Sandbox comparison · Reviewed July 2026
Modal is a broad serverless compute platform with container and VM Sandboxes. Run Cloud focuses on persistent agent computers, compatibility adapters, iOS simulators, and cloud Xcode builds behind one runtime API.
Compatibility layer
Keep the provider-shaped entry point while you validate lifecycle, network, image, and storage behavior against your application.
from modal import Sandboxfrom runcloud.compat.modal import SandboxDetailed comparison
This comparison focuses on architecture and workflow rather than temporary prices or benchmark claims.
| Area | Modal | Run Cloud |
|---|---|---|
| Runtime model | Container Sandboxes and VM Sandboxes managed inside Modal Apps. | KVM-backed Firecracker microVMs designed as persistent computers for agents. |
| State | Filesystem, directory, and alpha memory snapshots with type-specific retention. | Snapshot, fork, pause, and resume primitives centered on branching agent work. |
| SDK shape | Modal Sandbox APIs across Python and JavaScript. | Native TypeScript, Python, and Go SDKs plus Modal-compatible TypeScript and Python adapters. |
| Mobile workflow | General-purpose compute; mobile orchestration is assembled separately. | Linux sandboxes, iOS simulators, and Xcode builds share one product surface. |
| Migration path | Existing code imports Sandbox from modal. | Change the import to runcloud.compat.modal, then validate provider-specific edges. |
Provider details were reviewed against the Modal Sandbox snapshots documentation. Product capabilities change; validate requirements against current vendor documentation.
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FAQ
Run Cloud provides a Modal-shaped Sandbox adapter for incremental migration. Core lifecycle code can retain a familiar entry point, but teams should test Modal-specific image, scheduling, GPU, and App behavior before switching production workloads.
Modal documents filesystem, directory, and experimental memory snapshots. Run Cloud centers its state model on snapshots, copy-on-write forks, pause, and resume for branching agent sessions.
Evaluate Run Cloud when the same agent workflow needs isolated Linux compute, an interactive iOS simulator, and Xcode build infrastructure without stitching together separate products.
More comparisons
Bring one sandbox workflow, keep the familiar API shape, and measure the behavior that matters to your agents.