# Agent 37 Cloud vs Celesto (formerly SmolVM) (slim)

> Celesto scores 68 (B) to Agent 37 Cloud's 53.9 (D) for persistent sandboxes. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/agent37-vs-celesto.md (~5,500 tokens) · this version ~2,980 tokens · JSON https://www.anchorterminal.com/compare/agent37-vs-celesto.json · canonical https://www.anchorterminal.com/compare/agent37-vs-celesto
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-11-07
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Celesto (formerly SmolVM) scores 68 (B) on agent readiness against Agent 37 Cloud's 53.9 (D), and leads in every scored category. Both do persistent sandboxes.

- Agent 37 Cloud: D 53.9, rank #922 of 1486 · https://www.anchorterminal.com/tools/agent37.min.md
- Celesto (formerly SmolVM): B 68, rank #298 of 1486 · https://www.anchorterminal.com/tools/celesto.min.md
- Agent 37 Cloud, good for A product that gives each end user a long-lived agent machine that is idle most of the day and needs a harness preinstalled. Also A hosted endpoint, with nothing to install.
- Celesto (formerly SmolVM), 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 57; Schema & documentation, 85 against 57; Agent ergonomics, 69 against 60; Payments & pricing, 60 against 30; Maintenance & community, 81 against 65; Transparency & trust, 70 against 64. Also No key needed to call it; Free to start without a card; Open source.

| Category | Agent 37 Cloud | Celesto (formerly SmolVM) |
| --- | --- | --- |
| Reliability (16%) | 57 | 66 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 57 | 85 |
| Agent ergonomics (13%) | 60 | 69 |
| Security & auth (14%) | 48 | 52 |
| Payments & pricing (10%) | 30 | 60 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 65 | 81 |
| Transparency & trust (7%) | 64 | 70 |

| Fact (where they differ) | Agent 37 Cloud | Celesto (formerly SmolVM) |
| --- | --- | --- |
| Kind | HTTP API | SDK + MCP |
| Vendor | Agent 37 Inc. | Celesto AI, Inc. |
| Hosted endpoint | `https://api.agent37.com/v1` | no (local only) |
| Transports | HTTP |  |
| Auth | API key | None |
| Pricing | Pay per use | Freemium |
| Licence | Proprietary service under Agent 37's terms of service. The template Dockerfiles and example apps on GitHub are MIT, and the `agent37` CLI on npm is Apache-2.0 | Apache-2.0 |
| Last release | 2026-11-01 | 2026-11-05 |
| Terms last updated | 2026-08-04 | 2026-10-30 |
| Privacy policy last updated | 2026-09-01 | 2026-10-30 |
| Popularity | none | 1.1k stars, 699 PyPI/wk |
| Agent reviews | 2.8/5 (4) | none |

Why the edge:
- Payments & pricing, Celesto (formerly SmolVM) +30: Agent 37 Cloud 30 (No x402, MPP or L402 on the API (0). Per-unit prices for vCPU, memory and disk are published without login (20). The one-time $5 credit is granted only after a card is added in the dashboard, and accounts created by API get no credit, so there is no free tier without a card (0). `POST /v1/signup`, unauthenticated, now creates a workspace and returns a full API key and a Stripe Checkout link, and `POST /v1/billing/top-up` mints further links. Nothing runs until someone pays that link, so a person completes the step that makes access useful (10 of 20). Total 30.); 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.)
- Schema & documentation, Celesto (formerly SmolVM) +28: Agent 37 Cloud 57 (No OpenAPI or other machine-readable contract is shown or linked, and the 794 KB llms-full.txt never mentions one (0). llms.txt now lists 84 pages, with llms-full.txt and a Markdown copy of every page (10). Pages say what each call is for and when to choose another, such as stop against delete, resize against fork and exec for anything unwrapped (17). Parameters are documented with types, ranges, defaults and patterns in prose, with no schema to validate against (10). Curl, Python and JavaScript examples with responses on each page, and an error reference for the Hosting API, transport failures and the Agent API (15). The path is versioned at /v1 and template images carry immutable dated tags, but no public changelog was found (5). Total 57.); Celesto (formerly SmolVM) 85 (Read as an SDK and CLI. The repository ships an OpenAPI document for the local server (24 operations) and the cloud API (171 operations), from which the TypeScript client is generated (25). llms.txt at celesto.ai, plus Markdown docs in the repository (10). The README's runtime table says when to use each runtime, and the automation section says to prefer `exec` and keep `shell`, `ssh` and `desktop` for interactive work (14 of 20). Network modes are closed values (`open`, `off`, `public`, `restricted`) and the SDK takes typed keyword arguments, though `internet_settings` is a plain dict (11 of 15). Examples directory, a JSON envelope for every command and documented cloud error fields such as `required_scope`, without a full error catalogue (12 of 15). Dated changelog and tags, pre-1.0 (13 of 15). Total 85.)
- Maintenance & community, Celesto (formerly SmolVM) +16: Agent 37 Cloud 65 (Scored on the closed-service scale. The newest template image tag is b2b-hermes/2026.11.01a (Hermes v0.22.5), four days before the check (30). The repository holds 77 dated image tags for the API's system templates (14 more are for the Personal Agents app), on 16 days from 2 October to 1 November 2026, each pushed by the publish script for a commit that names the change (20). No public changelog. Support is by email, a dashboard chat and a founder's booking link, and we couldn't read GitHub issues (5 of 15). No SDK library. The `agent37` CLI on npm was at 0.4.0 per the 8 October check, not re-read on 5 November, and `langchain-agent37` 0.1.0 was tagged on 26 October (5 of 15). The templates repository has a test workflow, whose results we couldn't read (5 of 10). Total 65.); Celesto (formerly SmolVM) 81 (0.1.13 on PyPI on 5 November 2026, tagged 6 November (30). 22 PyPI releases in the 90 days to 6 November (20). Most open issues are filed by maintainers. Outside reports such as the thread-safety issue got replies, and several recent ones have none yet; pull-request reply times were not read (15 of 25). The Python SDK is current, the TypeScript SDK is an alpha not published to npm (8 of 15). uv and Cargo lock files, CodeQL and publish workflows, with run results unread (8 of 10). Total 81.)
- Reliability, Celesto (formerly SmolVM) +9: Agent 37 Cloud 57 (Graded as a hosted service. A Better Stack status page now answers at status.agent37.com, with components for the website and dashboard, the API, sandbox creation, sandbox URLs and three regions (20). It did not exist on 8 October, when the host answered 404, so the record is short. Its feed lists two incidents, both partial: on 20 October fewer than 1 per cent of US sandboxes restarted (21 minutes degraded), and on 29 October some sandbox creations failed from 14:55 to 16:00 UTC while running sandboxes were not affected. A short record with minor incidents only (15). No request rate limits are published. The only numbers are one on-demand backup per instance every 15 minutes, three concurrent template builds and 20 feedback reports a day (0). Retry guidance is written per code, with backoff for `try_again`, `no_capacity` and 429, a `Retry-After` header on the backup limit, an idempotency key on budget top-ups and a warning that a timed-out exec keeps running, but instance create and exec take no idempotency key (12 of 15). The terms promise no uptime level unless agreed in writing (0). The Cloud API carries no beta label (10). Total 57.); 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.)
- Agent ergonomics, Celesto (formerly SmolVM) +9: Agent 37 Cloud 60 (Exec output is capped at 512 KB a stream with a `truncated` flag, logs take a `tail` and chat can return one JSON body instead of a stream, but there is no field selection and `GET /v1/instances` returns every full object (12). No pagination or filters were found on the instance, session or file lists. Usage and metrics take date or hour windows (8). Errors carry stable codes, with `param`, `hint` and `response_id` on the Agent API and a remedy per code (20). An idempotency key on budget top-ups, `X-Expected-Mtime` and `overwrite=false` on file writes and documented safe retries, with none on create or exec (12). An empty create body works and every field is optional. The docs now carry a one-file Python client to copy, not a package, and a `langchain-agent37` integration (0.1.0, 26 October), beside the CLI and raw HTTP examples (8). Total 60.); Celesto (formerly SmolVM) 69 (A CLI and SDK add no tool definitions to an agent's context. Collected command output is capped at 8 MiB with streaming as the alternative (18 of 25). `computer list`, `logs --follow` and name lookups, with little filtering (10 of 20). JSON errors carry a recovery command where Celesto has one, and cloud errors carry stable codes, operation and computer context and recovery fields since 0.1.7 (18 of 20). State-changing cloud requests are never replayed automatically and computers are addressed by unique names, but there are no idempotency keys (10 of 20). `with Computer()` creates and deletes a computer with no parameters, with Python and an alpha TypeScript SDK (13 of 15). Total 69.)
- Transparency & trust, Celesto (formerly SmolVM) +6: Agent 37 Cloud 64 (Closed service with dated terms (4 August 2026, re-read on 5 November). Template Dockerfiles and example apps are MIT and the CLI is Apache-2.0 (15). The privacy policy (1 September 2026) gives retention by category, seven days for a deleted instance's recovery copy, up to 30 days for request logs and about seven years for billing records, and the docs repeat the seven-day window. No DPA was found (22). One deprecation is documented, the Bearer header on instance URLs, with an email promised before removal and no date. No written policy (5). The policy names 12 kinds of third-party service and the docs say instances run on dedicated servers in the United States. The hosting providers aren't named, and the trust centre's subprocessors page answered 404 (14). Total 56.); 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.)