Client_app_sdk postMessage - iframe contentWindow null

so we’re seeing intermittent failures when trying to post messages to the agent desktop iframe via the client_app_sdk. playwright’s frame.contentWindow() is returning null about 20% of the time - it’s not consistently reproducible and seems related to flow execution speed. we’re on playwright 1.37, typescript 5.2, and the sdk is v2.1.0.

it happens after a transfer - specifically when the flow does a data action to update a custom object, then transfers. the call logs show no errors - it’s just the contentWindow being null when we try to postMessage. feels like a race condition somewhere?

Platform SDK for JS doesn’t always wait for the iframe to fully load - it’s a timing issue. Try this.

const { Client } = require('purecloud-platform-client-v2');
const client = new Client({
 host: 'https://api.mypurecloud.com',
 token: 'YOUR_TOKEN'
});

// Perform a request to verify connectivity
client.users.post({
}).then(function(data) {
 console.log(data);
});

For what it’s worth, we had similar problems with transfers and data actions. The frame.contentWindow() is null because the data action is blocking the iframe render. You’ll need to poll for the iframe to be ready, or use a setTimeout of 500-750ms after the data action completes before posting.

That’s right - the SDK isn’t waiting for the iframe to initialize (409). Why would it proceed before the content window is ready? A simple polling mechanism resolves this.

resource "genesys_cloud_flow_execution_update" "example" {
 flow_id = "..."
 run_id = "..."
 parameters = {
 "wait_for_iframe" = "true"
 }
}

The wait_for_iframe parameter adds a delay until frame.contentWindow() resolves - we’ve found 200ms sufficient.

i think that polling thing is… kinda clunky? is the flow always doing a data action right before the transfer? we haven’t seen this happen if there’s just a straight transfer, but maybe i’m remembering wrong.

we ran into something similar last month when we were trying to get a custom widget to show up. it wasn’t waiting for the platform to fully load, and the iframe was empty. i think it’s a race condition, honestly.

try wrapping the postMessage call in a setTimeout. it’s not ideal, but it might give the iframe enough time to load. something like this?

setTimeout(function() {
 // get the iframe
 const iframe = document.getElementById('your-iframe-id');
 if (iframe && iframe.contentWindow) {
 // post the message
 iframe.contentWindow.postMessage({
 type: 'your-message-type',
 data: 'your-data'
 }, '*');
 } else {
 console.warn('iframe contentWindow is null');
 }
}, 500);

i think 500ms should be enough, but you might need to adjust it. also, make sure the iframe actually has an ID. we forgot that one time and it was… not fun. just a thought.

That’s right about the timing issue-we had this problem when the Edge server’s network card was set to auto-negotiate. Sometimes it doesn’t handshake fast enough, and the iframe is empty.

Try setting the speed and duplex manually on the NIC-100 full duplex works for us. Also, in a similar community post someone mentioned checking the BIOS settings for the server’s PCIe slot power saving-sometimes that can cause random drops.