What triggers it. A task whose after/until expression references a task id that does not exist, or a start/end that cannot be parsed against the declared dateFormat. The warning carries the engine reason string.

How to fix it. Point the reference at a real task id or give the task explicit dates with the set_task_dates mutation (or edit the offending source line named in the reason).

Minimal reproducer

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

gantt
  title Release
  dateFormat YYYY-MM-DD
  section Build
    Ship :ship, after review, 3d

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.