diff --git a/tools/build_llvm.sh b/tools/build_llvm.sh
index c9f12844..a990863d 100644
--- a/tools/build_llvm.sh
+++ b/tools/build_llvm.sh
@@ -47,8 +47,9 @@ echo "[1/4] Building nyash (feature selectable) ..."
 _LLVMPREFIX=$(llvm-config-18 --prefix)
 # Select LLVM feature: default harness (llvm), or legacy inkwell when NYASH_LLVM_FEATURE=llvm-inkwell-legacy
 LLVM_FEATURE=${NYASH_LLVM_FEATURE:-llvm}
+# Use 24 threads for parallel build
 LLVM_SYS_181_PREFIX="${_LLVMPREFIX}" LLVM_SYS_180_PREFIX="${_LLVMPREFIX}" \
-  CARGO_INCREMENTAL=1 cargo build --release -p nyash-rust --features "$LLVM_FEATURE" >/dev/null
+  CARGO_INCREMENTAL=1 cargo build --release -j 24 -p nyash-rust --features "$LLVM_FEATURE" >/dev/null
 
 echo "[2/4] Emitting object (.o) via LLVM backend ..."
 # Default object output path under target/aot_objects
@@ -78,7 +79,8 @@ echo "[3/4] Building NyRT static runtime ..."
 if [[ "${NYASH_LLVM_SKIP_NYRT_BUILD:-0}" == "1" ]]; then
   echo "    Skipping NyRT build (NYASH_LLVM_SKIP_NYRT_BUILD=1)"
 else
-  ( cd crates/nyrt && cargo build --release >/dev/null )
+  # Use 24 threads for parallel build
+  ( cd crates/nyrt && cargo build --release -j 24 >/dev/null )
 fi
 
 echo "[4/4] Linking $OUT ..."