Cloudflare Sandbox vs Railway Sandboxes

Cloudflare Sandbox SDK and Railway Sandboxes both run untrusted or agent-generated code in isolated Linux environments, but they fit different application architectures. Cloudflare embeds sandbox execution into Workers applications, while Railway provides branchable development workspaces connected to Railway projects.

• Cloudflare Sandbox SDK runs a dedicated Linux container in its own VM, coordinated by a Durable Object and controlled from a Worker. Railway Sandboxes run on Railway's virtual-machine primitive.
• Cloudflare Sandbox SDK provides a TypeScript SDK for Workers with command, file, process, interpreter, backup, storage, and tunnel APIs. Railway Sandboxes combine dashboard, CLI, TypeScript SDK, and SSH access with Docker and six preinstalled coding agents.
• Cloudflare keeps local state while a container is active and can explicitly restore R2 backups or mount object storage after a restart. Railway uses templates, checkpoints, and forks to prepare and branch workspace state.
• Cloudflare charges for active CPU plus provisioned memory and disk while the container runs. Railway charges allocated CPU and memory for the full running period, including idle time.
• Northflank is a stronger fit when teams need fast startup times, microVM or gVisor isolation, persistent CPU or GPU sandboxes without a separate session-duration limit, attached volumes, self-serve BYOC, or production-scale concurrency.

Cloudflare Sandbox SDK provides isolated Linux environments for AI agents, code assistants, data analysis, interactive development tools, and CI/CD systems. Each sandbox is a dedicated container in its own VM, with a Durable Object providing identity and lifecycle coordination and a Worker acting as the application-facing layer.

The TypeScript SDK can execute and stream commands, manage files, run background processes, interpret Python and JavaScript, expose services, and connect browser terminals. Dockerfile customisation and rootless Docker-in-Docker support container-based development and test workflows, although privileged containers and iptables-dependent networking are restricted.

Cloudflare Sandbox SDK became generally available in April 2026 and requires the Workers Paid plan.

Railway Sandboxes are short-lived Linux workspaces for coding agents, application testing, and tasks that need filesystem and shell access. They run on Railway's virtual-machine primitive and are available through the dashboard, CLI, TypeScript SDK, and SSH.

Each workspace includes Docker, git, Node.js, npm, and mise. The default image also bundles Claude Code, OpenAI Codex, Cursor agent, Droid, OpenCode, and Pi.

Templates define repeatable setup, checkpoints preserve named bootable disk states, and forks branch a running workspace. A Sandbox can also join its Railway environment's private network, making the model useful when an agent needs to work beside a database, Redis instance, or internal service already deployed on Railway.

Railway Sandboxes remain in Priority Boarding, Railway's opt-in beta program, as of 24 July 2026.

The comparison below reflects capabilities, access, and pricing on 24 July 2026. Northflank uses broader service and compute primitives for sandbox workloads, so its column focuses on production-scale execution, persistence, GPUs, and infrastructure control rather than presenting the products as direct API equivalents.

The main difference is workflow. Cloudflare Sandbox SDK is composed into an application: a Worker retrieves a sandbox by ID, executes commands, manages files, exposes services, and preserves state through explicit R2 backup and restore operations or object-storage mounts. Railway Sandboxes are interactive workspaces that developers and agents can enter directly, prepare once, checkpoint, and fork across parallel tasks.

Their persistence models reflect that distinction. Cloudflare keeps files, processes, and shell state while the container is active. State that must survive a restart needs an R2-backed backup or an R2, S3, or GCS mount. Railway checkpoints create bootable disk states that outlive the source Sandbox, while templates and forks support repeatable and branchable environments.

Networking also follows the surrounding platform. Cloudflare provides preview URLs, quick and named Cloudflare Tunnels, regional placement, and outbound Workers that can mediate traffic or inject credentials. Railway Sandboxes can join the private network of their Railway environment and reach project databases, Redis, internal services, and variables. CLI port forwarding exposes a Sandbox service locally during development.

Cloudflare containers sleep after ten idle minutes by default, although sleepAfter and keepAlive can change that behaviour. Railway supports idle timeouts up to 120 minutes on Hobby and Pro, with an active port-forward connection keeping the Sandbox alive. Neither product states a fixed maximum wall-clock Sandbox duration.

Cloudflare Sandbox SDK inherits Container pricing. The $5 monthly Workers Paid plan includes 375 vCPU-minutes, 25 GiB-hours of memory, and 200 GB-hours of disk. Beyond those allowances, CPU costs $0.000020 per active vCPU-second, memory costs $0.0000025 per provisioned GiB-second, and disk costs $0.00000007 per provisioned GB-second.

Cloudflare bills CPU on active use, while provisioned memory and disk accrue while the container runs. Workers, Durable Objects, R2, observability, and regional network egress can add separate charges.

Railway bills CPU and memory by the minute throughout the running period, including idle time. Platform rates are $20 per vCPU-month, $10 per GB-month, and $0.05 per GB of egress. Hobby costs $5 per month with $5 included usage, while Pro costs $20 with $20 included usage.

Choose Cloudflare Sandbox SDK when sandbox execution is one component of a Workers application. It fits AI agents, code interpreters, browser IDEs, and CI/CD systems that benefit from Durable Object identity, R2-backed state, Cloudflare Tunnels, outbound traffic mediation, and active-CPU billing.

Plan for explicit persistence when a workspace must survive a container restart. Also include Workers, Durable Objects, storage, observability, and regional network usage when modelling the complete bill.

Choose Railway Sandboxes when an agent or developer needs a ready-to-use Linux workspace with Docker, SSH, bundled coding agents, branchable disk state, and private access to services in a Railway environment.

This suits repository work, integration testing, and parallel agent tasks that start from one checkpoint. Account for Priority Boarding access and allocated-resource billing during idle periods.

Northflank Sandboxes cover more than isolated command execution. You can run persistent or ephemeral CPU and GPU sandboxes with workload-specific microVM or gVisor isolation on Northflank Cloud, deploy them self-serve into your own cloud account, or place them inside a customer’s VPC. Attached volumes retain data across restarts and scale-to-zero, with no platform-imposed session limit.

ComputeSDK measured Northflank sandboxes at a 67 ms median sequential startup and 198 ms under concurrent burst load, with 100% success in both tests on 24 July 2026.

Northflank can also run APIs, workers, jobs, databases, inference, training, and preview environments alongside the sandbox fleet. Agent-generated code can move from isolated execution into pull request previews, staging, and production workflows, with RBAC, audit logs, secrets, SSO, workload identities, and deployment controls applied across that path.

Northflank Skills lets Claude Code, Codex, Gemini CLI, and Cursor configure sandboxes, deploy services, manage databases, and create preview environments through the Northflank API and CLI. This gives coding agents a route from an isolated task environment to a controlled application platform.

Cloudflare Sandbox SDK embeds programmable code execution into Workers applications. Railway Sandboxes provide interactive, branchable development environments connected to Railway projects, while Northflank extends isolated execution into preview, staging, and production infrastructure.

Cloudflare runs each sandbox in its own VM, while Railway Sandboxes run on Railway’s virtual-machine primitive. Northflank uses workload-specific microVM or gVisor isolation across managed and customer-owned infrastructure.

Cloudflare retains local state while a container is active and supports explicit R2 backup and restore. Railway provides templates, checkpoints, and forks, while Northflank attaches persistent volumes that retain data across restarts and scale-to-zero.

Cloudflare bills active CPU plus provisioned memory and disk, with additional Workers-platform charges. Railway bills allocated resources while running, including idle time. Northflank offers lower published CPU and memory unit rates, although total cost depends on workload activity.

Cloudflare fits agents embedded in Workers applications, while Railway fits interactive agents connected to Railway services. Northflank suits persistent, GPU-backed, high-concurrency, or customer-cloud agent infrastructure, with Northflank Skills supporting Claude Code, Codex, Gemini CLI, and Cursor.

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