diff --git a/src/management/mod.rs b/src/management/mod.rs
index b0f3412..999b4a2 100644
--- a/src/management/mod.rs
+++ b/src/management/mod.rs
@@ -239,7 +239,7 @@ struct CreateInput {
     text_content: String,
     start_date: String,
     end_date: String,
-    #[serde(default)]
+    #[serde(default, deserialize_with = "one_or_many")]
     flags: Vec<String>,
 }
 
@@ -325,6 +325,24 @@ async fn delete_announcement(
 
 // ── Helpers ───────────────────────────────────────────────────────────────────
 
+fn one_or_many<'de, D: serde::Deserializer<'de>>(d: D) -> Result<Vec<String>, D::Error> {
+    use serde::de;
+    struct OneOrMany;
+    impl<'de> de::Visitor<'de> for OneOrMany {
+        type Value = Vec<String>;
+        fn expecting(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+            f.write_str("a string or list of strings")
+        }
+        fn visit_str<E: de::Error>(self, v: &str) -> Result<Vec<String>, E> {
+            Ok(vec![v.to_owned()])
+        }
+        fn visit_seq<A: de::SeqAccess<'de>>(self, seq: A) -> Result<Vec<String>, A::Error> {
+            de::Deserialize::deserialize(de::value::SeqAccessDeserializer::new(seq))
+        }
+    }
+    d.deserialize_any(OneOrMany)
+}
+
 fn escape_html(s: &str) -> String {
     s.replace('&', "&amp;")
         .replace('<', "&lt;")