Possibly related to themed and 960 events?
An Unexpected Addition to the Match Endpoint

Just checked a couple of in registration matches
https://api.chess.com/pub/match/1525347 this one has been open since 20th Aug and doesn't show the new setting.
https://api.chess.com/pub/match/1528565 opened today shows new setting.
So either the change is only for new registrations or it hasn't propagated through the whole dataset as yet
No doubt when (if) the spec changes we will get to know what it's for

It's listed as a parameter in the API documentation:
https://www.chess.com/announcements/view/published-data-api#pubapi-endpoint-match-profile

OK Thanks Martin. Strangely I thought I had looked in there before I checked a couple of matches. Still, must have missed it. I do notice that it doesn't have any description of use. No doubt that will be forthcoming.
I also see it's only in 'registration' phase so assume no impact on endpoint for 'in-progress' and 'finished'

It's listed as a parameter in the API documentation:
https://www.chess.com/announcements/view/published-data-api#pubapi-endpoint-match-profile
True but it's never been included by default before yesterday I think. More usually if a parameter hasn't been set, it's omitted altogether.
For example, there's no min/max rating given in the "settings" of a match unless these have been deliberately set. The same with min/max players per team.
So I wonder why this particular key-value has been added since it gives no additional information?

Thanks, it would be interesting to know the reason.
In the meantime I've amended my code to ignore that key-value for now, so if it's removed later on I'm fine.

Thinking about it this change seems to coincide with the web site move from daily match 'challenges' to 'seeks'

You'd think there must be a connection between the two but I've lived long enough to know that strange coincidences happen more often than we expect.
Couldn't work out why a 'match-settings' checking routine I use suddenly started returning errors in every match sampled but on checking a match I found something new!
"initial_setup":"" has suddenly appeared in the match "settings" data.
It doesn't appear to do anything at this stage but does anyone know anything about this?