DUPLICATE_EDGE

What triggers it. An agent re-adding an edge that already exists, typically an add_edge issued without checking the current edge list, or copy-pasted source lines.

How to fix it. Remove one copy with remove_edge (or delete the duplicate source line); if two parallel edges are intentional, give them distinct labels so they stop being duplicates.

See it fire

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

flowchart LR
  A[Start] --> B[Finish]
  A --> B

Open in the editor and watch it clear

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.