What triggers it. A bare header like flowchart TD with no statements after it, a body containing only comments, or a mutation sequence that removed the last node, message, or task.

How to fix it. Add at least one element — add_node/add_edge for flowcharts, add_participant/add_message for sequence, add_task for gantt/journey — or check that the intended body was not lost before serializing.

Minimal reproducer

This source triggers EMPTY_DIAGRAM — checked at build time against the same engine the editor runs.

flowchart TD

Open this reproducer in the editor

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.

Machine-readable: this page as Markdown.

Back to all warning codes, or open a blank editor to try a fix.