# Modal vs Prime Sandboxes: sandboxes for agent training

Modal and Prime both court reinforcement learning teams. The 2 vCPU, 4 GiB benchmark costs $3.97 on Modal and $1.52 on Prime Sandboxes.

**Runtime costs 84% less than Modal and 58% less than Prime for rollouts that
wait on a model.** In the benchmark, 1,000 one-minute runs of a 2 vCPU, 4 GiB
sandbox with 20 CPU-seconds of work each, Modal comes to $3.97, Prime to $1.52
and Runtime to $0.64.

## At a glance

|           | Modal Sandboxes                                          | Prime Sandboxes                                | Runtime                                                  |
| --------- | -------------------------------------------------------- | ---------------------------------------------- | -------------------------------------------------------- |
| Isolation | gVisor, a user-space kernel                              | Hardware-virtualized microVM, own guest kernel | Firecracker microVM, own kernel                          |
| CPU       | $0.1419 per physical core-hour (2 vCPUs), request or use | $0.02 per vCPU-hour while running              | $0.025 per vCPU-hour of measured CPU, with a small floor |
| Memory    | $0.0240 per GiB-hour, request or use                     | $0.0125 per GiB-hour                           | $0.0075 per reserved GiB-hour                            |
| Snapshots | Carry state past a session                               | Listed as coming soon                          | Pause and forks keep memory and processes                |
| GPUs      | Yes                                                      | Listed as coming soon                          | No                                                       |
| At once   | Set by plan                                              | 1,024 per account to start                     | 100 paid, after 50 in the first week                     |

## Training stacks

Modal's argument is one platform: GPU trainers and inference as functions,
environments as sandboxes beside them. Prime's is the environment itself at
scale and at a low price, microVMs by the thousand on its own compute. Runtime
is the environment layer too, billed by use, which suits rollouts that spend
most of each step waiting for a policy model to answer.

## Cost for the same job

The benchmark in full, 60 seconds a run (one physical core on Modal, Prime's 5 GiB disk):

```
Modal     CPU    1,000 × 60 s × 1 core × $0.00003942           = $2.37
          Memory 1,000 × 60 s × 4 × $0.00000667                = $1.60
          Total                                                  $3.97

Prime     CPU    1,000 × 60 s / 3,600 × 2 × $0.02              = $0.67
          Memory 1,000 × 60 s / 3,600 × 4 × $0.0125            = $0.83
          Disk   1,000 × 60 s / 3,600 × 5 × $0.0002            = $0.02
          Total                                                  $1.52

Runtime   CPU    1,000 × 20 s / 3,600 × $0.025                = $0.14
          Memory 1,000 × 60 s / 3,600 × 4 × $0.0075           = $0.50
          Total                                                  $0.64
```

For a month of 100,000 runs: $396.60 on Modal, $151.67 on Prime, $63.89 on
Runtime. When both CPUs stay busy for the whole minute, it is $3.97 on Modal, $1.52 on Prime and $1.33 on Runtime.

## Which one to pick

- **Modal** when environments and GPU training should live in one platform.
- **Prime Sandboxes** for a thousand microVMs at once inside Prime Intellect.
- **Runtime** for the lowest price per rollout, forks of a warmed-up
  environment today, and [Harbor](/docs/harbor) and [Inspect](/docs/inspect)
  integrations for eval suites.

See [Runtime vs Modal](/docs/modal-sandbox-alternative) and
[Runtime vs Prime Sandboxes](/docs/prime-sandboxes-alternative).

## Sources

Modal rates checked 23 September 2026; Prime rates checked 25 September 2026.

- [Modal pricing](https://modal.com/pricing), [Modal resources and billing](https://modal.com/docs/guide/resources)
- [Prime Sandboxes overview](https://docs.primeintellect.ai/sandboxes/overview), [Prime Sandboxes launch](https://www.primeintellect.ai/blog/sandboxes)
- Runtime [pricing](/docs/pricing)

Facts on this page were checked on 25 September 2026.