Best Agent Sandboxes in 2026: Cold Start, Per-Second Pricing, and Network Policy Across E2B, Daytona, Modal, Cloudflare, and Vercel

Every agent that writes code needs somewhere to run it, and no two vendors quote the same units.

This comparison measures burst cold start across E2B, Daytona, Modal, Cloudflare, and Vercel, normalizes per-second rates to cost per 1,000 executions, and maps filesystem persistence, idle billing, and egress policy against primary sources verified August 27, 2026.