Constant MAX_REQUEST_BYTES 

pub const MAX_REQUEST_BYTES: usize = _; // 16_384usize

The largest request message, after decompression, the reflection routes accept under request_limits: 16 KiB.

A ServerReflectionRequest carries a host plus one file name, symbol or type name, so a legitimate request is well under a kilobyte; 16 KiB leaves generous headroom while sizing the routes to their actual request profile rather than the general-purpose service-wide default. Reflection is a bidirectional stream, so this bounds each message, not how many a client may send.