fix(theme): skip host palette queries under wsl (#2852)

refs #2440

8 files changed, 38 insertions, 7 deletions

diff --git a/docs/next/CHANGELOG.md b/docs/next/CHANGELOG.md
index 8190fbc1..1ded91d0 100644
--- a/docs/next/CHANGELOG.md
+++ b/docs/next/CHANGELOG.md
@@ -23,6 +23,7 @@
 - Experimental pane graphics now support bounded named layers, acknowledged full-RGBA primary-layer direct file frames on audited local terminals, owned BGRA fallback, exact pixel mouse input, and placement-only resize replay.
 
 ### Fixed
+- Herdr no longer sends the full OSC 4 palette query burst under WSL, preventing reply fragments from leaking into the shell through ConPTY. (#2440)
 - Qwen Code panes now use locale-independent terminal-title states and localized confirmation fallbacks, preventing active or blocked turns from appearing idle. (#2756)
 - Closing a terminal running `herdr --remote` no longer produces a local client core dump while the remote session stays alive. (#2424)
 - Active Space and Agent rows now use dedicated theme colors that remain visible when the host terminal background matches the selected Herdr theme. (#2792)
diff --git a/src/app/theme_sync.rs b/src/app/theme_sync.rs
index 6bf06685..58f95bec 100644
--- a/src/app/theme_sync.rs
+++ b/src/app/theme_sync.rs
@@ -13,7 +13,9 @@ impl App {
     pub(super) fn query_host_terminal_theme(&self) {
         use std::io::Write;
 
-        let query = crate::terminal_theme::host_terminal_theme_query_sequence();
+        let query = crate::terminal_theme::host_terminal_theme_query_sequence(
+            crate::platform::should_query_host_terminal_palette(),
+        );
         let _ = std::io::stdout().write_all(query.as_bytes());
         let _ = std::io::stdout().flush();
     }
diff --git a/src/client/mod.rs b/src/client/mod.rs
index b70b6c9c..c33157fb 100644
--- a/src/client/mod.rs
+++ b/src/client/mod.rs
@@ -2571,7 +2571,9 @@ fn should_query_host_terminal_theme() -> bool {
 }
 
 fn write_host_terminal_theme_query(mut writer: impl io::Write) -> io::Result<()> {
-    let query = crate::terminal_theme::host_terminal_theme_query_sequence();
+    let query = crate::terminal_theme::host_terminal_theme_query_sequence(
+        crate::platform::should_query_host_terminal_palette(),
+    );
     writer.write_all(query.as_bytes())?;
     writer.flush()
 }
@@ -2999,7 +3001,10 @@ mod tests {
         write_host_terminal_theme_query(&mut output).unwrap();
         assert_eq!(
             output,
-            crate::terminal_theme::host_terminal_theme_query_sequence().as_bytes()
+            crate::terminal_theme::host_terminal_theme_query_sequence(
+                crate::platform::should_query_host_terminal_palette(),
+            )
+            .as_bytes()
         );
         assert!(!output
             .windows(crate::terminal_theme::HOST_COLOR_SCHEME_QUERY_SEQUENCE.len())
diff --git a/src/platform/fallback.rs b/src/platform/fallback.rs
index f0e5c2ca..1b02fae8 100644
--- a/src/platform/fallback.rs
+++ b/src/platform/fallback.rs
@@ -89,6 +89,10 @@ pub(crate) fn should_draw_host_cursor_by_default() -> bool {
     false
 }
 
+pub(crate) fn should_query_host_terminal_palette() -> bool {
+    false
+}
+
 pub(crate) fn hostname() -> Option<String> {
     None
 }
diff --git a/src/platform/linux.rs b/src/platform/linux.rs
index 89e6c96d..f84d9e96 100644
--- a/src/platform/linux.rs
+++ b/src/platform/linux.rs
@@ -41,6 +41,10 @@ pub(crate) fn should_draw_host_cursor_by_default() -> bool {
     running_inside_wsl()
 }
 
+pub(crate) fn should_query_host_terminal_palette() -> bool {
+    !running_inside_wsl()
+}
+
 fn running_inside_wsl() -> bool {
     proc_file_indicates_wsl("/proc/sys/kernel/osrelease")
         || proc_file_indicates_wsl("/proc/version")
diff --git a/src/platform/macos.rs b/src/platform/macos.rs
index d85da440..9c59b39c 100644
--- a/src/platform/macos.rs
+++ b/src/platform/macos.rs
@@ -26,6 +26,10 @@ pub(crate) fn should_draw_host_cursor_by_default() -> bool {
     false
 }
 
+pub(crate) fn should_query_host_terminal_palette() -> bool {
+    true
+}
+
 fn raw_command_argv(command: &str, flag: &str) -> Vec<std::ffi::OsString> {
     vec!["/bin/sh".into(), flag.into(), command.into()]
 }
diff --git a/src/platform/windows.rs b/src/platform/windows.rs
index 83f85e6a..4e444877 100644
--- a/src/platform/windows.rs
+++ b/src/platform/windows.rs
@@ -362,6 +362,10 @@ pub(crate) fn should_draw_host_cursor_by_default() -> bool {
     true
 }
 
+pub(crate) fn should_query_host_terminal_palette() -> bool {
+    false
+}
+
 /// The machine's node name, as shown by tmux's `#h`.
 pub(crate) fn hostname() -> Option<String> {
     std::env::var("COMPUTERNAME")
diff --git a/src/terminal_theme.rs b/src/terminal_theme.rs
index 3f04cc4c..2460731e 100644
--- a/src/terminal_theme.rs
+++ b/src/terminal_theme.rs
@@ -79,12 +79,14 @@ impl TerminalTheme {
     }
 }
 
-pub fn host_terminal_theme_query_sequence() -> String {
+pub fn host_terminal_theme_query_sequence(include_palette: bool) -> String {
     use std::fmt::Write as _;
 
     let mut sequence = String::from(HOST_COLOR_QUERY_SEQUENCE);
-    for index in 0..=u8::MAX {
-        let _ = write!(sequence, "\x1b]4;{index};?\x1b\\");
+    if include_palette {
+        for index in 0..=u8::MAX {
+            let _ = write!(sequence, "\x1b]4;{index};?\x1b\\");
+        }
     }
     sequence
 }
@@ -218,11 +220,16 @@ mod tests {
             ))
         );
 
-        let query = host_terminal_theme_query_sequence();
+        let query = host_terminal_theme_query_sequence(true);
         assert!(query.starts_with(HOST_COLOR_QUERY_SEQUENCE));
         assert!(query.contains("\x1b]4;0;?\x1b\\"));
         assert!(query.ends_with("\x1b]4;255;?\x1b\\"));
         assert_eq!(query.matches("\x1b]4;").count(), 256);
+
+        assert_eq!(
+            host_terminal_theme_query_sequence(false),
+            HOST_COLOR_QUERY_SEQUENCE
+        );
     }
 
     #[test]