Every agent that writes code needs a place to run it. That "place" has evolved into a product category with over a dozen vendors, four incompatible billing models, and marketing pages quoting cold-start times under conditions nobody publishes.
This comparison sets the record straight. We cover the five platforms most teams shortlist—E2B, Daytona, Modal Sandboxes, Cloudflare Sandbox SDK, and Vercel Sandbox—plus Runloop, Fly.io Sprites, and Northflank where they shift the answer.
The Four Questions That Actually Decide This
Feature matrices in this category are mostly noise. Four properties change your architecture; everything else is a preference.
- Cold Start Under Concurrency: An agent loop creating a sandbox per tool call pays this tax thousands of times a day. What's the real latency when 50 sandboxes spin up simultaneously?
- Filesystem Persistence Between Turns: Does turn 2 see the
pip installfrom turn 1, or does the agent rebuild its world each time? This determines whether you need an external state store. - Egress Policy: Can the sandbox reach the internet? Can you disable that access, and can you switch it on or off mid-run without killing the session?
- Resource Limits: CPU, memory, and GPU allocation vary widely. A sandbox that can't run a model inference or a large build may be a non-starter.
- Choose E2B if you need sub-second cold starts and filesystem persistence for AI agents.
- Choose Modal for GPU-heavy workloads where network egress must be locked down.
- Choose Cloudflare Sandbox SDK if your agents run on the edge and you need global low latency.
- Choose Vercel for tight integration with your existing deployment pipeline.
- Choose Daytona or Northflank when you need full control over environments and network policy.
The Shortlist: What Each Platform Offers in 2026
E2B
E2B specializes in AI agent sandboxes with per-second billing and sub-second cold starts. It provides SDKs for Python and JavaScript, supports custom base images, and offers filesystem snapshots for state persistence between runs. Its network policy allows granular egress control, letting agents access the internet only when needed.
Daytona
Daytona takes a DevOps-centric approach, offering prebuilt development environments with Git integration. Cold starts are fast, but the focus is on reproducibility. Billing is per-second, and network policies are configured per environment, giving teams full control.
Modal Sandboxes
Modal stands out with serverless GPU support, making it ideal for AI workloads. Cold starts can be as low as 100ms for lightweight images, and per-second pricing includes GPU time. Filesystem persistence is handled via volumes, and network egress is restricted by default—you must explicitly enable it.
Cloudflare Sandbox SDK
Built on Cloudflare's edge network, this sandbox SDK offers near-zero cold starts globally. It supports HTTP and WebSocket communication, with per-second billing. However, filesystem persistence is limited to Workers KV or Durable Objects, which require additional setup. Network policy is strict: egress is blocked unless you configure a proxy.
Vercel Sandbox
Vercel's sandbox integrates deeply with its deployment platform, offering ephemeral environments that mirror production. Cold starts are optimized for Node.js and Next.js apps, and billing is per-second. Persistence is not native—the sandbox resets after each session—so you'll need external storage. Egress is controlled via Vercel's network settings.
Where Others Change the Answer
Runloop
Runloop excels at long-running tasks with checkpointing, making it a strong choice for multi-hour agent workflows. Its per-second pricing and filesystem merge support are notable.
Fly.io Sprites
Fly.io Sprites offer lightweight microVMs that boot in under 50ms. They are ideal for rapid tool calls, but persistence and network policy require more manual configuration.
Northflank
Northflank provides a balanced option with per-second billing, combined with a suite of DevOps tools. Its network policy allows fine-grained controls, and persistence is handled through volumes.
Test Methodology: What We Measured (and What We Didn't)
We didn't run benchmarks—vendor marketing is too variable. Instead, we analyzed each platform's architecture, consulted public documentation, and interviewed engineers who use these tools in production. Cold-start claims are taken from vendor documentation but flagged where they're likely optimistic.
Pricing Models in 2026: Per-Second vs. Per-Minute vs. Per-Invocation
Most platforms now bill per second, but the minimum charge varies—some round up to 100ms, others to 1 second. E2B and Modal charge per second with no minimum, while Cloudflare and Vercel require a minimum of 1 second per invocation. Daytona and Northflank bill per second with a 10-second minimum.
Making the Choice: A Practical Guide
The Bottom Line
There's no single best sandbox—only the one that matches your agent's architecture. Decide which of the four questions matters most, and the platform choice follows.
This article was originally published in August 2026 and has been updated for clarity and 2026 market context.
via MarkTechPost