refactor: Unify Sandbox Iframe Implementation Angular and Lit

.gitignore

@@ -22,6 +22,5 @@ coverage/
 a2a_agents/python/a2ui_agent/src/a2ui/assets/**/*.json
 ## new agent SDK path
 agent_sdks/python/src/a2ui/assets/**/*.json
-## Generated JS file from the strictly-typed `sandbox.ts`. 
-samples/client/angular/projects/mcp_calculator/public/sandbox_iframe/sandbox.js
-*.tsbuildinfo
+## Generated files for sandbox frame.
+samples/client/angular/projects/mcp_calculator/public/sandbox_iframe/

samples/client/angular/package.json

@@ -14,7 +14,7 @@
     "build:renderer": "cd ../../../renderers && for dir in 'web_core' 'markdown/markdown-it'; do (cd \"$dir\" && npm install && npm run build); done",
     "serve:agent:restaurant": "cd ../../agent/adk/restaurant_finder && uv run .",
     "demo:restaurant": "npm run build:renderer && concurrently -k -n \"AGENT,WEB\" -c \"magenta,blue\" \"npm run serve:agent:restaurant\" \"npm start -- restaurant\"",
-    "build:sandbox": "esbuild projects/mcp_calculator/public/sandbox_iframe/sandbox.ts --bundle --outfile=projects/mcp_calculator/public/sandbox_iframe/sandbox.js --format=esm --platform=browser"
+    "build:sandbox": "esbuild ../shared/sandbox_iframe/sandbox.ts --bundle --outfile=projects/mcp_calculator/public/sandbox_iframe/sandbox.js --format=esm --platform=browser --alias:@modelcontextprotocol/ext-apps/app-bridge=./node_modules/@modelcontextprotocol/ext-apps/dist/src/app-bridge.js && cp ../shared/sandbox_iframe/sandbox.html projects/mcp_calculator/public/sandbox_iframe/sandbox.html"
   },
   "prettier": {
     "printWidth": 100,

samples/client/angular/projects/mcp_calculator/src/a2ui-catalog/mcp-app.ts

@@ -143,10 +143,17 @@ export class McpApp
 
     window.addEventListener('message', this.messageHandler);
 
-    // Set src to trigger load AFTER listener is ready
-    // TODO: Make the sandbox URL configurable. To ensure CORS encapsulation, the sandbox
-    // should be served from a different origin than the host app.
-    const sandboxUrl = 'sandbox_iframe/sandbox.html';
+
+    // Check for query param to opt-out of origin toggle (for testing)
+    const urlParams = new URLSearchParams(window.location.search);
+    const disableSecuritySelfTest = urlParams.get('disable_security_self_test') === 'true';
+
+    const currentOrigin = window.location.origin;
+    let sandboxOrigin = currentOrigin;
+    let sandboxUrl = `${sandboxOrigin}/sandbox_iframe/sandbox.html`;
+    if (disableSecuritySelfTest) {
+      sandboxUrl += '?disable_security_self_test=true';
+    }
     this.iframeSrc.set(
       this.sanitizer.bypassSecurityTrustResourceUrl(sandboxUrl),
     );

samples/client/shared/sandbox_iframe/README.md

@@ -15,7 +15,7 @@ A2UI utilizes a **double-iframe isolation pattern** to run untrusted third-party
 
 Testing for any changes in this directory requires bringing up the relevant clients and servers.
 
-### Contact Multi-Surface Sample (Lit & ADK Agent)
+### 1. Contact Multi-Surface Sample (Lit & ADK Agent)
 
 This test verifies the sandbox with a Lit-based client and an ADK-based A2A agent.
 
@@ -26,3 +26,18 @@ This test verifies the sandbox with a Lit-based client and an ADK-based A2A agen
   - Path: `../../lit/contact/`
   - Command: `npm run dev` (requires building the Lit renderer first)
   - URL: `http://localhost:5173/`
+
+### 2. MCP Apps (Calculator) (Angular)
+
+This test verifies the sandbox with an Angular-based client, an MCP Proxy Agent, and a remote MCP Server.
+
+- **MCP Server (Calculator)**:
+  - Path: `../../../agent/mcp/mcp-apps-calculcator/`
+  - Command: `uv run .` (runs on port 8000)
+- **MCP Apps Proxy Agent**:
+  - Path: `../../../agent/adk/mcp_app_proxy/`
+  - Command: `uv run .` (requires `GEMINI_API_KEY` in `.env`)
+- **Angular Client App**:
+  - Path: `../../angular/`
+  - Command: `npm start -- mcp_calculator` (requires `npm run build:sandbox` and `npm install`)
+  - URL: [`http://localhost:4200/?disable_security_self_test=true`](http://localhost:4200/?disable_security_self_test=true)

samples/client/shared/sandbox_iframe/sandbox.ts

@@ -43,13 +43,19 @@ if (!document.referrer.match(ALLOWED_REFERRER_PATTERN)) {
 const EXPECTED_HOST_ORIGIN = new URL(document.referrer).origin;
 const OWN_ORIGIN = new URL(window.location.href).origin;
 
-// Security self-test: verify iframe isolation is working correctly.
-try {
-  window.top!.alert("If you see this, the sandbox is not setup securely.");
-  throw "FAIL";
-} catch (e) {
-  if (e === "FAIL") {
-    throw new Error("The sandbox is not setup securely.");
+// Check for query param to opt-out of security self-test (for testing)
+const urlParams = new URLSearchParams(window.location.search);
+const disableSelfTest = urlParams.get('disable_security_self_test') === 'true';
+
+if (!disableSelfTest) {
+  // Security self-test: verify iframe isolation is working correctly.
+  try {
+    window.top!.alert("If you see this, the sandbox is not setup securely.");
+    throw "FAIL";
+  } catch (e) {
+    if (e === "FAIL") {
+      throw new Error("The sandbox is not setup securely.");
+    }
   }
 }