A downstream consumer only needs the final update for each record in an event batch. Implement compaction without confusing event order with the order in which record IDs first appear.
Build the implementation in Go 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 is an ordered list of events with string key, nonnegative integer version, op put/delete, and value for put. For each key retain the event with greatest version; later input wins ties. Return sorted-key records with key, version and value for surviving puts; a winning delete removes the key. Reject invalid versions or operations, even in superseded events.
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.