mosh does not transmit OSC 52 sequence to client

Similar to #549 and #552, this limitation prevents me from copying text from remote shell sessions into my local terminal via the OSC 52 escape sequence. It's also the reason I still use SSH instead of Mosh. 😱

I tried to patch this but got stuck. 😢 Any hints on how to write a string to the raw terminal device?

diff --git a/src/terminal/terminalfunctions.cc b/src/terminal/terminalfunctions.cc
index 35c8055..1983aec 100644
--- a/src/terminal/terminalfunctions.cc
+++ b/src/terminal/terminalfunctions.cc
@@ -558,6 +558,46 @@ void Dispatcher::OSC_dispatch( const Parser::OSC_End *act, Framebuffer *fb )
        * 2: set window title */
       cmd_num = OSC_string[ 0 ] - L'0';
       offset = 2;
+    } else if ( (OSC_string.size() >= 3) && (OSC_string[ 2 ] == L';') ) {
+      /* OSC of the form "\033]XX;<Pt>\007" where XX can be:
+       * 10: Change VT100 text foreground color to Pt.
+       * 11: Change VT100 text background color to Pt.
+       * 12: Change text cursor color to Pt.
+       * 13: Change mouse foreground color to Pt.
+       * 14: Change mouse background color to Pt.
+       * 15: Change Tektronix foreground color to Pt.
+       * 16: Change Tektronix background color to Pt.
+       * 17: Change highlight background color to Pt.
+       * 18: Change Tektronix cursor color to Pt.
+       * 19: Change highlight foreground color to Pt.
+       * 46: Change Log File to Pt.  (This is normally disabled by a compile-time option).
+       * 50: Set Font to Pt.
+       * 51: reserved for Emacs shell.
+       * 52: Manipulate Selection Data.
+       */
+      cmd_num = 10 * (OSC_string[ 0 ] - L'0') +
+                     (OSC_string[ 1 ] - L'0');
+      offset = 3;
+    } else if ( (OSC_string.size() >= 4) && (OSC_string[ 3 ] == L';') ) {
+      /* OSC of the form "\033]XXX;<Pt>\007" where XXX can be:
+       * 104: Reset Color Number c.
+       * 105: Reset Special Color Number c.
+       * 106: Enable/disable Special Color Number c.
+       * 110: Reset VT100 text foreground color.
+       * 111: Reset VT100 text background color.
+       * 112: Reset text cursor color.
+       * 113: Reset mouse foreground color.
+       * 114: Reset mouse background color.
+       * 115: Reset Tektronix foreground color.
+       * 116: Reset Tektronix background color.
+       * 117: Reset highlight color.
+       * 118: Reset Tektronix cursor color.
+       * 119: Reset highlight foreground color.
+       */
+      cmd_num = 100 * (OSC_string[ 0 ] - L'0') +
+                 10 * (OSC_string[ 1 ] - L'0') +
+                      (OSC_string[ 2 ] - L'0');
+      offset = 4;
     }
     bool set_icon = (cmd_num == 0 || cmd_num == 1);
     bool set_title = (cmd_num == 0 || cmd_num == 2);
@@ -569,6 +609,9 @@ void Dispatcher::OSC_dispatch( const Parser::OSC_End *act, Framebuffer *fb )

       act->handled = true;
     }
+    else {
+      // HELP ME: how can I write the OSC_string as-is to the terminal device?
+    }
   }
 }

Start in src/terminal/terminalfunctions.cc at Dispatcher::OSC_dispatch and trace how OSC sequences are parsed and how terminal output is written. Reproduce the issue with an OSC 52 clipboard sequence; done means the sequence reaches the client terminal without breaking existing OSC handling, with a regression check if an existing test path is identified.