METR: agent task length doubling every ~7 months

METR finds the length of tasks frontier agents complete with 50% reliability has doubled roughly every 7 months for six years.

What happened and why it matters

The "time horizon" metric reframed agent progress as a measurable exponential. Claude 3.7 Sonnet sat around one hour; extrapolation implied month-long tasks within years. It became the single most cited metric for autonomy.

Sources

• Measuring AI Ability to Complete Long Tasks ↗ METR · 19 Mar 2025