diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index c91a5d4db29a9691e9b43ef4d5d5e9a4db945ac8..00107b54e09137ee1af1c56b8c9e853a4ffe7264 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -13,6 +13,15 @@ ChromeUtils.importESModule("resource://gre/modules/NotificationDB.sys.mjs");
 
 // lazy module getters
 
+const ZEN_WELCOME_PATH = "zen-welcome";
+const ZEN_WELCOME_ELEMENT_ATTR = "zen-dialog-welcome-element";
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "ProfileService",
+  "@mozilla.org/toolkit/profile-service;1",
+  "nsIToolkitProfileService"
+);
+
 ChromeUtils.defineESModuleGetters(this, {
   AMTelemetry: "resource://gre/modules/AddonManager.sys.mjs",
   AboutNewTab: "resource:///modules/AboutNewTab.sys.mjs",
@@ -1664,6 +1673,7 @@ var gBrowserInit = {
     });
 
     updateFxaToolbarMenu(gFxaToolbarEnabled, true);
+    Services.scriptloader.loadSubScript("chrome://browser/content/zenThemeModifier.js", this);
 
     updatePrintCommands(gPrintEnabled);
 
@@ -1727,6 +1737,11 @@ var gBrowserInit = {
     }
 
     // Misc. inits.
+
+    // ZEN: Propagate the current profile used to the browser UI, such as 
+    // showing the avatar and profile info to the side bar
+    zenUpdateBrowserProfiles();
+    
     gUIDensity.init();
     TabletModeUpdater.init();
     CombinedStopReload.ensureInitialized();
@@ -6669,7 +6684,7 @@ function setToolbarVisibility(
       );
     }
 
-    const overlapAttr = "BookmarksToolbarOverlapsBrowser";
+    const overlapAttr = "BookmarksToolbarOverlapsBrowser__ignore"; // Original string was "BookmarksToolbarOverlapsBrowser" but it's not used and it only bugs the UI.
     switch (isVisible) {
       case true:
       case "always":
@@ -9789,6 +9804,13 @@ var gDialogBox = {
     parentElement.style.removeProperty("width");
     parentElement.style.removeProperty("height");
     document.documentElement.setAttribute("window-modal-open", true);
+
+    if (uri.includes(ZEN_WELCOME_PATH)) {
+      parentElement.setAttribute(ZEN_WELCOME_ELEMENT_ATTR, true);
+    } else if (parentElement.hasAttribute(ZEN_WELCOME_ELEMENT_ATTR)) {
+      parentElement.removeAttribute(ZEN_WELCOME_ELEMENT_ATTR);
+    }
+
     // Call this first so the contents show up and get layout, which is
     // required for SubDialog to work.
     parentElement.showModal();
@@ -10166,3 +10188,15 @@ var FirefoxViewHandler = {
     this.button?.toggleAttribute("attention", shouldShow);
   },
 };
+
+function zenUpdateBrowserProfiles() {
+  const mainWindowEl = document.documentElement;
+  // Dont override the sync avatar if it's already set
+  if (mainWindowEl.style.hasOwnProperty("--avatar-image-url")) {
+    return;
+  }
+  let profile = ProfileService.currentProfile;
+  if (!profile || profile.zenAvatarPath == "") return;
+  // TODO: actually use profile data to generate the avatar, instead of just using the name
+  mainWindowEl.style.setProperty("--avatar-image-url", `url(${profile.zenAvatarPath})`);
+}