UNKNOWN_SHAPE
UNKNOWN_SHAPE is a structural warning: a node carries a shape outside the renderer’s known vocabulary and falls back to a plain rectangle.
What triggers it. Shape syntax the parser modeled but the renderer does not draw — typically newer Mermaid shape names reaching a structured flowchart or state graph.
How to fix it. Switch the node to a supported shape (rectangle, rounded, diamond, stadium, circle, hexagon, cylinder, …) with a source edit; the diagram still renders meanwhile, so this is a warning rather than an error.
Run am verify diagram.mmd --json, inspect this code, and apply the smallest source or typed mutation that clears it. If it persists after two mechanical attempts, return the warning and ask for human review.
In the cloned repo, am is bun run bin/am.ts.
Back to all warning codes, or open the editor to watch this warning clear as you edit.