Compounding failure
The chance of finishing falls as the task gets longer.
- Is a
- Failure kind
- Guarded by
- Short checked segments
- Grows with
- Drift over time
The chance of finishing falls as the task gets longer. Ord argues that agent success on METR's tasks fits a constant failure rate per unit of task time (Ord, half-life of AI agent success). METR's 2026 report puts the public frontier 50% horizon at about 12 hours and the 80% horizon at about 1.5 hours, measured in the time a skilled human takes (METR frontier risk report, 2026). On Sierra's τ-bench, GPT-4o's retail score falls about 60% from one attempt to eight consistent ones (Sierra, τ-bench).
Guard: short checked segments. It grows with drift over time; both worsen with run length. Our own reading: compounding is a chance of error at each step, drift is loss of context over many steps.