Agent sandboxes / Deno Sandbox alternative

A Deno Sandbox alternative for an environment that keeps growing

Deno Sandbox can preserve more than a mounted project folder: a bootable writable volume can serve as its root filesystem. Distinguish that mode from booting a read-only snapshot, where session writes are ephemeral.

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

When Deno Sandbox fits

Deno fits teams using Deno Deploy, its TypeScript or Python sandbox SDKs, destination-scoped secrets, and regional block volumes. A prepared bootable snapshot is useful when many disposable sandboxes should start from the same installed toolchain.

When to consider Sandbox0

Consider Sandbox0 when an individual agent should keep one writable environment across work sessions, expand its RootFS online, and release compute while your application continues to inspect persistent files.

Capabilities

Deno Sandbox and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeDeno SandboxThe overview lists sessions up to thirty minutes, while the timeout API supports expiration extension and reconnection. Confirm the effective account limit and keep active lifetime separate from root-volume persistence.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 filesDeno SandboxRegional block volumes survive sandbox sessions.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSDeno SandboxA bootable writable volume can be the root filesystem; direct snapshot boots have ephemeral writes.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 stateDeno SandboxNot established in this reviewSandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateDeno SandboxNot established in this reviewSandbox0Experimental 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.

Deno volumes are provisioned with capacity and a region, and can be used as a writable root. The reviewed docs do not establish an automatic online root-volume growth policy; validate that separately from snapshot and volume persistence.

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 →

Choose a writable root volume for retained changes

Deno can boot a sandbox with a writable bootable volume, so package installs and system changes can persist. Booting a snapshot directly instead provides an immutable starting image: writes made during that session do not update the snapshot. Creating a new writable volume from a snapshot gives it independent changes.

Source 1 ↗

Separate reconnecting from restoring a stopped process

Deno’s timeout API supports duration-based lifetime, reconnection, and extension. Its overview lists sessions up to 30 minutes, while the timeout guide explains extending expiration. Confirm the effective account limit and extension policy for multi-hour jobs; reconnecting to a live sandbox is different from restoring its memory after compute stops.

Source 1 ↗Source 2 ↗

Sandbox access follows the Deploy plan

Deno’s current plan matrix includes Sandbox on Pro and above, with shared CPU, memory, and egress meters. Volume storage has its own allowance. Compare those plan allowances with the sandbox’s actual allocated memory and active CPU usage.

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.

Deno Sandbox

Pricing reviewed 2026-10-18

Active CPU over plan allowance
$0.10 per CPU-hour
Rate source ↗
Memory over plan allowance
$0.025 per GiB-hour
Rate source ↗
Volume storage over plan allowance
$0.20 per GiB-month
Rate source ↗
Pro subscription
$20/month
The plan matrix includes Sandbox access, 3 concurrent sandboxes per region, and 5 GiB of volume storage.
Rate source ↗

Pro includes 50 CPU-hours, 750 GiB-hours memory, and other shared Deploy allowances. Builder changes included usage and concurrency. Check the current plan matrix rather than the older prerelease concurrency figure in the overview.

Check current Deno Sandbox 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 Deno Sandbox

  1. Identify which Deno sandboxes boot a writable volume and which boot an immutable snapshot; export unsaved session changes first.
  2. Port destination-scoped secrets, network policy, exposed HTTP services, and SDK command execution.
  3. Run the agent past a normal session boundary and its initial disk capacity; verify saved packages, files, and expected process restart behavior.

Common questions

Is Sandbox0 a drop-in Deno Sandbox 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 ↗docs.deno.com/sandbox/volumes/ ↗docs.deno.com/sandbox/timeouts/ ↗docs.deno.com/sandbox/ ↗deno.com/deploy/pricing ↗deno.com/deploy/sandbox ↗Sandbox0 RootFS capacity →

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