ConTree is offered as Sandboxes inside Nebius Token Factory and remains in Beta with access approval; legacy early-access credentials and endpoints have a documented migration path. Read the source ↗

Agent sandboxes / Nebius ConTree (Token Factory Sandboxes) alternative

A Nebius ConTree alternative for a returning agent machine

ConTree now powers Sandboxes inside Nebius Token Factory. Each operation starts fresh compute from an immutable filesystem image, and can save changed files as the next image. This supports branching and rollback, but a sequence of saved images is a different runtime model from returning to the same live agent process.

Start building Compare capabilities ↓

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

When Nebius ConTree (Token Factory Sandboxes) fits

Nebius ConTree fits speculative code execution, reproducible evaluation branches, OCI-image preparation, and workflows that deliberately save or discard each step. Its image inspection can retrieve saved files without starting an execution.

When to consider Sandbox0

Consider Sandbox0 for a per-user mutable Linux computer that keeps its complete writable RootFS across tasks and expands it online. Use explicit compatible memory pause/resume when process state is needed; ordinary filesystem resume still starts fresh processes.

Capabilities

Nebius ConTree (Token Factory Sandboxes) and Sandbox0: what persists?

Feature comparison with documentation and verification status
Capability	Nebius ConTree (Token Factory Sandboxes)	Sandbox0
Environment and runtime lifetime	Nebius ConTree (Token Factory Sandboxes)Not established in this review	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	Nebius ConTree (Token Factory Sandboxes)Explicitly saved filesystem images preserve files and installed dependencies for future independent operations.View evidence ↗	Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFS	Nebius ConTree (Token Factory Sandboxes)The persisted artifact is an immutable filesystem image, including installed dependencies, rather than only a synchronized workspace; save must be requested.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	Nebius ConTree (Token Factory Sandboxes)Every operation starts fresh compute; reusing an image is not resuming a retained running runtime.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	Nebius ConTree (Token Factory Sandboxes)Images explicitly do not retain processes, memory, handles, connections, or live services.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.

Saving and branching filesystem images retains agent tools, but the reviewed guides do not establish automatic online expansion of one continuing mounted RootFS. Account-effective image and execution limits require separate confirmation.

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.

ConTree documents listing and downloading files from saved images without execution. That is a useful compute-free read path; it differs from editing the same paused Sandbox0 RootFS through supported Files API mutations.

See paused file operations →

Filesystem branches do not carry running processes

The current execution guide says every operation starts fresh compute and finalizes when its primary process ends, stopping remaining subprocesses. Saved images preserve installed dependencies and files, not RAM, open handles, connections, or live services. Restart a server deliberately in the next operation instead of assuming an image is a paused VM.

Source 1 ↗Source 2 ↗

Saving is explicit and depends on the chosen interface

The Python SDK and MCP default to disposable execution, while the CLI retains changes and the REST schema has its own default. A session does not override this choice. Save before submission, then verify a returned inspectable image UUID; a nonzero exit, timeout, or cancellation does not by itself prove a usable continuation image.

Source 1 ↗

Beta usage diagnostics are not an invoice

The current Beta guide documents 50 simultaneous operations and 180-day checkpoint-image retention, with possible cleanup of untagged/unreferenced images afterwards. Account limits can differ. Operation resource fields, including cost, require confirmed units and are explicitly unsuitable for invoice reconciliation; use actual billing records.

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.

Nebius ConTree (Token Factory Sandboxes)

Pricing reviewed 2026-10-18

Current Beta sandbox compute rate: No numeric rate verified in the reviewed public Beta guides; Rate source ↗
Account-effective limits and billing: Confirm Nebius Token Factory Sandboxes terms for the project; Rate source ↗
Operation cost/resource fields: Diagnostics; not an invoice reconciliation source; Rate source ↗

Nebius GPU, inference and general cloud prices are different products and are not applied to these sandboxes. No unsupported free-Beta or savings claim is made. Confirm compute units, saved-image storage/retention, and effective project terms before a numerical estimate.

Check current Nebius ConTree (Token Factory 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 Nebius ConTree (Token Factory Sandboxes)

Record input and result image UUIDs, tags, disposable/save settings, installed tools, retained files, project terms, and operation/session IDs.
Export needed images/files and port compatible commands, credentials, networking, branch orchestration, and result handling.
Validate repeated system-state retention, growing outputs, paused reads and writes, process expectations, retention and actual billing.

Common questions

Is Sandbox0 a drop-in Nebius ConTree (Token Factory 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.tokenfactory.nebius.com/sandboxes/concepts/execution-lifecycle.md ↗docs.tokenfactory.nebius.com/sandboxes/concepts/images-checkpoints-and-branches.md ↗docs.tokenfactory.nebius.com/sandboxes/operate/limits-retention-and-usage.md ↗docs.tokenfactory.nebius.com/sandboxes/overview.md ↗contree.dev/blog/contree-joins-token-factory/ ↗Sandbox0 RootFS capacity →

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