[Arknights] CR-EX-8 CM | 9 Medics Only 

This has previously been done on normal mode with just Kal'tsit and Reed before, but the increased stats proved to be too much in both phases to replicate, not to mention the extra enemies (especially the early Breacher). To get around all that, I found it more useful to instead reference the 6-op no-devices clear.
Since I still had both Reinforcement Devices at the end, you may think that I didn't need to burst the boss down as quickly as I did and could cut the op count down. Unfortunately, the barricade wasn't the limiting factor, but the smokescreen. Once the smokescreen clears, the bodyguards (particularly the leftmost one) lose their invisibility and take targeting priority from Mateo, keeping him safe (except from Folinic, but since adding her I always managed to defeat him before the smokescreen cleared).
As for why I had those devices but didn't use them: I forgot (there's a lot going on). But since I hadn't yet determined whether I needed the barricade up long-term or not, I decided to play it out.
Nightingale may not seem that important, but she has three roles here: stalling Mateo while I wait for Kal'tsit to come back, increasing Mon3tr's received healing during the final wave, and preventing the Grenadiers from getting stuck on the Originium explosives and blowing everyone up.
Last quick note to point out Vendela (with Silence's buff) being able to solo the one bodyguard with perfect timing. A little bit later and the Temporary Cover protecting Silence would've been used up prematurely.