Gosh yes, count me in the "I hate this behavior" group. I've hit such horrible issues, like "why does this work in chrome, I but not in Firefox and chromium?!"

Gosh yes, count me in the "I hate this behavior" group. I've hit such horrible issues, like "why does this work in chrome, I but not in Firefox and chromium?!" (ofc now that you know it's not related to the browser). It really made my heart hurt. Also if my memory is correct, when it is in cache, when looking at the cert chain in the browser it'll show the chain including the cache, without mentioning the cache. So you end up "why the fuck does my http server I just deployed does browser favoritism and change the exposed cert chain based on the user agent... Which it doesn't have???" then goes to "okay the simple logical explanation is that it's http2 vs http1" (because that was when http2 just started deployment). And of course at some point you hit the moment where you no longer reproduce the issue because you visited the wrong website. Thankfully I hit this issue only once, and it wasn't on a mission critical service that I had to fix ASAP, so it wasn't too horrible, but still.