Agent sandboxes / Freestyle alternative

Compare Freestyle VMs and Sandbox0 for persistent agents

Freestyle already offers persistent Linux VMs, live resource resizing, memory-preserving pause, and paused file reads. The comparison turns on automatic growth policy, capacity ceilings, write behavior while paused, and plan economics.

Start buildingCompare capabilities ↓

Reviewed 2026-10-18 · Published by the Sandbox0 team

When Freestyle fits

Freestyle fits workloads that want a full Linux VM with live CPU, RAM, and disk increases, native domain routing, and memory-preserving pause. Its paid plans enable persistent VMs and custom sizing.

When to consider Sandbox0

Sandbox0 is worth evaluating when a growing RootFS should expand automatically as free space runs low, and your control plane needs paused file edits as well as reads. Confirm that the workload fits its gVisor execution model.

Capabilities

Freestyle and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeFreestyleConfigurable per-run, total-run, deletion, and idle policies; effective retention remains subject to plan limits.View evidence ↗Sandbox0ttl and hard_ttl default to 0 (disabled). Configure idle pause and deletion policies for the same persistent sandbox identity; an idle running sandbox still accrues compute charges.Read documentation →
Persistent filesFreestylePersistent VM disks survive pause or stop; ephemeral VMs are deleted on stop.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSFreestylePersistent root filesystem with live upward-only disk resize.View evidence ↗Sandbox0Persistence extends beyond /workspace to paths such as /usr/local, /etc, and /home. Runtime tmpfs and virtual filesystems are excluded.Read documentation →
Release compute, keep stateFreestylePause freezes the VM and saves memory; stop discards memory.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateFreestylePause saves running processes, open files, and in-memory state.View evidence ↗Sandbox0Experimental memory checkpoints can preserve compatible process state. Use memory: true on both pause and resume on a compatible deployment. A filesystem checkpoint alone does not preserve running processes.Read documentation →

Online RootFS growth

On growth-enabled images, Sandbox0 automatically expands the writable RootFS as free space runs low, within a configured sparse logical ceiling up to 64 TiB. Agent processes keep running. Growth is enabled in the qualified Cloud region; confirm activation for other regions. Existing images and snapshots retain their captured storage geometry. The ceiling is logical capacity, not preallocated host disk.

Freestyle supports live root-disk increases through resize(), subject to plan and account limits. Sandbox0’s online growth is automatic on enabled templates, within the committed logical device ceiling.

Files while compute is paused

Sandbox0's Files API reads persistent files without resuming compute. Filesystem-only pauses also permit edits; retained-memory pauses are read-only and reject mutations with 409. SSH, SFTP, file watching, and runtime-only mounts require running compute.

Freestyle paused reads leave compute paused, while filesystem changes wake the VM. Sandbox0 filesystem-only pauses allow supported file mutations without waking compute.

See paused file operations →

Both products can grow a running filesystem

Freestyle documents live, upward-only resize of CPU, memory, and root storage. Sandbox0’s distinction is automatic XFS growth on enabled templates as disk fills. Freestyle’s public plan matrix lists maximum disk per VM of 32, 64, and 256 GiB for Free, Hobby, and Pro.

Source 1 ↗Source 2 ↗Source 3 ↗

Paused reads are a shared capability

Freestyle can browse and download files without resuming a paused VM; writes automatically wake it. Sandbox0 also reads persistent files while paused, and permits offline mutations during filesystem-only pauses. A retained-memory Sandbox0 checkpoint stays read-only.

Source 1 ↗Source 2 ↗

Compare allowances before adding the plan price

Freestyle lists shared monthly compute allowances across Free, Hobby, and Pro. On paid plans the subscription covers subsequent usage dollar for dollar before overage. On Free the allowances are hard stops, and persistent VM support differs from paid plans.

Source 1 ↗

Pricing

Compare billing models, then price your workload

CPU allocation, memory, billing minimums, disk, plan fees, and supported workload differ. These meters are not equal-performance machine quotes. Confirm region, resource units, and included allowances before estimating a total.

Same size. Lower compute cost.

2 vCPU · 4 GiB RAM · 730 running hours / month

Save $39.51 / month

The same CPU and memory allocation, with runtime aggregated across sessions. Monthly allowances and credits below are applied to this workload.

Freestyle

Hobby · $50/month with $50 usage coverage

$83.31

$0.13224/hour before monthly allowances

Sandbox0

Pay as you go · no monthly plan fee

$43.80

$0.06/hour · 47% lower in this example

Deducts 200 vCPU-hours and 400 GiB-hours of monthly free compute first. The $50 Hobby fee then covers the first $50 of remaining usage; it is not added twice. Free has hard stops rather than paid overage.

Compute and stated plan fees only. Storage, network, taxes and one-time credits are excluded; hardware and throughput can differ.

Calculation and billing assumptions

Freestyle: $83.3112 compute after 200 included vCPU-hours and 400 included GiB-hours, plus $50.00 plan fee, minus $50.00 applied monthly credit.

Sandbox0: 4 GiB × 730 hours × its published compute rate. CPU uses the Cloud allocation shown on the pricing page.

Includes compute and the selected plan. Excludes storage, network, taxes, one-time grants and negotiated discounts. Assumes this workload can use the full listed monthly allowances. CPU and memory counts do not guarantee equal hardware or throughput.

Checked Freestyle rate source ↗Sandbox0 rates ↗

Freestyle

Pricing reviewed 2026-10-18

CPU
$0.04032 per vCPU-hour
Rate source ↗
Memory
$0.0129 per GiB-hour
Rate source ↗
Storage
$0.000086 per GiB-hour
Rate source ↗
Hobby plan
$50/month, covering up to $50 of billed usage
Published free allowances apply first; usage above the covered amount is additional.
Rate source ↗

Monthly allowances include 200 vCPU-hours, 400 GiB-hours memory, and 60,000 GiB-hours storage. Transfer is $0.02/GB beyond the plan allowance. Pro is $500/month with the same dollar-for-dollar usage coverage structure.

Check current Freestyle pricing ↗

Sandbox0

$0.015/GiB-hour compute (billed by the second at approximately $0.000004167/GiB-second), plus $0.02/GiB-month of retained incremental RootFS and memory checkpoint data. Shared base images and platform recovery retention are excluded; paused sandboxes accrue storage charges only.

Compute / GiB-hour
$0.015
Retained data / GiB-month
$0.02
Paused compute
$0.00
Understand storage billing →

Before migrating from Freestyle

  1. Record persistent versus ephemeral Freestyle VM policy, live sizes, mounted data, and domain mappings.
  2. Translate idle and deletion policies; distinguish Freestyle memory pause from Sandbox0’s default filesystem-only pause.
  3. Test a file edit while paused and a workload crossing its starting disk capacity, then compare bills after allowances and plan coverage.

Common questions

Is Sandbox0 a drop-in Freestyle replacement?

Evaluate API compatibility and product scope. A shared sandbox category does not make SDKs, lifecycle semantics, or limits interchangeable.

Does keeping files also keep a running agent?

Filesystem state and volatile process state are separate. Sandbox0 requires explicit compatible memory checkpoints to preserve running processes; its default filesystem resume starts fresh processes.

Sources and review scope

The Boat team's Battleships directory is the discovery source. References below describe the product and plan discussed on this page. Check current availability, regional terms and billing units before migrating. Where the cited material does not establish a capability or price, the comparison identifies that uncertainty.

Battleships research record ↗www.freestyle.sh/docs/vms/lifecycle ↗www.freestyle.sh/pricing ↗/docs/sandbox/template/configuration ↗/docs/sandbox/files ↗Sandbox0 RootFS capacity →

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