diff --git a/CMakeLists.txt b/CMakeLists.txt
index f3ceb73f2..b2d0276c8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -205,6 +205,12 @@ find_package(Boost 1.81 REQUIRED COMPONENTS json url coroutine)
 message(STATUS "LaunchDarkly: using Boost v${Boost_VERSION}")
 
 set(FOXY_BUILD_TESTING OFF)
+
+# Keep Boost.Asio header-only, matching how consumers compile it. Foxy's
+# separate-compilation mode bakes Asio internals into our library whose layout can
+# diverge from a consumer's build, causing ODR violations when linked. Force off.
+set(FOXY_FAST_BUILD OFF CACHE BOOL "Keep Boost.Asio header-only for ABI compatibility with consumers" FORCE)
+
 add_subdirectory(vendor/foxy)
 
 
diff --git a/libs/networking/src/CMakeLists.txt b/libs/networking/src/CMakeLists.txt
index bf229726d..a3aa8f24a 100644
--- a/libs/networking/src/CMakeLists.txt
+++ b/libs/networking/src/CMakeLists.txt
@@ -35,8 +35,6 @@ target_compile_features(${LIBNAME} PUBLIC cxx_std_17)
 target_compile_definitions(${LIBNAME}
     PUBLIC
         LD_CURL_NETWORKING
-        BOOST_ASIO_SEPARATE_COMPILATION=1
-        BOOST_BEAST_SEPARATE_COMPILATION=1
 )
 
 # Using PUBLIC_HEADERS would flatten the include.