Agent sandboxes / Upstash Box alternative

An Upstash Box alternative for a growing agent computer

Upstash Box combines agent tooling with persistent box state and full-disk snapshots. Its fixed always-on option is priced differently from auto-pausing boxes. For a growing agent, compare that lifecycle and its selected-size disk limit with RootFS growth.

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

When Upstash Box fits

Upstash Box fits applications that want a built-in coding agent, prepared language runtimes, simple box APIs, and automatic wake on new work. The fixed keep-alive plan can suit an always-available small environment.

When to consider Sandbox0

Consider Sandbox0 when the agent needs its own evolving Linux environment, automatic RootFS expansion, and explicit filesystem or experimental memory pause modes. You can keep compute paused while supported Files API operations access persistent data.

Capabilities

Upstash Box and Sandbox0: what persists?

Feature comparison with documentation and verification status
Capability	Upstash Box	Sandbox0
Environment and runtime lifetime	Upstash BoxKeep-alive boxes stay running; standard boxes auto-pause under their idle policy.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 files	Upstash BoxPaused boxes preserve filesystem and environment.View evidence ↗	Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFS	Upstash BoxSnapshots capture full disk state plus agent configuration; schedules are excluded.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 state	Upstash BoxAvailable for standard boxes; fixed keep-alive boxes do not use it.View evidence ↗	Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process state	Upstash BoxNot established in this review	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.

Upstash publishes 5, 10, and 20 GB of storage for Small, Medium, and Large boxes. Full-disk snapshots preserve that state, while automatic RootFS growth beyond the selected size is not established in the reviewed documentation.

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 →

Keep-alive changes both lifecycle and billing

A standard Upstash box auto-pauses when idle and resumes for new work. Keep-alive boxes stay on and do not support the normal pause/resume operation. Their fixed monthly price includes CPU and storage, so compare the intended mode before estimating an always-on agent.

Source 1 ↗Source 2 ↗

Disk snapshots already cover the environment

Upstash snapshots include full disk state and agent configuration and can outlive the original box. Schedules do not transfer to the restored box. The documented lifecycle reruns an init command on resume, so test initialization and process continuity separately from retained files.

Source 1 ↗Source 2 ↗

An active CPU hour is a consumed core-hour

Upstash bills PAYG on actual CPU consumption, with different rates by box size. Idle compute and retained storage have separate behavior. Sandbox0 bills configured memory while running; compare a measured task rather than assuming the same nominal machine dimensions imply the same utilization bill.

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.

Upstash Box

Pricing reviewed 2026-10-18

Small PAYG active CPU: $0.10 per active CPU-hour; Small has 2 vCPU, 4 GB RAM, and 5 GB storage. A CPU-hour means one fully used core for one hour.; Rate source ↗
Medium / Large PAYG active CPU: $0.20 / $0.40 per active CPU-hour; Rates vary by selected size; storage limits are 10 GB and 20 GB respectively.; Rate source ↗
PAYG retained storage: $0.10 per GB-month; Includes disk data and snapshots.; Rate source ↗
Fixed keep-alive boxes: $8 / $16 / $32 per box-month; Small / Medium / Large respectively; CPU and storage are included in the fixed price.; Rate source ↗

Free includes 5 CPU-hours per month and up to 10 concurrent boxes. PAYG memory has no separate listed meter. LLM token budgets, BYOK, plan quotas, and the fixed versus auto-pausing mode must be evaluated separately.

Check current Upstash Box 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 Upstash Box

Export box disk state and inventory agent configuration, schedules, init commands, and model-provider credentials separately.
Choose whether the destination should stay running or pause between turns; do not copy keep-alive billing assumptions into a paused-compute design.
Run the same task with accumulated tool installations and data, then test RootFS growth, offline file edits, and any required process-state restoration.

Common questions

Is Sandbox0 a drop-in Upstash Box 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 ↗upstash.com/docs/box/overall/keep-alive ↗upstash.com/pricing/box ↗upstash.com/docs/box/overall/snapshots ↗upstash.com/docs/box/overall/how-it-works ↗/pricing ↗Sandbox0 RootFS capacity →

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