Experiment 1: Site keyed agent cluster

Page URL https://a.example.com:3000/index.html, with different iframe URL. Test send SharedArrayBuffer to iframe. If ok, then those two pages are in same agent cluster. If not, then those two pages are in different agent cluster.

iframe URL	Are in same agent cluster?
https://a.example.com:3000/index.html	✅
https://b.example.com:3000/index.html	✅
https://example.com:3000/index.html	✅
https://test.com:3000/index.html	❌

Experiment 2: Origin keyed agent cluster

Add Origin-Agent-Cluster: ?1 on the HTTP headers. To see weither those pages are in the same agent cluster.

iframe URL	Are in same agent cluster?
https://a.example.com:3000/index.html	✅
https://b.example.com:3000/index.html	❌
https://example.com:3000/index.html	❌
https://test.com:3000/index.html	❌