Me and @Jdrewniak met to discuss the list of options from part 1 of this spike, which also includes notes on pro/cons for each option.

In T371294#10039946, @Jdlrobson wrote:

@bwang something like the above hook is probably a good idea to support however we decide to run this experiment. This would allow us to avoid having to use MutationObserver is unpredictable ways when building out a <banner/gadget/browser extension/WikimediaEvents/insert type here> experiment.

If the negative margins are an issue, we could potentially take on the suggestion here in T366389 to replace negative margins with a different solution to potentially kill 2 birds with 1 stone. but this code has been very tricky and fragile across all the different spacing possibilities

@Jdlrobson and I discussed this, we landed on not needing to change the class names for now, this patch should be whats needed

@Krinkle im working on this now, is it a problem to have slashes inside unit like so?

unit( 14 / @font-size-browser, em ); // Equals `0.875em`.

Wikimedia Analytics owned by Data Products team seems like the only option for anon only stats. It includes APIs for things like most viewed pages, most requested media files, number of editors, most active editors, most edited pages, most edited or viewed WikiCommon categories. Some of these stats can be per project, but some seem to be overall. The analytics API doesnt have an option to query by year, we'd have to request 12 months and aggregate it, but considering everyone is seeing the same stats, this shouldnt be a problem.

@Jdlrobson Hm weird, the results in my comment above are with query strings on both light and dark mode. After all the light mode results are consistent for both your results and mine, with a TTFB of around 60ms. Only the dark mode was worse in my initial tests, and that was definitely using the query string.

Mobile isnt so bad, in face the TTFB is slightly faster interestingly enough

Using Peter's tool at https://wikiperformance.wmcloud.org, i got these results
Light mode:

@Peter has confirmed this is expected, and the alert threshold has been raised

I added an FAQ question linking to Manual:Dark_mode here
I added a notice on the gadget

yes i think so! @Jdlrobson

This should be fixed with T362939