System Velocity

System Velocity (plugin id systemproxy) is a standalone security and maintenance plugin for Velocity proxies. A five-stage chat pipeline — null-byte, flood, length, Log4Shell, Unicode — denies malicious payloads at the proxy, before backend servers ever see them: the Anti-Log4Shell filter flattens nested ${} obfuscation up to four levels deep and sanitizes console output so blocked payloads cannot forge logs, and the Unicode filter targets zero-width, RTL-override and invisible characters while normal Persian/Arabic script and standard emoji pass through untouched. A timezone-aware scheduler restarts the proxy at a fixed local time with a configurable countdown, and a log cleaner keeps the proxy's own logs directory inside a size budget and retention window — symlink-safe by construction.

It is deliberately tiny and dependency-free: ten classes, no database, no external services, snakeyaml shaded and relocated, an immutable config snapshot on the chat hot path, and atomic exception-safe reloads. A built-in /systemproxy test runs Log4Shell and Unicode self-tests so admins get live PASS/FAIL proof after every config change. Despite the shared family name it needs nothing from any backend plugin — no channels, no shared keys, no config coupling: install the jar on the proxy and it runs.