Lazy iframe Throttling in Chrome

Has anyone run into problems when using Stimulus inside a lazy loaded iframe in Chrome? We’re specifically seeing issues when a tab is opened in the background, and only occasionally. Inside the iframe’s Javascript context, Stimulus is defined, but there are no objects in Stimulus.controllers.

The closest other bug I can find is Turbo lazy loading not connecting stimulus controller · Issue #47 · hotwired/turbo · GitHub, but we’re on Stimulus 3. Because of the inconsistent nature of this problem, I’m suspicious of Chrome’s Tab Throttling feature, but I can’t say I understand exactly what it’s doing (and Stimulus seems to be using Google’s stated best practices eg use of MutationObserver).

So far we haven’t seen this in any other browser.

Do you have an example or a skeleton of the code? What’s the output after setting stimulus.debug = true?