Zindex is a stateful diagram runtime for agents. Agents create diagrams by sending structured operations through the Diagram Scene Protocol (DSP) - the platform validates, normalizes, and renders durable scene state rather than one-shot output.

how does Zindex compares to Mermaid?

I just use D2 for this.

I tried to find them on GitHub. Doesn't seem to be FOSS/OSS either.

Does address a real use-case - might be great as a library or a lightweight alternative to Mermaid.

As SaaS it's a very hard sell.

I’ve found that Claude can make decent mermaid diagrams pretty reliably. Not sure I quite understand what problem Zindex solves