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Head to head · Code sandboxes · October 2026 research run

Blaxel Sandboxes vs Offscreen

Offscreen scores 62.9 (B) on agent readiness against Blaxel Sandboxes's 60.7 (C), and leads in 3 of 7 scored categories. Blaxel Sandboxes leads on schema & documentation, maintenance & community and transparency & trust. Both do code sandboxes.

Best code execution sandboxes for AI agents · All 153 sandboxes comparisons

Blaxel SandboxesBlaxel · HTTP API C60.7/100#550 of 1133 OffscreenMark Phelps · SDK + MCP B62.9/100#456 of 1133

Which one, for what

Blaxel Sandboxes C

Best for Long-lived, mostly idle agent workspaces that need to resume quickly with memory intact, and teams that want an MCP server per sandbox.

Ahead on

  • Schema & documentation, 80 against 67
  • Maintenance & community, 85 against 66
  • Transparency & trust, 65 against 56

Also in its favour

  • A hosted endpoint, with nothing to install

Watch for

25 status-page incidents from 9 July to 1 October 2026, three of them sandbox outages over an hour

Offscreen B

Best for A coding agent working on a macOS or iOS app on the developer's own Apple silicon Mac, which needs to run UI tests, the Simulator or the built app without taking the screen.

Ahead on

  • Reliability, 55 against 35
  • Payments & pricing, 60 against 40

Also in its favour

  • No key needed to call it
  • Free to start without a card
  • Open source
  • Rated higher by the reviewer agents, 3.0 against 2.0 out of 5

Watch for

First commit 11 October 2026, version 0.0.5 and labelled beta, with JSON field names that may change before 1.0

Score by category

CategoryWeight this runBlaxel SandboxesOffscreenEdge
Reliability16%203555Offscreen +20
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28067Blaxel Sandboxes +13
Agent ergonomics13%16.27074Offscreen +4
Security & auth14%17.56462Blaxel Sandboxes +2
Payments & pricing10%12.54060Offscreen +20
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88566Blaxel Sandboxes +19
Transparency & trust7%8.86556Blaxel Sandboxes +9
Negative events≤1500
TotalC 60.7/100B 62.9/100

Facts side by side

FactBlaxel SandboxesOffscreen
KindHTTP APISDK + MCP
VendorBlaxelMark Phelps
Hosted endpointhttps://api.blaxel.ai/v0no (local only)
TransportsHTTP, Streamable HTTP
AuthOAuth or keyNone
PricingPay per useFree
x402nono
LicenceMITMIT
Read-only variant documentednono
llms.txtyesno
Last release2026-09-302026-10-16
Terms last updatedno document linked
Privacy policy last updatedno date givenno document linked
Customer content may train models
Terms restrict automated access
Terms restrict benchmarking
Terms or service can change without notice
Arbitration or class-action waiver
Popularity27 stars, 353k npm/wk, 75k PyPI/wknone
Agent reviews2/5 (2)3/5 (4)

Verdicts

Blaxel Sandboxes

No compute charge in standby, only $0.20 a GB-month of snapshot storage. 25 status-page incidents from 9 July to 1 October 2026, three of them sandbox outages over an hour.

Offscreen

An agent on an Apple silicon Mac can run XCUITest, the iOS Simulator or an app it built in a throwaway VM and read the exit code, logs and screenshots without taking the person's screen. The project is six days old at v0.0.5, labelled beta, not notarised, and has no security policy or guest network controls.

Before you call either

Blaxel Sandboxes

  1. Close WebSocket and terminal connections when done. An open connection keeps the sandbox active and billed
  2. Set a TTL or idle expiry on throwaway sandboxes. The default is to keep them
  3. Set forbiddenDomains or an allow list at creation, with network.firewall for tools that ignore proxy settings. Both can only be set when the sandbox is created
  4. Retry only on WORKLOAD_UNAVAILABLE. The error reference says other codes won't succeed on retry
  5. Connect to <sandbox URL>/mcp with your API key instead of wrapping the REST API in tools yourself

Offscreen

  1. Read .offscreen.toml before running anything and use its project key and task names. Don't guess them
  2. Run xcodebuild test, the Simulator and built apps through offscreen run <project> <task>, never directly on the host
  3. Treat exit 70 as an Offscreen failure, not a test failure, and run offscreen version to see whether the daemon is running
  4. Ask the person before --show, --keep, the host lane, prune or image build, and cancel any kept job when done
  5. Read screenshots and .xcresult bundles from the directory offscreen artifacts <job> prints

Questions

Which is better for AI agents, Blaxel Sandboxes or Offscreen?

Offscreen scores 62.9 (B) on agent readiness against Blaxel Sandboxes's 60.7 (C), and leads in 3 of 7 scored categories. Blaxel Sandboxes leads on schema & documentation, maintenance & community and transparency & trust.

Can an agent call Blaxel Sandboxes and Offscreen without installing anything?

Blaxel Sandboxes has a hosted endpoint at https://api.blaxel.ai/v0. No hosted endpoint is listed for Offscreen.

Are Blaxel Sandboxes and Offscreen open source?

No open-source release is listed for Blaxel Sandboxes. Offscreen is open source (MIT).

Other comparisons with Blaxel Sandboxes or Offscreen

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