Add a no_ibv

mlx/distributed/ibv/CMakeLists.txt

@@ -1,2 +1,8 @@
+if(MLX_BUILD_CPU
+   AND ${CMAKE_SYSTEM_NAME} MATCHES "Darwin"
+   AND MACOS_SDK_VERSION GREATER_EQUAL 26.2)
   target_sources(mlx PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/ibv.cpp)
   target_link_libraries(mlx PRIVATE rdma)
+else()
+  target_sources(mlx PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/no_ibv.cpp)
+endif()

mlx/distributed/ibv/ibv.cpp

@@ -1077,8 +1077,10 @@ class IBVGroup : public GroupImpl {
 };
 
 bool is_available() {
+  if (__builtin_available(macOS 26.2, *)) {
     return true;
   }
+}
 
 std::shared_ptr<GroupImpl> init(bool strict /* = false */) {
   const char* dev_file = std::getenv("MLX_IBV_DEVICES");

mlx/distributed/ibv/no_ibv.cpp

@@ -0,0 +1,20 @@
+// Copyright © 2025 Apple Inc.
+
+#include "mlx/distributed/ibv/ibv.h"
+
+namespace mlx::core::distributed::ibv {
+
+using GroupImpl = mlx::core::distributed::detail::GroupImpl;
+
+bool is_available() {
+  return false;
+}
+
+std::shared_ptr<GroupImpl> init(bool strict /* = false */) {
+  if (strict) {
+    throw std::runtime_error("Cannot initialize ibv distributed backend.");
+  }
+  return nullptr;
+}
+
+} // namespace mlx::core::distributed::ibv