Function parse_request 

pub fn parse_request(body: &[u8]) -> Result<Request, AgentError>

Parse a single agent request body (the bytes after the 4-byte frame length — i.e. starting at the message-type byte). Returns Err for any unknown opcode, trailing garbage, or malformed field; the daemon maps that to SSH_AGENT_FAILURE. Never panics (fuzz-target contract).