Agent sandboxes / Northflank Sandboxes alternative

A Northflank sandbox alternative for whole-RootFS continuity

Northflank’s managed sandboxes use isolated deployment services, with persistent volumes for retained data. In the documented deployment model, restarting or resizing a service loses files kept only in ephemeral storage. Plan installed software and system changes as well as the project directory.

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

When Northflank Sandboxes fits

Northflank fits teams combining agent execution with deployment services, databases, GPUs, and broader cloud operations. Its managed CPU sandboxes use microVMs; managed GPU sandboxes use gVisor, with region and access requirements.

When to consider Sandbox0

Sandbox0 fits a Linux agent whose system configuration, dependencies, and user data should persist as one writable RootFS. Online growth and paused file access can reduce the mount and rebuild work needed for repeated tasks.

Capabilities

Northflank Sandboxes and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeNorthflank SandboxesA deployment runs under its service lifecycle; pausing scales it to zero.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 filesNorthflank SandboxesAttached persistent volumes retain data while a service is paused.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSNorthflank SandboxesIn the reviewed deployment model, runtime storage outside mounted persistent volumes is ephemeral.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 stateNorthflank SandboxesScale to zero and start deployment instances again; retained volumes survive.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateNorthflank SandboxesThe documented service scale-to-zero path does not retain the running process image.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.

Northflank lets a deployment increase its ephemeral storage setting, restarting running deployments with the new capacity. A persistent volume is separate storage. Sandbox0 grows its mounted writable RootFS online on enabled templates.

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.

See paused file operations →

A persistent volume does not cover every system path

Northflank distinguishes ephemeral runtime storage from mounted persistent volumes. Files outside a retained mount can disappear when a deployment restarts. Build reproducible packages into the image or place the required data on volumes; compare that work with retaining Sandbox0’s full writable RootFS.

Source 1 ↗Source 2 ↗

Pause scales the service to zero

Northflank pause stops compute charges by reducing instances to zero. Retained volumes remain billed. Changing its resource plan restarts the sandbox, and the documented storage increase path also restarts running deployments. Treat process restoration separately from bringing the service back up.

Source 1 ↗Source 2 ↗

Price the selected plan and attached resources

Northflank compute is billed per second against a resource plan. Persistent SSD capacity and network egress have separate meters. The free platform tier called Sandbox is a plan name, not a statement that all agent-sandbox workloads are free.

Source 1 ↗Source 2 ↗

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.

Northflank Sandboxes

Pricing reviewed 2026-10-18

Published compute CPU unit
$0.01667 per vCPU-hour
Rate source ↗
Published compute memory unit
$0.00833 per GB-hour
Rate source ↗
Persistent SSD disk
$0.15 per GB-month
Rate source ↗
Network egress
$0.06 per GB
Rate source ↗

The selected resource plan determines the actual compute bill; small shared and dedicated plans differ. Volumes continue billing when paused. Cross-zone transfer, GPUs, BYOC, and Enterprise configurations have additional conditions.

Check current Northflank Sandboxes 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

A 4 GiB agent, 100 running hours

$6.00 compute

4 GiB × 100 hours, billed by the second. Keeping 20 GiB of billable incremental data for a full billing month adds $0.40. CPU is derived from memory by the platform; choose a tier that fits your workload.

Understand storage billing →

Before migrating from Northflank Sandboxes

  1. Inventory persistent volume mount paths and all changes currently kept only in ephemeral container storage.
  2. Build a Sandbox0 template for required system packages and translate service health checks, egress, secrets, and ingress.
  3. Run the same multi-task agent, then verify accumulated system changes, online RootFS growth, pause/resume, and the complete storage bill.

Common questions

Is Sandbox0 a drop-in Northflank Sandboxes 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 ↗northflank.com/docs/v1/application/scale/increase-storage ↗/docs/sandbox ↗northflank.com/docs/v1/application/sandboxes/sandboxes-on-northflank-cloud ↗northflank.com/pricing ↗Sandbox0 RootFS capacity →

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