diff --git a/src/backend/wayland/wl_backend.c b/src/backend/wayland/wl_backend.c
index fc460f2..7d277e7 100644
--- a/src/backend/wayland/wl_backend.c
+++ b/src/backend/wayland/wl_backend.c
@@ -1301,11 +1301,16 @@ wl_display_open(const char *name)
     wl_signal_add(&wl_state.xdg_shell->events.new_surface,
                   &wl_state.xdg_new_surface_listener);
 
-    /* Phase 17: start XWayland so X11 clients (e.g. GNUstep apps) can run
-     * under the Wayland compositor.  The third argument (lazy=false) starts
-     * the Xwayland process eagerly so DISPLAY is available immediately. */
+    /* Phase 17: register XWayland for X11 client support.
+     * Using lazy=true: the Xwayland process does NOT start at compositor
+     * boot.  It starts automatically on the first X11 client connect.
+     * This avoids a startup race where Xwayland's Wayland client tries to
+     * negotiate globals before the compositor's event loop is running,
+     * causing "Broken pipe" and "xcb connect failed" on the first frame.
+     * The display number is pre-allocated immediately so DISPLAY can be
+     * set for child processes even before any X11 client connects. */
     wl_state.xwayland = wlr_xwayland_create(wl_state.display,
-                                             wl_state.compositor, false);
+                                             wl_state.compositor, true);
     if (wl_state.xwayland) {
         wl_state.xwayland_new_surface_listener.notify = handle_xwayland_new_surface;
         wl_signal_add(&wl_state.xwayland->events.new_surface,
@@ -1313,7 +1318,7 @@ wl_display_open(const char *name)
         wlr_xwayland_set_seat(wl_state.xwayland, wl_state.seat);
         if (wl_state.xwayland->display_name) {
             setenv("DISPLAY", wl_state.xwayland->display_name, 1);
-            wwarning("wl_backend: XWayland started DISPLAY=%s",
+            wwarning("wl_backend: XWayland DISPLAY=%s (lazy: starts on first X11 client)",
                      wl_state.xwayland->display_name);
         } else {
             wwarning("wl_backend: XWayland created (display_name pending)");
@@ -1405,6 +1410,7 @@ wl_display_close(void)
          * still valid because the event loop is stopped and the socket closure
          * has not been dispatched, so wlroots' wl_client_destroy() succeeds. */
         if (wl_state.xwayland->server) {
+            int xdisp = wl_state.xwayland->server->display;
             if (wl_state.xwayland->server->pid > 0)
                 kill(wl_state.xwayland->server->pid, SIGKILL);
             /* wlroots 0.15 bug: after any Wayland client has connected and
@@ -1417,6 +1423,17 @@ wl_display_close(void)
              * clean it up; if it is stale, it has already been removed from
              * the display's client list and nothing more is needed. */
             wl_state.xwayland->server->client = NULL;
+            /* Clean up X lock file and Unix socket left by SIGKILL'd Xwayland.
+             * Without this, the next run may find a stale lock file whose PID
+             * has been reused by an unrelated process, causing wlroots to
+             * refuse to reclaim the display number → "xcb connect failed". */
+            {
+                char path[64];
+                snprintf(path, sizeof(path), "/tmp/.X%d-lock", xdisp);
+                unlink(path);
+                snprintf(path, sizeof(path), "/tmp/.X11-unix/X%d", xdisp);
+                unlink(path);
+            }
         }
         wl_state.xwayland = NULL;
         unsetenv("DISPLAY");
diff --git a/tests/wl-smoke-test.sh b/tests/wl-smoke-test.sh
index cf17316..c85cfae 100755
--- a/tests/wl-smoke-test.sh
+++ b/tests/wl-smoke-test.sh
@@ -118,10 +118,11 @@
 #      so handle_backend_new_output finds a valid scene when it fires.
 #      Verified by "scene graph created" + "scene output created" +
 #      "headless compositor mode" logs.
-#  39. (Phase 17) XWayland started: wlr_xwayland_create() is called in
-#      wl_display_open(); compositor logs "XWayland started DISPLAY=:<n>"
-#      so X11 clients (GNUstep apps) can connect.  DISPLAY env var is set.
-#      Verified by "XWayland started DISPLAY=" log.
+#  39. (Phase 17) XWayland display allocated (lazy start): wlr_xwayland_create()
+#      is called with lazy=true; Xwayland only starts on first X11 client.
+#      Compositor logs "XWayland DISPLAY=:<n> (lazy: starts on first X11 client)".
+#      DISPLAY env var is set from the pre-allocated display number.
+#      Verified by "XWayland DISPLAY=.*lazy" log.
 #  38. (Phase 11) noclip/nodock set in wl_screen_create_internals: wDockCreate
 #      requires X11 rendering resources unavailable in Wayland mode; disabling
 #      the dock/clip prevents crashes when wWorkspaceNew is called to create
@@ -267,14 +268,16 @@ grep -q 'dock/clip disabled in Wayland mode' /tmp/wl-smoke-stderr \
     || die "compositor did not log dock/clip disabled (noclip/nodock not set in wl_screen_create_internals)"
 echo "  nodock check: dock/clip disabled in Wayland mode (noclip=1 nodock=1)"
 
-# -- 4g. Phase 17: XWayland started and DISPLAY set ----------------------
+# -- 4g. Phase 17: XWayland display number allocated (lazy start) --------
 #
-# wl_display_open() logs "XWayland started DISPLAY=:<n>" when
-# wlr_xwayland_create() succeeds; verify the log line is present.
+# wl_display_open() logs "XWayland DISPLAY=:<n> (lazy: starts on first
+# X11 client)" when wlr_xwayland_create() succeeds with lazy=true.
+# The Xwayland process does not start until the first X11 client connects,
+# avoiding the startup race that caused "Broken pipe" with lazy=false.
 # (Falls back gracefully if XWayland is unavailable.)
-if grep -q 'XWayland started DISPLAY=' /tmp/wl-smoke-stderr; then
+if grep -q 'XWayland DISPLAY=.*lazy' /tmp/wl-smoke-stderr; then
     XDISP=$(grep -o 'DISPLAY=:[0-9]*' /tmp/wl-smoke-stderr | head -1 | sed 's/DISPLAY=//')
-    echo "  xwayland check: XWayland started DISPLAY=$XDISP"
+    echo "  xwayland check: XWayland DISPLAY=$XDISP (lazy start)"
 elif grep -q 'XWayland unavailable' /tmp/wl-smoke-stderr; then
     echo "  xwayland check: XWayland unavailable (skipped)"
 else