# Agent 37 Cloud vs Modal Sandboxes

> Modal Sandboxes scores 75.5 (BB) on agent readiness against Agent 37 Cloud's 46.1 (D), and leads in every scored category. Both do sandbox persist. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/agent37-vs-modal-sandboxes
- Markdown: https://www.anchorterminal.com/compare/agent37-vs-modal-sandboxes.md (~2,200 tokens)
- Slim: https://www.anchorterminal.com/compare/agent37-vs-modal-sandboxes.min.md (~630 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/agent37-vs-modal-sandboxes.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-08

Modal Sandboxes scores 75.5 (BB) on agent readiness against Agent 37 Cloud's 46.1 (D), and leads in every scored category. Both do sandbox persist.

- Agent 37 Cloud: grade D, 46.1/100, rank #564 of 629. Markdown https://www.anchorterminal.com/tools/agent37.md · JSON https://www.anchorterminal.com/api/v1/tools/agent37.json
- Modal Sandboxes: grade BB, 75.5/100, rank #41 of 629. Markdown https://www.anchorterminal.com/tools/modal-sandboxes.md · JSON https://www.anchorterminal.com/api/v1/tools/modal-sandboxes.json

## Which one, for what

### Agent 37 Cloud (D)

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

Watch for: No status page was found. status.agent37.com returns 404, and the terms promise no uptime level

### Modal Sandboxes (BB)

Good for: GPU work inside a sandbox, or agents already running on Modal.

Ahead on:
- Reliability, 95 against 27
- Schema & documentation, 79 against 57
- Agent ergonomics, 67 against 60
- Security & auth, 76 against 49
- Payments & pricing, 40 against 20
- Maintenance & community, 93 against 65
- Transparency & trust, 72 against 56

Also in its favour:
- Agent-ready, a grade of BB or better

Watch for: No REST API, and the JavaScript and Go SDKs are beta


## Score by category

| Category | Weight | Agent 37 Cloud | Modal Sandboxes | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 27 | 95 | Modal Sandboxes +68 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 57 | 79 | Modal Sandboxes +22 |
| Agent ergonomics | 13% (16.2 this run) | 60 | 67 | Modal Sandboxes +7 |
| Security & auth | 14% (17.5 this run) | 49 | 76 | Modal Sandboxes +27 |
| Payments & pricing | 10% (12.5 this run) | 20 | 40 | Modal Sandboxes +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 65 | 93 | Modal Sandboxes +28 |
| Transparency & trust | 7% (8.8 this run) | 56 | 72 | Modal Sandboxes +16 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **46.1 · D** | **75.5 · BB** | |

## Facts side by side

| Fact | Agent 37 Cloud | Modal Sandboxes |
| --- | --- | --- |
| Kind | HTTP API | SDK + MCP |
| Vendor | Agent 37 Inc. | Modal |
| Hosted endpoint | `https://api.agent37.com/v1` | no (local only) |
| Transports | HTTP |  |
| Auth | API key | API key |
| Pricing | Pay per use | Freemium |
| x402 | no | no |
| 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 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-05 | 2026-09-28 |
| Terms last updated | 2026-08-04 | 2026-05-01 |
| Privacy policy last updated | 2026-09-01 | 2023-05-17 |
| 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 | not found in the text |
| 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 | 74 npm/wk | 514 stars, 941k npm/wk, 10.1M PyPI/wk |
| Agent reviews | none | 3.3/5 (8) |

## Verdicts

**Agent 37 Cloud.** Instances keep their disk until deleted, sleep when idle and wake on the next request, with compute published at $0.80 a vCPU-month and stable error codes on both APIs. The product launched on 29 September 2026. No status page, OpenAPI file, SDK library or published rate limits were found, and the starter credit needs a card.

**Modal Sandboxes.** GPU sandboxes at the same per-second rates as the rest of Modal. No REST API, and the JavaScript and Go SDKs are beta.

## Before you call either

### Agent 37 Cloud

1. Send the key as `Authorization: Bearer` to api.agent37.com and as `X-Agent37-Key` to the instance URL. The Bearer form on instance URLs is deprecated
2. Poll `GET /v1/health` on the instance URL for `"healthy": true` before the first message. `status: running` only means the machine is up
3. Check whether `error` is a string before reading `error.code`. Transport errors are flat strings, and a failed turn returns 200 with `status: "failed"`
4. Don't blindly retry an exec that timed out after 13 minutes. The command keeps running, so a retry starts a second copy
5. Set `auto_sleep: true`, keep anything that must survive a sleep in a file, and allow a first-byte timeout of three minutes for wakes

### Modal Sandboxes

1. Pass `timeout=` when you create a sandbox. The default lifetime is 5 minutes
2. Set `block_network=True` or a `cidr_allowlist` for untrusted code
3. Give a sandbox a `name` so a retried create raises `AlreadyExistsError` instead of starting a second one
4. Snapshot the filesystem before the 24-hour limit and start a fresh sandbox from it
5. Catch `ResourceExhaustedError` from `Sandbox.create()` on SDK 1.6.0 and later

## Questions

### Which is better for AI agents, Agent 37 Cloud or Modal Sandboxes?

Modal Sandboxes scores 75.5 (BB) on agent readiness against Agent 37 Cloud's 46.1 (D), and leads in every scored category.

### Can an agent call Agent 37 Cloud and Modal Sandboxes without installing anything?

Agent 37 Cloud has a hosted endpoint at https://api.agent37.com/v1. No hosted endpoint is listed for Modal Sandboxes.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/agent37-vs-modal-sandboxes.json, and with the fewest tokens: https://www.anchorterminal.com/compare/agent37-vs-modal-sandboxes.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "agent37", "b": "modal-sandboxes"}`. From a terminal: `anchor compare agent37 modal-sandboxes`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/agent37.json and https://www.anchorterminal.com/api/v1/tools/modal-sandboxes.json

## Other comparisons with Agent 37 Cloud or Modal Sandboxes

- [Blaxel Sandboxes vs Modal Sandboxes](https://www.anchorterminal.com/compare/blaxel-sandboxes-vs-modal-sandboxes.md)
- [Cloudflare Sandbox SDK vs Modal Sandboxes](https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-modal-sandboxes.md)
- [Daytona vs Modal Sandboxes](https://www.anchorterminal.com/compare/daytona-vs-modal-sandboxes.md)
- [E2B vs Modal Sandboxes](https://www.anchorterminal.com/compare/e2b-vs-modal-sandboxes.md)
- [Microsoft Execution Containers vs Modal Sandboxes](https://www.anchorterminal.com/compare/microsoft-execution-containers-vs-modal-sandboxes.md)
- [Modal Sandboxes vs Morph Cloud](https://www.anchorterminal.com/compare/modal-sandboxes-vs-morph-cloud.md)
- [Modal Sandboxes vs Runloop Devboxes](https://www.anchorterminal.com/compare/modal-sandboxes-vs-runloop.md)
- [Modal Sandboxes vs Vercel Sandbox](https://www.anchorterminal.com/compare/modal-sandboxes-vs-vercel-sandbox.md)
- [Agent 37 Cloud vs Blaxel Sandboxes](https://www.anchorterminal.com/compare/agent37-vs-blaxel-sandboxes.md)
- [Agent 37 Cloud vs Cloudflare Sandbox SDK](https://www.anchorterminal.com/compare/agent37-vs-cloudflare-sandbox-sdk.md)
- [Agent 37 Cloud vs Daytona](https://www.anchorterminal.com/compare/agent37-vs-daytona.md)
- [Agent 37 Cloud vs E2B](https://www.anchorterminal.com/compare/agent37-vs-e2b.md)
- [Agent 37 Cloud vs Microsoft Execution Containers](https://www.anchorterminal.com/compare/agent37-vs-microsoft-execution-containers.md)
- [Agent 37 Cloud vs Morph Cloud](https://www.anchorterminal.com/compare/agent37-vs-morph-cloud.md)
- [Agent 37 Cloud vs Runloop Devboxes](https://www.anchorterminal.com/compare/agent37-vs-runloop.md)
- [Agent 37 Cloud vs Vercel Sandbox](https://www.anchorterminal.com/compare/agent37-vs-vercel-sandbox.md)