Everything the model can't do alone

Started writing a skeptical take on 'the leverage has moved off the model and onto the harness.' Couldn't finish it. The more I pushed back, the more I kept agreeing: memory, tool routing, fallback logic, context shaping, none of that lives in the weights. If you're building agents, you're mostly writing harness.

Tried to write a rebuttal to 'agent builders are harness engineers now.' Couldn't land a punch.

Memory, fallback logic, tool routing, context shaping. None of it lives in the weights. The model is one part. The rest is plumbing you build. https://www.jakelawrence.xyz/blog/everything-the-model-cant-do-alone

Sat down to argue against the claim that AI engineering leverage has moved off the model and onto the harness. Kept writing myself into agreement instead. Memory, tool routing, fallback handling, context shaping: the model doesn't own any of that. The weights are one component. Everything around them is craft.

Tried to write a skeptical response to a simple claim: the real engineering leverage in AI has moved off the model and onto the harness, so if you're building agents, you're a harness engineer. Couldn't finish the rebuttal. Every counterexample I reached for dissolved. Memory management, tool routing, fallback logic, context shaping, retry behavior: none of that lives in the weights. The model answers. The harness decides what it's answering, with what context, after what checks, and what happens when it's wrong. Turns out 'skeptical note' became something closer to a concession. https://www.jakelawrence.xyz/blog/everything-the-model-cant-do-alone

Tried to write a rebuttal to 'agent builders are harness engineers.' Couldn't land one.

Memory, fallbacks, tool routing, context shaping. None of it lives in the weights. The model is one part. The rest is craft you build around it. https://www.jakelawrence.xyz/blog/everything-the-model-cant-do-alone

Went in skeptical: 'the leverage has moved off the model and onto the harness' felt too tidy. Kept writing myself into agreement. Memory, tool routing, fallback logic, none of it lives in the weights. The harness is the actual work.