Basically, don't use Intent flags you don't need to use. FLAG_ACTIVITY_NEW_TASK will launch the external activity in its own back stack according to its `launch

Basically, don't use Intent flags you don't need to use. FLAG_ACTIVITY_NEW_TASK will launch the external activity in its own back stack according to its `launchMode` rules. If you just launch the Intent with no flags, the default behavior is to add the activity to your own task, which is usually what you want. The other half of the equation is: don't override Back behavior unless you "own" the current task (it's rooted at one of your activities). When handling "Up" navigation and deep-links, you want Back to behave like "Up" and go to the logical parent of the current screen. When being launched in someone else's task, "Up" should launch a new task at the logical parent and "Back" should perform the default behavior (usually, Activity.finish()).