A task that needs many planned steps, steady work, and fixes along the way.
It is like running the school play. The cast list is only the start. Then the dragon costume vanishes.
You see it in coding. You also see it in workflows and software work. When the steps get long, AI can skip parts or wander off.
Agent
Many Agent systems are built to finish this kind of multi-step task.
Memory
Long-horizon tasks need Memory, or the AI loses the thread.
Computer use
Real software and websites often turn work into a long-horizon task.
Reasoning-model
A Reasoning-model can help split the steps, but long paths can still drift.