Infrastructure
Does Robinhood Chain support WebSocket subscriptions?
Yes. Robinhood Chain supports standard eth_subscribe over WebSocket for newHeads, logs, newPendingTransactions and syncing. Most commercial providers expose a wss:// endpoint alongside their HTTPS one.
Separately, the chain exposes a raw Nitro sequencer feed at wss://feed.mainnet.chain.robinhood.com. That is a different thing from eth_subscribe: it carries pre-confirmation transactions at sequencing time rather than confirmed events at block time.
A limitation worth planning around: standard WebSocket subscriptions have no resumption semantics. If the connection drops you cannot ask for what you missed, so a gap is undetectable unless you reconcile against block numbers yourself.