About Runtime
Linux sandboxes for agent code, each a Firecracker microVM, billed on active CPU, with pause, forks, snapshots, custom images, an MCP server and SDKs.
Code Sandboxes
Alternatives to Runtime
12 code sandboxes tools you can use instead of Runtime, 3 of them open source. Summaries come from each vendor's own site. Links checked Oct 26, 2026.
At a glance
Runtime alternatives compared
| Tool | What it does | Open source | Head to head |
|---|---|---|---|
| Agent 37 | Cloud sandboxes for running AI agents, positioned as lower-cost agent infrastructure. | No | Not compared yet |
| AIO Sandbox | All-in-one agent sandbox with browser, shell, file access, VSCode Server, and MCP in one container. | Yes | Not compared yet |
| Celesto | Hardware-isolated cloud computers for AI agents, with browser, desktop, shell and file access, pause, resume and forking, via CLI and SDK; Apache-2.0 microVM core you can self-host. | Yes | Not compared yet |
| Cloudflare Sandbox SDK | Run untrusted or generated code in Linux VMs or isolated Workers on Cloudflare. | No | Not compared yet |
| Cosmonic | WebAssembly sandboxes for agent code, MCP servers and tools, with no access until you grant it: the free Cosmonic Desktop app (public beta) and Cosmonic Control for Kubernetes. Open source core: CNCF wasmCloud. | No | Not compared yet |
| Daytona | Secure sandboxes for running AI-generated code. Its public GitHub repo is archived: core development moved to a private codebase in June 2026. | No | Not compared yet |
| E2B | Isolated cloud machines for agents to run code, browse, and use tools. | Yes | Not compared yet |
| Modal | Serverless cloud for running, training, and serving AI workloads, including sandboxes. | No | Not compared yet |
| Runloop | Code sandboxes (Devboxes) for AI coding agents, plus evaluations. | No | Not compared yet |
| Sandbox0 | Cloud computers for AI agents that keep the whole writable root filesystem, pause compute between tasks and resume on demand, via API, SDKs and CLI. | No | Not compared yet |
| Vercel Sandbox | Isolated Linux microVMs on Vercel for untrusted or agent-generated code. | No | Not compared yet |
| VoidRun | Isolated microVM sandboxes where AI agents and developers run untrusted code, via REST API, TypeScript and Python SDKs, and an MCP server (beta). | No | Not compared yet |
Code Sandboxes
All 12 alternatives
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Agent 37
agent37.comCloud sandboxes for running AI agents, positioned as lower-cost agent infrastructure.
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AIO Sandbox
sandbox.agent-infra.comAll-in-one agent sandbox with browser, shell, file access, VSCode Server, and MCP in one container.
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Celesto
celesto.aiHardware-isolated cloud computers for AI agents, with browser, desktop, shell and file access, pause, resume and forking, via CLI and SDK; Apache-2.0 microVM core you can self-host.
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Cloudflare Sandbox SDK
developers.cloudflare.comRun untrusted or generated code in Linux VMs or isolated Workers on Cloudflare.
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Cosmonic
cosmonic.comWebAssembly sandboxes for agent code, MCP servers and tools, with no access until you grant it: the free Cosmonic Desktop app (public beta) and Cosmonic Control for Kubernetes. Open source core: CNCF wasmCloud.
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Daytona
daytona.ioSecure sandboxes for running AI-generated code. Its public GitHub repo is archived: core development moved to a private codebase in June 2026.
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E2B
e2b.devIsolated cloud machines for agents to run code, browse, and use tools.
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Modal
modal.comServerless cloud for running, training, and serving AI workloads, including sandboxes.
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Runloop
runloop.aiCode sandboxes (Devboxes) for AI coding agents, plus evaluations.
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Sandbox0
sandbox0.aiCloud computers for AI agents that keep the whole writable root filesystem, pause compute between tasks and resume on demand, via API, SDKs and CLI.
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Vercel Sandbox
vercel.comIsolated Linux microVMs on Vercel for untrusted or agent-generated code.
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VoidRun
void-run.comIsolated microVM sandboxes where AI agents and developers run untrusted code, via REST API, TypeScript and Python SDKs, and an MCP server (beta).
FAQ
Questions
What are the alternatives to Runtime?
Agent Stack Directory lists 12 other code sandboxes tools: Agent 37, AIO Sandbox, Celesto, Cloudflare Sandbox SDK, Cosmonic, Daytona, E2B, Modal, Runloop, Sandbox0, Vercel Sandbox, VoidRun.
Is there an open-source alternative to Runtime?
Yes. Among the alternatives we list, these are marked open source: AIO Sandbox, Celesto, E2B.
What does Runtime do?
Linux sandboxes for agent code, each a Firecracker microVM, billed on active CPU, with pause, forks, snapshots, custom images, an MCP server and SDKs. (Summary based on withruntime.com, link checked 2026-10-26.)