diff --git a/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.cc b/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.cc
index 6034c4db18cb..836c7a0447c8 100644
--- a/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.cc
+++ b/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.cc
@@ -27,12 +27,14 @@
 
 namespace {
 
-static base::NoDestructor<std::string> g_observing_script("");
-
 static base::NoDestructor<std::vector<std::string>> g_vetted_search_engines(
     {"duckduckgo", "qwant", "bing", "startpage", "google", "yandex", "ecosia",
      "brave"});
 
+// Entry point to content_cosmetic.ts script.
+const char kObservingScriptletEntryPoint[] =
+    "window.content_cosmetic.tryScheduleQueuePump()";
+
 const char kScriptletInitScript[] =
     R"((function() {
           let text = %s;
@@ -193,9 +195,6 @@ CosmeticFiltersJSHandler::CosmeticFiltersJSHandler(
     : render_frame_(render_frame),
       isolated_world_id_(isolated_world_id),
       enabled_1st_party_cf_(false) {
-  if (g_observing_script->empty()) {
-    *g_observing_script = LoadDataResource(kCosmeticFiltersGenerated[0].id);
-  }
   EnsureConnected();
 }
 
@@ -231,6 +230,7 @@ void CosmeticFiltersJSHandler::AddJavaScriptObjectToFrame(
   v8::Context::Scope context_scope(context);
 
   CreateWorkerObject(isolate, context);
+  bundle_injected_ = false;
 }
 
 void CosmeticFiltersJSHandler::CreateWorkerObject(
@@ -366,9 +366,7 @@ void CosmeticFiltersJSHandler::ApplyRules() {
   web_frame->ExecuteScriptInIsolatedWorld(
       isolated_world_id_, blink::WebString::FromUTF8(pre_init_script),
       blink::BackForwardCacheAware::kAllow);
-  web_frame->ExecuteScriptInIsolatedWorld(
-      isolated_world_id_, blink::WebString::FromUTF8(*g_observing_script),
-      blink::BackForwardCacheAware::kAllow);
+  ExecuteObservingBundleEntryPoint();
 
   CSSRulesRoutine(resources_dict_.get());
 }
@@ -443,11 +441,8 @@ void CosmeticFiltersJSHandler::CSSRulesRoutine(
     }
   }
 
-  if (!enabled_1st_party_cf_) {
-    web_frame->ExecuteScriptInIsolatedWorld(
-        isolated_world_id_, blink::WebString::FromUTF8(*g_observing_script),
-        blink::BackForwardCacheAware::kAllow);
-  }
+  if (!enabled_1st_party_cf_)
+    ExecuteObservingBundleEntryPoint();
 }
 
 void CosmeticFiltersJSHandler::OnHiddenClassIdSelectors(base::Value result) {
@@ -478,11 +473,31 @@ void CosmeticFiltersJSHandler::OnHiddenClassIdSelectors(base::Value result) {
         blink::BackForwardCacheAware::kAllow);
   }
 
-  if (!enabled_1st_party_cf_) {
+  if (!enabled_1st_party_cf_)
+    ExecuteObservingBundleEntryPoint();
+}
+
+void CosmeticFiltersJSHandler::ExecuteObservingBundleEntryPoint() {
+  blink::WebLocalFrame* web_frame = render_frame_->GetWebFrame();
+  DCHECK(web_frame);
+
+  if (!bundle_injected_) {
+    static base::NoDestructor<std::string> s_observing_script(
+        LoadDataResource(kCosmeticFiltersGenerated[0].id));
+    bundle_injected_ = true;
+
     web_frame->ExecuteScriptInIsolatedWorld(
-        isolated_world_id_, blink::WebString::FromUTF8(*g_observing_script),
+        isolated_world_id_, blink::WebString::FromUTF8(*s_observing_script),
         blink::BackForwardCacheAware::kAllow);
+
+    // kObservingScriptletEntryPoint was called by `s_observing_script`.
+    return;
   }
+
+  web_frame->ExecuteScriptInIsolatedWorld(
+      isolated_world_id_,
+      blink::WebString::FromUTF8(kObservingScriptletEntryPoint),
+      blink::BackForwardCacheAware::kAllow);
 }
 
 }  // namespace cosmetic_filters
diff --git a/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.h b/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.h
index 5f949334ba4c..1dd8a4633ca4 100644
--- a/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.h
+++ b/components/cosmetic_filters/renderer/cosmetic_filters_js_handler.h
@@ -49,6 +49,9 @@ class CosmeticFiltersJSHandler {
   bool EnsureConnected();
   void OnRemoteDisconnect();
 
+  // Injects content_cosmetic bundle (if needed) and calls the entry point.
+  void ExecuteObservingBundleEntryPoint();
+
   void CreateWorkerObject(v8::Isolate* isolate, v8::Local<v8::Context> context);
 
   // A function to be called from JS
@@ -70,6 +73,10 @@ class CosmeticFiltersJSHandler {
   std::vector<std::string> exceptions_;
   GURL url_;
   std::unique_ptr<base::DictionaryValue> resources_dict_;
+
+  // True if the content_cosmetic.bundle.js has injected in the current frame.
+  bool bundle_injected_ = false;
+
   base::WeakPtrFactory<CosmeticFiltersJSHandler> weak_ptr_factory_{this};
 };
 
diff --git a/components/cosmetic_filters/resources/data/content_cosmetic.ts b/components/cosmetic_filters/resources/data/content_cosmetic.ts
index 24c5af616991..34e7ebf4c294 100644
--- a/components/cosmetic_filters/resources/data/content_cosmetic.ts
+++ b/components/cosmetic_filters/resources/data/content_cosmetic.ts
@@ -534,9 +534,15 @@ const scheduleQueuePump = (hide1pContent: boolean, genericHide: boolean) => {
   }, { timeout: maxTimeMSBeforeStart })
 }
 
-if (!CC.observingHasStarted) {
-  CC.observingHasStarted = true
-  scheduleQueuePump(CC.hide1pContent, CC.generichide)
-} else {
-  scheduleQueuePump(false, false)
+const tryScheduleQueuePump = () => {
+  if (!CC.observingHasStarted) {
+    CC.observingHasStarted = true
+    scheduleQueuePump(CC.hide1pContent, CC.generichide)
+  } else {
+    scheduleQueuePump(false, false)
+  }
 }
+
+CC.tryScheduleQueuePump = CC.tryScheduleQueuePump || tryScheduleQueuePump
+
+tryScheduleQueuePump()
diff --git a/components/definitions/global.d.ts b/components/definitions/global.d.ts
index f04ca20e3a0b..3a9e23cbfe12 100644
--- a/components/definitions/global.d.ts
+++ b/components/definitions/global.d.ts
@@ -40,6 +40,7 @@ declare global {
       alreadyKnownFirstPartySubtrees: WeakSet
       _hasDelayOcurred: boolean
       _startCheckingId: number | undefined
+      tryScheduleQueuePump: (() => void)
     }
   }
 }