diff --git a/CMakeLists.txt b/CMakeLists.txt
index abe3072..16f61bc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -237,9 +237,10 @@ foreach(t ${_CST_SMALL_TESTS})
   elseif(t STREQUAL test_json_baseline)
     add_executable(${t} tests/${t}.c src/json_baseline.c vendor/cjson/cJSON.c)
   elseif(t STREQUAL test_replay_starvation OR t STREQUAL test_replay_real)
-    # cst_test_util.h static helpers reference os_*; gcc -O0 keeps unused ones
+    # cst_test_util.h static helpers reference os_*; gcc -O0 keeps unused ones.
+    # On Windows os_win.c also needs util.c (cst_buf_*, cst_utf8_valid).
     add_executable(${t} tests/${t}.c src/ctl_parse.c src/json_baseline.c
-      vendor/cjson/cJSON.c src/os_compat.c src/os_win.c)
+      vendor/cjson/cJSON.c src/os_compat.c src/os_win.c src/util.c)
     if(WIN32)
       target_link_libraries(${t} PRIVATE advapi32 user32)
     endif()
diff --git a/scripts/bootstrap_windows.sh b/scripts/bootstrap_windows.sh
index c031116..6d92ce2 100755
--- a/scripts/bootstrap_windows.sh
+++ b/scripts/bootstrap_windows.sh
@@ -41,7 +41,8 @@ echo "==> cmake (Windows, TUI)"
 cmake -S . -B build-win-tui -G Ninja \
   -DCMAKE_TOOLCHAIN_FILE=cmake/mingw-w64-x86_64.cmake \
   -DCMAKE_BUILD_TYPE=Release -DCST_BUILD_TUI=ON
-cmake --build build-win-tui
+# Package only needs the agent binary; skip host-unrunnable Win32 tests.
+cmake --build build-win-tui --target cst-agent
 
 echo "==> package"
 scripts/package_windows.sh