The toughest part was getting the Go-written runtime to be able to run arbitrary code in multiple languages. The other tough part was getting the logs and state of the bots to be queryable and streamable in real time. One fun feature is that you can create custom dashboards in React for each bot and stream the logs into them, there is a React sdk that helps you do this. It was a challenge getting this to work and involved treating each bot as a two phased bundle deployment and hydrating the frontend with the state of the bot and metrics from logs (I was inspired by the way Datadog does this).
The way bots send information such as logs and state is done through a daemon process that runs alongside the bot in its container (again inspired by Datadog). The daemon handles what I call the dirty work, persistence of logs and state to the Object Store (MinIO), behind the scenes; the bot just sends information via standard logging and persistence calls from the SDK. Its decoupled, the bot can run without the daemon, but then you lose the ability to query the state of the bot and stream logs.
Stack: the runtime is written in Go and uses NATS for messaging, PostgreSQL, MongoDB and MinIO for persistence. The frontend is React and the CLI is Go. It runs locally through docker or in k8s via helm charts. The0 can theoretically be scaled to run thousands of bots on a k8s cluster (this is based on your own code and the resources you have available).
In terms of whats next... honestly most of the major work is done, the0 is stable and I use it to run my own bots. I think most of the work is in extending the MCP server to support more features and making it easier for AI agents to interact with the bots. The next step is to get some honest feedback on what people want to see in the0 and how they would use it.