Best sandbox runners for AI agents and code execution in 2026

Sandbox runners cover a wider range of tools than most comparisons acknowledge, from browser-based execution environments to production-grade microVM platforms running at scale.

This article compares the best sandbox runners in 2026 across isolation model, persistence, BYOC (Bring Your Own Cloud) support, GPU access, and platform scope, so you can match the right one to your use case.

A sandbox runner is an isolated execution environment where code runs without affecting your host system, other tenants, or production infrastructure. The isolation boundary determines the security model: standard Linux containers share the host kernel and rely on namespace separation, while microVMs (Firecracker, Kata Containers) give each workload a dedicated kernel, and gVisor intercepts system calls in user space to reduce the kernel attack surface.

Sandbox runners are used for AI agent code execution, user-submitted scripts, code interpretation, and any workload where you cannot trust the code being run. See what is a sandbox environment? and what is an AI sandbox? for deeper breakdowns.

The evaluation criteria depend on your workload, but these questions are worth working through before committing to a platform:

• What isolation model does it use? Containers, gVisor, and microVMs offer meaningfully different security guarantees. For untrusted code at scale, microVM-level isolation provides a dedicated kernel per workload. See Kata Containers vs Firecracker vs gVisor for a technical breakdown.
• Does it support both ephemeral and persistent environments? Ephemeral environments handle stateless, short-lived execution. Persistent environments let agents maintain state across sessions without rebuilding from scratch. Many platforms support only one model.
• Can it deploy inside your own infrastructure? If workloads cannot leave your network for compliance or data residency reasons, check whether BYOC (Bring Your Own Cloud) is available self-serve or only on an enterprise plan requiring a sales process.
• Does it cover the full workload runtime? A sandbox API is not the same as a full platform. If you need databases, background workers, GPU jobs, and production services alongside sandbox execution, check whether the platform covers all of this or only code execution.
• Does it support GPU workloads? Not all sandbox runners include GPU access. Confirm this is available within the same platform if your workloads require it.
• What compliance certifications does it hold? SOC 2, HIPAA, and GDPR coverage varies across platforms.

Each platform below takes a different approach to sandbox execution. Here is what they provide and where they fit.

Northflank provides production-grade sandbox infrastructure backed by Firecracker, Kata Containers, and gVisor, with orchestration, multi-tenant isolation, autoscaling, and bin-packing handled at the infrastructure level. It is the only platform in this list that covers sandboxed code execution alongside production deployments, databases, and GPU workloads in one control plane.

Key capabilities:

• Firecracker, Kata Containers, and gVisor applied depending on the workload
• Both ephemeral and persistent environments with no forced time limits
• End-to-end sandbox creation at 1-2 seconds, covering the full stack
• Self-serve BYOC (Bring Your Own Cloud) across AWS EKS, GKE, AKS, Oracle Kubernetes, CoreWeave, Civo, bare-metal, and on-premises distributions including OpenShift and RKE2, or run on Northflank's managed cloud
• On-demand GPU access (NVIDIA H100, A100, L4, and others) with no quota requests
• Full workload runtime: APIs, workers, databases, and background jobs run alongside sandboxes in the same control plane
• API, CLI, and SSH access
• Multi-tenant architecture
• SOC 2 Type 2 certified, in production since 2021 across startups, public companies, and government deployments
• CPU at $0.01667/vCPU-hour, memory at $0.00833/GB-hour. See full GPU and compute pricing

Northflank is the right choice when you need isolation guarantees beyond containers, want to avoid managing separate infrastructure for execution and production, or require workloads to stay within your own cloud under compliance constraints.

E2B provides isolated sandbox environments for AI agents and code execution, with Python and JavaScript SDKs.

Key capabilities:

• Isolated Linux VMs created on demand via API
• Pause and resume with full state preserved (filesystem and memory)
• Paused sandboxes retained indefinitely with no automatic deletion
• Continuous runtime limit of 24 hours (Pro) or 1 hour (Base) per session, reset on pause and resume
• AutoResume for automatic sandbox resumption on network reconnection
• Snapshots for saving and restoring sandbox state
• SSH access, interactive terminal, proxy tunneling, and custom domain support
• Git integration and cloud storage bucket connectivity
• MCP gateway
• BYOC available on Enterprise for AWS and GCP only (requires contacting sales)

Modal is a serverless compute platform with a sandbox interface for executing untrusted or dynamically defined code.

Key capabilities:

• gVisor-based sandbox isolation
• Sandbox environments defined and spawned at runtime with custom container images
• Sandbox timeouts configurable up to 24 hours, with Filesystem Snapshots for longer workflows
• GPU access configurable per sandbox
• Tunnels for direct external connections and granular egress network policies
• Filesystem snapshots for state preservation and restoration
• Python SDK (primary), JavaScript and Go SDKs
• No BYOC deployment option

Sprites are persistent, hardware-isolated Linux environments built on Fly.io's infrastructure.

Key capabilities:

• Firecracker microVM isolation per Sprite
• Persistent ext4 filesystem backed by NVMe hot storage during execution and durable object storage at rest
• Sprites create in approximately 1-2 seconds
• Automatic idle behaviour: compute charges stop when idle, filesystem is preserved
• Warm and cold states: warm Sprites resume quickly from hibernation
• Checkpoints with copy-on-write (approximately 300ms, non-disruptive to the running environment)
• Unique HTTPS URL per Sprite for exposing services or APIs
• Up to 8 vCPUs and 16GB RAM per Sprite
• CLI, JavaScript, and Go SDKs
• No BYOC

Vercel Sandbox provides on-demand, isolated microVM environments for running untrusted code, tightly integrated with Vercel's deployment infrastructure.

Key capabilities:

• Firecracker microVM isolation
• Node.js 22 and Python 3.13 runtimes on Amazon Linux 2023
• Session limits: 5 minutes default, up to 45 minutes on Hobby, up to 5 hours on Pro and Enterprise
• Snapshotting for saving and restoring sandbox state
• Up to 8 vCPUs and 2GB RAM per vCPU
• Active CPU billing only (billed when code is actively running)
• TypeScript and Python SDKs, CLI
• Runs on Vercel's infrastructure only, no BYOC

Cloudflare Sandbox provides isolated Linux container environments for running untrusted code, built on Cloudflare Containers and Durable Objects. It is currently in Beta and available on the Workers Paid plan.

Key capabilities:

• Isolated Linux containers (not microVMs), each with a full Ubuntu environment
• State is maintained while the container is active; state resets after inactivity (10 minutes by default, configurable)
• Python and Node.js code interpreter with persistent execution contexts while active
• Docker-in-Docker support
• Preview URLs via automatic subdomain routing
• WebSocket support for real-time streaming
• Browser terminal access
• S3-compatible object storage mounting (R2, S3, GCS) for persistence across sessions
• TypeScript SDK
• Integrates with Cloudflare Workers, R2, KV, and Workers AI
• No BYOC

CodeSandbox, now part of Together AI, provides microVM-based sandbox environments for AI agents, code interpretation, and developer workflows.

Key capabilities:

• MicroVM infrastructure with snapshot and restore
• VM restore within 2 seconds
• Sandbox state persistence across sessions via snapshots
• Customisable hibernation periods
• CodeSandbox SDK for programmatic sandbox management
• Supports AI agents, development environments, code interpretation, and CI/CD
• No BYOC

The right platform depends on your primary requirement. Use the table below to narrow down your options.

The questions below cover what engineering teams most commonly ask when evaluating sandbox runners.

A sandbox runner is designed to execute arbitrary or untrusted code safely, typically for AI agents, user-submitted scripts, or code interpretation. A development environment is designed for developers to write, run, and iterate on code they own. Some platforms serve both purposes, but the security requirements and isolation models differ significantly between the two use cases.

Northflank supports BYOC self-serve across AWS EKS, GKE, AKS, Oracle Kubernetes, CoreWeave, Civo, bare-metal, and on-premises infrastructure, including OpenShift and RKE2. E2B BYOC is available on Enterprise for AWS and GCP only and requires contacting their team. Modal, Vercel Sandbox, Cloudflare Sandbox, and Fly.io Sprites run on the vendor's infrastructure only.

Northflank supports both ephemeral and persistent environments with no forced time limits. Fly.io Sprites maintain a persistent ext4 filesystem across sessions with automatic idle behaviour. E2B supports persistent state via pause and resume, with continuous runtime limits per session that reset on pause. CodeSandbox supports persistence via snapshots with VM restore within 2 seconds. Modal supports snapshot-based state preservation. Cloudflare Sandbox state resets after inactivity unless S3-compatible object storage is mounted. Vercel Sandbox sessions run up to 5 hours on Pro and Enterprise with snapshotting available.

Northflank supports on-demand GPU workloads (NVIDIA H100, A100, L4, and others) within the same platform as sandbox execution. Modal also provides GPU access configurable per sandbox.

The articles below go deeper on isolation technologies, deployment models, and sandbox infrastructure covered in this guide.

• What is an AI sandbox?: A detailed explainer on AI sandbox infrastructure, isolation models, and use cases.
• Top AI sandbox platforms for code execution: A full ranked comparison of AI sandbox platforms with pricing, isolation, and session lifecycle breakdowns.
• Kata Containers vs Firecracker vs gVisor: A technical comparison of the isolation technologies used across the sandbox runners in this guide.
• Top BYOC AI sandboxes: A comparison of sandbox providers that support deployment inside your own cloud infrastructure.
• Self-hosted AI sandboxes: Covers the three deployment models for running sandbox infrastructure in your own infrastructure.
• Ephemeral sandbox environments: Explains the tradeoffs between ephemeral and persistent sandbox models and when each fits the workload.