I hit this problem when trying to integrate Mermaid into a Swift Package Manager build tool. SPM sandboxes build tool access to specific folders and this causes the headless Chromium used by Mermaid-CLI to blow up.

I'm currently evaluating whether to decouple Mermaid from the browser by using a minimal fake DOM, or just rewriting it in pure Swift. It would be nice if DocC could support Mermaid in Swift doc comments.