Constant MAX_CONSUMER_MESSAGE 

pub(crate) const MAX_CONSUMER_MESSAGE: usize = _; // 4_096usize

The largest message, and the largest frame, a subscribeRepos consumer may send.

A consumer sends nothing this server reads: the incoming half is polled only to see the close. WebSocket control frames carry at most 125 bytes (RFC 6455 §5.5), and four kibibytes is thirty times that. axum’s own defaults, 64 MiB a message and 16 MiB a frame, are what one consumer could otherwise make this server buffer on each slot subscriber_slot gives it. A consumer that sends more is disconnected.