Your best AX fixes are hiding in agent trajectories

An eval score tells you whether the agent finished the task. To improve how agents work with your product, you need to see where they struggled, and that’s in the trajectory, the record of every step the agent took and why. Agents are persistent. They guess another URL after a 404 and try values until an error goes away, so the struggle rarely shows up in the score. We saw this when we evaluated Dev Proxy, a local proxy that intercepts your app’s HTTP requests. We asked GitHub Copilot Chat with Claude Sonnet 5.5 and no extensions, five times, to write a CI script that uses the Dev Proxy API to record which GitHub APIs a Node.js tool calls. All five scripts worked. Yet the trajectories showed 15 problems, and each run took 29 to 39 requests and up to 1.2 million tokens. Agents can trip over your technology in many ways. We picked the patterns we think you’re most likely to find in your own trajectories, from the obvious to the surprising, and for each one show what it looked like with Dev Proxy and which fix it pointed to. Agents often skip the search. They fetch the URL…