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What triggers it. Adding a second exit to a diamond without a condition label. ISO 5807 / ANSI X3.5 require each exit of a multi-exit decision to be labeled with its condition value.

How to fix it. Label every exit — set_label on the unlabeled edge (e.g. yes/no) or add |condition| to the source line.

See it fire

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

flowchart TD
  A{Ready?} -->|yes| B[Ship]
  A --> C[Wait]

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.