# Celesto (formerly SmolVM) vs Together Code Sandbox

> Celesto scores 68 (B) to Together Code Sandbox's 54.7 (C) for code sandboxes. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/celesto-vs-together-code-sandbox
- Markdown: https://www.anchorterminal.com/compare/celesto-vs-together-code-sandbox.md (~4,900 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

Celesto (formerly SmolVM) scores 68 (B) on agent readiness against Together Code Sandbox's 54.7 (C), and leads in 4 of 7 scored categories. Both do code sandboxes.

- Celesto (formerly SmolVM): grade B, 68/100, rank #298 of 1486. Markdown https://www.anchorterminal.com/tools/celesto.md · JSON https://www.anchorterminal.com/api/v1/tools/celesto.json
- Together Code Sandbox: grade C, 54.7/100, rank #896 of 1486. Markdown https://www.anchorterminal.com/tools/together-code-sandbox.md · JSON https://www.anchorterminal.com/api/v1/tools/together-code-sandbox.json
- Best code execution sandboxes for AI agents: https://www.anchorterminal.com/best/code-sandboxes/index.md
- All 231 sandboxes comparisons: https://www.anchorterminal.com/compare/code-sandboxes/index.md

## Which one, for what

### Celesto (formerly SmolVM) (B)

Good for: Local microVM sandboxes for agent code, browsers and desktops on Linux and macOS, with a path to a hosted cloud.

Ahead on:
- Reliability, 66 against 32
- Security & auth, 52 against 46
- Payments & pricing, 60 against 20
- Transparency & trust, 70 against 59

Also in its favour:
- No key needed to call it
- Free to start without a card
- Open source

Watch for: Version 0.1.13 and declared pre-1.0 in SECURITY.md, with the TypeScript SDK an alpha installed from a GitHub tarball

### Together Code Sandbox (C)

Good for: Teams already buying from Together, and former CodeSandbox SDK users, who want Docker-defined sandboxes with disk and memory snapshots from Python or TypeScript.

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: The SDK and CLI work only for organisations Together has enabled, and the docs say to contact Together for access


## Why the edge

### Payments & pricing: Celesto (formerly SmolVM) +40

- Celesto (formerly SmolVM) (60): Read with the self-hosted rule, scoring the hosted option for the price lines. No x402, MPP or L402 (0 of 40). Celesto Cloud publishes hourly prices for six sizes without a login (20). A one-time $5 Micro credit needs no card, and the local SDK is free (20). The graded local SDK installs from PyPI and runs with no account, so an agent needs no signup (20). Cloud use needs a browser signup and a card top-up. Total 60.
- Together Code Sandbox (20): No x402, MPP or L402 found (0). The pricing page still lists Code Sandbox at $0.0446 per vCPU-hour and $0.0149 per GiB of RAM per hour without a login, and does not say whether the rate covers the new SDK as well as the legacy one (20). The billing docs say Together has no free trial and that platform access needs a minimum $15 credit purchase (0). Access needs a browser signup, a payment and a request to Together to enable the organisation (0). 0 + 20 + 0 + 0 = 20.

### Reliability: Celesto (formerly SmolVM) +34

- Celesto (formerly SmolVM) (66): Read with the local-software lines, because the graded surface runs on the owner's machine. Installs from PyPI as `celesto` with Python 3.11 or newer on Linux and macOS stated, plus an install script (20). The repository has pytest, e2e, lint, TypeScript and smoke-test workflows and 38 test packages, but GitHub's API answered with a rate limit, so no run result was read (15 of 25, unchecked). 22 open issues and pull requests against about 188 commits in 90 days. The open bugs include a snapshot restore that can lose a VM's disk if interrupted and a thread-safety issue with five replies (18 of 25). A dated changelog with Security, Fixed, Added and Removed sections, and the rename to Celesto marked as a breaking release, though versions stay below 1.0 (13 of 15). Pre-1.0 per SECURITY.md (0). Total 66.
- Together Code Sandbox (32): Read with the hosted lines. status.together.ai lists the website, the playground and inference models with no component for the sandbox service, and a vendor status page with no component for the product takes 15. Incident line kept at 5. The Together page posts no incident since 6 January 2025, while status.codesandbox.io, which lists the CodeSandbox API and two clusters, wasn't re-read on 4 November (codesandbox.io answers a bot check, so its terms are unread), per the 8 October check (5). No rate or concurrency limits found, and the migration guide says the concurrency count and limit are not exposed (0). Both SDKs retry 408, 429, 500, 502, 503 and 504 three times with exponential backoff from 0.5 seconds plus jitter, and the SDK references say `snapshots.create` is not idempotent and should be excluded from retries. That is safe-retry guidance with no idempotency keys (12). No SLA found, and the terms make no uptime guarantee outside an order form (0). The docs still say the SDK must be enabled for an organisation, on request to sales, which is not general availability (0). 15 + 5 + 0 + 12 + 0 + 0 = 32.

### Transparency & trust: Celesto (formerly SmolVM) +11

- Celesto (formerly SmolVM) (70): Apache-2.0 in LICENSE and on PyPI (30). The privacy policy of 30 October 2026 links a subprocessor registry and describes the CLI telemetry in the same terms as the docs, but gives no retention periods beyond as long as necessary. Stopped cloud disks are kept 30 days per the pricing page (18 of 30). The changelog marks removals and the breaking rename, and the glossary lists older names still accepted, with no written deprecation policy (10 of 20). Telemetry is disclosed in the README, CLI reference and privacy policy, with three opt-outs, but it is on by default after the notice (16 of 20). Total 74.
- Together Code Sandbox (59): A closed service under Together's terms of service (19 May 2026). The SDKs, CLI and OpenAPI documents are MIT, which doesn't raise the line for a closed API, as for the Together inference and fine-tuning listings (15). The privacy policy (17 December 2025) says data is not used for training without opt-in. Its table of data types covers inference, fine-tuning and GPU clusters with no sandbox row, and no retention period for sandbox filesystems or snapshots was found beyond an optional snapshot `ttl` (12). The legacy `@codesandbox/sdk` page is still marked deprecated with no end date, the deprecations page covers models only, and breaking SDK changes are marked in the changelog. Kept as a partial (8). No sub-processor list or data locations for sandboxes found. A docs example names a cluster `na-us-ce-01`, and the trust centre was unread (3). 15 + 12 + 8 + 3 = 38.

### Security & auth: Celesto (formerly SmolVM) +6

- Celesto (formerly SmolVM) (52): Framework reading for local software. No credential is needed for local use, and the local API server and dashboard each require a bearer token, and cloud keys carry named permissions (22 of 30). Each computer has its own guest kernel, browser and display access uses capability URLs with a read-only option, and raw VNC is off. Against that, outbound networking is open by default and the restricting modes are opt-in (12 of 20). The security doc warns against giving connection URLs to a model as page content, but there is no guidance on treating command or page output as untrusted (5 of 15). `computer logs` shows startup output, with no audit log of commands (5 of 15). SECURITY.md with GitHub private vulnerability reporting and a supported-versions table, Security sections in the changelog, no security.txt, bug bounty or certification (8 of 20). Total 52.
- Together Code Sandbox (46): Project-scoped API keys, revocable within about five minutes, with optional expiry and rotation guidance, read as the Together inference and fine-tuning listings read the same key model (30). The in-VM OpenAPI document still lists `?token=` as a documented way to authenticate the WebSocket exec path, so the checklist's fixed 10 comes off (20). Each sandbox is a virtual machine. Every port is open to everyone unless the experimental inbound policy is set, no outbound rules exist, and project roles are admin and editor with no read-only role (8). The sandbox returns the output of code the agent ran, with no guidance on untrusted output found (8). Sandboxes can be listed with tags and `status_reason`. No audit log found (3). A PGP-signed security.txt (Expires 2028-09-30) points Contact and Policy at HackerOne with no acknowledgement time, the value this run gives a disclosure route with no stated time (7). 20 + 8 + 8 + 3 + 7 = 46.

## Score by category

| Category | Weight | Celesto (formerly SmolVM) | Together Code Sandbox | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 66 | 32 | Celesto (formerly SmolVM) +34 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 86 | Together Code Sandbox +1 |
| Agent ergonomics | 13% (16.2 this run) | 69 | 70 | Together Code Sandbox +1 |
| Security & auth | 14% (17.5 this run) | 52 | 46 | Celesto (formerly SmolVM) +6 |
| Payments & pricing | 10% (12.5 this run) | 60 | 20 | Celesto (formerly SmolVM) +40 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 81 | 83 | Together Code Sandbox +2 |
| Transparency & trust | 7% (8.8 this run) | 70 | 59 | Celesto (formerly SmolVM) +11 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **68 · B** | **54.7 · C** | |

## Facts side by side

| Fact | Celesto (formerly SmolVM) | Together Code Sandbox |
| --- | --- | --- |
| Kind | SDK + MCP | HTTP API |
| Vendor | Celesto AI, Inc. | Together AI |
| Hosted endpoint | no (local only) | `https://api.bartender.codesandbox.io` |
| Transports |  | HTTP |
| Auth | None | API key |
| Pricing | Freemium | Pay per use |
| x402 | no | no |
| Licence | Apache-2.0 | Proprietary service under Together's terms of service. The SDKs, CLI and OpenAPI documents on GitHub are MIT |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-11-05 | 2026-10-07 |
| Terms last updated | 2026-10-30 | no date given |
| Privacy policy last updated | 2026-10-30 | no date given |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 1.1k stars, 699 PyPI/wk | 3 stars, 1.3k npm/wk |

## How the scores have moved

### Celesto (formerly SmolVM)

No score change since it was listed.

### Together Code Sandbox

- +0.9 on 4 November 2026 (D to C): correction
- +0.1 on 28 October 2026: new evidence
- +0.1 on 27 October 2026: checklist

## Verdicts

**Celesto (formerly SmolVM).** Celesto runs each agent task in a local Firecracker or QEMU microVM with its own kernel, driven by a CLI with a stable JSON envelope and a Python SDK, free under Apache-2.0. It is pre-1.0, renamed from SmolVM on 19 September 2026, sends usage telemetry after a first-use notice, and leaves outbound networking open unless a mode is set.

**Together Code Sandbox.** Two public OpenAPI documents, MIT clients for Python and TypeScript, cursor pagination and SDK retries with guidance on which writes not to retry make the surface easy for an agent to drive. Access is the limit. Together enables the SDK per organisation on request, publishes no rate limits or SLA, and its status page has no sandbox component.

## Before you call either

### Celesto (formerly SmolVM)

1. Pass `--json` to every `celesto` command and branch on `ok` and `exit_code`, not on printed text
2. Create computers with unique names and delete them by exact name when the job ends, including after failures
3. Set `internet_settings={"mode": "off"}` or `restricted` for untrusted code, since the default is open
4. Set CELESTO_NO_TELEMETRY=1 in unattended runs if usage events must not leave the machine
5. Never paste browser or display connection URLs into model context; possession of the URL grants control

### Together Code Sandbox

1. Confirm the organisation is on Together's allowlist before installing. A valid `TOGETHER_API_KEY` alone is not enough
2. Build a snapshot first with `snapshots.create`. No default image exists, and every sandbox needs `snapshot_id` or `snapshot_alias`
3. Set `ttl` at creation or call `terminate()`. Nothing stops a sandbox otherwise, and closing the Python client leaves it running
4. Store the snapshot alias, not the sandbox ID. A terminated sandbox can't restart, and its state lives at `sandbox:<id>`
5. Exclude `snapshots.create` from retries with `should_retry`, and set `experimental.network_policy` before serving anything private on a port

## Questions

### Which is better for AI agents, Celesto (formerly SmolVM) or Together Code Sandbox?

Celesto (formerly SmolVM) scores 68 (B) on agent readiness against Together Code Sandbox's 54.7 (C), and leads in 4 of 7 scored categories.

### Can an agent call Celesto (formerly SmolVM) and Together Code Sandbox without installing anything?

No hosted endpoint is listed for Celesto (formerly SmolVM). Together Code Sandbox has a hosted endpoint at https://api.bartender.codesandbox.io.

### Are Celesto (formerly SmolVM) and Together Code Sandbox open source?

Celesto (formerly SmolVM) is open source (Apache-2.0). No open-source release is listed for Together Code Sandbox.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/celesto-vs-together-code-sandbox.json, and with the fewest tokens: https://www.anchorterminal.com/compare/celesto-vs-together-code-sandbox.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "celesto", "b": "together-code-sandbox"}`. From a terminal: `anchor compare celesto together-code-sandbox`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/celesto.json and https://www.anchorterminal.com/api/v1/tools/together-code-sandbox.json

## Other comparisons with Celesto (formerly SmolVM) or Together Code Sandbox

- [Amazon Bedrock AgentCore Code Interpreter vs Celesto (formerly SmolVM)](https://www.anchorterminal.com/compare/agentcore-code-interpreter-vs-celesto.md)
- [Amazon Bedrock AgentCore Code Interpreter vs Together Code Sandbox](https://www.anchorterminal.com/compare/agentcore-code-interpreter-vs-together-code-sandbox.md)
- [Blaxel Sandboxes vs Celesto (formerly SmolVM)](https://www.anchorterminal.com/compare/blaxel-sandboxes-vs-celesto.md)
- [Blaxel Sandboxes vs Together Code Sandbox](https://www.anchorterminal.com/compare/blaxel-sandboxes-vs-together-code-sandbox.md)
- [Celesto (formerly SmolVM) vs Cloudflare Sandbox SDK](https://www.anchorterminal.com/compare/celesto-vs-cloudflare-sandbox-sdk.md)
- [Celesto (formerly SmolVM) vs Daytona](https://www.anchorterminal.com/compare/celesto-vs-daytona.md)
- [Celesto (formerly SmolVM) vs DeltaBox Lite](https://www.anchorterminal.com/compare/celesto-vs-deltabox-lite.md)
- [Celesto (formerly SmolVM) vs Deno Sandbox](https://www.anchorterminal.com/compare/celesto-vs-deno-sandbox.md)
- [Celesto (formerly SmolVM) vs E2B](https://www.anchorterminal.com/compare/celesto-vs-e2b.md)
- [Celesto (formerly SmolVM) vs Freestyle](https://www.anchorterminal.com/compare/celesto-vs-freestyle.md)
- [Celesto (formerly SmolVM) vs InstaVM](https://www.anchorterminal.com/compare/celesto-vs-instavm.md)
- [Celesto (formerly SmolVM) vs Maritime](https://www.anchorterminal.com/compare/celesto-vs-maritime.md)
- [Celesto (formerly SmolVM) vs Microsoft Execution Containers](https://www.anchorterminal.com/compare/celesto-vs-microsoft-execution-containers.md)
- [Celesto (formerly SmolVM) vs Modal Sandboxes](https://www.anchorterminal.com/compare/celesto-vs-modal-sandboxes.md)
- [Celesto (formerly SmolVM) vs Morph Cloud](https://www.anchorterminal.com/compare/celesto-vs-morph-cloud.md)
- [Celesto (formerly SmolVM) vs Offscreen](https://www.anchorterminal.com/compare/celesto-vs-offscreen.md)
- [Celesto (formerly SmolVM) vs SPACE](https://www.anchorterminal.com/compare/celesto-vs-perplexity-space.md)
- [Celesto (formerly SmolVM) vs Runloop Devboxes](https://www.anchorterminal.com/compare/celesto-vs-runloop.md)
- [Celesto (formerly SmolVM) vs Sandbox0](https://www.anchorterminal.com/compare/celesto-vs-sandbox0.md)
- [Celesto (formerly SmolVM) vs Sprites](https://www.anchorterminal.com/compare/celesto-vs-sprites.md)
- [Celesto (formerly SmolVM) vs Vercel Sandbox](https://www.anchorterminal.com/compare/celesto-vs-vercel-sandbox.md)
- [Cloudflare Sandbox SDK vs Together Code Sandbox](https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-together-code-sandbox.md)
- [Daytona vs Together Code Sandbox](https://www.anchorterminal.com/compare/daytona-vs-together-code-sandbox.md)
- [Deno Sandbox vs Together Code Sandbox](https://www.anchorterminal.com/compare/deno-sandbox-vs-together-code-sandbox.md)
- [E2B vs Together Code Sandbox](https://www.anchorterminal.com/compare/e2b-vs-together-code-sandbox.md)
- [Freestyle vs Together Code Sandbox](https://www.anchorterminal.com/compare/freestyle-vs-together-code-sandbox.md)
- [InstaVM vs Together Code Sandbox](https://www.anchorterminal.com/compare/instavm-vs-together-code-sandbox.md)
- [Maritime vs Together Code Sandbox](https://www.anchorterminal.com/compare/maritime-vs-together-code-sandbox.md)
- [Microsoft Execution Containers vs Together Code Sandbox](https://www.anchorterminal.com/compare/microsoft-execution-containers-vs-together-code-sandbox.md)
- [Modal Sandboxes vs Together Code Sandbox](https://www.anchorterminal.com/compare/modal-sandboxes-vs-together-code-sandbox.md)
- [Morph Cloud vs Together Code Sandbox](https://www.anchorterminal.com/compare/morph-cloud-vs-together-code-sandbox.md)
- [Offscreen vs Together Code Sandbox](https://www.anchorterminal.com/compare/offscreen-vs-together-code-sandbox.md)
- [SPACE vs Together Code Sandbox](https://www.anchorterminal.com/compare/perplexity-space-vs-together-code-sandbox.md)
- [Runloop Devboxes vs Together Code Sandbox](https://www.anchorterminal.com/compare/runloop-vs-together-code-sandbox.md)
- [Sandbox0 vs Together Code Sandbox](https://www.anchorterminal.com/compare/sandbox0-vs-together-code-sandbox.md)
- [Sprites vs Together Code Sandbox](https://www.anchorterminal.com/compare/sprites-vs-together-code-sandbox.md)
- [Together Code Sandbox vs Vercel Sandbox](https://www.anchorterminal.com/compare/together-code-sandbox-vs-vercel-sandbox.md)
- [Agent 37 Cloud vs Celesto (formerly SmolVM)](https://www.anchorterminal.com/compare/agent37-vs-celesto.md)
- [Agent 37 Cloud vs Together Code Sandbox](https://www.anchorterminal.com/compare/agent37-vs-together-code-sandbox.md)
- [DeltaBox Lite vs Together Code Sandbox](https://www.anchorterminal.com/compare/deltabox-lite-vs-together-code-sandbox.md)

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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp