I've been building VT Code for about a year as a way to understand how coding-agent harnesses work in practice.

Most of the code has been built with the help of coding agents, including VT Code itself. My focus has been on designing and iterating on the harness: tool execution, context management, sandboxing, permissions, verification, long-running sessions, subagents, and provider support.

It's written in Rust and runs primarily in the terminal.

https://github.com/vinhnx/VTCode

I'd be interested in feedback from others building coding agents, especially around long-running reliability and harness design.