Crypto ETF Sentinel — SEC filing tracker for US spot crypto ETFs across Bitcoin, Ethereum, Solana, XRP and 30+ assets. Freshest filings surface within ~10 minutes of detection — last 50 newest-first by default, built for continuous, high-volume monitoring. Covers S-1, 424B, 8-A12B, CERT, EFFECT. Optional filters: ``currency``, ``filing_type``, ``date_after``.