Custom Protocol Handler for Isolated Web App Not Working After ChromeOS Update (May be).

Hello,

After my ChromeOS device updated on September 25, 2025 (though not certain this is the direct cause), custom protocol handlers (web+collab:// and collab://) for my Isolated Web App (IWA) stopped working. Triggering these links in Chrome no longer launches the app—they simply do nothing. This was functional until two days ago.

 

App Type: Isolated Web App (IWA)

Manifest excerpt:

{
  "name": "someapp",
  "id": "/",
  "short_name": "some-app",
  "version": "0.1.0",
  "update_manifest_url": "https://github.com/--some-repo--/iwa-release/releases/latest/download/update.json",
  "icons": [
    { "src": "/192x192.png", "sizes": "192x192", "type": "image/png", "purpose": "any maskable" },
    { "src": "/144x144.png", "sizes": "144x144", "type": "image/png", "purpose": "any maskable" }
  ],
  "start_url": "/",
  "scope": "/",
  "display": "standalone",
  "display_override": ["borderless"],
  "background_color": "#ffffff",
  "theme_color": "#3B82F6",
  "isolated_storage": true,
  "permissions_policy": {
    "cross-origin-isolated": ["self"],
    "direct-sockets": ["self"],
    "controlled-frame": ["self"],
    "window-management": ["self"],
    "display-capture": ["self"],
    "all-screens-capture": ["self"]
  },
  "protocol_handlers": [
    { "protocol": "web+collab", "url": "/?data=%s" },
    { "protocol": "collab", "url": "/?data=%s" }
  ],
  "launch_handler": { "client_mode": "navigate-existing" },
  "window_controls_overlay": { "enabled": true }
}

 

Recent Changes

Enrolled new users in Google enterprise

Updated the app manifest (see above)

ChromeOS device updated on 2025-09-25

 

Observed Behavior

Protocol links for both my IWA (web+collab://) and the official ChromeOS IWA SINK app (web+cf://) no longer launch the installed apps

No errors, warnings, or manifest validation issues

Clicking protocol links does nothing (both in managed and unmanaged device states)

 

What I've Tried

Checked manifest and protocol handler registration

Tested after app reinstall and in different device policy states

Reviewed enterprise Admin Console for new/relevant policy changes

Searched for protocol handler or IWA-related changelogs/updates

Compared behavior with different protocol URLs and schemes

 

Questions

Is anyone else experiencing protocol handler breakages for IWAs since a recent Chrome/ChromeOS update?

Have there been changes in policy, manifest format, or handler registration that could affect this?

Any ideas or diagnostics for discovering if Chrome or policy is blocking/ignoring the protocol?

Any leads, recent experiences, or possible workarounds would be greatly appreciated