Vercel Sandbox creation now returns a ready sandbox

Vercel changed when its Sandbox service reports a new sandbox as usable. Per the Vercel changelog, the call that creates a sandbox now finishes only after the sandbox's saved starting state (a snapshot) has been restored. Previously that restoration happened during the first command or file operation, so the first operation absorbed the wait and any startup failure showed up there.

The practical effect is where time and errors appear. Vercel says creation is about 50 ms longer at the median, with a larger increase possible for snapshots that are not cached, while the total time through the first operation stays the same. Startup errors now reject the creation call itself. Vercel says the change applies automatically with no SDK upgrade or configuration.