Sandboxer vs Replicas

Replicas is a background coding-agent product: you delegate tasks from its app, Slack, Linear, GitHub or API, and each workspace is an isolated VM with your repos, a Linux desktop and your chosen agent. It is a finished agent product with team workflow on top, while Sandboxer is the VM layer you build on, with SSH, nested KVM and fixed-size machines. Pick Replicas if your team wants a ready-made agent workflow; pick Sandboxer to run and control the machines yourself.

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

At a glance

Sandboxer and Replicas compared
Capability	Sandboxer	Replicas
Isolation	microVM Cloud Hypervisor, its own kernel	virtual machine 'A workspace is an isolated virtual machine'; hypervisor not named.
Full Linux with root	Ubuntu 24.04, sudo, systemd	Docs' Docker start hook uses 'sudo service docker start'.
Docker inside	Preinstalled	The default agent skill can start the Docker daemon, build/run containers and use docker compose.
Nested virtualization (/dev/kvm)
Pause and resume with memory	Running processes come back	Workspaces sleep after 30 min idle; desktop processes survive sleep on the default pause mode; sleeping workspaces are not billed.
Fork a sandbox	Copy-on-write disk copy that boots fresh	partial Environments (configuration) and chats can be forked; forking a running workspace's disk is not documented.
HTTPS URL per port	Private with a token, or public	Create a public URL for a port, optionally requiring Replicas sign-in.
Longest session	No limit on paid plans Auto-stop is up to 30 days or off	sleeps after 30 min idle Idle workspaces sleep after 30 minutes, are archived after 7 days asleep and deleted 3 days after archiving.
Billing	Per second, flat rate per size Stopped sandboxes are free	per awake minute by size, inside a monthly plan small 2 vCPU/8 GB $0.004/min, large 4 vCPU/16 GB $0.008/min, ultra 8/32 $0.016/min (included rate; overage 1.5x); one-minute minimum per session.
GPUs		partial Workspaces have no GPU; separate GPU sandboxes (T4 to B200, powered by Modal) are started from a workspace via CLI and billed at cost.
Self-host or open source		partial Enterprise customers can use a dedicated single-tenant deployment or self-host in their own infrastructure.
Regions	US East (Virginia) and EU Central (Finland)

= not documented publicly.

Price for one 4 vCPU, 8 GB machine

Sandboxer

$0.036/hour

Flat per-second rate for the default size

Replicas

$0.48/hour

Nearest size is large, 4 vCPU / 16 GB (not 8 GB): $0.008/min × 60 = $0.48/h at the included rate ($0.72/h overage)

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

Where Replicas is strong

Agents are triggered from Slack, Linear, GitHub, the app, CLI, MCP or API and open pull requests.
Every workspace includes a Linux desktop with Chrome you can watch and control.
Sleeping workspaces keep processes on the default pause mode and are not billed.
Enterprise can run it dedicated single-tenant or self-hosted.

Where Sandboxer differs

Replicas is a coding-agent product with team workflow; Sandboxer is VM infrastructure with a prompt API and SSH.
Replicas workspaces sleep after 30 minutes idle; Sandboxer auto-stop is configurable up to 30 days or off.
Replicas' 4 vCPU size has 16 GB and costs $0.48/h; Sandboxer's 4 vCPU / 8 GB default is $0.036/h.
Replicas offers on-demand GPU sandboxes through Modal; Sandboxer has no GPUs.

Pick Replicas if

Your team wants a ready-made background agent that works from Slack, Linear and GitHub.
You need occasional GPU jobs launched from the agent's workspace.
You need a self-hosted or single-tenant deployment.

Pick Sandboxer if

You are building your own agent product and need raw VMs via API, CLI and SDKs.
You need nested KVM, SSH and machines that can run with no time limit.
You want lower per-hour machine cost: $0.036/h for 4 vCPU / 8 GB.

Sources

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

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