Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0 With Nightly moving to version 57 I decided to try to get rid of my final legacy extensions, among them "Session Manager". While I probably really should move some of my open tabs to bookmarks, for now my session consists of about ~525 tabs, spread pretty much equally among two windows. As expected, after uninstalling all legacy addons, the initial move to the internal Session Restore feature worked perfectly. However, after a restart the tab details for my second window were not restored, i.e. the expected number of tabs was created, the right tab was selected, but all tabs were completely empty and all but the current tab with an empty title, while the current tab has "New Tab" for a title. Checking the Browser Console revealed the following stacktrace: TypeError: access to strict mode caller function is censored Stack trace: NS_ASSERT@resource://gre/modules/debug.js:50:7 restoreTab@resource:///modules/sessionstore/SessionStore.jsm:3594:5 restoreTabs@resource:///modules/sessionstore/SessionStore.jsm:3581:7 ssi_restoreWindow@resource:///modules/sessionstore/SessionStore.jsm:3410:7 ssi_restoreWindows@resource:///modules/sessionstore/SessionStore.jsm:3526:5 initializeWindow@resource:///modules/sessionstore/SessionStore.jsm:1157:11 onBeforeBrowserWindowShown/<@resource:///modules/sessionstore/SessionStore.jsm:1306:9 promise callback*onBeforeBrowserWindowShown@resource:///modules/sessionstore/SessionStore.jsm:1291:5 ssi_observe@resource:///modules/sessionstore/SessionStore.jsm:758:9 onLoad@chrome://browser/content/browser.js:1351:5 onload@chrome://browser/content/browser.xul:1:1 After closing Firefox, restoring the session backup and making a profile copy, I tried to track down a cause in my profile. But even after uninstalling all AddOns, be they Legacy or WebExtension, I could still reproduce the bug. I failed to reproduce the bug when starting normally but with the "-jsconsole" parameter. I failed to reproduce the bug when starting in safe mode. I haven't yet tried to reduce the session and reproduce again. My attempts at reproducing this bug in a completely fresh profile, during a normal start, have failed until now. The first start restores without an issue, the second start clears my session completely except for the pinned tabs in my primary window, without any obvious errors in the Browser Console. A different bug? TL;DR: STR: - Start firefox ER: - Firefox restores the previous session completely AR: - Firefox fails to restore the session completely (missing tab content/details in the secondary window) and logs the above stack trace in the Browser Console. If there's anything else you guys need like logs from debugging options set via parameters/properties, feel free to ask.

(In reply to Asteaguinity from comment #0) > I failed to reproduce the bug when starting normally but with the > "-jsconsole" parameter. Scratch that, I just reproduced despite using the "-jsconsole" parameter. So much for that workaround...

Forward duping to Bug 1388628 with more activity.