Agent sandboxes / Blaxel alternative

A Blaxel sandbox alternative for data that keeps growing

Blaxel preserves both processes and the filesystem in standby. Its writable local layer lives in RAM, with volumes, archives, and Agent Drive serving different retention needs. An agent’s data layout therefore matters as much as its resume behavior.

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

When Blaxel fits

Blaxel fits bursty agents that benefit from managed standby and memory-preserving reconnection. Its separately mounted storage options can also suit data shared among sandboxes or retained independently of one sandbox.

When to consider Sandbox0

Sandbox0 can suit environments where packages, configuration, repositories, and outputs grow together on one disk-backed durable RootFS. Compute pauses and storage retention are explicit, with online filesystem growth on enabled templates.

Capabilities

Blaxel and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeBlaxelNot established in this reviewSandbox0ttl 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 filesBlaxelStandby snapshots and archives preserve filesystem state; volumes have independent retention.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSBlaxelStandby includes the entire filesystem and processes.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 stateBlaxelManaged idle standby restores saved state; archive uses a different path.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateBlaxelStandby preserves memory; archival does not. External connections may expire.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.

Blaxel’s local writable layer uses sandbox RAM; volumes and Agent Drive add separate mounted storage. Compare a growing package/data workload across that layout before assuming filesystem persistence implies expandable root-disk capacity.

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 →

Budget writable files alongside application RAM

Blaxel documents a read-only EROFS image under a writable tmpfs layer in sandbox RAM. A large dependency cache or generated dataset can compete with application memory. Its volumes or Agent Drive provide separate storage paths; Sandbox0 persists the writable RootFS in regional object storage.

Source 1 ↗Source 2 ↗

Standby and archive preserve different state

Blaxel standby captures memory and filesystem state. Archival instead exports filesystem changes and later restarts configured processes with new PIDs. Keep these modes separate when an agent has a live interpreter, open handles, or expensive initialization.

Source 1 ↗

Price the storage mode you actually retain

The sandbox compute rate is tied to allocated memory, with CPU assigned accordingly. Standby snapshots, images, and provisioned volumes have distinct storage charges. Do not substitute the cheaper Batch Jobs meter for an interactive sandbox.

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.

Blaxel

Pricing reviewed 2026-10-18

Sandbox active compute
$0.0000115 per allocated GB RAM-second
CPU scales with the selected memory; it is not a separately charged CPU-second.
Rate source ↗
Memory and filesystem snapshots
$0.20 per GB-month
Rate source ↗
Deployment images
$0.045 per GB-month
Rate source ↗
Volumes
$0.12 per provisioned GB-month
Provisioned capacity is billed even when not fully written.
Rate source ↗

Suspended time does not accrue active compute. Top-up tiers control quotas; Agent Drive is listed free during beta, and the separate Agent Runtime product is marked coming soon.

Check current Blaxel 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 Blaxel

  1. Measure writable-layer size separately from application memory, and inventory volume and Agent Drive mounts.
  2. Choose whether each workload needs filesystem-only restart or live interpreter restoration; standby and archive are different source states.
  3. Port the agent image, secrets, and egress controls, then verify accumulated data and retained-storage charges after a pause.

Common questions

Is Sandbox0 a drop-in Blaxel 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.blaxel.ai/Sandboxes/Overview ↗/docs/sandbox ↗blaxel.ai/pricing ↗Sandbox0 RootFS capacity →

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