diff --git a/remote/cdp/domains/content/Page.jsm b/remote/cdp/domains/content/Page.jsm
index 92e4e25471e1..1f97970061b7 100644
--- a/remote/cdp/domains/content/Page.jsm
+++ b/remote/cdp/domains/content/Page.jsm
@@ -55,14 +55,8 @@ class Page extends ContentProcessDomain {
 
   async enable() {
     if (!this.enabled) {
-      this.session.contextObserver.on(
-        "docshell-created",
-        this._onFrameAttached
-      );
-      this.session.contextObserver.on(
-        "docshell-destroyed",
-        this._onFrameDetached
-      );
+      this.session.contextObserver.on("frame-attached", this._onFrameAttached);
+      this.session.contextObserver.on("frame-detached", this._onFrameDetached);
       this.session.contextObserver.on(
         "frame-navigated",
         this._onFrameNavigated
@@ -96,14 +90,8 @@ class Page extends ContentProcessDomain {
 
   disable() {
     if (this.enabled) {
-      this.session.contextObserver.off(
-        "docshell-created",
-        this._onFrameAttached
-      );
-      this.session.contextObserver.off(
-        "docshell-destroyed",
-        this._onFrameDetached
-      );
+      this.session.contextObserver.off("frame-attached", this._onFrameAttached);
+      this.session.contextObserver.off("frame-detached", this._onFrameDetached);
       this.session.contextObserver.off(
         "frame-navigated",
         this._onFrameNavigated
@@ -260,8 +248,8 @@ class Page extends ContentProcessDomain {
     return this.content.location.href;
   }
 
-  _onFrameAttached(name, { id }) {
-    const bc = BrowsingContext.get(id);
+  _onFrameAttached(name, { frameId, window }) {
+    const bc = BrowsingContext.get(frameId);
 
     // Don't emit for top-level browsing contexts
     if (!bc.parent) {
@@ -270,19 +258,19 @@ class Page extends ContentProcessDomain {
 
     // TODO: Use a unique identifier for frames (bug 1605359)
     this.emit("Page.frameAttached", {
-      frameId: bc.id.toString(),
+      frameId: frameId.toString(),
       parentFrameId: bc.parent.id.toString(),
       stack: null,
     });
 
-    const loaderId = this.frameIdToLoaderId.get(bc.id);
+    const loaderId = this.frameIdToLoaderId.get(frameId);
     const timestamp = Date.now() / 1000;
-    this.emit("Page.frameStartedLoading", { frameId: bc.id.toString() });
-    this.emitLifecycleEvent(bc.id, loaderId, "init", timestamp);
+    this.emit("Page.frameStartedLoading", { frameId: frameId.toString() });
+    this.emitLifecycleEvent(frameId, loaderId, "init", timestamp);
   }
 
-  _onFrameDetached(name, { id }) {
-    const bc = BrowsingContext.get(id);
+  _onFrameDetached(name, { frameId }) {
+    const bc = BrowsingContext.get(frameId);
 
     // Don't emit for top-level browsing contexts
     if (!bc.parent) {
@@ -290,7 +278,7 @@ class Page extends ContentProcessDomain {
     }
 
     // TODO: Use a unique identifier for frames (bug 1605359)
-    this.emit("Page.frameDetached", { frameId: bc.id.toString() });
+    this.emit("Page.frameDetached", { frameId: frameId.toString() });
   }
 
   _onFrameNavigated(name, { frameId }) {
diff --git a/remote/cdp/observers/ContextObserver.jsm b/remote/cdp/observers/ContextObserver.jsm
index c2e6f14a5bb3..49b1a99e022f 100644
--- a/remote/cdp/observers/ContextObserver.jsm
+++ b/remote/cdp/observers/ContextObserver.jsm
@@ -41,6 +41,8 @@ class ContextObserver {
     this.chromeEventHandler = chromeEventHandler;
     EventEmitter.decorate(this);
 
+    this._fissionEnabled = Services.appinfo.fissionAutostart;
+
     this.chromeEventHandler.addEventListener("DOMWindowCreated", this, {
       mozSystemGroup: true,
     });
@@ -55,7 +57,11 @@ class ContextObserver {
 
     Services.obs.addObserver(this, "inner-window-destroyed");
 
-    Services.obs.addObserver(this, "webnavigation-create");
+    // With Fission disabled the `DOMWindowCreated` event is fired too late.
+    // Use the `webnavigation-create` notification instead.
+    if (!this._fissionEnabled) {
+      Services.obs.addObserver(this, "webnavigation-create");
+    }
     Services.obs.addObserver(this, "webnavigation-destroy");
   }
 
@@ -72,7 +78,9 @@ class ContextObserver {
 
     Services.obs.removeObserver(this, "inner-window-destroyed");
 
-    Services.obs.removeObserver(this, "webnavigation-create");
+    if (!this._fissionEnabled) {
+      Services.obs.removeObserver(this, "webnavigation-create");
+    }
     Services.obs.removeObserver(this, "webnavigation-destroy");
   }
 
@@ -87,6 +95,14 @@ class ContextObserver {
         // that is destroyed. Instead, pass the frameId and let the listener figure out
         // what ExecutionContext(s) to destroy.
         this.emit("context-destroyed", { frameId });
+
+        // With Fission enabled the frame is attached early enough so that
+        // expected network requests and responses are handles afterward.
+        // Otherwise send the event when `webnavigation-create` is received.
+        if (this._fissionEnabled) {
+          this.emit("frame-attached", { frameId, window });
+        }
+
         this.emit("frame-navigated", { frameId, window });
         this.emit("context-created", { windowId: id, window });
         // Delay script-loaded to allow context cleanup to happen first
@@ -134,14 +150,14 @@ class ContextObserver {
   }
 
   onDocShellCreated(docShell) {
-    this.emit("docshell-created", {
-      id: docShell.browsingContext.id,
+    this.emit("frame-attached", {
+      frameId: docShell.browsingContext.id,
     });
   }
 
   onDocShellDestroyed(docShell) {
-    this.emit("docshell-destroyed", {
-      id: docShell.browsingContext.id,
+    this.emit("frame-detached", {
+      frameId: docShell.browsingContext.id,
     });
   }
 }