I did saw browser.tabs.onUpdated being triggered however.

Can you please be more explicit about the problem you are seeing? What are the steps to reproduce this problem? Can you attach a sample of WebExtension code that reproduces this problem? I tested this myself by closing a tab and then restoring it via History -> Recently Closed Tabs, and I did get an onCreated event.

I'm currently using https://github.com/eoger/tabcenter-redux (which is not very minimal). STR: 1. Start the browser. 2. Open 2-3 tabs. 3. Crash the browser. 4. Start the browser again. 5. about:sessionrestore is shown, click the "Restore" button. Expected: 5. Tabs are present in the sidebar because onCreated listeners were called. Actual: 5. Tabs are not present, onCreated is not triggered.

Sounds like a timing issue where the listeners are not registered before the tabs are restored, or perhaps we're not listening for the correct event. I'll leave this to be discussed in the weekly triage next week.

> Sounds like a timing issue where the listeners are not registered before the tabs are restored I leave plenty of time for the extension to load before clicking the "Restore" button.

Need the addEventListener("SSTabRestoring" ... in onCreated?

It looks like the problem is resolved, I can't reproduce anymore.

WFM for now in 56.0a1 (2017-07-23) x86 with Tab Center Redux 0.4.0.