diff --git a/sgl-model-gateway/src/routers/grpc/harmony/builder.rs b/sgl-model-gateway/src/routers/grpc/harmony/builder.rs
index e6ece6937..64f84947a 100644
--- a/sgl-model-gateway/src/routers/grpc/harmony/builder.rs
+++ b/sgl-model-gateway/src/routers/grpc/harmony/builder.rs
@@ -33,8 +33,10 @@ static HARMONY_ENCODING: OnceLock<HarmonyEncoding> = OnceLock::new();
 /// Uses HarmonyGptOss encoding which supports the gpt-oss model family.
 pub(super) fn get_harmony_encoding() -> &'static HarmonyEncoding {
     HARMONY_ENCODING.get_or_init(|| {
-        openai_harmony::load_harmony_encoding(HarmonyEncodingName::HarmonyGptOss)
-            .expect("Failed to load Harmony encoding")
+        tokio::task::block_in_place(|| {
+            openai_harmony::load_harmony_encoding(HarmonyEncodingName::HarmonyGptOss)
+                .expect("Failed to load Harmony encoding")
+        })
     })
 }