diff --git a/server-rs/crates/shared-contracts/src/assets.rs b/server-rs/crates/shared-contracts/src/assets.rs
index c1dd65e71..f5345a67e 100644
--- a/server-rs/crates/shared-contracts/src/assets.rs
+++ b/server-rs/crates/shared-contracts/src/assets.rs
@@ -659,8 +659,11 @@ impl<'de> Deserialize<'de> for EditorSoundEffectGenerationMetadataV2 {
     }
 }
 
+/// OpenAPI 对该请求体声明了 `additionalProperties: false`，实现必须同样拒绝未知字段：
+/// 否则 `loopEnabled` 这类拼错的字段会被静默丢弃，按 `loop=false` 入队并计费，
+/// 客户端拿不到 400，只能从生成结果反推自己写错了参数。
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
-#[serde(rename_all = "camelCase")]
+#[serde(rename_all = "camelCase", deny_unknown_fields)]
 pub struct EditorSoundEffectGenerateRequest {
     pub prompt: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
@@ -1613,6 +1616,20 @@ mod tests {
             assert!(!parsed.loop_enabled);
         }
 
+        // OpenAPI 声明 additionalProperties: false，实现必须拒绝而不是静默丢弃。
+        // loopEnabled 是最容易写错的那个：丢弃后会按 loop=false 入队并照常计费。
+        for unknown_field_payload in [
+            json!({ "prompt": "按钮确认短促音", "loopEnabled": true }),
+            json!({ "prompt": "按钮确认短促音", "tempo": 120 }),
+            json!({ "prompt": "按钮确认短促音", "priceMudPoints": 0 }),
+        ] {
+            assert!(
+                serde_json::from_value::<EditorSoundEffectGenerateRequest>(unknown_field_payload)
+                    .is_err(),
+                "sound effect requests must reject unknown fields"
+            );
+        }
+
         let music_payload = serde_json::to_value(EditorBackgroundMusicGenerateRequest {
             gpt_description_prompt: "森林冒险背景音乐".to_string(),
             make_instrumental: true,