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

The comparison, based on data from the open-source ComputeSDK sandbox leaderboard, measured Time to Interactive (TTI) from a 4-vCPU host in Northern Virginia on August 21, 2026. The test launched 100 concurrent iterations per provider and recorded the time from create() to the first successful command. Results varied widely: Vercel Sandbox had a median TTI of 0.67 seconds, Modal 0.88 seconds, Runloop 0.89 seconds, E2B 1.61 seconds, and Cloudflare 5.06 seconds. Daytona's median was 0.27 seconds, but its success rate fell to 37%, meaning its advertised sub-90-millisecond creation time is not achievable under burst conditions.

The report emphasizes that tail latency matters more than medians for agent UX. Runloop's median was only 10 milliseconds from Modal's, but its P95 was 3.3 times higher. Cloudflare's slower median reflects a different architecture: Sandbox SDK sits on Cloudflare Containers, which boots a full container instance rather than resuming a pre-warmed microVM, making it a heavier operation.

Pricing also diverges. E2B charges $0.0504 per vCPU-hour and $0.0162 per GiB-hour, billed per second with a free hobby tier and $150/month Pro plan. Daytona has the same per-resource rates but no plan floor and offers a $200 credit. Modal Sandbox charges $0.1419 per core-hour (about $0.0710 per vCPU-hour) and $0.0240 per GiB-hour, billed on max(request, actual) per second, with a free starter and $250/month team plan. Vercel Sandbox charges $0.128 per vCPU-hour for active CPU time only.

The report advises teams to benchmark their own workloads rather than rely on vendor claims, suggesting a harness that times create, ready, dependency installation, and task execution separately. It recommends reporting both TTI and task time, pinning the region and image, and publishing sequential and concurrent series separately.