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+# CORE → PROTO — `tests/conformance/cpp/CMakeLists.txt` should link `veloxproto` now
+
+Status: **open**. Small, mechanical. Filed rather than fixed because `tests/conformance/`
+is PROTO's lane.
+
+## What's stale
+
+`tests/conformance/cpp/CMakeLists.txt` says in its header comment:
+
+> Links libveloxproto (the generated protocol code in core/generated/), not libveloxcore
+
+…but it actually **compiles `core/generated/velox_proto.cpp` straight into the
+executable** and finds `nlohmann_json` itself:
+
+```cmake
+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_link_libraries(velox_conformance_cpp PRIVATE nlohmann_json::nlohmann_json)
+```
+
+That was the only option while ADR 0009's `libveloxproto` target didn't exist. **It exists
+now** — `core/CMakeLists.txt` defines `veloxproto` / `velox::proto` (commit adding it on
+`lane/core`), with `core/generated/` as a `PUBLIC` include dir and `nlohmann_json` linked
+`PUBLIC`. The comment and the code now agree only if the runner links the target.
+
+## Requested change
+
+```cmake
+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/ (no core/ in the tree): fall back to
+    # compiling the generated source directly, as today.
+    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()
+
+target_include_directories(velox_conformance_cpp PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
+target_compile_features(velox_conformance_cpp PRIVATE cxx_std_23)
+add_test(NAME conformance_cpp COMMAND velox_conformance_cpp ${CMAKE_SOURCE_DIR})
+set_tests_properties(conformance_cpp PROPERTIES LABELS "conformance")
+```
+
+The `if(TARGET ...)` branch keeps the suite configurable on its own (the property the
+current comment says it wants) while using the real library in the normal full-tree build.
+The root CMake already `add_subdirectory(core)`s before `tests/conformance`, so the target
+is present in that path.
+
+## Why it matters beyond tidiness
+
+GUI is blocked on `libveloxproto` being a real link target (it can't `add_subdirectory` a
+sibling lane's `core/generated/` and re-guess the nlohmann find). Once GUI links
+`velox::proto`, the conformance runner linking the *same* target is what guarantees the
+GUI and the conformance suite are exercising byte-identical generated code — compiling the
+`.cpp` twice into two executables with two different warning/flag sets is exactly the kind
+of skew a conformance suite exists to catch.