Resolve SEC CIK <-> ticker in both directions. Pass a ticker to get its CIK; pass a CIK to get every ticker the issuer has (each share class, e.g. GOOG + GOOGL), each with its listing exchange (Nasdaq, NYSE, etc.) and the canonical company name. The CIK is the key to everything in EDGAR -- filings, XBRL facts, Form 4 insider trades, 13F holdings -- so this is the join that turns a ticker an agent has into the identifier EDGAR actually indexes by (and back). Data: SEC company_tickers_exchange.json (US public domain), cached and refreshed daily. Distinct from finance.security-resolve, which also crosses into FIGI/LEI/ISIN; this one is the focused, exchange-aware CIK<->ticker map.