Function decode_frame_with_consumed 

pub fn decode_frame_with_consumed(
    buf: &[u8],
    max_frame_bytes: usize,
) -> Result<(Frame, usize), CodecError>

Decode one complete length-prefixed frame from buf and report the number of bytes consumed: LENGTH_PREFIX_BYTES plus the declared payload length. Bytes beyond the consumed prefix — if any — belong to the next frame, letting a transport split a buffered stream into frames without re-parsing the length prefix itself. decode_frame is this function with the consumed count discarded.

max_frame_bytes is PAYLOAD-ONLY, as in decode_frame.

Decode errors are connection-terminal. An error from this function carries NO consumed count: once a frame fails to decode, this crate cannot say where the failed frame ends, so the stream position is unrecoverable. A transport must map the error through CodecError::wire_code, send the corresponding wire error, and close the connection — never attempt to resynchronize and keep reading.