Sail raises $80M for long-horizon AI agents

AI agents are getting better at short tasks, but long-running work still breaks easily. Sail Research is building infrastructure for agents that need to operate over longer time horizons.

What happened

Sail Research raised $80M across seed and Series A funding at a $450M valuation.

The Series A was led by Kleiner Perkins, while the seed round was led by Sequoia. The company is building infrastructure for long-horizon AI agents, including an inference stack aimed at lower token costs and sandbox environments that can run for days rather than seconds.

Why it matters

This is a strong AI agent infrastructure signal.

If agents are going to handle complex work, they need more than short chat sessions. They need persistent environments, cheaper inference and safer ways to run multi-step tasks over time.

The bigger picture

The next AI infrastructure wave may focus on durability. The winners will not only build smarter agents, but the systems that let those agents work reliably for hours or days without falling apart.