App Bug Causing Streak Loss
There's a bug in the app that causes you to lose your streak. If you set the goal XP to 1 on the website and then use the app even once, your streak will be gone if you don't do at least 10 XP every day on the website.
To reproduce this issue: 1. Set goal XP to 1/day on the website. 2. Use the app to do a lesson. 3. On the website you'll see goal XP is now 10/day.
I understand the reasoning behind the goal XP differences between the website and the app. The goal of 1 XP per day makes sense on the website since it's the minimum XP you can get on the website. You can get 1 XP by translating a sentence. The goal of 10 XP makes sense on the app since it's the minimum XP you can get on the app. You can get 10 XP by completing one lesson with three mistakes. The website and app sync the XP goal whenever changed and boom, now you have a bug.
One solution would be maintaining separate goal XP values for the website and the app. But, I think that'd be difficult for Duolingo to do because they're most likely keeping track of XP on the backend to determine streak and not separately maintaining streak count. A solution that may be easier to implement is adding a goal XP option of 1 to the app. Sure you can't actually get 1 XP in the app but what does that matter to the end user? It's far less confusing than losing a streak for no apparent reason.
Disclaimer: I have the Android app so I'm not sure if it's also occurring in the iOS app as well but it seems probable considering Duolingo usually maintains feature parity between the two.
I have not seen this problem. I have my goal set to 1 XP and I use the iOS app to do lessons. On the web, I always see my daily performance as x/1. Admittedly I usually do at least one new lesson per day so my actual XP ranges from 10 to 13 but my goal is always 1 on the website.