CI and test infrastructure / CircleCI alternative

CircleCI alternative for persistent agent workers

CircleCI orchestrates builds and tests across several execution environments. Caches, workspaces and artifacts preserve selected data with explicit retention. Compare those CI outputs with the complete installed system state that an agent needs when returning to the same environment.

Start buildingCompare capabilities ↓

Reviewed 2026-10-19 · Published by the Sandbox0 team

When CircleCI fits

Choose CircleCI for workflow orchestration, test reporting, its integrations and managed multi-OS build infrastructure. Preserve that delivery and testing layer when moving only persistent agent execution.

When to consider Sandbox0

Consider Sandbox0 for a returning compatible Linux worker with durable system tools and a growing RootFS. A runtime integration still needs scheduling, job isolation, test/report publication and any platform-specific build hosts.

Capabilities

CircleCI and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeCircleCINot 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 filesCircleCIExplicit caches, workspaces and artifacts retain selected files under expiry rules.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSCircleCIThe selected-object retention contract does not establish full mutable RootFS preservation.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 stateCircleCIWorkflow continuation and object restoration do not establish machine checkpoint/resume.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateCircleCINo arbitrary process-memory checkpoint is established.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.

A cache/workspace’s selected files and fixed retention differ from a whole writable Linux RootFS that grows online with the agent. More CI resource capacity is not itself a persistence guarantee.

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.

Published cache/workspace/artifact objects can survive execution, but they do not expose every supported system path of a paused worker through a whole-RootFS file interface.

See paused file operations →

Three storage interfaces have different purposes

Caches reuse dependencies, workspaces pass files to downstream jobs and artifacts preserve outputs. Current default/maximum retention is 15 days for caches and workspaces and 30 days for artifacts. These are selected objects with retention policies, rather than an indefinite whole-machine filesystem checkpoint.

Source 1 ↗

Resource class and generation change credit consumption

The rate card lists first-generation x86 Docker Small at 5 credits/minute and Medium at 10, while Gen 2 Medium uses 12. Linux VMs, Arm, Windows, macOS and GPUs have other shapes and credit rates. A credit count without class and generation is not a useful compute comparison.

Source 1 ↗

Compute is only part of credit usage

Credits also cover users and other features. The Free plan’s up-to-6,000-minute headline assumes Small Docker; it is not 6,000 minutes on every machine. Storage and restoring data to self-hosted runners have their own usage accounting.

Source 1 ↗Source 2 ↗Source 3 ↗

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.

CircleCI

Pricing reviewed 2026-10-19

Free
$0/month; 30,000 credits/month
Up to 6,000 minutes assumes the 5-credit Small Docker class.
Rate source ↗
Performance
From $15/month
Current table lists 30,000 included credits, then $15 per additional 25,000; bulk terms can differ.
Rate source ↗
x86 Docker Medium, original generation
10 credits per minute
2 CPU and 4 GB RAM; Gen 2 Medium is a separate 12-credit shape.
Rate source ↗
M4 Pro Medium macOS VM
200 credits per minute
6 CPU and 28 GB RAM; plan availability and other meters apply.
Rate source ↗

The paid plan and credit purchase terms determine actual dollars. Seats, retention, network egress and premium features can also consume credits. No universal credit-to-runtime-hour conversion or equal-throughput savings claim is asserted.

Check current CircleCI 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 CircleCI

  1. Inventory executor classes and generations, credit plan, caches, workspaces, artifacts and retention.
  2. Retain CI orchestration and map compatible worker execution to Sandbox0 with explicit transfer and isolation policies.
  3. Test installed-tool retention, growing files, paused access and the complete compute, seats, storage, network and model budget.

Common questions

Is Sandbox0 a drop-in CircleCI replacement?

Evaluate API compatibility and product scope. These products serve different core workflows, so a change may require a different architecture.

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 ↗circleci.com/docs/guides/optimize/persist-data/ ↗circleci.com/pricing/price-list/ ↗circleci.com/pricing/ ↗Sandbox0 RootFS capacity →

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