From e9d275298d8219115bc241c563a7bafd04240568 Mon Sep 17 00:00:00 2001
From: David Heinemeier Hansson <david@hey.com>
Date: Mon, 25 May 2026 10:30:16 +0200
Subject: [PATCH] Give kitty alt+shift+enter power for tmux vertical splits

---
 config/kitty/kitty.conf  |  2 ++
 config/tmux/tmux.conf    |  1 +
 migrations/1779696759.sh | 22 ++++++++++++++++++++++
 3 files changed, 25 insertions(+)
 create mode 100644 migrations/1779696759.sh

diff --git a/config/kitty/kitty.conf b/config/kitty/kitty.conf
index 7d550d78..af2da6dc 100644
--- a/config/kitty/kitty.conf
+++ b/config/kitty/kitty.conf
@@ -13,6 +13,8 @@ confirm_os_window_close 0
 # Keybindings
 map ctrl+insert copy_to_clipboard
 map shift+insert paste_from_clipboard
+# Kitty legacy encoding sends Alt+Shift+Enter the same as Alt+Enter; send CSI-u so tmux can match M-S-Enter.
+map alt+shift+enter send_text all \e[13;4u
 
 # Allow remote access
 allow_remote_control yes
diff --git a/config/tmux/tmux.conf b/config/tmux/tmux.conf
index 53990431..f24361d7 100644
--- a/config/tmux/tmux.conf
+++ b/config/tmux/tmux.conf
@@ -77,6 +77,7 @@ setw -g aggressive-resize on
 set -g detach-on-destroy off
 set -g extended-keys on
 set -g extended-keys-format csi-u
+set -g terminal-features[3] "xterm-kitty:extkeys"
 set -sg escape-time 10
 
 # Status bar
diff --git a/migrations/1779696759.sh b/migrations/1779696759.sh
new file mode 100644
index 00000000..f7303e60
--- /dev/null
+++ b/migrations/1779696759.sh
@@ -0,0 +1,22 @@
+echo "Make Alt+Shift+Enter distinguishable for Kitty and tmux"
+
+kitty_config="$HOME/.config/kitty/kitty.conf"
+tmux_config="$HOME/.config/tmux/tmux.conf"
+
+if [[ -f $kitty_config ]] && ! grep -Eq '^map[[:space:]]+alt\+shift\+enter[[:space:]]' "$kitty_config"; then
+  if grep -qxF 'map shift+insert paste_from_clipboard' "$kitty_config"; then
+    sed -i '/^map shift+insert paste_from_clipboard$/a # Kitty legacy encoding sends Alt+Shift+Enter the same as Alt+Enter; send CSI-u so tmux can match M-S-Enter.\nmap alt+shift+enter send_text all \\e[13;4u' "$kitty_config"
+  else
+    printf '\n# Kitty legacy encoding sends Alt+Shift+Enter the same as Alt+Enter; send CSI-u so tmux can match M-S-Enter.\nmap alt+shift+enter send_text all \\e[13;4u\n' >>"$kitty_config"
+  fi
+fi
+
+if [[ -f $tmux_config ]] && grep -qxF "set -as terminal-features ',xterm-kitty:extkeys'" "$tmux_config"; then
+  sed -i 's/^set -as terminal-features '"'"',xterm-kitty:extkeys'"'"'$/set -g terminal-features[3] "xterm-kitty:extkeys"/' "$tmux_config"
+elif [[ -f $tmux_config ]] && ! grep -q 'xterm-kitty:extkeys' "$tmux_config" && ! grep -Eq '^(set|set-option)[[:space:]].*terminal-features' "$tmux_config"; then
+  if grep -qxF 'set -g extended-keys-format csi-u' "$tmux_config"; then
+    sed -i '/^set -g extended-keys-format csi-u$/a set -g terminal-features[3] "xterm-kitty:extkeys"' "$tmux_config"
+  else
+    printf '\nset -g terminal-features[3] "xterm-kitty:extkeys"\n' >>"$tmux_config"
+  fi
+fi