Firecracker microVMs on bare metal. Not owned by any foundation-model vendor. Priced like electricity. Click below -- you're in a live Claude Code session in under ten seconds. No signup, no API key, no waitlist.
Every sandbox provider gives your agent an isolated environment to run code. When the session ends, everything disappears.
For a 4-minute task, that's fine.
For a 14-hour research pipeline, a week-long code migration, or a multi-agent system that builds on previous results -- you need execution that remembers.
upstream is a turn executor. Each turn produces structured output. Context accumulates. The next turn starts where the last one ended.
Create a sandbox. Run code. Get results. The SDK handles everything else.
One API call. A Firecracker VM boots from a pre-warmed snapshot in 200ms. Claude Code, git, and your toolchain are ready.
---
image: python:3.12
---
# Data Analysis
```bash
pip install pandas
python analyze.py
```
upstream pulls the image, executes each bash block in an isolated VM, and captures the output.
$ upstream run pipeline.md
Pulling python:3.12 ... done
Step 1: pip install ..... done (3.1s)
Step 2: python analyze .. done (1.4s)
Results are written back into the markdown. Exit codes, stdout, timing -- all inline. The document is now a complete execution report.
**Result:** exit 0 (1.4s)
```
Found 847 records
Mean: 42.3, Median: 38.1
Report saved to output.csv
```
Honest numbers. We win on cost, context, and self-hosting. Others win on SDK breadth and enterprise traction.
| E2B | Daytona | upstream | |
|---|---|---|---|
| Self-hosted | Enterprise only | No | Free + open source |
| Context store | No | No | Built-in |
| Interface | Python/JS SDK | Python/JS SDK | Markdown |
| Cold start | ~150ms | ~90ms | ~5ms (warm pool) |
| Cost per session | ~$0.01 | ~$0.01 | ~$0.0002 (self-hosted) |
| Isolation | Firecracker microVM | Firecracker microVM | Firecracker microVM |
| Max session | 24 hours | Unlimited | Unlimited |
Run on your own metal for $0. Or let us host it -- still 2-5x cheaper than alternatives.
Or download a prebuilt binary from GitHub Releases