Server: - DedupTracker in AppState: bounded HashSet (10,000 IDs, FIFO eviction) - send_message: extracts message ID from bincode, drops duplicates - WS handler: dedup on both binary and JSON message frames - extract_message_id() parses all WireMessage variants Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>