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Limits

Defaults during the public beta. The beta is free — every account starts with a one-time grant of 100 sandbox-hours.

Account quotas

Item	Default
Credit	100 sandbox-hours of running time, one-time (no monthly reset) — paused time doesn't consume it
Concurrent running sandboxes	5
Concurrent paused sandboxes	50

A running sandbox with no recorded activity for 300 s pauses automatically. The threshold is one global setting, not per-sandbox — and CPU usage is not part of the decision, so background computation pauses too.
Exception — paused quota full: auto-pause only runs while your account has paused-sandbox quota left. If your 50 paused slots are full (user-paused sandboxes count too), an idle sandbox is not paused: it stays running, keeps consuming running time, and is retried on the next sweep until a paused slot frees up.
An open connection streaming to or from the sandbox counts as activity.
Pause keeps full memory and running processes; the next request to the sandbox's endpoints resumes it — measured ~160 ms.
No session length cap on the gateway side. The v2 API defaults timeout to 300 s; set it at create time or change it later with setTimeout.
Paused time doesn't consume your hours — only running time does.

Internet on by default — sandboxes can reach the public internet outbound (model APIs, package registries, git hosts).
SMTP egress is blocked (ports 25, 465, 587).
Shared egress IP (NAT). Sustained high CPU use (e.g. cryptomining) is detected automatically: the sandbox is paused, and repeated findings suspend the account.

Over the running-sandbox cap → 429 with your current count and the limit.
Credit exhausted → 402; running sandboxes are paused, not deleted.
Platform saturated → create requests queue briefly, then 503 + Retry-After. We return honest errors instead of degraded sandboxes.