Reliably disable modifyOtherKeys on WezTerm

WezTerm allows applications to enable modifyOtherKeys by default.
Its implementation has issues on non-English or non-QWERTY layouts,
see wezterm/wezterm#6087 and fish-shell#11204.

fish 4.0.1 disabled modifyOtherKeys on WezTerm specifically
(7ee6d91 (Work around keyboard-layout related bugs in WezTerm's
modifyOtherKeys, 2025-03-03)), fish 4.1.0 didn't, because at that
time, WezTerm would advertise support for the kitty keyboard protocol
(even if applications are not allowed to enable it) which would make
fish skip requesting the legacy modifyOtherKeys.

WezTerm no longer advertises that if config.enable_kitty_keyboard
is false.  Let's work around it in another way.

Author: krobelus

CHANGELOG.rst

@@ -7,6 +7,7 @@ fish 4.1.1 (released ???)
 This release fixes the following regressions identified in 4.1.0:
 
 - Some :doc:`fish_config <cmds/fish_config>` subcommands for prompts and themes were broken in standalone Linux builds (those using the ``embed-data`` cargo feature), which has been fixed (:issue:`11832`).
+- Our new workaround for WezTerm's `issues with modifyOtherKeys <https://github.com/wezterm/wezterm/issues/6087>`__ breaking shifted keys was broken on some versions of WezTerm, which has been fixed (:issue:`11204`).
 
 fish 4.1.0 (released September 27, 2025)
 ========================================

src/tty_handoff.rs

@@ -64,6 +64,8 @@ pub enum TtyQuirks {
     PreKittyIterm2,
     // Whether we are running under tmux.
     Tmux,
+    // Whether we are running under WezTerm.
+    Wezterm,
 }
 
 impl TtyQuirks {
@@ -74,6 +76,8 @@ impl TtyQuirks {
             PreKittyIterm2
         } else if xtversion.starts_with(L!("tmux ")) {
             Tmux
+        } else if xtversion.starts_with(L!("WezTerm ")) {
+            Wezterm
         } else {
             None
         }
@@ -85,7 +89,8 @@ impl TtyQuirks {
 enum ProtocolKind {
     KittyKeyboard, // Kitty keyboard support, producing CSI-u style encoding.
     Other,         // Other protocols (e.g., modifyOtherKeys)
-    None,          // No protocols
+    WorkAroundWezTerm,
+    None, // No protocols
 }
 
 // Commands to emit to enable or disable TTY protocols. Each of these contains
@@ -95,6 +100,7 @@ enum ProtocolKind {
 struct ProtocolBytes {
     kitty_keyboard: Box<[u8]>,
     other: Box<[u8]>,
+    wezterm_workaround: Box<[u8]>,
     none: Box<[u8]>,
 }
 
@@ -123,6 +129,7 @@ impl TtyProtocolsSet {
         match protocol {
             ProtocolKind::KittyKeyboard => &cmds.kitty_keyboard,
             ProtocolKind::Other => &cmds.other,
+            ProtocolKind::WorkAroundWezTerm => &cmds.wezterm_workaround,
             ProtocolKind::None => &cmds.none,
         }
     }
@@ -141,13 +148,19 @@ impl TtyQuirks {
     // Determine which keyboard protocol.
     // This is used from a signal handler.
     fn safe_get_supported_protocol(&self) -> ProtocolKind {
-        use TtyQuirks::PreKittyIterm2;
+        use TtyQuirks::{PreKittyIterm2, Wezterm};
         if *self == PreKittyIterm2 {
             return ProtocolKind::Other;
         }
         match KITTY_KEYBOARD_SUPPORTED.get() {
             Some(&true) => ProtocolKind::KittyKeyboard,
-            Some(&false) => ProtocolKind::Other,
+            Some(&false) => {
+                if *self == Wezterm {
+                    ProtocolKind::WorkAroundWezTerm
+                } else {
+                    ProtocolKind::Other
+                }
+            }
             None => ProtocolKind::None,
         }
     }
@@ -178,6 +191,10 @@ impl TtyQuirks {
                 ModifyOtherKeysEnable,       // XTerm's modifyOtherKeys
                 ApplicationKeypadModeEnable, // set application keypad mode, so the keypad keys send unique codes
             ])),
+            wezterm_workaround: serialize_commands(maybe_enable_focus_reporting(&[
+                DecsetBracketedPaste,
+                ApplicationKeypadModeEnable, // set application keypad mode, so the keypad keys send unique codes
+            ])),
             none: serialize_commands(maybe_enable_focus_reporting(&[DecsetBracketedPaste])),
         };
         let disablers = ProtocolBytes {
@@ -190,6 +207,10 @@ impl TtyQuirks {
                 ModifyOtherKeysDisable,
                 ApplicationKeypadModeDisable,
             ])),
+            wezterm_workaround: serialize_commands(maybe_disable_focus_reporting(&[
+                DecrstBracketedPaste,
+                ApplicationKeypadModeDisable,
+            ])),
             none: serialize_commands(maybe_disable_focus_reporting(&[DecrstBracketedPaste])),
         };
         TtyProtocolsSet {
@@ -273,6 +294,7 @@ fn set_tty_protocols_active(on_write: fn(), enable: bool) -> bool {
     match protocols.quirks.safe_get_supported_protocol() {
         ProtocolKind::KittyKeyboard => FLOG!(reader, mode, "kitty keyboard protocol"),
         ProtocolKind::Other => FLOG!(reader, mode, "other extended keys"),
+        ProtocolKind::WorkAroundWezTerm => FLOG!(reader, mode, "wezterm; no modifyOtherKeys"),
         ProtocolKind::None => (),
     };
     (on_write)();