Embedded App iframe blank - postMessage origin mismatch (Remix + Fly.io)

Shopify App Store
1

Error: Failed to execute ‘postMessage’ on ‘DOMWindow’:
The target origin (‘https://receipt-app-lzgr.fly.dev’)
does not match recipient window’s origin (‘https://admin.shopify.com’)

Environment:

Confirmed working:

  • AppProvider: isEmbeddedApp apiKey={apiKey} host={host} ✓
  • authenticate.admin(request) in loader ✓
  • CSP frame-ancestors https://admin.shopify.com ✓
  • App returns 200 ✓

Problem: URL shows ?country=JP but no ?host= parameter.
App Bridge targets fly.dev instead of admin.shopify.com.

How do we get ?host= parameter appended correctly?

2

Hey @yo_zu, this could be an issue with your deployment file.

Make sure your application_url in shopify.app.toml points to your Fly.io domain, then run shopify app deploy to push that config live.

After that, reinstall the app on your store to trigger a fresh OAuth flow with the correct ?host= parameter.

3

Hey @yo_zu are you still experiencing this issue, or can I mark this as solved?