The Layer Between You and the Model

When you send a message to an LLM, what happens before the model sees it? Something has to load context, decide what tools are available, shape what the model can and can’t do. That’s the harness. Everyone building agents has one, most people just don’t call it that. This is a code walkthrough of a harness I’ve been building. I’ll show what’s actually in that layer: context loading, command constraints, persona switching, conversation branching. Not polished or a product pitch. Just the guts of what sits between me and the model. If you’ve been building something similar and didn’t know the name for it, find me afterwards.