diff --git a/apps/ai-game-creator-shell/src-tauri/src/project/resource_editor.rs b/apps/ai-game-creator-shell/src-tauri/src/project/resource_editor.rs
index 693b34dd9..89a57806f 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/project/resource_editor.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/project/resource_editor.rs
@@ -5450,6 +5450,10 @@ pub(crate) fn prepare_local_project_audio_generation(
 /// 在派发时刻读成当前值（提交之后用户仍可能编辑项目），以及把产物素材 id 交回任务账本。
 /// 拿不到当前 revision 或 CAS 冲突时按失败返回，不静默重试——静默重试会把这次生成写到用户
 /// 没预期的基线上。
+///
+/// `generation_mode: Create` 下源快照的媒体类型由 `edit_kind` 推出（音频恒为 `audio/mpeg`），
+/// 所以这里固定传 `None`：这条通道根本不读 `input.source_media_type`，填一个值只会让读者
+/// 以为它对生成有影响。
 pub(crate) async fn run_local_project_audio_generation_at(
     project_path: &str,
     request: &LocalProjectAudioGenerationRequest,
@@ -5470,7 +5474,7 @@ pub(crate) async fn run_local_project_audio_generation_at(
         source_resource_id: format!("create:{}", request.operation_id),
         source_asset_id: None,
         source_path: None,
-        source_media_type: Some("audio/mpeg".to_string()),
+        source_media_type: None,
         source_subtype: None,
         producer_task_id: None,
         source_version_id: None,