Constant WINDOW_CAP 

pub const WINDOW_CAP: usize = _ /* 64usize */;

Derived: the doubling’s ceiling (window_for), as many full texts (WIRE_TEXT, at a byte per character) as one member’s share of the log (MEMBER_BYTES) holds. It promises no room: a line takes more than its text (its fields, up to 4 bytes a character), and the share is the node’s, across all its senders and recipients. So send refuses a message that would push one of its sender’s unread messages to the same recipient out of the log (SendError::Share); another pair’s newer lines may still push it out, oldest first, and that cut is counted (stats::MSG_DROPPED, why bounds). Also what the mesh lets through unread from one sender to one recipient within one V1_RATE_MS (within_windows): no window lets more.