The event buffer keeps the wrong entries after its write cursor wraps. Repair the buffer logic so the retained events and their order remain correct as it fills and overwrites older entries.
Build the implementation in C 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 positive integer capacity and operations: push with value, or snapshot. Retain the most recent capacity values in oldest-to-newest order. Return one list per snapshot, each independent of later mutations. Unknown operations and invalid capacity must be rejected. Repair the faulty starter.
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.