diff --git a/src/backend/x11/backend.c b/src/backend/x11/backend.c
index 7c00e73..efc3226 100644
--- a/src/backend/x11/backend.c
+++ b/src/backend/x11/backend.c
@@ -22,8 +22,10 @@
 #include "base/macros.h"
 #include "base/memory.h"
 #include "base/window_list.h"
+#include "core/event.h"
 #include "core/plan.h"
 #include "core/types.h"
+#include "core/window.h"
 #include "internal.h"
 
 typedef struct atom_item_t {
@@ -625,3 +627,54 @@ bool backend_apply_effect(
   xcb_flush(backend->conn);
   return true;
 }
+
+backend_scan_result_t *backend_scan_windows(backend_t *backend) {
+  auto conn   = backend->conn;
+  auto root   = backend->screen->root;
+  auto cookie = xcb_query_tree_unchecked(conn, root);
+  auto reply  = xcb_query_tree_reply(conn, cookie, nullptr);
+  if (!reply) return nullptr;
+
+  auto length = xcb_query_tree_children_length(reply);
+  if (!length) {
+    p_delete(&reply);
+    return nullptr;
+  }
+
+  auto list = xcb_query_tree_children(reply);
+
+  backend_scan_result_t *result = p_new(backend_scan_result_t, 1);
+
+  for (int i = 0; i < length; i++) {
+    auto slot = (window_map_request_event_t *)
+      array_push(result->windows, result->count, result->capacity);
+    if (!populate_window_event(backend, list[i], slot)) {
+      window_layer_props_cleanup(&slot->props);
+      window_metadata_cleanup(&slot->metadata);
+      result->count--;
+    }
+  }
+
+  p_delete(&reply);
+
+  if (result->count == 0) {
+    backend_scan_result_destroy(result);
+    result = nullptr;
+    return nullptr;
+  }
+
+  return result;
+}
+
+void backend_scan_result_destroy(backend_scan_result_t *result) {
+  if (!result) return;
+
+  for (size_t i = 0; i < result->count; i++) {
+    window_map_request_event_t *ev = &result->windows[i];
+    window_layer_props_cleanup(&ev->props);
+    window_metadata_cleanup(&ev->metadata);
+  }
+
+  p_delete(&result->windows);
+  p_delete(&result);
+}
diff --git a/src/backend/x11/event.c b/src/backend/x11/event.c
index 4662354..ef45313 100644
--- a/src/backend/x11/event.c
+++ b/src/backend/x11/event.c
@@ -91,18 +91,13 @@ static bool urgent_from_states(
   return false;
 }
 
-static bool handle_map_request(
+bool populate_window_event(
   backend_t *backend,
-  event_t *event,
-  const xcb_map_request_event_t *xcb_event
+  xcb_window_t window,
+  window_map_request_event_t *ev
 ) {
-  xcb_window_t window = xcb_event->window;
-
-  event->type = ZDWM_EVENT_WINDOW_MAP_REQUEST;
-
-  window_map_request_event_t *ev = &event->as.window_map_request;
-  ev->window                     = (window_id_t)window;
-  ev->transient_for              = window_get_transient_for(backend, window);
+  ev->window        = (window_id_t)window;
+  ev->transient_for = window_get_transient_for(backend, window);
 
   xcb_get_window_attributes_reply_t *wa =
     window_get_attributes(backend, window);
@@ -167,6 +162,19 @@ static bool handle_map_request(
   return true;
 }
 
+static bool handle_map_request(
+  backend_t *backend,
+  event_t *event,
+  const xcb_map_request_event_t *xcb_event
+) {
+  event->type = ZDWM_EVENT_WINDOW_MAP_REQUEST;
+  return populate_window_event(
+    backend,
+    xcb_event->window,
+    &event->as.window_map_request
+  );
+}
+
 static bool handle_unmap_notify(
   backend_t *backend,
   event_t *event,
diff --git a/src/backend/x11/internal.h b/src/backend/x11/internal.h
index d1cefa4..7a19ca7 100644
--- a/src/backend/x11/internal.h
+++ b/src/backend/x11/internal.h
@@ -7,6 +7,7 @@
 #include <xcb/xproto.h>
 
 #include "base/window_list.h"
+#include "core/event.h"
 
 #define ATOM_LIST(X)                   \
   X(COMPOUND_TEXT)                     \
@@ -94,3 +95,9 @@ struct backend_t {
   window_list_t map;
   window_list_t kill;
 };
+
+bool populate_window_event(
+  struct backend_t *backend,
+  xcb_window_t window,
+  window_map_request_event_t *ev
+);
diff --git a/src/core/backend.h b/src/core/backend.h
index e8c4581..9b5b571 100644
--- a/src/core/backend.h
+++ b/src/core/backend.h
@@ -37,3 +37,17 @@ bool backend_apply_effect(
   const effect_t *effects,
   size_t effect_count
 );
+
+typedef struct backend_scan_result_t {
+  window_map_request_event_t *windows;
+  size_t count;
+  size_t capacity;
+} backend_scan_result_t;
+
+/**
+ * @brief 扫描已有窗口
+ *
+ * @details 仅扫描窗口并获取其基础信息
+ */
+backend_scan_result_t *backend_scan_windows(backend_t *backend);
+void backend_scan_result_destroy(backend_scan_result_t *result);
diff --git a/src/core/policy.c b/src/core/policy.c
index ad42a9f..d5c5476 100644
--- a/src/core/policy.c
+++ b/src/core/policy.c
@@ -53,6 +53,7 @@ static void route_map_request(
   const window_map_request_event_t *e,
   command_buffer_t *out
 ) {
+  if (e->override_redirect) return;
   if (state_window_get(state, e->window)) return;
 
   window_layer_type_t layer_type = window_classify_layer(&e->props);
diff --git a/src/core/runtime.c b/src/core/runtime.c
index 12cde03..b48cad7 100644
--- a/src/core/runtime.c
+++ b/src/core/runtime.c
@@ -257,20 +257,14 @@ static void runtime_arrange(runtime_t *runtime) {
   }
 }
 
-void runtime_run(runtime_t *runtime) {
-  runtime->running = true;
-
-  backend_t *backend               = runtime->backend;
-  command_buffer_t *command_buffer = &runtime->command_buffer;
-  plan_t *plan                     = &runtime->plan;
-
+policy_context_t policy_context_init(runtime_t *runtime) {
   policy_context_t ctx = {
-    .bind_table = runtime->binding_table,
-    .state      = &runtime->state,
-    .rules      = &runtime->rules,
-    .border     = &runtime->border,
-    .layouts    = &runtime->layouts,
-    .runtime    = runtime,
+    .bind_table = (runtime)->binding_table,
+    .state      = &(runtime)->state,
+    .rules      = &(runtime)->rules,
+    .border     = &(runtime)->border,
+    .layouts    = &(runtime)->layouts,
+    .runtime    = (runtime),
     .action_api = {
       .spawn                = spawn,
       .quit                 = quit,
@@ -284,6 +278,46 @@ void runtime_run(runtime_t *runtime) {
       .cycle_current_output = cycle_current_output,
     },
   };
+  return ctx;
+}
+
+void runtime_scan(runtime_t *runtime) {
+  auto result = backend_scan_windows(runtime->backend);
+  if (!result) return;
+
+  policy_context_t ctx = policy_context_init(runtime);
+
+  auto backend        = runtime->backend;
+  auto command_buffer = &runtime->command_buffer;
+  auto plan           = &runtime->plan;
+
+  command_buffer_reset(command_buffer);
+  plan_reset(plan);
+
+  for (size_t i = 0; i < result->count; i++) {
+    event_t event = {
+      .type                  = ZDWM_EVENT_WINDOW_MAP_REQUEST,
+      .as.window_map_request = result->windows[i],
+    };
+    policy_route_event(&ctx, &event, command_buffer);
+  }
+
+  policy_apply_command(&ctx, command_buffer, plan);
+  if (plan->need_relayout) runtime_arrange(runtime);
+  if (plan->count) backend_apply_effect(backend, plan->effects, plan->count);
+
+  backend_scan_result_destroy(result);
+  result = nullptr;
+}
+
+void runtime_run(runtime_t *runtime) {
+  runtime->running = true;
+
+  backend_t *backend               = runtime->backend;
+  command_buffer_t *command_buffer = &runtime->command_buffer;
+  plan_t *plan                     = &runtime->plan;
+
+  policy_context_t ctx = policy_context_init(runtime);
 
   while (runtime->running) {
     event_t event = {0};
diff --git a/src/core/runtime.h b/src/core/runtime.h
index 0a2f34d..42a0037 100644
--- a/src/core/runtime.h
+++ b/src/core/runtime.h
@@ -46,4 +46,5 @@ bool runtime_init(runtime_t *runtime, runtime_init_desc_t *desc);
 void runtime_init_desc_cleanup(runtime_init_desc_t *desc);
 void runtime_shutdown(runtime_t *runtime);
 void runtime_setup(runtime_t *runtime);
+void runtime_scan(runtime_t *runtime);
 void runtime_run(runtime_t *runtime);