Sandboxer vs OpenReward

OpenReward is a platform for hosting reinforcement-learning and evaluation environments built on the Open Reward Standard, and its sandboxes are containers tied to an environment workspace rather than general compute. Sandboxer is a general-purpose VM sandbox with root, Docker, nested KVM and memory-preserving stop/resume. Pick OpenReward to build, host, train and evaluate on agent environments (including L4 GPU tasks); pick Sandboxer for long-lived full Linux machines for agents or people.

Checked against OpenReward's public docs on October 24, 2026. Sources are linked in the table and listed below.

At a glance

Sandboxer and OpenReward compared
Capability	Sandboxer	OpenReward
Isolation	microVM Cloud Hypervisor, its own kernel	container Docs describe a sandbox as an isolated container started from a chosen image, with optional sidecar containers.
Full Linux with root	Ubuntu 24.04, sudo, systemd	Not stated; you choose any container image.
Docker inside	Preinstalled	partial You bring a Docker image for the sandbox and can add sidecar containers; running Docker inside the sandbox is not documented.
Nested virtualization (/dev/kvm)		Not documented.
Pause and resume with memory	Running processes come back	Lifecycle documented is start, run, stop (delete); no pause is described.
Fork a sandbox	Copy-on-write disk copy that boots fresh	Not documented.
HTTPS URL per port	Private with a token, or public	Not documented for sandboxes.
Longest session	No limit on paid plans Auto-stop is up to 30 days or off	Sandboxes usually live for one environment session; no limit stated.
Billing	Per second, flat rate per size Stopped sandboxes are free	per second, CPU + RAM (+ GPU) $0.0504 per vCPU-hour, $0.0162 per GiB-hour, NVIDIA L4 $1.51 per GPU-hour, billed by the second.
GPUs		machine_size "nvidia-l4" gives an NVIDIA L4; capacity is limited.
Self-host or open source		partial Enterprise plan offers on-premise setup; the ORS standard is open source.
Regions	US East (Virginia) and EU Central (Finland)	Not stated.

= not documented publicly.

Price for one 4 vCPU, 8 GB machine

Sandboxer

$0.036/hour

Flat per-second rate for the default size

OpenReward

$0.33/hour

4 vCPU × $0.0504/h + 8 GiB × $0.0162/h (4:8 machine size)

List prices from each provider's pricing page, before free credits, plans and storage. This compares price only.

Where OpenReward is strong

Purpose-built for agent RL: environments expose tasks, splits, tools and rewards through the open ORS standard.
Sandboxes can mount environment storage buckets read-only and block network egress to prevent answer leakage.
NVIDIA L4 GPU sandboxes are available per second.
Environments work with other sandbox providers too, and there are integrations with several RL training frameworks.

Where Sandboxer differs

OpenReward sandboxes are containers tied to an environment workspace; Sandboxer sandboxes are standalone full VMs with their own kernel.
OpenReward documents no pause/resume or fork; Sandboxer stop keeps memory and processes and forks from disk snapshots.
OpenReward offers L4 GPUs; Sandboxer has no GPUs.
A 4 vCPU / 8 GiB OpenReward sandbox costs about $0.33/h at list price versus $0.036/h on Sandboxer.

Pick OpenReward if

You are building or hosting RL training or evaluation environments and want rewards, tasks and splits handled for you.
Your tasks need a GPU, such as evaluating CUDA kernels.
You want environment storage mounts and network blocking designed for benchmark integrity.

Pick Sandboxer if

You need a general-purpose machine with root, systemd, Docker and nested KVM rather than a per-session container.
Agent sessions should stop and resume later with running processes intact.
You want lower per-hour cost for 4 vCPU / 8 GB CPU machines.

Sources

Products change. If something here is out of date, email hello@sandboxer.com and we'll fix it. OpenReward is a trademark of its owner. Sandboxer is an independent product and is not affiliated with OpenReward.

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