VX-One: Typed, Calibrated Decision Heads for Real-Time Perimeter Triage

Abstract

Perimeter triage faces a latency/semantics trade-off: signature engines are fast and format-safe but blind to unseen attacks, while generative models are semantic but slow and unparseable. We present VX-One, a small multi-head network (100K--10M parameters) with calibrated typed outputs: a binary gate, a closed-set choice with an explicit unknown option where the benchmark supports it (and abstention elsewhere), and an ordinal score. Heads are temperature-calibrated, with 0.7--1.7 ms single-event CPU p50 latency. We evaluate UNSW-NB15, CIC-IDS2017, and EMBER2024 against calibrated XGBoost, Random Forest, MLP, and Kitsune baselines, and measure a Suricata-to-VX-One cascade over five days of CIC-IDS2017. Results are deliberately double-sided: on UNSW the gate ties the best baseline (0.9837+/-0.0002 versus MLP 0.9835+/-0.0013 across three seeds), while VX-One wins temporal CIC detection (0.734+/-0.022 versus 0.639+/-0.027) but loses multi-class attribution to XGBoost. Under leave-one-family-out, the gate detects all nine UNSW families but drops below chance on CIC recon; CIC trees transfer better. Suricata resolves only about 0.1% of attacks on flow reconstructions and 0.2--2.2% on payload-bearing PCAPs; the strictly by-day Phase 2 recovers only the in-scope DoS/DDoS share on the wave day (recall 0.34, precision 0.97). Calibration collapses under temporal drift (ECE 0.04->0.40) for every method while ranking partly survives. We contribute a measured account of where typed calibrated decisions help perimeter triage, and where they fail.