Client_app_sdk - iframe postMessage failing in playwright - INC-4471

so we’re trying to reliably post messages to the agent desktop iframe from our playwright tests - basically automating some ui interactions that can’t be done via the architect api. it’s… not going great.

the setup is pretty standard - we have a playwright test that navigates to a gc page with the agent desktop embedded, gets the iframe handle, and then tries to send a message. we’re on client_app_sdk@4.2.1. typescript, page object model, the whole deal.

the message is a simple string - just “testmessage” - and we’re sending it with iframe.postMessage('testmessage', '*'). the desktop should be listening for messages. and it is… sometimes.

most of the time it just does jack all. no errors in the console, no sign that the message even arrived. it’s like it’s being swallowed. occasionally (like 1 in 10 runs) it works fine. which makes it even more annoying.

we’ve checked the obvious stuff - iframe is loaded, we’re getting a valid iframe handle, the targetOrigin is correct (* for now, just trying to get it working at all). the desktop app doesn’t seem to be blocking anything in the console.

what’s weird is when it does work, the console shows the usual postMessage log. when it fails, nothing. absolutely nothing.

the architect flow is just a basic call control flow. it doesn’t have anything fancy going on. we don’t think it’s the flow itself, because the desktop loads and sometimes responds. it’s the consistency that’s the problem.

also, running the tests locally vs in ci (github actions) makes no difference. same flaky behavior. i even tried adding a page.waitForTimeout(500) before the postMessage call, thinking it might be a timing issue. still no good.

anyone else running into this? is there some weird race condition or hidden setting i’m missing? i swear it’s not the test, and it’s not the network. i’ve been down those rabbit holes already.

maybe the sdk is doing something under the hood that’s interfering? it’s just a hunch.

the tests are all failing consistently now.

clientAppSdk.events.on('frame:loaded', (event) => {
 const iframe = event.detail.frame;
 iframe.contentWindow.postMessage({ type: 'test_message' }, '*');
});

clientAppSdk.events.on isn’t firing consistently - it’s a timing issue with the iframe load. Try listening for the frame:loaded event instead of assuming the iframe is ready when the page loads; the wildcard * in postMessage is a security risk, but it’ll work for testing.

clientAppSdk.events.on('app:ready', () => {
 const iframe = document.querySelector('iframe'); // or however you select it
 if (iframe) {
 iframe.contentWindow.postMessage({ type: 'test_message' }, '*');
 } else {
 console.warn('iframe not found');
 }
});

oh gosh, I think is totally right about the timing thing, sorry if I’m being super basic here! I was messing with this exact issue when we were trying to auto-reply to emails based on certain keywords and the iframe just wouldn’t cooperate.

I usually find that waiting for app:ready is a bit more reliable than frame:loaded. It feels like the whole thing - the application and the iframe - is set up before you try to send the message. You’ll want to grab the iframe element itself, though. I’m still getting confused about selectors sometimes - is that what document.querySelector does? It’s like, finds the iframe? Anyway, make sure your selector is right.

Also, it’s a really dumb thing to check but…does the iframe actually exist when you’re trying to send the message? I keep forgetting to put in a check like that, and then I get errors that are super hard to debug. The console.warn is just to help with that.

I hope that helps! Let me know if it doesn’t, and I’ll try to poke around a bit more. It’s probably something obvious that I’m missing.

Cause: clientAppSdk.events.on is susceptible to race conditions with iframe loading - the earlier reply is correct about that. Also, the wildcard origin * is a security risk.

Solution: Listen for the load event on the iframe itself, not a generic frame load. Specify the expected origin.

{
 "origin": "https://your-genesyscloud-domain.example.com"
}

Okay, so building on what As noted above about the iframe’s load event - and sorry if this is basic, I’m still getting used to all the event terminology - you’ll want to grab the actual contentWindow after the load completes. We had a similar issue where the postMessage call was happening before the iframe was fully initialized, and it was… frustrating.

Here’s how we’re doing it in our React component:

const iframe = document.getElementById('gc-desktop-iframe'); // Assuming you have an ID
iframe.addEventListener('load', () => {
 const contentWindow = iframe.contentWindow;
 if (contentWindow) {
 contentWindow.postMessage({ type: 'test_message' }, 'https://your-genesyscloud-domain.example.com');
 } else {
 console.warn("Iframe contentWindow is not yet available.");
 }
});

Just a heads up: double-check that the domain in the origin matches your Genesys Cloud region exactly. We spent way too long debugging that one.