Upstreaming from https://phabricator.wikimedia.org/T366118 , I can also reproduce locally:
**Steps to reproduce:**
1. Phorge at `03092ca422025df6bc394bee4cc2958c34ccef4f`, PHP 8.3.9 (irrelevant)
2. Configure https://phabricator.wikimedia.org/config/edit/notification.servers/ ; make sure `bin/aphlict` and `bin/phd` are running
3. Trigger a real-time notification in a Maniphest task by editing its status
4. In another browser window, in the Aphlict real-time notification in the bottom left corner, hover over the task link
**Actual outcome:**
```
Uncaught TypeError: spec is undefined
_newHovercardKey https://phab.wmfusercontent.org/res/contrastX/phabricator/2eeda9e0/core.pkg.js:1224
getCard https://phab.wmfusercontent.org/res/contrastX/phabricator/2eeda9e0/core.pkg.js:1213
<anonymous> https://phab.wmfusercontent.org/res/contrastX/phabricator/2eeda9e0/core.pkg.js:1253
pass https://phab.wmfusercontent.org/res/contrastX/phabricator/2eeda9e0/core.pkg.js:164
_dispatchProxy https://phab.wmfusercontent.org/res/contrastX/phabricator/2eeda9e0/core.pkg.js:159
dispatch https://phab.wmfusercontent.org/res/contrastX/phabricator/2eeda9e0/core.pkg.js:142
__rawEventQueue https://phab.wmfusercontent.org/res/contrastX/phabricator/98e6504a/rsrc/externals/javelin/core/init.js:19
```
**Comments:**
In https://we.phorge.it/source/phorge/browse/master/webroot/rsrc/js/core/behavior-hovercard.js$34 , `var node = e.getNode('hovercard')` is still successful.
`node` is something like `<a class="phui-handle" href="/T3509" data-sigil="hovercard" data-meta="11_1">`.
In the next line, `var data = e.getNodeData('hovercard').hovercardSpec` fails:
```
Uncaught Error: JX.Stratcom.getData(<node>): Tried to access data (block 11, index 1) that was not present. This probably means you are calling getData() before the block is provided by mergeData().
```
(`getNodeData : function(key)` simply does `return JX['Stratcom'].getData(this.getNode(key));` in `Event.js`.)