The workflow log should move only along declared transitions. Implement replay so invalid events are recorded as rejected and do not change the state used for later events.
Build the implementation in Java under /app, with /app/run.sh as its entry point. Read one JSON request from standard input and write one JSON result to standard output. Input has initial state string, transitions mapping state to event-to-state mapping, and events strings. Process in order: if the current state defines the event, transition and append the new state to history; otherwise retain state and append the zero-based event index to rejected. History begins with initial state. A transition to the same state is still accepted. Return state, history and rejected.
Reject inputs that violate an explicit validation rule with exit status 2, no standard output, and {"error":"invalid_input"} on standard error. For valid input, exit with status 0. Keep the implementation reusable for new inputs; it must work offline and must not depend on the example data being the only data it receives.
Repair or replace the unfinished /app/run.sh and add source files under /app. Malformed JSON must use the same invalid-input response. Do not read /tests or /oracle from the application.