You’ve been told your agent is unreliable because you picked the wrong model.
You didn’t. You picked the wrong layer.
I know because I did it first. Upgraded the model. Same failure. Now more expensive.
Last week a founder ripped out Claude, swapped in a “smarter” model, and got the same broken agent back. The failure was never in the model. It was in the machinery around it - three layers everyone keeps blending into one buzzword soup.
Agent harness. Loop engineering. Graph engineering.
I spent the week pulling apart a research agent that kept lying about being finished. By the end of this issue, you will get the exact diagnostic I now use to fix any agent in under a minute - plus a free Agent Failure Diagnostic Cheatsheet.
By the end of this, you’ll stop paying for a smarter model to fix a problem the model was never causing. You’ll look at a broken agent - one that lies about being done, burns tokens in circles, or falls apart across sessions - and know in thirty seconds which of three things to fix. Not guess. Know.
That’s the difference between someone who uses AI and someone who engineers it.
