Also replicable on the iOS app.

A few notes for investigating this issue:

• For the specific case of Chinese, the content service doesn't use Parsoid, but instead uses action=parse from regular MediaWiki. (because Parsoid still has some unresolved issues with Chinese variants)
  • And in fact, it was using action=mobileview until recently-ish when mobileview was deprecated, and it was switched to use action=parse. I'm guessing the content service was relying on certain structures in mobileview that are no longer available (or structured differently?) in action=parse.

In T370569#10027672, @Dbrant wrote:

• And in fact, it was using action=mobileview until recently-ish when mobileview was deprecated, and it was switched to use action=parse. I'm guessing the content service was relying on certain structures in mobileview that are no longer available (or structured differently?) in action=parse.

IIRC there were some changes to ToC around the time when Vector 2022 was deployed to Chinese Wikipedia. I don't know if this is related.

Is there a quick fix to this? This is an experience degradation for Chinese users.

@Diskdance hugely appreciate that context. Looks like it might be T306862 as a possible root cause and there were some changes that occurred about a month ago.

T306862 has been closed for a year. I'm not aware of any recent changes to the TOC code.

Is there something that can be reverted to fix this issue?

Change #1059165 had a related patch set uploaded (by Dbrant; author: Dbrant):

[mediawiki/services/mobileapps@master] [WIP] Fix section/heading formatting for non-parsoid requests.

https://gerrit.wikimedia.org/r/1059165

Hello @Dbrant, can we push this forward? We have received multiple complaints in user groups and social media platforms.

Change #1059165 merged by jenkins-bot:

[mediawiki/services/mobileapps@master] Fix section/heading formatting for non-parsoid requests.

https://gerrit.wikimedia.org/r/1059165