Agent Series (20): Harness in Production — From Single File to Reusable Package

From Demo Code to a Reusable Package

Article 19 used a 900-line harness_full_demo.py to demonstrate eight defense layers. That file is good for explaining concepts, but not for reuse — all layers are coupled together, nothing can be tested in isolation, and nothing can be imported by another project.

A production-grade Agent project needs something you can actually import:

harness/

├── __init__.py Public API exports