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Validation errors

Programs are validated at load time before execution. Common errors:

ErrorCause
invalid_initialprogram.initial names a state that does not exist
invalid_transitionon: target names an undefined state
missing_node_refActive state without node:
undefined_nodeActive state references unknown node ID
no_final_stateNo state with type: final
unreachable_finalNo final state reachable from initial

Fixing validation errors

  1. Read the error message — it includes state names and paths.
  2. Ensure every on: target exists in states:.
  3. Ensure active states have valid node: references.
  4. Add at least one final state on a reachable path.

Missing program fields

Loader errors when program lacks id, version, or initial.

Try it: Intentionally break example.yml (bad transition target) and run definitively run to see the error format.