400), 0, strings.Repeat("x", 255) + "…"},
+		{"negative maxRunes defaults to 256", strings.Repeat("x", 400), -1, strings.Repeat("x", 255) + "…"},
 	}
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
-			got := SanitizePublicChallengeSummary(tc.in, fb, 255)
+			got := SanitizePublicChallengeSummary(tc.in, fb, tc.maxRunes)
 			if got != tc.want {
-				t.Fatalf("SanitizePublicChallengeSummary(%q) = %q, want %q", tc.in, got, tc.want)
+				t.Fatalf("SanitizePublicChallengeSummary(%q, %d) = %q, want %q", tc.in, tc.maxRunes, got, tc.want)
 			}
 		})
 	}