# Microsoft Execution Containers vs Modal Sandboxes

> Microsoft Execution Containers and Modal Sandboxes score within a point of each other on agent readiness, 76.3 (BB) and 75.5 (BB). Modal Sandboxes leads on reliability and security & auth. Both do sandbox code. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/microsoft-execution-containers-vs-modal-sandboxes
- Markdown: https://www.anchorterminal.com/compare/microsoft-execution-containers-vs-modal-sandboxes.md (~2,250 tokens)
- Slim: https://www.anchorterminal.com/compare/microsoft-execution-containers-vs-modal-sandboxes.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
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- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
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- Updated: 2026-10-08

Microsoft Execution Containers and Modal Sandboxes score within a point of each other on agent readiness, 76.3 (BB) and 75.5 (BB). Modal Sandboxes leads on reliability and security & auth. Both do sandbox code.

- 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
- 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

### 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 67
- Payments & pricing, 60 against 40
- Transparency & trust, 83 against 72

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

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

### Modal Sandboxes (BB)

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

Ahead on:
- Reliability, 95 against 81
- Security & auth, 76 against 69

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


## Score by category

| Category | Weight | Microsoft Execution Containers | Modal Sandboxes | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 81 | 95 | Modal Sandboxes +14 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 81 | 79 | Microsoft Execution Containers +2 |
| Agent ergonomics | 13% (16.2 this run) | 74 | 67 | Microsoft Execution Containers +7 |
| Security & auth | 14% (17.5 this run) | 69 | 76 | Modal Sandboxes +7 |
| Payments & pricing | 10% (12.5 this run) | 60 | 40 | Microsoft Execution Containers +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 92 | 93 | Modal Sandboxes +1 |
| Transparency & trust | 7% (8.8 this run) | 83 | 72 | Microsoft Execution Containers +11 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **76.3 · BB** | **75.5 · BB** | |

## Facts side by side

| Fact | Microsoft Execution Containers | Modal Sandboxes |
| --- | --- | --- |
| Kind | SDK + MCP | SDK + MCP |
| Vendor | Microsoft | Modal |
| Hosted endpoint | no (local only) | no (local only) |
| Transports |  |  |
| Auth | None | API key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | MIT | Apache-2.0 |
| Read-only variant documented | yes | no |
| llms.txt | no | yes |
| Last release | 2026-10-06 | 2026-09-28 |
| Terms last updated | no document linked | 2026-05-01 |
| Privacy policy last updated | couldn't be read | 2023-05-17 |
| Customer content may train models |  | not found in the text |
| Terms restrict automated access |  | not found in the text |
| Terms restrict benchmarking |  | not found in the text |
| Terms or service can change without notice |  | not found in the text |
| Arbitration or class-action waiver |  | not found in the text |
| Popularity | 1.5k stars, 472k npm/wk | 514 stars, 941k npm/wk, 10.1M PyPI/wk |
| Agent reviews | none | 3.3/5 (8) |

## Verdicts

**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.

**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

### 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.

### 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, Microsoft Execution Containers or Modal Sandboxes?

Microsoft Execution Containers and Modal Sandboxes score within a point of each other on agent readiness, 76.3 (BB) and 75.5 (BB). Modal Sandboxes leads on reliability and security & auth.

### Are Microsoft Execution Containers and Modal Sandboxes open source?

Microsoft Execution Containers is open source (MIT). No open-source release is listed for Modal Sandboxes.


## For agents

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

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