Agent sandboxes / LangSmith Sandboxes alternative

A LangSmith sandbox alternative for a growing agent environment

LangSmith Sandboxes retains filesystem state after stop and can resume memory on supported runtime configurations. The comparison is about its execution backend, while tracing, evaluation, and other LangSmith products remain separate decisions.

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

When LangSmith Sandboxes fits

LangSmith Sandboxes fits teams that want first-party LangChain and Deep Agents execution integration, managed snapshots, authenticated service access, and LangSmith workspace controls.

When to consider Sandbox0

Consider Sandbox0 as the execution environment for an agent that needs an automatically growing durable RootFS and supported file reads or edits during compute pauses. Your application can keep separate observability and model integrations.

Capabilities

LangSmith Sandboxes and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeLangSmith SandboxesNot 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 filesLangSmith SandboxesStopped sandboxes retain their filesystem; later requests wake them.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSLangSmith SandboxesReusable sandbox filesystem snapshots; attached mounts remain separate.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 stateLangSmith SandboxesStop retains files; memory retention is opt-in on supported runtimes.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateLangSmith SandboxesREST-only controls on supported backends; overlay-rootfs memory capture is unsupported.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.

LangSmith snapshots retain a filesystem and can seed later sandboxes. The reviewed snapshot and mount documentation does not establish automatic expansion of the running root filesystem as it fills; inspect the chosen backend and capacity separately.

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.

LangSmith documents request-driven wake of a stopped sandbox whose files were retained. The cited snapshot and mount guides do not establish a complete no-wake RootFS editing interface. Sandbox0 explicitly supports paused persistent-file operations, with retained-memory mutations blocked.

See paused file operations →

Stopped filesystem state is retained

LangSmith documents stopping a sandbox while keeping its filesystem, with a later request waking it. It also builds reusable filesystem snapshots from images or running sandboxes. Independently mounted buckets and repositories have their own storage semantics.

Source 1 ↗Source 2 ↗

Memory restoration depends on runtime and API

LangSmith exposes memory snapshot and preserve-memory-on-stop controls through REST. Its Python and TypeScript sandbox clients do not yet expose those fields, and overlay-rootfs runtimes cannot capture a memory image. Default voluntary stop keeps files and discards RAM.

Source 1 ↗

Use Sandbox LSU rates, not deployment or tracing rates

LangSmith publishes separate LSU meters for sandbox CPU, RAM, and storage, billed per second. Other LangSmith products use different meters. Apply the published $1 per LSU conversion and plan allowances before comparing the machine cost with Sandbox0.

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.

Same size. Lower compute cost.

2 vCPU · 4 GiB RAM · 730 running hours / month

Save $86.17 / month

The same CPU and memory allocation, with runtime aggregated across sessions. Monthly allowances and credits below are applied to this workload.

LangSmith Sandboxes

Developer · 8 LSU monthly Sandbox allowance

$129.97

$0.189/hour before monthly allowances

Sandbox0

Pay as you go · no monthly plan fee

$43.80

$0.06/hour · 66% lower in this example

Converts Sandbox usage at the published $1 per LSU and deducts the 8 LSU monthly Sandbox allowance. Deployment and trace meters are separate; paid workspace seats are not assumed for this Developer example.

Compute and stated plan fees only. Storage, network, taxes and one-time credits are excluded; hardware and throughput can differ.

Calculation and billing assumptions

LangSmith Sandboxes: $137.97 compute after 0 included vCPU-hours and 0 included GiB-hours, plus $0.00 plan fee, minus $8.00 applied monthly credit.

Sandbox0: 4 GiB × 730 hours × its published compute rate. CPU uses the Cloud allocation shown on the pricing page.

Includes compute and the selected plan. Excludes storage, network, taxes, one-time grants and negotiated discounts. Assumes this workload can use the full listed monthly allowances. CPU and memory counts do not guarantee equal hardware or throughput.

Checked LangSmith Sandboxes rate source ↗Sandbox0 rates ↗

LangSmith Sandboxes

Pricing reviewed 2026-10-18

Sandbox CPU
0.0576 LSU per vCPU-hour
Rate source ↗
Sandbox memory
0.01845 LSU per GiB-hour
Rate source ↗
Sandbox storage
0.000123 LSU per GiB-hour
Rate source ↗
Published unit conversion
$1.00 per LSU
The price page lists 8 LSU of included monthly Sandbox usage. Developer sandbox count and paid-seat entitlements differ.
Rate source ↗
Plus workspace seats
$39 per seat-month
Usage is additional after applicable included allowances; this is not a required fee for every sandbox configuration.
Rate source ↗

Do not apply LangSmith Deployment, database, trace, or LLM Gateway rates to Sandbox execution. Memory and storage units use GiB; configured resources, included allowances, and the current workspace plan determine the total.

Check current LangSmith 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
Understand storage billing →

Before migrating from LangSmith Sandboxes

  1. Inventory snapshots, current stopped state, runtime backend, memory flags, and all external mounts.
  2. Port the execution backend and network/auth proxy rules while keeping tracing and evaluation integrations where needed.
  3. Validate installed packages, repeated-task file state, automatic RootFS growth, paused file operations, and the required process restoration mode.

Common questions

Is Sandbox0 a drop-in LangSmith 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 ↗docs.langchain.com/langsmith/sandbox-snapshots ↗docs.langchain.com/langsmith/sandbox-mounts ↗www.langchain.com/pricing ↗/pricing ↗Sandbox0 RootFS capacity →

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