Dennis, what is the current state of devtools notifications when an intervention is active?

Unfortunately, it's more complicated after our webextension rewrite. In the case of JS injections, we can add a simple console.log() to our injection, because that JS is executed within the website itself. However, that does not work for CSS injections, or user agent overrides.

Running console.log() in the background script where UA overrides and injecting the CSS happens would result in the message being logged into the browser console. For our use case, this is pretty much useless, because web developers will not see the message there.

And unfortunately, there also is no way of "finding the proper console API to write directly to the tab", because of webextension framework limitations. The only way I can think of to do site-console logging at the moment is to add a content script into every single website, then pass some messages between the content script and the background script to see if any interventions got applied, and if so, log something to the console. However, this sounds like it will have a significant performance hit.

This needs more research, unfortunately. :(

Thanks for the reply Dennis.

Would a webext experimental API help us?

However, this sounds like it will have a significant performance hit.

We could measure this, I guess.

Follwing this commit, all interventions now get a very visible console notification.

Shipping this new feature will happen as part of v16 in bug 1663967, but since the PR is merged upstream, I'll close this as fixed!