Agent sandboxes / Brimble Sandboxes alternative

A Brimble Sandboxes alternative for a growing Linux agent

Brimble offers ephemeral sandboxes alongside its application platform, plus independent volumes and named filesystem snapshots. Those are real persistence options, but ordinary resume starts a fresh container around retained workspace data. Compare that boundary with an agent whose system environment changes across tasks.

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

When Brimble Sandboxes fits

Brimble fits teams that want sandbox APIs beside Git-based app delivery, coding-agent templates, named snapshots, and workspace volumes. Its paid plans bundle sandbox allowances with broader platform features.

When to consider Sandbox0

Consider Sandbox0 when package installs and system configuration beyond the workspace should persist on one durable RootFS, storage should grow automatically online, and supported file operations should work while compute remains paused.

Capabilities

Brimble Sandboxes and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeBrimble SandboxesCurrent Hacker sandbox maximum is 120 minutes and Developer maximum is 360 minutes; neither means unlimited lifetime.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 filesBrimble SandboxesIndependent single-attach volumes retain workspace data after pause or sandbox destruction; region and plan limits apply.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSBrimble SandboxesNamed filesystem images exist, but ordinary resume retains workspace volume data and starts a fresh template container. Uniform full-RootFS coverage is not established.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 stateBrimble SandboxesPause stops compute; resume creates a fresh container with the retained workspace volume.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateBrimble SandboxesPause does not retain RAM, processes, or open sockets; named snapshots are documented as filesystem images.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.

Brimble volumes are currently fixed-size once created; expanding data requires creating a larger volume and copying files. This differs from enabled Sandbox0 RootFS growth while the agent and its open files continue running.

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 volume survives the machine, but resume starts a new container

Brimble’s persistent development recipe keeps a volume while sandboxes pause or are destroyed, then reattaches it for subsequent work. Pause releases compute billing and resume starts a fresh container of the template: retained workspace files return, RAM, processes, and sockets do not. System changes elsewhere need an image or appropriate snapshot strategy.

Source 1 ↗Source 2 ↗

Snapshots and fixed-size volumes serve different reuse paths

Named snapshots are point-in-time filesystem images restored into independent fresh sandboxes. Persistent volumes are separate single-attach, region-pinned objects backed by the storage fabric. Their current size cannot be changed after creation: growing beyond it requires a larger volume and data copy. That differs from expanding the complete mounted RootFS online.

Source 1 ↗Source 2 ↗

Use sandbox entitlements rather than the app calculator

The price page offers sandboxes only on paid plans, with different concurrency, resource ceilings, maximum runtime, and included CPU/RAM hours. Its app calculator and object-storage rate are separate products. The overview’s older resource sizing also differs from the current plan table; verify the effective create limits instead of combining the two.

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.

Brimble Sandboxes

Pricing reviewed 2026-10-18

Hacker base plan
$3 per month
Includes 5 sandbox CPU-hours and 10 GB-hours, up to 3 concurrent sandboxes, 2 vCPU / 4 GB ceiling, and 120-minute runtime.
Rate source ↗
Developer base plan
$11 per month
Includes 20 sandbox CPU-hours and 40 GB-hours, up to 15 concurrent sandboxes, 4 vCPU / 8 GB ceiling, and 360-minute runtime.
Rate source ↗
Persistent volumes
GB-month meter; effective rate shown in dashboard
Current guide describes metering while attached; confirm detached retention charges and plan caps.
Rate source ↗
Enterprise
Custom pricing
Rate source ↗

Included CPU-hours and GB-hours are separate allowances, not guaranteed free whole-machine hours. Verify sandbox overage rates and current create limits; the app calculator is not a sandbox rate card. The separate $0.032 per GB-month object-storage product is not assumed to be the persistent-volume rate.

Check current Brimble 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 Brimble Sandboxes

  1. Export volume data and required snapshots, and distinguish workspace files from installed tools or configuration elsewhere.
  2. Build the required system environment in a Sandbox0 template and port sandbox command/file, network, credentials, and lifecycle calls.
  3. Test return visits, package/configuration persistence, online RootFS growth, paused file access, process expectations, and paid-plan plus storage charges.

Common questions

Is Sandbox0 a drop-in Brimble 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 ↗paper.brimble.io/sandboxes/cookbook/persistent-dev-env.md ↗paper.brimble.io/api-reference/sandboxes/pause-a-sandbox.md ↗paper.brimble.io/sandboxes/snapshots.md ↗paper.brimble.io/volumes/overview.md ↗www.brimble.io/pricing ↗paper.brimble.io/sandboxes/overview.md ↗Sandbox0 RootFS capacity →

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