Best code execution sandbox for AI agents in 2026

A code execution sandbox is an isolated environment where an AI agent can run generated code, install dependencies, manipulate files, and return results. The sandbox supplies the execution boundary; the agent decides which actions to take. For the interfaces your application uses to send commands, stream output, and collect results, see our guide to code execution APIs for AI agents.

For example, a coding agent might clone a repository, change a function, run the test suite, and inspect failures inside one sandbox. An API-building agent might start a generated server and send requests to it. A data agent might execute Python against uploaded files and return a chart.

These tasks need more than a function that evaluates a code snippet. They may require shell access, background processes, custom system packages, accessible ports, or persistent files.

Isolation reduces the impact of buggy or malicious code, but it does not make credentials or network access safe automatically. Give each sandbox only the permissions and data its task needs.

Start with the execution requirements, then compare providers against them.

For a production agent, measure the whole loop: create sandbox → prepare workspace → execute → collect results → clean up. A fast provisioning response is useful only if the agent can start doing work shortly afterward.

Compare each sandbox’s execution model, persistence, and limits against the tasks your AI agent needs to complete.

Check session limits, hardware availability, and concurrency allowances for the plan you intend to use.

These five providers cover coding agents, generated applications, and other isolated execution workloads.

Northflank runs isolated sandboxes for coding agents, code interpreters, generated applications, and parallel execution jobs. You can use the same sandbox workflow for a short script, a test suite, or an API that needs to keep running while an agent works on it.

• Startup speed and concurrency: Northflank Sandboxes support thousands of concurrent agent sessions, with sub-second sandbox boot times on Northflank Cloud. Use them for parallel agent tasks, test runs, and isolated user sessions.
• Custom images and execution tools: Package your language runtime, build tools, and dependencies in a container image. JavaScript and Python clients support sandbox creation, command execution, file transfers, and cleanup, as shown in the sandbox quickstart.
• CPU and GPU isolation: On Northflank’s managed cloud, CPU sandboxes use microVMs and GPU sandboxes use gVisor. Isolation is selected automatically for the workload; GPU availability depends on the region.
• Deployment options: Use Northflank’s managed infrastructure or bring your own cloud (BYOC), where Northflank acts as the control plane to run coding agents and their sandboxes in your virtual private cloud (VPC). Sandbox isolation requires a supported runtime configured in your cluster.
• Session duration and persistent files: Sandboxes have no fixed session timeout, and attached volumes preserve files across restarts. Pausing stops processes and terminal sessions and deletes ephemeral data, while retaining configuration and attached volumes. Resume restarts the environment without restoring process memory.

Choose Northflank when: you need fast, concurrent sandboxes for several kinds of agent tasks, with custom images, persistent storage, and control over where agent code executes.

E2B provides sandboxes designed for AI-generated code, with session controls for agents that return to an environment across multiple tasks.

• Session duration: Hobby sessions can run for one hour and Pro sessions for 24 hours. Enterprise offers longer-lived sessions.
• Pause and resume: A normally paused sandbox resumes with its files and memory state preserved. Filesystem-only pause preserves files but reboots on resume, so processes and memory state are lost. Session timeout and concurrency limits depend on your plan.
• Managed concurrency: Hobby includes 20 concurrent sandboxes and Pro includes 100. Paid concurrency add-ons increase Pro capacity to 1,100; Enterprise offers higher capacity.
• Networking and deployment: The enterprise offering includes network access controls and bring your own cloud (BYOC) options for AWS and GCP.

Choose E2B when: its agent execution model fits your application and the selected plan covers your concurrency and session requirements. For longer workflows, decide whether you need continuous execution or can pause between tasks.

Modal supports programmatically configured sandboxes for agent tasks, including workloads that need GPU compute.

• Custom environments: Create sandboxes through SDKs, configure dependencies, and use existing container images.
• Session limits and recovery: Sandboxes have a default five-minute timeout, configurable up to 24 hours. Filesystem snapshots let an agent continue from saved files in another sandbox.
• VM isolation option: VM Sandboxes provide a real Linux kernel in beta. This option is CPU-only and should be evaluated separately from GPU configurations.
• GPU execution and billing: Choose GPU resources for tasks that need accelerated computation. CPU and memory billing uses the greater of requested and actual usage.

Choose Modal when: you want to manage execution environments programmatically and its compute model fits your agent. Test the exact runtime, snapshot behavior, and hardware combination you plan to deploy.

Together Code Sandbox provides development environments for agents that repeatedly return to the same workspace.

• Workspace persistence: Hibernation preserves memory and disk state, supporting workflows that resume with their tools and dependencies in place.
• Application previews: Preview ports let agents expose and inspect applications running in the environment.
• Startup and resume: Together reports a 2.7-second P95 cold start and a 500-millisecond P95 resume. These measure different operations; compare cold starts and resumes separately.

Choose Together Code Sandbox when: resuming an existing development environment is central to the agent workflow. Confirm current access, pricing, SDK requirements, and workspace limits for your deployment.

Vercel Sandbox provides isolated execution for generated code and is worth evaluating for applications already using Vercel.

• Isolation: Sandboxes use Firecracker microVMs to isolate code execution.
• Session duration: Hobby sessions have a 45-minute limit; Pro and Enterprise sessions can run for 24 hours. Resuming starts a new timeout window, so session duration differs from total sandbox lifetime.
• Concurrency: Pro and Enterprise support up to 10,000 concurrent sandboxes, subject to the plan’s documented limits.
• Usage costs: Include active CPU, provisioned memory, sandbox creation, data transfer, snapshot storage, and drive storage and operations when estimating your agent’s execution costs.

Choose Vercel Sandbox when: its developer workflow fits your application and its session model covers your tasks. Account for idle memory and retained storage as well as active execution.

Compare the total cost of a completed agent task, including setup, idle time, retries, and stored state. The lowest CPU rate alone does not determine the cheapest workflow.

Prices below are in USD as of September 28, 2026, with per-second rates converted to hourly equivalents.

GB and GiB measure memory differently, and a physical core is not the same billing unit as a vCPU. Some providers charge for allocated resources; others meter active CPU. Include these differences, storage, and network charges when estimating your total.

Use a small workload suite drawn from your actual agents. Include a normal task, a resource-heavy task, a long-running task, and a task that fails.

1. Measure readiness under load. Record time to the first successful command at normal and peak concurrency. Track failures and P95/P99 latency as well as the median.
2. Check execution compatibility. Run your real language runtimes, package installation, browser dependencies, and test commands. Verify how subprocesses and servers behave.
3. Test session recovery. Pause, resume, restart, and expire a sandbox. Check files, process memory, open connections, and agent state separately.
4. Verify access boundaries. Attempt connections that should be allowed and blocked. Confirm that one session cannot read another session’s credentials or files.
5. Measure cost per completed task. Include failures, retries, idle periods, persistent storage, and cleanup. Estimate burst usage separately from steady-state usage.

Keep the image, region, concurrency level, and measurement definitions consistent. Comparing a warm resume against a cold start can produce an attractive number without answering how your agent will perform.

The Northflank sandbox quickstart provides JavaScript and Python examples for creating an environment, executing commands, working with files, and cleaning up.

To evaluate your first agent task:

1. Create a Northflank account and project.
2. Choose an image containing the runtime and tools your task requires.
3. Create a sandbox with suitable CPU and memory resources.
4. Run the agent’s commands and capture outputs, errors, and generated files.
5. Add persistent storage if subsequent sessions need those files, then test cleanup and recovery.

Repeat the task at your expected concurrency before moving production traffic. For bring your own cloud (BYOC), Northflank acts as the control plane to run coding agents and their sandboxes in your virtual private cloud (VPC). Follow the sandbox runtime configuration guide to configure isolation for that deployment.

Northflank is our recommendation for teams combining varied agent workloads with high concurrency and flexible deployment. E2B, Modal, Together Code Sandbox, and Vercel Sandbox are also worth evaluating. Choose using your workload’s runtime, persistence, isolation, and cost requirements, then validate with real tasks.

Yes, if it supports the necessary runtime, long-running processes, and network ports. A sandbox used only for short code snippets may not meet those needs. Test server startup, request handling, authentication, and shutdown as part of your evaluation.

No. Some implementations preserve process memory; others stop processes and retain only configuration or persistent files. Check the provider’s documented behavior for the exact sandbox type. Your agent may need to recreate shell sessions, reconnect clients, or restart tools after resuming.

MicroVMs provide an isolation boundary, but secure execution also depends on permissions, resource limits, network controls, and credential handling. A sandbox can still misuse an API key you intentionally give it. Limit access to what the task requires and monitor execution.

Yes. Northflank and Modal offer GPU sandbox options. Hardware availability and isolation differ by configuration. Confirm the required GPU, region, drivers, and runtime before choosing an environment.

Bring your own cloud (BYOC) runs workloads in your cloud account while the provider manages agreed parts of the service. With self-hosting, your team deploys and operates the software, including maintenance and upgrades.