The error seems to only happen on the main page but not https://en.wikipedia.beta.wmflabs.org/wiki/Special:Preferences (and presumably other pages)

https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Wikibase/+/450216/

is the only recent thing I could find. Adding @Pablo-WMDE and @Jakob_WMDE

Marking as blocking the next train just to keep track of this.

I don't think it has to do with the travis changes.

It looks like this one is related: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/442253

At a quick guess, the new code in WikiPageEntityRevisionLookup does not work correctly for cross-wiki access. It would trigger on any page that accesses a wikidata entity. Seems like I did not test this thoroughly enough. I'll try to get a fix in by tomorrow. If I don't manage that, we'll have to revert https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/442253

Ok, confirmed locally: this is caused by the new WikiPageEntityRevisionLookup code.

Analysis: RevisionStore loads the correct revision content from the correct database (wikidatawiki), but since rev_content_model is NULL in the database, it falls back to using the default content model configured for that namespace locally. For NS_MAIN, that's wikitext on most client wikis. For content loaded from Wikidata, this is of course wrong.

Permanent solution: with the new MCR schema, this problem vanishes, since the content model is always recorded explicitly.

Intermediate solution (draft): defined per-namespace content model overrides in RevisionStore. These can be set by RevisionStoreFactory. But how do they get into RevisionStoreFactory? The only option I see is to introduce a new config setting. Which seems annoying, given the fact that t his will go away anyway.

Change 450476 had a related patch set uploaded (by Daniel Kinzler; owner: Daniel Kinzler):
[mediawiki/extensions/Wikibase@master] Revert "Use PageUpdater & RevisionStore in Wikibase"

https://gerrit.wikimedia.org/r/450476

Change 450477 had a related patch set uploaded (by Daniel Kinzler; owner: Daniel Kinzler):
[mediawiki/extensions/Wikibase@master] Warn about unexpected content models when loading entities.

https://gerrit.wikimedia.org/r/450477

Change 450476 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@master] Revert "Use PageUpdater & RevisionStore in Wikibase"

https://gerrit.wikimedia.org/r/450476

With the reverted merged and https://en.wikipedia.beta.wmflabs.org/wiki/Main_Page?debug=true looking OK, I guess the priority can be lowered?

Change 450477 abandoned by Daniel Kinzler:
Warn about unexpected content models when loading entities.

Reason:
Redundant per If94f8cb11

https://gerrit.wikimedia.org/r/450477

Change 450551 had a related patch set uploaded (by Daniel Kinzler; owner: Daniel Kinzler):
[mediawiki/core@master] Add safeguard against loading content across wikis.

https://gerrit.wikimedia.org/r/450551

Change 450551 merged by jenkins-bot:
[mediawiki/core@master] Add safeguard against loading content across wikis.

https://gerrit.wikimedia.org/r/450551