diff --git a/transformer_vm/model/transformer.cpp b/transformer_vm/model/transformer.cpp
index b287f61..9ba0f10 100644
--- a/transformer_vm/model/transformer.cpp
+++ b/transformer_vm/model/transformer.cpp
@@ -22,6 +22,8 @@
 #ifdef __APPLE__
 #define ACCELERATE_NEW_LAPACK
 #include <Accelerate/Accelerate.h>
+#elif defined(USE_OPENBLAS)
+#include <cblas.h>
 #endif
 
 #include "hull2d_cht.h"
@@ -158,7 +160,7 @@ static inline void add_position_encoding(double* x, int pos) {
 static inline void matvec(const double* __restrict__ W,
                            const double* __restrict__ x,
                            double* __restrict__ y, int rows, int cols) {
-#if defined(__APPLE__) && !defined(NO_BLAS)
+#if (defined(__APPLE__) || defined(USE_OPENBLAS)) && !defined(NO_BLAS)
     cblas_dgemv(CblasRowMajor, CblasNoTrans, rows, cols,
                 1.0, W, cols, x, 1, 0.0, y, 1);
 #else
diff --git a/transformer_vm/runner.py b/transformer_vm/runner.py
index 6a6b84e..1ae186b 100644
--- a/transformer_vm/runner.py
+++ b/transformer_vm/runner.py
@@ -113,6 +113,16 @@ def _build_cpp_engine():
         ]
     else:
         cmd = ["g++", "-std=c++17", "-O3", "-I", attn_dir, source, "-o", binary]
+        # Opt into OpenBLAS for the matvec path if cblas.h is discoverable.
+        # Falls back silently to the scalar nested loop when not installed.
+        try:
+            pkg = subprocess.run(
+                ["pkg-config", "--cflags", "--libs", "openblas"],
+                capture_output=True, text=True, check=True,
+            )
+            cmd += ["-DUSE_OPENBLAS"] + pkg.stdout.split()
+        except (subprocess.CalledProcessError, FileNotFoundError):
+            pass
     try:
         subprocess.check_call(cmd)
         logger.info("[engine] Built: %s", binary)