diff --git a/CHANGELOG.md b/CHANGELOG.md
index 41d4b159..2d6c33ce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,8 @@
   undid `--blink-settings` overrides. `mobile:` defaults to `nil` and leaves touch as is, `false` turns it off [#664]
 - A click or navigation timed out when the last loading iframe moved to another process, e.g. submitting a form that
   opens an inline PDF in Chrome 145+, where the PDF viewer runs out of process [#672]
+- A click or navigation didn't wait for an out-of-process iframe to load, e.g. a cross-site iframe with site isolation
+  on. Ferrum now follows its loading in the iframe's own target [#685]
 
 ### Removed
 
diff --git a/lib/ferrum/contexts.rb b/lib/ferrum/contexts.rb
index c9a68d07..b1215efa 100644
--- a/lib/ferrum/contexts.rb
+++ b/lib/ferrum/contexts.rb
@@ -230,17 +230,18 @@ def handle_attach(target, session_id, params, parent)
       elsif target.worker? || target.shared_worker?
         connect_worker(target)
       else
-        add_extensions_and_resume(session_id, params["waitingForDebugger"])
+        add_extensions_and_resume(target, session_id, params["waitingForDebugger"])
       end
     end
 
     # A page or iframe is paused until we resume it, so the extensions we
     # register now run before any script of its first document. An
-    # out-of-process iframe ignores them until the Page domain is enabled.
-    def add_extensions_and_resume(session_id, waiting)
+    # out-of-process iframe ignores them until the Page domain is enabled,
+    # and its parent page needs the Page domain to see it finish loading.
+    def add_extensions_and_resume(target, session_id, waiting)
       extensions = @client.options.extensions
       session = @client.session(session_id)
-      session.command("Page.enable", async: true) if extensions.any?
+      session.command("Page.enable", async: true) if extensions.any? || target.iframe?
       extensions.each do |source|
         session.command("Page.addScriptToEvaluateOnNewDocument", async: true, source: source)
       end
diff --git a/lib/ferrum/page.rb b/lib/ferrum/page.rb
index 3597d5b0..35704faa 100644
--- a/lib/ferrum/page.rb
+++ b/lib/ferrum/page.rb
@@ -107,6 +107,7 @@ def initialize(client, context_id:, target_id:, proxy: nil)
       @options = client.options
 
       @frames = Concurrent::Map.new
+      @remote_frames = Concurrent::Map.new
       @main_frame = Frame.new(nil, self)
       @event = Utils::Event.new.tap(&:set)
       @document_version = 0
diff --git a/lib/ferrum/page/frames.rb b/lib/ferrum/page/frames.rb
index 447a61df..1a864db2 100644
--- a/lib/ferrum/page/frames.rb
+++ b/lib/ferrum/page/frames.rb
@@ -74,6 +74,7 @@ def frame_by(id: nil, name: nil, execution_id: nil)
       def frames_subscribe
         subscribe_frame_attached
         subscribe_frame_detached
+        subscribe_remote_frames
         subscribe_frame_started_navigating
         subscribe_frame_started_loading
         subscribe_frame_navigated
@@ -104,11 +105,50 @@ def subscribe_frame_detached
             frame.execution_id = nil
           else
             @frames.delete(params["frameId"])
-            @event.set if @main_frame.idle? && frame&.idle? == false && frames.size == 1
+            forget_remote_frame(params["frameId"]) unless params["reason"] == "swap"
+            @event.set if @main_frame.idle? && frame&.idle? == false && frames.size == 1 && @remote_frames.values.none?
           end
         end
       end
 
+      # A frame swapped into another process (`Page.frameDetached` with reason `swap`) leaves the page's frame tree
+      # and loads in its own `iframe` target, so its loading events come over that target's session. Until it stops
+      # loading there {#idling?} stays false, as it does for any other loading frame.
+      def subscribe_remote_frames
+        on("Target.attachedToTarget") do |params|
+          info, session_id = params.values_at("targetInfo", "sessionId")
+          next unless info["type"] == "iframe"
+
+          frame_id = info["targetId"]
+          @remote_frames.put_if_absent(frame_id, true)
+          subscribe_remote_frame_loading(client.session(session_id), frame_id)
+        end
+
+        on("Target.detachedFromTarget") do |params|
+          forget_remote_frame(params["targetId"])
+        end
+      end
+
+      def subscribe_remote_frame_loading(session, frame_id)
+        session.on("Page.frameStartedLoading") do |params|
+          next unless params["frameId"] == frame_id && @remote_frames.key?(frame_id)
+
+          @remote_frames[frame_id] = true
+          @event.reset
+        end
+
+        session.on("Page.frameStoppedLoading") do |params|
+          next unless params["frameId"] == frame_id && @remote_frames.key?(frame_id)
+
+          @remote_frames[frame_id] = false
+          @event.set if idling?
+        end
+      end
+
+      def forget_remote_frame(frame_id)
+        @event.set if @remote_frames.delete(frame_id) && idling?
+      end
+
       # Tracks the +loaderId+ for each navigating frame and clears stale
       # lifecycle events from the previous navigation.
       def subscribe_frame_started_navigating
@@ -257,11 +297,12 @@ def subscribe_execution_contexts_cleared
           end
 
           children.each { |id| @frames.delete(id) }
+          @remote_frames.clear
         end
       end
 
       def idling?
-        @frames.values.all?(&:idle?)
+        @frames.values.all?(&:idle?) && @remote_frames.values.none?
       end
     end
   end
diff --git a/sig/ferrum/contexts.rbs b/sig/ferrum/contexts.rbs
index ba9fbcaf..0352d0e9 100644
--- a/sig/ferrum/contexts.rbs
+++ b/sig/ferrum/contexts.rbs
@@ -55,7 +55,7 @@ module Ferrum
 
     def connect_worker: (Target target) -> void
 
-    def add_extensions_and_resume: (String session_id, bool? waiting) -> void
+    def add_extensions_and_resume: (Target target, String session_id, bool? waiting) -> void
 
     def resume: (String session_id) -> void
 
diff --git a/sig/ferrum/page.rbs b/sig/ferrum/page.rbs
index b73620fe..fca351f8 100644
--- a/sig/ferrum/page.rbs
+++ b/sig/ferrum/page.rbs
@@ -32,6 +32,7 @@ module Ferrum
     @target_id: String
     @options: Browser::Options
     @frames: ::Concurrent::Map[String, Frame]
+    @remote_frames: ::Concurrent::Map[String, bool]
     @main_frame: Frame
     @event: Utils::Event
     @mouse: Mouse
diff --git a/sig/ferrum/page/frames.rbs b/sig/ferrum/page/frames.rbs
index fd4d23ae..c05a01df 100644
--- a/sig/ferrum/page/frames.rbs
+++ b/sig/ferrum/page/frames.rbs
@@ -15,6 +15,12 @@ module Ferrum
 
       def subscribe_frame_detached: () -> untyped
 
+      def subscribe_remote_frames: () -> untyped
+
+      def subscribe_remote_frame_loading: (SessionClient session, String frame_id) -> untyped
+
+      def forget_remote_frame: (String? frame_id) -> untyped
+
       def subscribe_frame_started_navigating: () -> untyped
 
       def subscribe_frame_started_loading: () -> untyped
diff --git a/spec/frame_spec.rb b/spec/frame_spec.rb
index c3127df8..4ec27234 100644
--- a/spec/frame_spec.rb
+++ b/spec/frame_spec.rb
@@ -148,6 +148,17 @@
     expect(page.evaluate("location.pathname")).to eq("/slow")
   end
 
+  it "waits for a cross-site frame a click adds", :launch do
+    browser = Ferrum::Browser.new(base_url: base_url,
+                                  browser_options: { "site-per-process" => nil, "disable-features" => "Translate" })
+    browser.go_to("/cross_site_iframe")
+    browser.at_css("button").click
+
+    expect(browser.evaluate("window.frameLoaded")).to be(true)
+  ensure
+    browser&.quit
+  end
+
   context "with lazy loading iframes" do
     it "does not block visit on lazy iframe" do
       expect { page.go_to("/lazy_iframe") }.not_to raise_error
diff --git a/spec/support/views/cross_site_iframe.erb b/spec/support/views/cross_site_iframe.erb
new file mode 100644
index 00000000..a3dfd394
--- /dev/null
+++ b/spec/support/views/cross_site_iframe.erb
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+  <body>
+    <button>Add cross-site iframe</button>
+
+    <script>
+      window.frameLoaded = false;
+
+      document.querySelector("button").addEventListener("click", function () {
+        var frame = document.createElement("iframe");
+        frame.onload = function () { window.frameLoaded = true; };
+        frame.src = location.origin.replace("127.0.0.1", "localhost") + "/slow_image";
+        document.body.appendChild(frame);
+      });
+    </script>
+  </body>
+</html>
diff --git a/spec/support/views/slow_image.erb b/spec/support/views/slow_image.erb
new file mode 100644
index 00000000..801effc2
--- /dev/null
+++ b/spec/support/views/slow_image.erb
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<html>
+  <body>
+    <img src="/show_cookies/set_cookie_slow">
+  </body>
+</html>