CodeSandbox SDK
Last verified 2026-07-26
CodeSandbox SDK (rebranding as Together Code Sandbox under Together AI) offers Firecracker microVMs with a git-versioned filesystem, ~500ms resume, sub-second forking and a 2.7s P95 cold start. It is focused on web-development agents.
Key specs
| Isolation | Firecracker microVM |
| Cold start | 500ms |
| Price / vCPU-hr | $0.05 |
| Pricing model | Usage-based |
| GPU | No |
| Session limit | Configurable |
| Persistence | Git-versioned filesystem, forking |
| Languages | JavaScript/TypeScript, Node, others |
| MCP support | n/a |
| Integrations | REST/API |
| Deployment | Managed cloud |
| Free tier | Free tier |
| P95 cold start | 2.7s |
| Resume | ~500ms |
Strengths
- Git-versioned filesystem
- Sub-second forking
- Firecracker isolation
Trade-offs
- Web-dev-centric
- Mid-transition to Together branding
Best for: Web-development agents that fork and branch environments frequently.
How CodeSandbox SDK works
CodeSandbox SDK, now rebranding as Together Code Sandbox under Together AI, runs Firecracker microVMs with a git-versioned filesystem. Resume from a paused sandbox takes about 500ms, and forking a running environment is sub-second, so an agent can branch a workspace and explore variants cheaply. Cold start sits around 2.7 seconds at the 95th percentile. It leans toward JavaScript, TypeScript and Node, and the whole thing is tuned for web-development agents that spin up, edit and preview projects rather than run general compute.
Pricing in practice & watch-outs
Billing is usage-based at around $0.05 per vCPU-hour, in line with the cheaper Firecracker options, and the forking model keeps costs down when agents branch environments instead of rebuilding them. Two things to weigh. It is web-development-centric, so if you are running data pipelines or non-JavaScript workloads, the ergonomics fight you. And it is mid-rebrand to Together Code Sandbox under Together AI, which means docs, package names and URLs are in flux right now, so budget time for churn and double-check which identity current guides refer to.
Head-to-head
Alternatives to CodeSandbox SDK
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Sources: CodeSandbox SDK docs ↗
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