Beam Sandboxes vs Modal Sandboxes
Choose Beam Sandboxes for teams that want an open-source, self-hostable sandbox runtime with GPU access; choose Modal Sandboxes for high-concurrency and GPU-backed sandboxes — RL rollouts, evals and coding agents at scale. Beam Sandboxes uses gVisor isolation and is open source; Modal Sandboxes uses gVisor or VM isolation.
Beam Sandboxes vs Modal Sandboxes at a glance
| Attribute | Beam Sandboxes | Modal Sandboxes |
|---|---|---|
| What it is | Serverless AI compute platform whose sandboxes are gVisor-isolated containers with memory snapshots, optional GPUs and an open-source, self-hostable runtime. | Sandboxes on Modal’s serverless compute platform for running untrusted code at very high scale, with GPUs, snapshots and tunnels. |
| Isolation | gVisor + runc containers (Beam recommends microVM providers for hostile multi-tenant code) | gVisor by default, or VMs with their own Linux kernel; GPU sandboxes use gVisor |
| Open source | Yes (AGPL-3.0 (beta9 runtime)) | No (Client SDK Apache-2.0) |
| Self-host / BYOC | Yes / Yes | No / Not documented |
| SDKs | Python, TypeScript | Python, JavaScript/TypeScript, Go |
| Cold start (vendor claim) | About half a second; 100 concurrent sandboxes in 0.55 s (vendor claim) | Sub-second, including for large custom images (vendor claim) |
| Max session | 600 s default lifetime, extendable or disabled | 5 minutes default, configurable up to 24 hours; snapshots carry state beyond that |
| Persistence | Filesystem snapshots, memory snapshots, pause/restore, volumes and durable disks | Filesystem snapshots, directory snapshots, memory snapshots (alpha) and Modal Volumes |
| GPU | Yes — GPUs attachable to sandboxes (e.g. RTX 4090 $0.69/hour) | Yes — Modal’s full GPU range (T4 to B300) at standard per-second rates, e.g. H100 $0.001097/s |
| Networking | Public preview URLs via expose_port (add your own auth); runtime egress policies | Outbound open by default; block all, CIDR allowlists or domain allowlists (beta), updatable at runtime; encrypted tunnels with public URLs and connect tokens |
| Pricing | Billed by the millisecond: performance tier $0.05/vCPU-hour + $0.01/GiB-hour; cheaper shared and spot tiers; plans from $20/month | Per second at sandbox (non-preemptible) rates: $0.00003942 per physical core-second (1 core = 2 vCPU) + $0.00000667 per GiB-second; GPUs at standard rates. Team plan $250/month |
| Compliance | SOC 2 Type II | SOC 2 on all plans; HIPAA on Enterprise |
| Best for | Teams that want an open-source, self-hostable sandbox runtime with GPU access | High-concurrency and GPU-backed sandboxes — RL rollouts, evals and coding agents at scale |
Verified November 8, 2026 from each provider’s documentation. Cold-start figures are vendor claims, not our measurements.
Which should you choose?
Choose Beam Sandboxes if…
- You want GPUs inside sandboxes at low rates
- You want an open-source runtime you can self-host
- You want spot and shared tiers for cheap batch work
Choose Modal Sandboxes if…
- You need very high concurrency (RL, evals, batch agents)
- You need GPUs inside the sandbox
- You already use Modal for inference or training
- You want Go as well as Python and TypeScript SDKs
Both are worth piloting with your own image and region. See the full Beam Sandboxes profile and Modal Sandboxes profile, or the complete comparison.
Frequently asked questions
Is Beam Sandboxes or Modal Sandboxes better for AI agents?
Which is open source, Beam Sandboxes or Modal Sandboxes?
How do Beam Sandboxes and Modal Sandboxes isolate code?
Sources
Cite this page
Agent Sandboxes. (2026). Beam Sandboxes vs Modal Sandboxes. agentsandboxes.org. Last reviewed November 8, 2026. https://agentsandboxes.org/compare/beam-vs-modal/
Found an error or a missing sandbox? Submit a correction — every entry links to the sources it relies on.