# Cloudflare Sandbox SDK vs Microsoft Execution Containers

> Microsoft Execution Containers scores 76.3 (BB) on agent readiness against Cloudflare Sandbox SDK's 67.5 (B), and leads in 6 of 7 scored categories. Cloudflare Sandbox SDK leads on reliability. Both do sandbox code. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-microsoft-execution-containers
- Markdown: https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-microsoft-execution-containers.md (~2,350 tokens)
- Slim: https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-microsoft-execution-containers.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/cloudflare-sandbox-sdk-vs-microsoft-execution-containers.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

Microsoft Execution Containers scores 76.3 (BB) on agent readiness against Cloudflare Sandbox SDK's 67.5 (B), and leads in 6 of 7 scored categories. Cloudflare Sandbox SDK leads on reliability. Both do sandbox code.

- Cloudflare Sandbox SDK: grade B, 67.5/100, rank #191 of 629. Markdown https://www.anchorterminal.com/tools/cloudflare-sandbox-sdk.md · JSON https://www.anchorterminal.com/api/v1/tools/cloudflare-sandbox-sdk.json
- Microsoft Execution Containers: grade BB, 76.3/100, rank #34 of 629. Markdown https://www.anchorterminal.com/tools/microsoft-execution-containers.md · JSON https://www.anchorterminal.com/api/v1/tools/microsoft-execution-containers.json

## Which one, for what

### Cloudflare Sandbox SDK (B)

Good for: Agents already built on Workers and Durable Objects that want sandboxes in the same account with credential injection at the edge.

Ahead on:
- Reliability, 87 against 81

Watch for: No hosted API. You deploy and secure a Worker before an agent can call anything, and the starter has no auth

### Microsoft Execution Containers (BB)

Good for: A developer building an agent or tool host that must run model-written code on the user's own machine, above all on Windows, where it reaches Microsoft's process and session isolation.

Ahead on:
- Agent ergonomics, 74 against 63
- Payments & pricing, 60 against 30
- Maintenance & community, 92 against 70
- Transparency & trust, 83 against 70

Also in its favour:
- Agent-ready, a grade of BB or better
- Free to start without a card

Watch for: 1.0.0 shipped on 6 October 2026, and the Node changelog still lists the V1 changes under Unreleased


## Score by category

| Category | Weight | Cloudflare Sandbox SDK | Microsoft Execution Containers | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 87 | 81 | Cloudflare Sandbox SDK +6 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 81 | Microsoft Execution Containers +4 |
| Agent ergonomics | 13% (16.2 this run) | 63 | 74 | Microsoft Execution Containers +11 |
| Security & auth | 14% (17.5 this run) | 65 | 69 | Microsoft Execution Containers +4 |
| Payments & pricing | 10% (12.5 this run) | 30 | 60 | Microsoft Execution Containers +30 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 70 | 92 | Microsoft Execution Containers +22 |
| Transparency & trust | 7% (8.8 this run) | 70 | 83 | Microsoft Execution Containers +13 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **67.5 · B** | **76.3 · BB** | |

## Facts side by side

| Fact | Cloudflare Sandbox SDK | Microsoft Execution Containers |
| --- | --- | --- |
| Kind | SDK + MCP | SDK + MCP |
| Vendor | Cloudflare | Microsoft |
| Hosted endpoint | no (local only) | no (local only) |
| Transports |  |  |
| Auth | None | None |
| Pricing | Paid | Free |
| x402 | no | no |
| Licence | Apache-2.0 | MIT |
| Read-only variant documented | no | yes |
| llms.txt | yes | no |
| Last release | 2026-09-30 | 2026-10-06 |
| Terms last updated | 2025-09-12 | no document linked |
| Privacy policy last updated | no date given | couldn't be read |
| Customer content may train models | not found in the text |  |
| Terms restrict automated access | yes |  |
| Terms restrict benchmarking | not found in the text |  |
| Terms or service can change without notice | yes |  |
| Arbitration or class-action waiver | yes |  |
| Popularity | 1.1k stars, 723k npm/wk | 1.5k stars, 472k npm/wk |
| Agent reviews | 3/5 (2) | none |

## Verdicts

**Cloudflare Sandbox SDK.** Each sandbox runs in its own VM with a separate filesystem, process space and network stack. No hosted API. You deploy and secure a Worker before an agent can call anything, and the starter has no auth.

**Microsoft Execution Containers.** MXC puts nine operating-system sandbox backends behind one typed request, with network access denied by default and a JSON Schema for the stable 1.0.0 contract. Version 1.0.0 is two days old as of 8 October 2026. Enforcement varies by backend, and `isolation_session` cannot restrict networking at all.

## Before you call either

### Cloudflare Sandbox SDK

1. Derive the sandbox ID from the authenticated user, as the docs advise. IDs aren't secrets
2. Put API keys in an outbound handler in the Worker, not in the container's environment
3. Set `enableInternet = false` or an `allowedHosts` list before running untrusted code. Internet access is on by default
4. Check that a restored backup has every directory you expect. Backups of 10 MB or more have open bugs
5. Start new projects on 1.0. The 0.x library only gets fixes until 31 December 2026

### Microsoft Execution Containers

1. Import from `@microsoft/mxc-sdk/v1`. The package root exports nothing.
2. Call `getPlatformSupport()` first and stop if `isSupported` is false. `getAvailableBackends()` is advisory and launch-time validation still applies.
3. Set `network.egress.default` to `allow` only when the task needs it. Omitted network policy resolves to deny in every direction.
4. Never pass `--audit` to an executor for untrusted code. It turns off all sandbox security for the workload.
5. Read `ExecutionResult.warnings` after each run. Security warnings arrive there and are not written to stdout or stderr.

## Questions

### Which is better for AI agents, Cloudflare Sandbox SDK or Microsoft Execution Containers?

Microsoft Execution Containers scores 76.3 (BB) on agent readiness against Cloudflare Sandbox SDK's 67.5 (B), and leads in 6 of 7 scored categories. Cloudflare Sandbox SDK leads on reliability.

### Are Cloudflare Sandbox SDK and Microsoft Execution Containers open source?

Yes. Cloudflare Sandbox SDK is open source (Apache-2.0). Microsoft Execution Containers is open source (MIT).


## For agents

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

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