Constant SERVER_MAX_LINE_BYTES 

pub const SERVER_MAX_LINE_BYTES: usize = _; // 16_777_216usize

Maximum accepted line/body length (bytes) for both the stdio JSONL-RPC reader and the HTTP transport’s request line/headers/body — the same 16MiB-class cap P5-2 established for crate::mcp’s SSE frame reader (MCP_MAX_SSE_FRAME_BYTES), reused here so an adversarial or simply broken client can never make either transport buffer an unbounded amount of data in memory.