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Fix sandbox proxy ready detection in simple-host example (#47)

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Replace Zod schema's internal _def.value access with a direct string
literal. The previous approach failed due to multiple Zod instances
being bundled, causing schema.shape.method._def.value to return
undefined.

The fix uses a typed string constant that provides compile-time safety
via McpUiSandboxProxyReadyNotification["method"] while avoiding runtime
dependency on Zod internals.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Jonathan Hefner 2025-12-01 14:07:40 -06:00 • committed by GitHub
commit 484768c3d1
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1 changed files with 5 additions and 6 deletions
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11
examples/simple-host/src/app-host-utils.ts
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@ -1,4 +1,4 @@
import { McpUiSandboxProxyReadyNotificationSchema } from "@modelcontextprotocol/ext-apps";
import type { McpUiSandboxProxyReadyNotification } from "@modelcontextprotocol/ext-apps";
import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { Tool } from "@modelcontextprotocol/sdk/types.js";
@ -8,6 +8,9 @@ export async function setupSandboxProxyIframe(sandboxProxyUrl: URL): Promise<{
iframe: HTMLIFrameElement;
onReady: Promise<void>;
}> {
const SANDBOX_PROXY_READY_METHOD: McpUiSandboxProxyReadyNotification["method"] =
"ui/notifications/sandbox-proxy-ready";
const iframe = document.createElement("iframe");
iframe.style.width = "100%";
iframe.style.height = "600px";
@ -18,11 +21,7 @@ export async function setupSandboxProxyIframe(sandboxProxyUrl: URL): Promise<{
const onReady = new Promise<void>((resolve, _reject) => {
const initialListener = async (event: MessageEvent) => {
if (event.source === iframe.contentWindow) {
if (
event.data &&
event.data.method ===
McpUiSandboxProxyReadyNotificationSchema.shape.method._def.value
) {
if (event.data && event.data.method === SANDBOX_PROXY_READY_METHOD) {
window.removeEventListener("message", initialListener);
resolve();
}