Every agent user hits the same wall: it can't go the distance.
Give an agent a complex, multi-app task, and somewhere along the way it loses the plot — the context window fills up and it forgets its progress, or one step fails and the whole task restarts from zero, or it claims "done" and you have no way to verify. The problem isn't a lack of smarts. It's a missing layer of loop engineering: how an agent sustains state, verifies results, and recovers from failure over hours, not minutes.
LongHorizon-Harness (1.5k stars, MIT) is built for exactly this — and it comes with an arXiv paper (2608.01964), which already tells you it's not another toy.
The core loop
Plan → act → verify → checkpoint or recover → repeat, until the work is actually done.
