Bug or Desiging? Blackflame +Archon of the flame = 0 Damage

I love Blackflame Covenant. It makes my girl look like IoriYagami‌ in KOF. And I love Archon of the flame too cuz it looks like Malzahar in LOL.
But when i both have blackflame and archon of the flame. I could do NO DAMAGE to anyone.Is this a BUG or it just works like this "plz dont have them both. they are conflict ones"? But truly they are both in my passive tree and stay so close!

Not a bug, just questionable design choice. The 3 Archons have the follow line:

"Cannot deal non-X Damage with Spells"

So chaos is not Fire, thus you deal no damage. You have to take one or the other, not both.

Thanks for your replies, but this is really not a great design—at the very least, there should be a warning in advance that these two conflict with each other. Instead, I only found out about it in the middle of an intense battle with the boss. After that, I had to grit my teeth and get through the fight (since I couldn’t use my favorite skills anymore) before going back to reallocate my points.

Welcome to Path of Exile is all I can say. There's way too many systems like that where you can effectively deal no damage if the player creates anti-synergy. Creating any kind of notification for every anti-synergy in the game (plus any future ones) is going to be way too many checks and balances when the current design is mostly give the player some options and see what they come up with. Try stuff, make mistakes, try something else.

In my opinion, the whole archon system is bad and needs rework. The current system is at least a step up for supports. PoE 1 you could socket any support with any gem. Whether or not they were actually supported was for the player to realize. PoE 2 you can't put a spell support with an attack.

Also note, this is the PoE 1 bug report section.

PoE 2 Bug Reports:
https://www.pathofexile.com/forum/view-forum/2214

PoE 2 Suggestions:
https://www.pathofexile.com/forum/view-forum/2213