diff --git a/apps/pwa/src/components/MemberEditorSheet.tsx b/apps/pwa/src/components/MemberEditorSheet.tsx
index 32c32d1..c33d43a 100644
--- a/apps/pwa/src/components/MemberEditorSheet.tsx
+++ b/apps/pwa/src/components/MemberEditorSheet.tsx
@@ -576,6 +576,12 @@ export function MemberEditorSheet({
                 </button>
               </div>
 
+              {/* IN-01: helper text when display name is empty (e.g. null-displayName
+                  OIDC member) so the admin knows why Save is disabled */}
+              {displayName.trim().length === 0 && !profileError && (
+                <p style={helperTextStyle}>Enter a display name to enable Save.</p>
+              )}
+
               {/* Last-admin guard inline error */}
               {profileError && (
                 <div id="profile-error" style={inlineErrorStyle}>