=== Repro Steps
Run this command a number of times and observe the title of the page in the output. Using only the title here for simplicity, the whole page has the same problem.
```curl -sv -H "Accept-Language: zh-hant" https://zh.wikipedia.org/api/rest_v1/page/mobile-html/2019冠状病毒病疫情 | egrep -ohi '(?:<h1 data-id="0" class="pcs-edit-section-title">)[^<]+'```
=== Expected results
The language is zh-hant every time
=== Actual results
Sometimes the language is zh-hans
Here's an example request with the correct variant (only including the relevant headers):
```
> GET /api/rest_v1/page/mobile-html/2019冠状病毒病疫情 HTTP/2
> Host: zh.wikipedia.org
> User-Agent: curl/7.64.1
> Accept: */*
> Accept-Language: zh-hant
...
< content-language: zh-hant
< date: Fri, 03 Apr 2020 09:57:33 GMT
< x-request-id: b1f4750b-ab56-451a-8e18-2ac07882bf19
< server: restbase1026
< etag: W/"58953070/8a350660-7591-11ea-8066-dfe689212e6d"
< age: 1
< x-cache: cp1075 miss, cp1083 pass
< x-cache-status: pass
< server-timing: cache;desc="pass"
```
And one with the incorrect variant:
```
> GET /api/rest_v1/page/mobile-html/2019冠状病毒病疫情 HTTP/2
> Host: zh.wikipedia.org
> User-Agent: curl/7.64.1
> Accept: */*
> Accept-Language: zh-hant
...
< content-language: zh
< date: Fri, 03 Apr 2020 09:48:47 GMT
< x-request-id: 0f208c8f-f961-4e63-88ad-0e102d082f36
< server: restbase1019
< etag: W/"58953070/503dcfb0-7590-11ea-9def-6cf346db56c5"
< age: 529
< x-cache: cp1083 hit, cp1083 pass
< x-cache-status: hit-local
< server-timing: cache;desc="hit-local"
```
When running it against the mobileapps service locally, I see the correct title every time:
```curl -sv -H "Accept-Language: zh-hant" http://localhost:8888/zh.wikipedia.org/v1/page/mobile-html/2019%E5%86%A0%E7%8A%B6%E7%97%85%E6%AF%92%E7%97%85%E7%96%AB%E6%83%85 | egrep -ohi '(?:<h1 data-id="0" class="pcs-edit-section-title">)[^<]+'```
== Original bug report:
This can be reproduced on the Wikipedia Android beta app.
Please note that this issue does not happen on every `zh.wiki` articles.
=== Steps to reproduce ===
1. Open article: [[ https://zh.wikipedia.org/wiki/2019%E5%86%A0%E7%8A%B6%E7%97%85%E6%AF%92%E7%97%85%E7%96%AB%E6%83%85 | 嚴重特殊傳染性肺炎疫情]] in Traditional Chinese
2. Refresh the page after it's fully loaded.
3. You will see the article's variant is changed which includes the article content, ToC data, and footer.
DEMO: https://www.youtube.com/watch?v=_gZ8lMg5O60