diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
index 64c5020..ccb5153 100644
--- a/core/CMakeLists.txt
+++ b/core/CMakeLists.txt
@@ -20,7 +20,6 @@ add_library(veloxcore STATIC
     src/net/probe.cpp
     src/io/sparse_file.cpp
     src/io/write_buffer.cpp
-    src/io/platform/linux/file_ops.cpp
     src/meta/veloxpart.cpp
     src/segment/segmenter.cpp
     src/segment/budget.cpp
@@ -33,6 +32,11 @@ add_library(veloxcore STATIC
 )
 add_library(velox::core ALIAS veloxcore)
 
+# Per-OS backend behind src/io/platform/*.hpp (docs/adr/0020, docs/08-porting.md). Only
+# the Linux backend exists (Phase 0); source selection lives in cmake/platform.cmake and
+# nowhere else, so PORT's platform/macos/ addition needs no edit here.
+velox_platform_sources(veloxcore src/io)
+
 target_include_directories(veloxcore
     PUBLIC  ${CMAKE_CURRENT_SOURCE_DIR}/include
     PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src   # net/*.cpp -> "net/curl_error.hpp"