diff --git a/server-rs/crates/platform-tripo/src/common/types.rs b/server-rs/crates/platform-tripo/src/common/types.rs
index 0600e6d36..00326cc7d 100644
--- a/server-rs/crates/platform-tripo/src/common/types.rs
+++ b/server-rs/crates/platform-tripo/src/common/types.rs
@@ -293,6 +293,10 @@ fn fallback_artifact_extension(content_type: Option<&str>) -> &'static str {
         "png"
     } else if content_type.starts_with("image/jpeg") {
         "jpg"
+    } else if content_type.starts_with("image/jpg") {
+        // `image/jpg` 不是标准写法，但确有 provider 这么回；落到默认 `.glb` 会让一张
+        // 预览图带上模型后缀，这里按声明值给回 jpg。
+        "jpg"
     } else if content_type.starts_with("image/webp") {
         "webp"
     } else {
@@ -341,6 +345,27 @@ mod tests {
         assert!(!stem.contains('.'), "`..` 必须被中性化：{stem}");
     }
 
+    #[test]
+    fn fallback_extension_follows_the_declared_image_content_type() {
+        assert_eq!(
+            artifact_filename("preview", Some("image/png"), &artifact_url("/artifact")),
+            "preview.png"
+        );
+        assert_eq!(
+            artifact_filename("preview", Some("image/jpg"), &artifact_url("/artifact")),
+            "preview.jpg"
+        );
+        assert_eq!(
+            artifact_filename("preview", Some("image/webp"), &artifact_url("/artifact")),
+            "preview.webp"
+        );
+        // 读不出形态时仍按模型产物兜底。
+        assert_eq!(
+            artifact_filename("model", None, &artifact_url("/artifact")),
+            "model.glb"
+        );
+    }
+
     #[test]
     fn blank_stem_falls_back_to_a_fixed_name() {
         assert_eq!(