Robinhood's symbol mapping.

Its native symbol is already canonical BASE-QUOTE — BTC-USD — so the conversion is effectively identity. It is declared anyway, for two reasons.

The contract is uniform: every venue implements both directions, so nothing above the facade needs to know that one venue's conversion happens to be free.

And it is a defensive boundary. Any un-canonical form the venue ever returns is normalised here rather than leaking upward — a lowercase btc-usd, or a separatorless form from an endpoint nobody has looked at lately. Running the normaliser over an already-canonical string costs nothing; one venue quietly emitting a form the rest of the family does not recognise costs a symbol that matches no catalogue entry and collects nothing.