diff --git a/browser_patches/firefox-beta/BUILD_NUMBER b/browser_patches/firefox-beta/BUILD_NUMBER
index 035d2fca14..17e02a52df 100644
--- a/browser_patches/firefox-beta/BUILD_NUMBER
+++ b/browser_patches/firefox-beta/BUILD_NUMBER
@@ -1,2 +1,2 @@
-1316
-Changed: aslushnikov@gmail.com Wed Jan 26 17:24:09 MST 2022
+1317
+Changed: pavel.feldman@gmail.com Mon 14 Feb 2022 03:52:34 PM PST
diff --git a/browser_patches/firefox-beta/juggler/TargetRegistry.js b/browser_patches/firefox-beta/juggler/TargetRegistry.js
index a12d9f96b3..0ec90afd1b 100644
--- a/browser_patches/firefox-beta/juggler/TargetRegistry.js
+++ b/browser_patches/firefox-beta/juggler/TargetRegistry.js
@@ -144,7 +144,7 @@ class TargetRegistry {
           return;
 
         return {
-          scriptsToEvaluateOnNewDocument: target.browserContext().scriptsToEvaluateOnNewDocument,
+          initScripts: target.browserContext().initScripts,
           bindings: target.browserContext().bindings,
           settings: target.browserContext().settings,
         };
@@ -361,6 +361,7 @@ class PageTarget {
     this._screencastRecordingInfo = undefined;
     this._dialogs = new Map();
     this.forcedColors = 'no-override';
+    this._pageInitScripts = [];
 
     const navigationListener = {
       QueryInterface: ChromeUtils.generateQI([Ci.nsIWebProgressListener, Ci.nsISupportsWeakReference]),
@@ -523,8 +524,13 @@ class PageTarget {
     await this._channel.connect('').send('ensurePermissions', {}).catch(e => void e);
   }
 
-  async addScriptToEvaluateOnNewDocument(script) {
-    await this._channel.connect('').send('addScriptToEvaluateOnNewDocument', script).catch(e => void e);
+  async setInitScripts(scripts) {
+    this._pageInitScripts = scripts;
+    await this.pushInitScripts();
+  }
+
+  async pushInitScripts() {
+    await this._channel.connect('').send('setInitScripts', [...this._browserContext.initScripts, ...this._pageInitScripts]).catch(e => void e);
   }
 
   async addBinding(worldName, name, script) {
@@ -708,7 +714,7 @@ class BrowserContext {
     this.forcedColors = 'no-override';
     this.reducedMotion = 'none';
     this.videoRecordingOptions = undefined;
-    this.scriptsToEvaluateOnNewDocument = [];
+    this.initScripts = [];
     this.bindings = [];
     this.settings = {};
     this.pages = new Set();
@@ -804,9 +810,9 @@ class BrowserContext {
     await Promise.all(Array.from(this.pages).map(page => page.updateViewportSize()));
   }
 
-  async addScriptToEvaluateOnNewDocument(script) {
-    this.scriptsToEvaluateOnNewDocument.push(script);
-    await Promise.all(Array.from(this.pages).map(page => page.addScriptToEvaluateOnNewDocument(script)));
+  async setInitScripts(scripts) {
+    this.initScripts = scripts;
+    await Promise.all(Array.from(this.pages).map(page => page.pushInitScripts()));
   }
 
   async addBinding(worldName, name, script) {
diff --git a/browser_patches/firefox-beta/juggler/content/FrameTree.js b/browser_patches/firefox-beta/juggler/content/FrameTree.js
index ccb49bf4e2..61ff889e75 100644
--- a/browser_patches/firefox-beta/juggler/content/FrameTree.js
+++ b/browser_patches/firefox-beta/juggler/content/FrameTree.js
@@ -73,15 +73,20 @@ class FrameTree {
     return this._runtime;
   }
 
-  addScriptToEvaluateOnNewDocument(script, worldName) {
-    worldName = worldName || '';
-    const existing = this._isolatedWorlds.has(worldName);
-    const world = this._ensureWorld(worldName);
-    world._scriptsToEvaluateOnNewDocument.push(script);
-    // FIXME: 'should inherit http credentials from browser context' fails without this
-    if (worldName && !existing) {
-      for (const frame of this.frames())
-        frame._createIsolatedContext(worldName);
+  setInitScripts(scripts) {
+    for (const world of this._isolatedWorlds.values())
+      world._scriptsToEvaluateOnNewDocument = [];
+
+    for (let { worldName, script } of scripts) {
+      worldName = worldName || '';
+      const existing = this._isolatedWorlds.has(worldName);
+      const world = this._ensureWorld(worldName);
+      world._scriptsToEvaluateOnNewDocument.push(script);
+      // FIXME: 'should inherit http credentials from browser context' fails without this
+      if (worldName && !existing) {
+        for (const frame of this.frames())
+          frame._createIsolatedContext(worldName);
+      }
     }
   }
 
diff --git a/browser_patches/firefox-beta/juggler/content/PageAgent.js b/browser_patches/firefox-beta/juggler/content/PageAgent.js
index 234c6b0801..c941cabca7 100644
--- a/browser_patches/firefox-beta/juggler/content/PageAgent.js
+++ b/browser_patches/firefox-beta/juggler/content/PageAgent.js
@@ -134,7 +134,6 @@ class PageAgent {
       this._runtime.events.onBindingCalled(this._onBindingCalled.bind(this)),
       browserChannel.register('page', {
         addBinding: ({ worldName, name, script }) => this._frameTree.addBinding(worldName, name, script),
-        addScriptToEvaluateOnNewDocument: ({script, worldName}) => this._frameTree.addScriptToEvaluateOnNewDocument(script, worldName),
         adoptNode: this._adoptNode.bind(this),
         crash: this._crash.bind(this),
         describeNode: this._describeNode.bind(this),
diff --git a/browser_patches/firefox-beta/juggler/content/main.js b/browser_patches/firefox-beta/juggler/content/main.js
index 04d1cf7c36..d471ab9553 100644
--- a/browser_patches/firefox-beta/juggler/content/main.js
+++ b/browser_patches/firefox-beta/juggler/content/main.js
@@ -84,11 +84,10 @@ function initialize() {
   if (!response)
     return;
   const {
-    scriptsToEvaluateOnNewDocument = [],
+    initScripts = [],
     bindings = [],
     settings = {}
   } = response || {};
-
   // Enforce focused state for all top level documents.
   docShell.overrideHasFocus = true;
   docShell.forceActiveState = true;
@@ -99,14 +98,13 @@ function initialize() {
   }
   for (const { worldName, name, script } of bindings)
     frameTree.addBinding(worldName, name, script);
-  for (const script of scriptsToEvaluateOnNewDocument)
-    frameTree.addScriptToEvaluateOnNewDocument(script);
+  frameTree.setInitScripts(initScripts);
 
   pageAgent = new PageAgent(messageManager, channel, frameTree);
 
   channel.register('', {
-    addScriptToEvaluateOnNewDocument(script) {
-      frameTree.addScriptToEvaluateOnNewDocument(script);
+    setInitScripts(scripts) {
+      frameTree.setInitScripts(scripts);
     },
 
     addBinding({worldName, name, script}) {
diff --git a/browser_patches/firefox-beta/juggler/protocol/BrowserHandler.js b/browser_patches/firefox-beta/juggler/protocol/BrowserHandler.js
index cbc1953fbe..31a59bae43 100644
--- a/browser_patches/firefox-beta/juggler/protocol/BrowserHandler.js
+++ b/browser_patches/firefox-beta/juggler/protocol/BrowserHandler.js
@@ -253,8 +253,8 @@ class BrowserHandler {
     await this._targetRegistry.browserContextForId(browserContextId).applySetting('scrollbarsHidden', nullToUndefined(hidden));
   }
 
-  async ['Browser.addScriptToEvaluateOnNewDocument']({browserContextId, script}) {
-    await this._targetRegistry.browserContextForId(browserContextId).addScriptToEvaluateOnNewDocument(script);
+  async ['Browser.setInitScripts']({browserContextId, scripts}) {
+    await this._targetRegistry.browserContextForId(browserContextId).setInitScripts(scripts);
   }
 
   async ['Browser.addBinding']({browserContextId, worldName, name, script}) {
diff --git a/browser_patches/firefox-beta/juggler/protocol/PageHandler.js b/browser_patches/firefox-beta/juggler/protocol/PageHandler.js
index 1f5e06a06d..46dc8265d8 100644
--- a/browser_patches/firefox-beta/juggler/protocol/PageHandler.js
+++ b/browser_patches/firefox-beta/juggler/protocol/PageHandler.js
@@ -334,8 +334,8 @@ class PageHandler {
     return await this._contentPage.send('scrollIntoViewIfNeeded', options);
   }
 
-  async ['Page.addScriptToEvaluateOnNewDocument'](options) {
-    return await this._contentPage.send('addScriptToEvaluateOnNewDocument', options);
+  async ['Page.setInitScripts']({ scripts }) {
+    return await this._pageTarget.setInitScripts(scripts);
   }
 
   async ['Page.dispatchKeyEvent'](options) {
diff --git a/browser_patches/firefox-beta/juggler/protocol/Protocol.js b/browser_patches/firefox-beta/juggler/protocol/Protocol.js
index 714b4fbda9..afb153d2f6 100644
--- a/browser_patches/firefox-beta/juggler/protocol/Protocol.js
+++ b/browser_patches/firefox-beta/juggler/protocol/Protocol.js
@@ -97,6 +97,10 @@ pageTypes.Clip = {
   height: t.Number,
 };
 
+pageTypes.InitScript = {
+  script: t.String,
+  worldName: t.Optional(t.String),
+};
 
 const runtimeTypes = {};
 runtimeTypes.RemoteObject = {
@@ -381,10 +385,10 @@ const Browser = {
         hidden: t.Boolean,
       }
     },
-    'addScriptToEvaluateOnNewDocument': {
+    'setInitScripts': {
       params: {
         browserContextId: t.Optional(t.String),
-        script: t.String,
+        scripts: t.Array(pageTypes.InitScript),
       }
     },
     'addBinding': {
@@ -802,10 +806,9 @@ const Page = {
         rect: t.Optional(pageTypes.Rect),
       },
     },
-    'addScriptToEvaluateOnNewDocument': {
+    'setInitScripts': {
       params: {
-        script: t.String,
-        worldName: t.Optional(t.String),
+        scripts: t.Array(pageTypes.InitScript)
       }
     },
     'navigate': {
diff --git a/browser_patches/firefox/BUILD_NUMBER b/browser_patches/firefox/BUILD_NUMBER
index 035d2fca14..17e02a52df 100644
--- a/browser_patches/firefox/BUILD_NUMBER
+++ b/browser_patches/firefox/BUILD_NUMBER
@@ -1,2 +1,2 @@
-1316
-Changed: aslushnikov@gmail.com Wed Jan 26 17:24:09 MST 2022
+1317
+Changed: pavel.feldman@gmail.com Mon 14 Feb 2022 03:52:34 PM PST
diff --git a/browser_patches/firefox/juggler/TargetRegistry.js b/browser_patches/firefox/juggler/TargetRegistry.js
index a12d9f96b3..0ec90afd1b 100644
--- a/browser_patches/firefox/juggler/TargetRegistry.js
+++ b/browser_patches/firefox/juggler/TargetRegistry.js
@@ -144,7 +144,7 @@ class TargetRegistry {
           return;
 
         return {
-          scriptsToEvaluateOnNewDocument: target.browserContext().scriptsToEvaluateOnNewDocument,
+          initScripts: target.browserContext().initScripts,
           bindings: target.browserContext().bindings,
           settings: target.browserContext().settings,
         };
@@ -361,6 +361,7 @@ class PageTarget {
     this._screencastRecordingInfo = undefined;
     this._dialogs = new Map();
     this.forcedColors = 'no-override';
+    this._pageInitScripts = [];
 
     const navigationListener = {
       QueryInterface: ChromeUtils.generateQI([Ci.nsIWebProgressListener, Ci.nsISupportsWeakReference]),
@@ -523,8 +524,13 @@ class PageTarget {
     await this._channel.connect('').send('ensurePermissions', {}).catch(e => void e);
   }
 
-  async addScriptToEvaluateOnNewDocument(script) {
-    await this._channel.connect('').send('addScriptToEvaluateOnNewDocument', script).catch(e => void e);
+  async setInitScripts(scripts) {
+    this._pageInitScripts = scripts;
+    await this.pushInitScripts();
+  }
+
+  async pushInitScripts() {
+    await this._channel.connect('').send('setInitScripts', [...this._browserContext.initScripts, ...this._pageInitScripts]).catch(e => void e);
   }
 
   async addBinding(worldName, name, script) {
@@ -708,7 +714,7 @@ class BrowserContext {
     this.forcedColors = 'no-override';
     this.reducedMotion = 'none';
     this.videoRecordingOptions = undefined;
-    this.scriptsToEvaluateOnNewDocument = [];
+    this.initScripts = [];
     this.bindings = [];
     this.settings = {};
     this.pages = new Set();
@@ -804,9 +810,9 @@ class BrowserContext {
     await Promise.all(Array.from(this.pages).map(page => page.updateViewportSize()));
   }
 
-  async addScriptToEvaluateOnNewDocument(script) {
-    this.scriptsToEvaluateOnNewDocument.push(script);
-    await Promise.all(Array.from(this.pages).map(page => page.addScriptToEvaluateOnNewDocument(script)));
+  async setInitScripts(scripts) {
+    this.initScripts = scripts;
+    await Promise.all(Array.from(this.pages).map(page => page.pushInitScripts()));
   }
 
   async addBinding(worldName, name, script) {
diff --git a/browser_patches/firefox/juggler/content/FrameTree.js b/browser_patches/firefox/juggler/content/FrameTree.js
index ccb49bf4e2..61ff889e75 100644
--- a/browser_patches/firefox/juggler/content/FrameTree.js
+++ b/browser_patches/firefox/juggler/content/FrameTree.js
@@ -73,15 +73,20 @@ class FrameTree {
     return this._runtime;
   }
 
-  addScriptToEvaluateOnNewDocument(script, worldName) {
-    worldName = worldName || '';
-    const existing = this._isolatedWorlds.has(worldName);
-    const world = this._ensureWorld(worldName);
-    world._scriptsToEvaluateOnNewDocument.push(script);
-    // FIXME: 'should inherit http credentials from browser context' fails without this
-    if (worldName && !existing) {
-      for (const frame of this.frames())
-        frame._createIsolatedContext(worldName);
+  setInitScripts(scripts) {
+    for (const world of this._isolatedWorlds.values())
+      world._scriptsToEvaluateOnNewDocument = [];
+
+    for (let { worldName, script } of scripts) {
+      worldName = worldName || '';
+      const existing = this._isolatedWorlds.has(worldName);
+      const world = this._ensureWorld(worldName);
+      world._scriptsToEvaluateOnNewDocument.push(script);
+      // FIXME: 'should inherit http credentials from browser context' fails without this
+      if (worldName && !existing) {
+        for (const frame of this.frames())
+          frame._createIsolatedContext(worldName);
+      }
     }
   }
 
diff --git a/browser_patches/firefox/juggler/content/PageAgent.js b/browser_patches/firefox/juggler/content/PageAgent.js
index 234c6b0801..c941cabca7 100644
--- a/browser_patches/firefox/juggler/content/PageAgent.js
+++ b/browser_patches/firefox/juggler/content/PageAgent.js
@@ -134,7 +134,6 @@ class PageAgent {
       this._runtime.events.onBindingCalled(this._onBindingCalled.bind(this)),
       browserChannel.register('page', {
         addBinding: ({ worldName, name, script }) => this._frameTree.addBinding(worldName, name, script),
-        addScriptToEvaluateOnNewDocument: ({script, worldName}) => this._frameTree.addScriptToEvaluateOnNewDocument(script, worldName),
         adoptNode: this._adoptNode.bind(this),
         crash: this._crash.bind(this),
         describeNode: this._describeNode.bind(this),
diff --git a/browser_patches/firefox/juggler/content/main.js b/browser_patches/firefox/juggler/content/main.js
index 04d1cf7c36..d471ab9553 100644
--- a/browser_patches/firefox/juggler/content/main.js
+++ b/browser_patches/firefox/juggler/content/main.js
@@ -84,11 +84,10 @@ function initialize() {
   if (!response)
     return;
   const {
-    scriptsToEvaluateOnNewDocument = [],
+    initScripts = [],
     bindings = [],
     settings = {}
   } = response || {};
-
   // Enforce focused state for all top level documents.
   docShell.overrideHasFocus = true;
   docShell.forceActiveState = true;
@@ -99,14 +98,13 @@ function initialize() {
   }
   for (const { worldName, name, script } of bindings)
     frameTree.addBinding(worldName, name, script);
-  for (const script of scriptsToEvaluateOnNewDocument)
-    frameTree.addScriptToEvaluateOnNewDocument(script);
+  frameTree.setInitScripts(initScripts);
 
   pageAgent = new PageAgent(messageManager, channel, frameTree);
 
   channel.register('', {
-    addScriptToEvaluateOnNewDocument(script) {
-      frameTree.addScriptToEvaluateOnNewDocument(script);
+    setInitScripts(scripts) {
+      frameTree.setInitScripts(scripts);
     },
 
     addBinding({worldName, name, script}) {
diff --git a/browser_patches/firefox/juggler/protocol/BrowserHandler.js b/browser_patches/firefox/juggler/protocol/BrowserHandler.js
index cbc1953fbe..31a59bae43 100644
--- a/browser_patches/firefox/juggler/protocol/BrowserHandler.js
+++ b/browser_patches/firefox/juggler/protocol/BrowserHandler.js
@@ -253,8 +253,8 @@ class BrowserHandler {
     await this._targetRegistry.browserContextForId(browserContextId).applySetting('scrollbarsHidden', nullToUndefined(hidden));
   }
 
-  async ['Browser.addScriptToEvaluateOnNewDocument']({browserContextId, script}) {
-    await this._targetRegistry.browserContextForId(browserContextId).addScriptToEvaluateOnNewDocument(script);
+  async ['Browser.setInitScripts']({browserContextId, scripts}) {
+    await this._targetRegistry.browserContextForId(browserContextId).setInitScripts(scripts);
   }
 
   async ['Browser.addBinding']({browserContextId, worldName, name, script}) {
diff --git a/browser_patches/firefox/juggler/protocol/PageHandler.js b/browser_patches/firefox/juggler/protocol/PageHandler.js
index 1f5e06a06d..46dc8265d8 100644
--- a/browser_patches/firefox/juggler/protocol/PageHandler.js
+++ b/browser_patches/firefox/juggler/protocol/PageHandler.js
@@ -334,8 +334,8 @@ class PageHandler {
     return await this._contentPage.send('scrollIntoViewIfNeeded', options);
   }
 
-  async ['Page.addScriptToEvaluateOnNewDocument'](options) {
-    return await this._contentPage.send('addScriptToEvaluateOnNewDocument', options);
+  async ['Page.setInitScripts']({ scripts }) {
+    return await this._pageTarget.setInitScripts(scripts);
   }
 
   async ['Page.dispatchKeyEvent'](options) {
diff --git a/browser_patches/firefox/juggler/protocol/Protocol.js b/browser_patches/firefox/juggler/protocol/Protocol.js
index 714b4fbda9..afb153d2f6 100644
--- a/browser_patches/firefox/juggler/protocol/Protocol.js
+++ b/browser_patches/firefox/juggler/protocol/Protocol.js
@@ -97,6 +97,10 @@ pageTypes.Clip = {
   height: t.Number,
 };
 
+pageTypes.InitScript = {
+  script: t.String,
+  worldName: t.Optional(t.String),
+};
 
 const runtimeTypes = {};
 runtimeTypes.RemoteObject = {
@@ -381,10 +385,10 @@ const Browser = {
         hidden: t.Boolean,
       }
     },
-    'addScriptToEvaluateOnNewDocument': {
+    'setInitScripts': {
       params: {
         browserContextId: t.Optional(t.String),
-        script: t.String,
+        scripts: t.Array(pageTypes.InitScript),
       }
     },
     'addBinding': {
@@ -802,10 +806,9 @@ const Page = {
         rect: t.Optional(pageTypes.Rect),
       },
     },
-    'addScriptToEvaluateOnNewDocument': {
+    'setInitScripts': {
       params: {
-        script: t.String,
-        worldName: t.Optional(t.String),
+        scripts: t.Array(pageTypes.InitScript)
       }
     },
     'navigate': {