Time Horizon (50%)
also: 50% time horizon · task time horizon
The length of task an AI agent can complete at 50% reliability — a single trendable measure of capability.
The time horizon measures capability by task length: how long a task, in human time, the agent finishes at a given success rate — usually 50%. Popularized by METR, it has grown roughly exponentially across frontier models. Because 50% is far from production-grade, a long horizon signals reach, not trustworthy autonomy.