I can confirm this issue on zh-cn, zh-hk and zh-hant, but it shows different title for me, and maybe a little randomness.
It seems this issue doesn't affect another zh variants, it's weird.

See: T247493: Incorrect namespace displayed in ns4 page title on Chinese Wikiquote and Wikivoyage

Caused by commit d372626b97e83ec1f82b88e75fbaadf99ad2f89b for T358346

In T361177#9668179, @Func wrote:

Caused by commit d372626b97e83ec1f82b88e75fbaadf99ad2f89b for T358346

Can you explain how that patch is causing the problem? I fail to see the connection.

In T361177#9668964, @daniel wrote:

In T361177#9668179, @Func wrote:

Caused by commit d372626b97e83ec1f82b88e75fbaadf99ad2f89b for T358346

Can you explain how that patch is causing the problem? I fail to see the connection.

I have commented on gerrit, I will explain further below.

Previously, the wikiId (WikiMap::getCurrentWikiDbDomain()->getId()) would be used as the fallback for cache keyspace in case the wgCachePrefix config is an empty string. Without a keyspace, the message cache was messed up across sites, so this is a regression of T247562/T247493.

In T361177#9668971, @Func wrote:

Previously, the wikiId (WikiMap::getCurrentWikiDbDomain()->getId()) would be used as the fallback for cache keyspace in case the wgCachePrefix config is an empty string. Without a keyspace, the message cache was messed up across sites, so this is a regression of T247562/T247493.

So the fix would be this line? https://gerrit.wikimedia.org/r/c/mediawiki/core/+/1013392/9/includes/objectcache/ObjectCacheFactory.php#106

In T361177#9669232, @daniel wrote:

So the fix would be this line? https://gerrit.wikimedia.org/r/c/mediawiki/core/+/1013392/9/includes/objectcache/ObjectCacheFactory.php#106

Yes.

In T361177#9669239, @Func wrote:

In T361177#9669232, @daniel wrote:

So the fix would be this line? https://gerrit.wikimedia.org/r/c/mediawiki/core/+/1013392/9/includes/objectcache/ObjectCacheFactory.php#106

Yes.

Ok. @pmiazga and @Tgr are on it.

Change #1013392 had a related patch set uploaded (by Gergő Tisza; author: Derick Alangi):

[mediawiki/core@master] objectcache: Dependency inject the wiki ID & some improvements

https://gerrit.wikimedia.org/r/1013392

@Ladsgroup wrote in 2020 at https://gerrit.wikimedia.org/r/58057

Can this have some regression tests please?

Indeed. I've amended the patch to include a high-level regression test.

Change #1015204 had a related patch set uploaded (by Gergő Tisza; author: Derick Alangi):

[mediawiki/core@wmf/1.42.0-wmf.24] objectcache: Restore default keyspace for LocalServerCache service

https://gerrit.wikimedia.org/r/1015204

In T361177#9670370, @Krinkle wrote:

@Ladsgroup wrote in 2020 at https://gerrit.wikimedia.org/r/58057

Can this have some regression tests please?

Indeed. I've amended the patch to include a high-level regression test.

Correct link: https://gerrit.wikimedia.org/r/c/mediawiki/core/+/580577/1#message-2878732bc9cf7aaffabdac144196cb155784d678

I've been officially promoted to the position of Senior Cassandra in Residence.

Change #1015204 merged by jenkins-bot:

[mediawiki/core@wmf/1.42.0-wmf.24] objectcache: Restore default keyspace for LocalServerCache service

https://gerrit.wikimedia.org/r/1015204

Mentioned in SAL (#wikimedia-operations) [2024-03-28T18:54:24Z] <jhuneidi@deploy1002> Started scap: Backport for [[gerrit:1015204|objectcache: Restore default keyspace for LocalServerCache service (T358346 T361177)]]

Mentioned in SAL (#wikimedia-operations) [2024-03-28T18:56:52Z] <jhuneidi@deploy1002> tgr and jhuneidi: Backport for [[gerrit:1015204|objectcache: Restore default keyspace for LocalServerCache service (T358346 T361177)]] synced to the testservers (https://wikitech.wikimedia.org/wiki/Mwdebug)

Mentioned in SAL (#wikimedia-operations) [2024-03-28T19:28:24Z] <jhuneidi@deploy1002> Finished scap: Backport for [[gerrit:1015204|objectcache: Restore default keyspace for LocalServerCache service (T358346 T361177)]] (duration: 34m 00s)

Change #1013392 merged by jenkins-bot:

[mediawiki/core@master] objectcache: Restore default keyspace for LocalServerCache service

https://gerrit.wikimedia.org/r/1013392

Or is it just cache? I cannot reproduce it stably.

Can anyone check this problem, thank you. If it cannot be reproduced, you can close this freely.

https://zh.wikivoyage.org/wiki/Wikivoyage:Resources/%E4%B8%AD%E5%B1%B1%E5%85%AC%E4%BA%A4B1%E8%B7%AF%E7%BA%BF Can also reproduce this bug.

In T361177#9744616, @SD_hehua wrote:

Or is it just cache? I cannot reproduce it stably.

It appears that the parser cache expiry is 30 days, and the page fixed itself after I purged it, so we can close this safely. Search engine crawlers may still suffer from the remaining impact though.