verde@ -- Thanks for reporting this issue. Could you please help us by providing the detailed screencast reproducing the issue. This will help us in understanding the issue better. Also please share the device details, OS version on which the issue is reproduced.

You can also verify by updating your device to latest Stable #70.0.3538.64 and let us know your observations.

Thanks in advance!

Interesting. I looked at the code and the right header should be added for the right optimization, but as I understand it, the headers should only be added for the frame request.

Adding dougarnett@ to look into it.

Maybe my understanding is wrong, and every request in the frame gets the same header added.

I think the LoFi intervention header (6072546726248448) should be added to all subresources (since in general it is not clear ahead of time whether the resource will end up being an image or not). So that first case might be expected - if LoFi was triggered for that page load.

But I believe we only want the NoScript header (4775088607985664) on the main frame request, so I can fix that. 

My understanding was that for a given navigation, all subresources should get the same entry for the intervention header. I am not sure why we are adding different entries for different resources.

cc-ing bengr

The original intent for NoScript was to add the header just on the main frame (I double checked also in go/cacao-client-design). We could discuss further about Selective Resources Blocking (since originally we wanted to use Reporting API and it is not mentioned in the design doc) but it certainly couldn't be on the blocked subresource so main frame makes sense with ability for the Developer to return cache-control:no-transform header on main frame response.

Discussed offline. Lets also add the intervention header on browser initiated navigations. That would go somewhere here:
https://cs.chromium.org/chromium/src/content/browser/frame_host/navigation_request.cc?rcl=a8234d9a57aceea5014e8865da19cfea3f2764f0&l=183

Discussed offline with bengr@ and others. We want to deprecated the intervention header in favor of using the new Reporting API so deprioritizing making changes to existing intervention header behavior. Plan to replace with Reporting API in M-73.

 Issue 887657  tracks the work of using Reporting API to report previews interventions.

Can we mark this as WontFix?