@mfreed7 see the above comment about mutation events.

I'm also seeing the MutationEvent interface gone in Chrome 126 beta in the collector: https://mdn-bcd-collector.gooborg.com/tests/api/MutationEvent.
However, this posts says they will be gone in 127 only: https://developer.chrome.com/blog/mutation-events-deprecation
Either it is a beta thing or the interface is gone early. I've not added this topic to this PR, maybe we can try to sort it separately.

Hmm, I'm not sure what tech the "collector" uses, but if it happens to be a version of Chrome that accepts Finch features, then that could be what's happening. In non-stable Chrome (i.e. Canary, Dev, and Beta) from 124-126, I've had a 99% experiment running that disables mutation events to try to suss out compat problems. So that's the most likely explanation?

Thank you so much @mfreed7!

To prevent this from happening to me in the future when collecting compat data, I found https://chromium.googlesource.com/chromium-variations/ which has open -a Google\ Chrome\ Beta --args --fake-variations-channel=stable that I think will allow me to open Chrome beta without Finch features. Let me know if you have other pointers for me to disable Finch features effectively.

I also always re-test things when there is an actual stable release, but for MDN, baseline, and various other efforts, we need the compat data in BCD as early as possible so we've been collecting it during the beta cycle using the beta channels.

Thank you so much @mfreed7!

No problem!

To prevent this from happening to me in the future when collecting compat data, I found https://chromium.googlesource.com/chromium-variations/ which has open -a Google\ Chrome\ Beta --args --fake-variations-channel=stable that I think will allow me to open Chrome beta without Finch features. Let me know if you have other pointers for me to disable Finch features effectively.

It's a tricky balance here. We launch things a number of ways, including via Finch. That set of flags will definitely work, and will cause your Beta Chrome to receive Stable channel finch features. But if your goal is to get "early" testing of features before stable, that might cause you to miss things that are rolling out early via Finch. It's quite rare to have a case like Mutation Events, where I've been running a Finch in only pre-stable releases, without those rolling out to stable along with that version. So you might actually be better off, generally, keeping the default flags, since it should do the right thing in more cases. Up to you!

I also always re-test things when there is an actual stable release, but for MDN, baseline, and various other efforts, we need the compat data in BCD as early as possible so we've been collecting it during the beta cycle using the beta channels.

I get it, and I'm glad you're trying to capture things early! I only wish more production sites did the same and tested with Beta. 😄

Thanks so much for the insights, @mfreed7 👍 I will definitely play around with the flags and keep it in mind when collecting compat data.

@chrisdavidmills With Mutation Events sorted, this is ready for review :)

Things not included in the PR, which maybe should have been:

• OpusEncoderConfig signal and application parameters

Yeah, we don't automatically collect dictionary members for everything. Something to look into at some point.