diff --git a/tests/conformance/cpp/CMakeLists.txt b/tests/conformance/cpp/CMakeLists.txt
index f892f66..2286f81 100644
--- a/tests/conformance/cpp/CMakeLists.txt
+++ b/tests/conformance/cpp/CMakeLists.txt
@@ -1,27 +1,34 @@
 # Conformance runner, C++ side. Owned by lane PROTO.
 #
-# Links libveloxproto (the generated protocol code in core/generated/), not libveloxcore:
-# this exercises the wire types, which is a separate concern from the engine. See
-# docs/adr/0009-generated-protocol-library.md.
+# Links libveloxproto (the generated wire code, ADR 0009's velox::proto target), not
+# libveloxcore: this exercises the wire types, which is a separate concern from the engine.
+#
+# Linking the same target GUI and daemon link — rather than compiling
+# core/generated/velox_proto.cpp into a second executable with its own flag set — is what
+# guarantees the conformance suite is checking byte-identical generated code to what the
+# clients ship. Two compiles of one .cpp under two warning configs is exactly the skew a
+# conformance suite exists to catch.
 
-# The root CMakeLists.txt only find_package(nlohmann_json)'s when daemon/CMakeLists.txt
-# exists (daemon is its real consumer), so this target may not exist yet when this
-# directory configures on its own — this suite must not depend on daemon having landed.
-# Self-sufficient rather than reaching into the root file to widen that guard.
-if(NOT TARGET nlohmann_json::nlohmann_json)
-    find_package(nlohmann_json 3.11 REQUIRED)
+if(TARGET velox::proto)
+    add_executable(velox_conformance_cpp conformance_main.cpp)
+    target_link_libraries(velox_conformance_cpp PRIVATE velox::proto)
+else()
+    # Standalone configure of tests/conformance/ with no core/ in the tree: compile the
+    # generated source directly, as before the velox::proto target existed. Keeps the
+    # suite buildable on its own.
+    if(NOT TARGET nlohmann_json::nlohmann_json)
+        find_package(nlohmann_json 3.11 REQUIRED)
+    endif()
+    add_executable(velox_conformance_cpp
+        conformance_main.cpp
+        ${CMAKE_SOURCE_DIR}/core/generated/velox_proto.cpp)
+    target_include_directories(velox_conformance_cpp PRIVATE
+        ${CMAKE_SOURCE_DIR}/core/generated)
+    target_link_libraries(velox_conformance_cpp PRIVATE nlohmann_json::nlohmann_json)
 endif()
 
-add_executable(velox_conformance_cpp
-    conformance_main.cpp
-    ${CMAKE_SOURCE_DIR}/core/generated/velox_proto.cpp)
-
-target_include_directories(velox_conformance_cpp PRIVATE
-    ${CMAKE_SOURCE_DIR}/core/generated
-    ${CMAKE_CURRENT_SOURCE_DIR})
-
+target_include_directories(velox_conformance_cpp PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
 target_compile_features(velox_conformance_cpp PRIVATE cxx_std_23)
-target_link_libraries(velox_conformance_cpp PRIVATE nlohmann_json::nlohmann_json)
 
 # The runner needs the repository root so it can find contracts/fixtures.
 add_test(NAME conformance_cpp