Fix corruption in copy-paste over nested tmux

config/tmux.conf

@@ -60,14 +60,15 @@ bind C-y run 'tmux save-buffer - | $HOME/dotfiles/bin/clipboard-copy'
 # option, so only set it when the running tmux is new enough.
 if-shell "tmux -V | awk '{print $2}' | awk -F. '{if ($1*1000+$2 >= 3003) exit 0; else exit 1}'" 'set -g allow-passthrough on'
 
-# Let tmux tell Shift+Enter apart from plain Enter and forward that
-# distinction inward, so Claude Code's Shift+Enter-inserts-newline shortcut
-# works. extended-keys/terminal-features need tmux >= 3.2. The terminal
-# name is matched with '*' rather than the commonly-suggested 'xterm*',
-# because a nested tmux's "terminal" is the outer tmux, which reports
-# itself using default-terminal above (screen-256color) -- 'xterm*' would
-# never match that, breaking the nested case this is meant to support.
-if-shell "tmux -V | awk '{print $2}' | awk -F. '{if ($1*1000+$2 >= 3002) exit 0; else exit 1}'" 'set -s extended-keys on; set -as terminal-features "*:extkeys"'
+# Deliberately OFF, do not re-enable: extended-keys makes tmux re-encode raw
+# control-equivalent bytes (Tab, CR, Backspace, Escape, and LF/Ctrl-J) into
+# CSI 27;<mod>;<key>~ sequences instead of passing the plain byte through,
+# any time it doesn't recognize the data as bracketed paste. Turning this on
+# previously mangled every LF byte -- both literal Ctrl+J keypresses and
+# every newline in pasted text -- into that unrecognized CSI sequence before
+# it reached the app in the pane, breaking Ctrl+J-as-newline and corrupting
+# multi-line pastes with literal escape-sequence garbage.
+set -s extended-keys off
 
 # Accept pane-originated OSC 52 clipboard-set attempts into a real tmux
 # buffer. Only on-vs-off matters here -- off would refuse to even look at