Replace `unload` event with `pagehide` — Chrome 146+ deprecation causes Permissions Policy violation

[gutenye]

Description

PowerSyncDatabase registers a window.addEventListener('unload', ...) listener when enableMultiTabs is true (the default):

powersync-js/packages/web/src/db/PowerSyncDatabase.ts

Lines 144 to 147 in f720d62

	if (this.resolvedFlags.enableMultiTabs && !this.resolvedFlags.externallyUnload) {
	this.unloadListener = () => this.close({ disconnect: false });
	window.addEventListener('unload', this.unloadListener);
	}

if (this.resolvedFlags.enableMultiTabs && !this.resolvedFlags.externallyUnload) {
  this.unloadListener = () => this.close({ disconnect: false });
  window.addEventListener('unload', this.unloadListener);
}

Starting with Chrome 146 (March 2026), Chrome is rolling out unload deprecation to all origins — currently 1% of page loads, reaching 100% by Chrome 153 (September 2026). When the deprecation is active, this triggers:

[Violation] Permissions policy violation: unload is not allowed in this document.

Reference: https://developer.chrome.com/docs/web-platform/deprecating-unload

Suggested Fix

Replace unload with pagehide, which is the recommended alternative and does not block bfcache:

if (this.resolvedFlags.enableMultiTabs && !this.resolvedFlags.externallyUnload) {
  this.unloadListener = () => this.close({ disconnect: false });
  window.addEventListener('pagehide', this.unloadListener);
}

And in close():

if (this.unloadListener) {
  window.removeEventListener('pagehide', this.unloadListener);
}

Current Workaround

Users can set externallyUnload: true and handle cleanup themselves:

const db = new PowerSyncDatabase({
  schema,
  database: { dbFilename: 'app.sqlite' },
  flags: { externallyUnload: true },
})

window.addEventListener('pagehide', () => {
  db.close({ disconnect: false })
})

Environment

• @powersync/web: 1.37.0
• Chrome 146+
• Affects all users with default enableMultiTabs: true flag

[simolus3]

Thanks for the report! I agree we should migrate away from unload events.

Replace unload with pagehide, which is the recommended alternative and does not block bfcache:

I don't think pagehide is appropriate because we use this.close() which is a terminal action. For pagehide events, it's possible for the tab to be resumed again and we'd then end up with a closed database.

Since this has been added in #72, I assume the original motivation for this was to unregister tabs from a sync worker as they close, so that the worker can pick another tab as a source for database connections.
We now use a more reliable (I hope) mechanism based on navigator locks to detect this, so I think we can just remove the unload listeners altogether.