diff --git a/packages/playwright-core/src/server/bidi/bidiBrowser.ts b/packages/playwright-core/src/server/bidi/bidiBrowser.ts
index cc3fbc0562..0c658a82b4 100644
--- a/packages/playwright-core/src/server/bidi/bidiBrowser.ts
+++ b/packages/playwright-core/src/server/bidi/bidiBrowser.ts
@@ -195,8 +195,12 @@ export class BidiBrowserContext extends BrowserContext {
     this._authenticateProxyViaHeader();
   }
 
+  private _bidiPages() {
+    return [...this._browser._bidiPages.values()].filter(bidiPage => bidiPage._browserContext === this);
+  }
+
   pages(): Page[] {
-    return [];
+    return this._bidiPages().map(bidiPage => bidiPage._initializedPage).filter(Boolean) as Page[];
   }
 
   async newPageDelegate(): Promise<PageDelegate> {
@@ -269,11 +273,13 @@ export class BidiBrowserContext extends BrowserContext {
   }
 
   async doSetHTTPCredentials(httpCredentials?: types.Credentials): Promise<void> {
+    this._options.httpCredentials = httpCredentials;
+    for (const page of this.pages())
+      await (page._delegate as BidiPage).updateHttpCredentials();
   }
 
   async doAddInitScript(initScript: InitScript) {
-    // for (const page of this.pages())
-    //   await (page._delegate as WKPage)._updateBootstrapScript();
+    await Promise.all(this.pages().map(page => (page._delegate as BidiPage).addInitScript(initScript)));
   }
 
   async doRemoveNonInternalInitScripts() {
diff --git a/packages/playwright-core/src/server/bidi/bidiPage.ts b/packages/playwright-core/src/server/bidi/bidiPage.ts
index 9ecb5c789b..f06924d70f 100644
--- a/packages/playwright-core/src/server/bidi/bidiPage.ts
+++ b/packages/playwright-core/src/server/bidi/bidiPage.ts
@@ -47,6 +47,7 @@ export class BidiPage implements PageDelegate {
   readonly _browserContext: BidiBrowserContext;
   readonly _networkManager: BidiNetworkManager;
   _initializedPage: Page | null = null;
+  private _initScriptIds: string[] = [];
 
   constructor(browserContext: BidiBrowserContext, bidiSession: BidiSession, opener: BidiPage | null) {
     this._session = bidiSession;
@@ -92,9 +93,14 @@ export class BidiPage implements PageDelegate {
       this.updateHttpCredentials(),
       this.updateRequestInterception(),
       this._updateViewport(),
+      this._addAllInitScripts(),
     ]);
   }
 
+  private async _addAllInitScripts() {
+    return Promise.all(this._page.allInitScripts().map(initScript => this.addInitScript(initScript)));
+  }
+
   potentiallyUninitializedPage(): Page {
     return this._page;
   }
@@ -318,15 +324,20 @@ export class BidiPage implements PageDelegate {
   }
 
   async addInitScript(initScript: InitScript): Promise<void> {
-    await this._updateBootstrapScript();
+    const { script } = await this._session.send('script.addPreloadScript', {
+      // TODO: remove function call from the source.
+      functionDeclaration: `() => { return ${initScript.source} }`,
+      // TODO: push to iframes?
+      contexts: [this._session.sessionId],
+    });
+    if (!initScript.internal)
+      this._initScriptIds.push(script);
   }
 
   async removeNonInternalInitScripts() {
-    await this._updateBootstrapScript();
-  }
-
-  async _updateBootstrapScript(): Promise<void> {
-    throw new Error('Method not implemented.');
+    const promises = this._initScriptIds.map(script => this._session.send('script.removePreloadScript', { script }));
+    this._initScriptIds = [];
+    await Promise.all(promises);
   }
 
   async closePage(runBeforeUnload: boolean): Promise<void> {