To decide whether to show the checkbox in about:preferences, we actually rely on both the value of the `browser.startup.windowsLaunchOnLogin.enabled` pref _and_ [this check](https://searchfox.org/mozilla-central/source/browser/components/preferences/main.js#434-443). This isn't a perfect match to the targeting used for [the related in-tree messages](https://searchfox.org/mozilla-central/search?q=browser.startup.windowsLaunchOnLogin.enabled&path=*asrouter*&case=false®exp=false). Another possible route for investigation: It looks like we [disabled launch on login for Windows builds in Fx127](https://phabricator.services.mozilla.com/D207595), then [reenabled it in Fx128](https://bugzilla.mozilla.org/show_bug.cgi?id=1893341). It looks like [the messages about this feature](https://searchfox.org/mozilla-central/search?q=browser.startup.windowsLaunchOnLogin.enabled&path=*asrouter*&case=false®exp=false) might not have recieved the corresponding targeting update that would exclude MSIX builds until Fx128.
Bug 1909888 Comment 3 Edit History
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Another possible route for investigation: It looks like we [disabled launch on login for Windows builds in Fx127](https://phabricator.services.mozilla.com/D207595), then [reenabled it in Fx128](https://bugzilla.mozilla.org/show_bug.cgi?id=1893341). It looks like [the messages about this feature](https://searchfox.org/mozilla-central/search?q=browser.startup.windowsLaunchOnLogin.enabled&path=*asrouter*&case=false®exp=false) might not have recieved the corresponding targeting update that would exclude MSIX builds until Fx128.