The issue can also be seen on the German Wikipedia: e.g.

• https://de.wikipedia.org/wiki/Vorlage:Zeitleiste_Bundespr%C3%A4sidenten_(Deutschland)
• https://de.wikipedia.org/wiki/Vorlage:Zeitleiste_Ligazugeh%C3%B6rigkeit_FC_Ingolstadt_04
• https://de.wikipedia.org/wiki/Vorlage:Zeitleiste_Bayerische_Ministerpr%C3%A4sidenten_seit_1945

Interestingly, the first timeline („Vorlage:Zeitleiste Bundespräsidenten (Deutschland)“) hasn't been edited since 2022, so it doesn't only affects timelines which were edited recently.

It looks like the example article's timeline has re-appeared since this June 4 edit. I don't know if that's a helpful clue or not. (I'd guess the original problem is something more back-end, than that.)

According to the diff and the HTML comment which was added by OreoStar-fait it seems to have something to do with wiki links.

I can confirm this as well: If I remove all links from the timelines mentioned above in deWP the timelines are working again.

Hmm ...

The timeline extension tries to store an additional .map file for timelines with wikilinks. That must be the thing that is failing to save properly.

I think Timeline files go to Swift, so something there must have changes. Tagging SRE accordingly.

In T428063#11986815, @GuardianOfArcadia wrote:

According to the diff and the HTML comment which was added by OreoStar-fait it seems to have something to do with wiki links.

I can confirm this as well: If I remove all links from the timelines mentioned above in deWP the timelines are working again.

What’s interesting is that compared to the German wiki one which hasn’t been edited since 2022, timelines on the English Wiki that haven’t been edited since the problem first arose still manage to correctly display the timeline with the wiki links. Wonder why that’s the case since if it’s affecting other wikis then all timelines not yet edited on the English wiki with links should’ve broken, but they haven’t. Something to note as well.

The first German one uses "#tag:timeline" and "till:{{#time: d/m/Y}}". This cases the timeline to be dynamic, and be considered "edited" every day. The third German one does the same. The second German was was recenty edited.

So is it resolved? I've seen that it's been fixed.

In T428063#11987314, @TheEssay26 wrote:

So is it resolved? I've seen that it's been fixed.

It’s not, on newer timelines edited since the bug started wikilinks were removed as a temp fix until the issues resolved.

In T428063#11986831, @Pppery wrote:

Hmm ...

The timeline extension tries to store an additional .map file for timelines with wikilinks. That must be the thing that is failing to save properly.

I think Timeline files go to Swift, so something there must have changes. Tagging SRE accordingly.

Note: The cause is known and described on a private task.

Also happens on Chinese wiki, both <timeline> and {{#tag:timeline}} format code, will invoke “Timeline error: Cannot store output files." once edited. eg,

• https://zh.wikipedia.org/wiki/Template:%E9%95%B7%E5%BE%81%E7%B3%BB%E5%88%97%E9%81%8B%E8%BC%89%E7%81%AB%E7%AE%AD%E6%99%82%E9%96%93%E8%BB%B8
• https://zh.wikipedia.org/wiki/Template:%E7%A5%9E%E8%88%9F%E9%A3%9E%E8%88%B9%E6%97%B6%E9%97%B4%E7%BA%BF

This is (presumably) happening on all WMF wikis - "it's also happening on my wiki" comments aren't helpful.

Will anything need to be done manually on existing pages experiencing this issue? Or once the source code issue is resolved, suddenly all of broken ones will generate without an additional touch?

Either way, I'm making a note of these that are currently experiencing it:
https://en.wikipedia.org/wiki/Template:Timeline_of_Kindle_models
https://en.wikipedia.org/wiki/Template:Surface_timeline
https://en.wikipedia.org/wiki/Template:Timeline_Windows
https://en.wikipedia.org/wiki/Template:Timeline_of_Mac_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_Apple_Inc._products
https://en.wikipedia.org/wiki/Template:Timeline_of_iOS_and_derivative_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_iPad_models
https://en.wikipedia.org/wiki/Template:Complete_timeline_of_Mac_models
https://en.wikipedia.org/wiki/Template:Timeline_of_iOS_and_derivative_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_Mac_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_iPhone_models
https://en.wikipedia.org/wiki/Template:Timeline_of_Power_Macintosh,_Pro,_and_Studio_models
https://en.wikipedia.org/wiki/Template:Timeline_of_portable_Macintoshes
https://en.wikipedia.org/wiki/Template:Timeline_of_Mac_model_families
https://en.wikipedia.org/wiki/Template:Timeline_of_iMac_models
https://en.wikipedia.org/wiki/Template:Timeline_of_Macintosh_servers
https://en.wikipedia.org/wiki/Template:Timeline_of_compact_iPod_models
https://en.wikipedia.org/wiki/Template:Timeline_of_iOS_and_derivative_operating_systems

If manual touching is required I can go back later once there's an update here. Just didn't re-find these if they do require an effort.

In T428063#12007957, @Colinstu wrote:

Will anything need to be done manually on existing pages experiencing this issue? Or once the source code issue is resolved, suddenly all of broken ones will generate without an additional touch?

Either way, I'm making a note of these that are currently experiencing it:
https://en.wikipedia.org/wiki/Template:Timeline_of_Kindle_models
https://en.wikipedia.org/wiki/Template:Surface_timeline
https://en.wikipedia.org/wiki/Template:Timeline_Windows
https://en.wikipedia.org/wiki/Template:Timeline_of_Mac_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_Apple_Inc._products
https://en.wikipedia.org/wiki/Template:Timeline_of_iOS_and_derivative_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_iPad_models
https://en.wikipedia.org/wiki/Template:Complete_timeline_of_Mac_models
https://en.wikipedia.org/wiki/Template:Timeline_of_iOS_and_derivative_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_Mac_operating_systems
https://en.wikipedia.org/wiki/Template:Timeline_of_iPhone_models
https://en.wikipedia.org/wiki/Template:Timeline_of_Power_Macintosh,_Pro,_and_Studio_models
https://en.wikipedia.org/wiki/Template:Timeline_of_portable_Macintoshes
https://en.wikipedia.org/wiki/Template:Timeline_of_Mac_model_families
https://en.wikipedia.org/wiki/Template:Timeline_of_iMac_models
https://en.wikipedia.org/wiki/Template:Timeline_of_Macintosh_servers
https://en.wikipedia.org/wiki/Template:Timeline_of_compact_iPod_models
https://en.wikipedia.org/wiki/Template:Timeline_of_iOS_and_derivative_operating_systems

If manual touching is required I can go back later once there's an update here. Just didn't re-find these if they do require an effort.

As far as I know it’ll be an automatic fix, but that’s just my theory. We’ll see when the issue is fixed however.

Also happens on Malay Wikipedia, see https://ms.wikipedia.org/w/index.php?title=Templat:Statistik_Penyelia_dan_Birokrat&oldid=6872043