Source: Dev.to

Six weeks ago, running code on jhansi.io meant curl + sandbox IDs + manual cleanup. Today it looks like this: from jhansi import Sandbox

with Sandbox(language=“python”) as sb: sb.upload_file(“main.py”) result = sb.exec(“python main.py”) print(result[“output”])

That’s the milestone. The SDK is live. The API was always there. Petri — the execution engine underneath — has been running code in isolated Docker containers since v0.1. But you had to understand HTTP, manage container lifecycle, and remember to delete sandboxes or you’d leak resources. The SDK removes all of that. You write Python. jhansi.io handles the rest. If you create a sandbox and forget to delete it, you leak containers and workspace storage. That’s not acceptable — especially when AI agents are creating sandboxes programmatically. The context manager makes cleanup automatic: with Sandbox(language=“python”) as sb: # sandbox created here sb.upload_file(“main.py”) result = sb.exec(“python main.py”)

sandbox deleted here — even if exec raised an exception

No leaked containers. No cleanup code. No surprises. Self-hosting Petri via docker compose up uncovered something we hadn’t anticipated. Petri runs inside a Docker container. But Petri’s job is to spin up Docker containers to run your code. So Petri needs access to Docker — from inside Docker. Fix one: mount the Docker socket. volumes:

• /var/run/docker.sock:/var/run/docker.sock

Fix two: shared workspace path. Petri creates workspace folders inside its container. When it mounts those into sandbox containers, Docker looks for the path on the host — not inside Petri. The path doesn’t exist. volumes:

• /var/run/docker.sock:/var/run/docker.sock
• /tmp/petri-workspaces:/tmp/petri-workspaces environment:
• PETRI_WORKSPACE_ROOT=/tmp/petri-workspaces

Same path both sides. Docker finds it. Problem solved.

Start Petri

git clone https://github.com/jhansi-io/petri.git cd petri docker compose up

Install the SDK

pip install jhansi

Full docs at docs.jhansi.io. v0.6 — persistent registry so sandboxes survive Petri restarts v0.7 — streaming exec, real-time output as your code runs MCP server — Cursor and Claude Code use Petri directly instead of their own cloud. The MCP server is the one I’m most excited about. More on that soon. Star the repo if you’re following the build. ⭐ github.com/jhansi-io/jhansi