gate4agent is an open-source Rust-based agent harness and runtime orchestrator developed by ZENG3LD. It serves as a supervisory control layer designed to execute, monitor, and manage terminal-based AI coding agents across multiple operating systems with rigorous process boundaries. At runtime, gate4agent provides both an interactive terminal user interface (TUI) and a command-line control tool (`harnessctl`). It handles child agent lifecycles by spawning processes inside an in-house, zero-dependency pseudoterminal layer (`gate4agent-pty`), enabling full PTY stream interaction, winsize negotiation, and process signal management across Windows ConPTY, macOS, and Linux. What differentiates gate4agent is its focus on low-level systems engineering, process hygiene, and isolation. It enforces strict environment variable isolation to prevent ambient host credentials and API tokens from leaking to child agents, maintains a loopback-only default network surface, and abstracts diverse CLI agent tools behind a modular adapter registry. gate4agent is open source on GitHub and targets environments requiring secure, deterministic agent orchestration without relying on heavy external runtime dependencies.
Tags: agent harness, cli, coding agent, OpenSource, terminal