Windsurf's agent was still working.
Your Mac didn't care.

Why your Mac sleeps while Windsurf's agent is still going

Windsurf's AI agent often spends most of a task waiting on a model response — which barely uses any CPU. macOS only looks at CPU and user input to decide whether to sleep, so an agent that's "thinking" hard but computing little looks idle to the OS. After your screen-sleep or system-sleep timer runs out, macOS suspends the Mac, and Windsurf's agent process is frozen along with everything else until you wake it back up.

The fix is to stop macOS from sleeping for as long as Windsurf's agent is actually running a task — then let it sleep normally again shortly after the agent goes quiet — within your grace window, 90 seconds by default. You can do that for free in two minutes, or with a tool that knows the difference between "agent working" and "agent idle" so you don't have to babysit it.

If you only run Windsurf occasionally, you don't need to buy anything. Two solid free options:

• The built-in caffeinate command. Open Terminal and run caffeinate -i before you kick off a long Windsurf task. It'll hold sleep off until you close the Terminal window or press Ctrl+C. Simple, free, already on your Mac.
• Amphetamine (free, Mac App Store). Gives you a menu-bar toggle and basic process triggers, so you can set it to stay awake while specific apps are running.

Both are a fine choice if Windsurf runs for a few minutes here and there. The catch: neither one knows when Windsurf's agent actually finished. You either turn it off yourself, or it keeps your Mac awake — and your battery draining — long after the task is done.