Runtime vs Prime Sandboxes

• You pay for the CPU you use. Prime bills the vCPUs, memory and disk a sandbox is given for as long as it runs. Runtime measures the CPU your code actually uses. Time spent waiting on a model costs only a small floor, a twentieth of a vCPU. Even with both CPUs busy the whole minute, the example job costs $1.33 on Runtime and $1.52 on Prime.
• Waiting costs storage, not compute. Left idle for 300 seconds, a Runtime sandbox pauses by itself with its memory kept. While paused, it pays $0.08 per GB (10⁹ bytes) a month until a request wakes it.
• A written uptime promise. Paid accounts get 99% API uptime a month, measured from outside. If a month falls short, 10% of that month's charges is returned as credit automatically (Uptime Promise).
• Cheaper memory. $0.0075 per GiB-hour, against Prime's $0.0125. Memory is most of what an agent sandbox costs while it waits.
• Pause and fork with memory. A paused Runtime sandbox keeps its memory and running processes while you have credit. A fork copies a running sandbox into up to 100 copies. Prime's checkpoints and forks save the filesystem only: processes start fresh and nothing in memory carries over.
• Prices that do not lapse. Prime's published rates hold through 22 December 2026. Runtime's rates are fixed in each resource's quote. There is no plan fee: prepaid credit from $10.
• Secrets stay outside the sandbox. Code inside sees a placeholder. The real key is added at the egress proxy, only on HTTPS to the hosts you allow (security).
• Your agent sets itself up. It runs npx withruntime sandboxes run -- ..., shows you a link, and starts once you approve in the browser. No API key goes into a prompt or a config file. The MCP server reuses the same connection.
• Guardrails for agents. Read-only keys, a daily spending limit per key and maxTotalCostMicros on each sandbox keep an agent inside its budget. Every write takes an idempotency key.

Also included: a code interpreter, network allow and deny lists, custom images, volumes backed up daily, private previews, a Linux desktop, metrics, webhooks, OpenTelemetry export, S3, R2 and GCS bucket mounts, MCP servers from a catalog, identity tokens for AWS and Google Cloud, and free single sign-on. Paid accounts add custom domains, TCP ports, dedicated outbound addresses and WireGuard private networks. See products.

Prime's figures come from its sandbox documentation and launch post. Last checked 25 October 2026.

Take 1,000 runs of a 2 vCPU, 4 GiB sandbox. Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds. This is an agent that spends most of its time waiting for a model. Prime's sandbox keeps its default 5 GiB disk.

• Saving: 58%, or $0.88 per 1,000 runs.
• Per month: at 100,000 runs, $63.89 on Runtime against $151.67 on Prime.
• Busier work: with both CPUs busy for the whole minute, $1.33 on Runtime against $1.52 on Prime. At this size, Runtime is cheaper however busy the sandbox is.

Network, taxes and free allowances are excluded from both. On Runtime, inbound traffic is free. Each account's first 100 GiB out a month is free, then $0.02 per GB (10⁹ bytes). See pricing for Runtime's terms.

Give your coding agent the one instruction in migration. It replaces the Prime calls on a branch, tests them on the free usage, and tells you what you save each month. Your old code stays on the main branch until you merge.

An RL rollout that sets up an environment once and runs many episodes from it is a good fit for a fork. Install once, then start every episode from the same running machine.

TypeScriptimport { Sandbox } from "withruntime";await using base = await Sandbox.create();await base.exec("pip install --quiet numpy");const episodes = await base.fork({ count: 4 }); // four running copies, memory includedawait Promise.all(episodes.map((episode) => episode.stop()));

• Thousands running at the same time from day one. An account starts at 1,024 active sandboxes and 4,096 vCPUs. A paid Runtime account runs 100, and raises it on request.
• Training on Prime Intellect. Prime Sandboxes are built for agentic RL training on Prime's own platform. Prime Tunnels reach inference running on its cluster nodes.

Checked 26 October 2026.

• Prime Sandboxes overview
• Prime Sandboxes launch
• Runtime pricing, security and products