X_BENCH_URL_REQUIRED
Means
the restart benchmark's client shard was started without --url
Typical cause
the shard has no endpoint to connect its clients to, and the orchestrator had already spawned it — a bare Error said nothing a --json reader could act on
Fix
bun run scripts/bench/restart-bench-client-worker.ts --url <ws-url> --count <n> --offset <n>