OpenBook vs Windmill
Windmill and OpenBook are both open-source and self-hostable, but aimed at different users. Windmill is a developer-centric engine that turns Python/TypeScript/Go scripts into workflows, internal UIs, and APIs, with strong performance and code-first control. OpenBook is agentic-first and lower-code: AI agents with long-term memory, an AI builder, a visual canvas, and human-in-the-loop pause/resume.
At a glance
OpenBook and Windmill, capability by capability.
| Capability | OpenBook | Windmill |
|---|---|---|
| Open source & self-hostable | ||
| Visual + AI builder | Flow editor + code | |
| First-class AI agents with memory | ||
| Run scripts in Python/TS/Go as steps | Via actions | |
| Conditional branching | ||
| Error-path routing | ||
| Human-in-the-loop pause/resume | Suspend / approval steps | |
| Generic HTTP connector | ||
| Code-first performance & control | Some |
Why teams pick OpenBook over Windmill
Agentic and lower-code
OpenBook centers on AI agents with memory and a visual/AI builder, so non-engineers can build. Windmill is built around writing scripts.
AI builder
Describe a workflow and OpenBook creates the agents and wires the graph. In Windmill you author scripts and compose them into flows.
Long-term memory by default
OpenBook agents remember across runs without extra plumbing. Windmill has no built-in agent memory model.
Human-in-the-loop with an inbox
Pause for approval or input and resume from an approvals inbox. Windmill has suspend/approval steps but a more code-driven model.
MIT, self-host, your keys.
AGPLv3 core (enterprise edition separately licensed); self-hostable.
When to choose which
- You want AI agents with memory and a low-code or AI builder, not a script-first engine
- You want human-in-the-loop with an approvals inbox built in
- You want non-engineers to build alongside developers
- You're a developer team that wants to turn scripts into workflows, UIs, and APIs
- You need code-first performance, control, and a fast self-hosted job runner
Wrap Windmill scripts as OpenBook actions and recompose flows as workflow graphs. Suspend/approval steps become human.handoff nodes, and triggers map to OpenBook trigger nodes.
Frequently asked questions
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OpenBook is free and open source. Self-host it in minutes, or read the docs to see how far the engine goes.