A sandbox runs while it works
There is no lease to manage any more: a sandbox has no time limit unless you set one, runs for as long as it is busy and pauses itself when idle, until you stop it or credit runs out. Nothing needs extending, and code that extends, sets timeoutSeconds or calls keepAlive keeps working: a time limit you set is still kept. endsAt says when a sandbox will stop or pause by itself, and is null when it never will. The E2B, Daytona, Vercel, Blaxel, Modal and Runloop adapters do the same when your code sets no timeout. See the API.
Runtime for Startups
A venture-backed startup building with AI agents can apply at withruntime.com/startups for $5,000 of credit, added over 12 months (since 7 October 2026, the startup pot instead: 10,000 startup hours, each an hour of a 2 vCPU, 4 GB sandbox, given once, to use within 12 months). An accepted startup's account counts as paid from the day it is accepted. See pricing.
Two error codes are renamed
A command whose timeout outlasts the sandbox's time limit or its funded time is refused with 409 time_limit_too_short, and details.secondsLeft says how long is left: time_limit_too_short replaces lease_too_short. A host that is busy answers 503 busy, safe to retry with the same key: busy replaces fence_conflict. Code that matched the old names should match the new ones. See errors.
More requests at once for accounts with many sandboxes
An organization may have 192 requests in flight, and two more for each sandbox it holds that is not stopped, up to 1,024, so every sandbox can stream a command and a watch at once. See limits.