I got this with a reflexive cyberblade installed, but after a fair bit of fighting. The last round of combat when I got it:
You punch the ganger, throwing the whole weight of your body behind it and dealing 18 melee damage.
The ganger fires a short burst into you, dealing 2 ranged damage.You hammer the ganger unrelentingly, dealing 23 melee damage.
You latch onto the ganger and tear a chunk out of him with your teeth, dealing 16 melee damage.
You slip behind the ganger and extend a cyberblade into his back for 27 stealth damage.
You've won the battle!
You gained 12 credits!
You found: heavy pistol
You found: 5 tablets of Eclipse
You found: brass knuckles
You learned a new Technique: CyberbladeYou learned a new Technique: Reflexive Blade
You've earned 4 XP in Strength
From the description, it may have to do with starting a chain with some sort of punch and then ending with Backstab?
Equipment:
Hat: guard helm
Weapon: silk whip
Offhand: spider nest
Shirt: silk vest
Pants: silk pants
Gadget: Myers sampling kit
Only effect was Chitin Hands, and only cyberware was the reflexive cyberblade.
Edit: I've gotten 3 copies now, and it's not super clear what's triggering it. Maybe just possible from any stealth following a punch? The original trigger might not be from that round of combat I logged, since there was the first ganger I killed, and I didn't save that round.
Another edit: Looks like the 'too close' variant is just against melee, and doesn't trigger versus stealth.