fix(client): handle remote terminal hangup (backport #2827)

docs/next/CHANGELOG.md

@@ -19,6 +19,7 @@
 - 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
+- Closing a terminal running `herdr --remote` no longer produces a local client core dump while the remote session stays alive. (#2424)
 - OpenCode panes now track the root conversation selected in their own TUI for native restore without adopting activity from attached clients. (#2450)
 - Server stop requests now bypass pane and API traffic, preventing busy sessions from blocking shutdown or admitting a client while shutdown is pending. (#2612)
 - Fish `Ctrl+Alt` keybindings now work in panes after legacy Alt-prefixed control bytes are decoded with both modifiers. (#2514)

src/client/mod.rs

@@ -421,6 +421,7 @@ fn setup_terminal_with_capabilities(
     Ok(TerminalGuard {
         reset_modify_other_keys: modify_other_keys_mode.is_some(),
         reset_host_color_scheme_reports: host_color_scheme_reports,
+        restored: false,
         #[cfg(windows)]
         restore_windows_input_mode: windows_virtual_terminal_input.restore_mode,
     })
@@ -434,6 +435,7 @@ fn should_enable_host_color_scheme_reports(enable_client_protocols: bool) -> boo
 struct TerminalGuard {
     reset_modify_other_keys: bool,
     reset_host_color_scheme_reports: bool,
+    restored: bool,
     #[cfg(windows)]
     restore_windows_input_mode: Option<u32>,
 }
@@ -582,7 +584,7 @@ fn restore_terminal_state(
     reset_modify_other_keys: bool,
     reset_host_color_scheme_reports: bool,
     #[cfg(windows)] restore_windows_input_mode: Option<u32>,
-) {
+) -> io::Result<()> {
     let _ = clear_received_kitty_graphics(&mut io::stdout());
 
     // Reset modifyOtherKeys if we enabled it.
@@ -606,13 +608,16 @@ fn restore_terminal_state(
         restore_windows_input_mode_value(mode);
     }
 
-    let _ = ratatui::try_restore();
-    let _ = write_terminal_restore_postlude(&mut io::stdout(), reset_host_color_scheme_reports);
+    let restore_result = ratatui::try_restore();
+    let postlude_result =
+        write_terminal_restore_postlude(&mut io::stdout(), reset_host_color_scheme_reports);
 
     #[cfg(windows)]
     if windows_vti_input_backend_enabled() && windows_win32_input_mode_enabled() {
         let _ = disable_windows_win32_input_mode(&mut io::stdout());
     }
+
+    restore_result.and(postlude_result)
 }
 
 #[cfg(not(windows))]
@@ -657,14 +662,28 @@ fn disable_windows_win32_input_mode(writer: &mut impl std::io::Write) -> io::Res
     writer.flush()
 }
 
-impl Drop for TerminalGuard {
-    fn drop(&mut self) {
+impl TerminalGuard {
+    fn restore(mut self) -> io::Result<()> {
+        self.restored = true;
         restore_terminal_state(
             self.reset_modify_other_keys,
             self.reset_host_color_scheme_reports,
             #[cfg(windows)]
             self.restore_windows_input_mode,
-        );
+        )
+    }
+}
+
+impl Drop for TerminalGuard {
+    fn drop(&mut self) {
+        if !self.restored {
+            let _ = restore_terminal_state(
+                self.reset_modify_other_keys,
+                self.reset_host_color_scheme_reports,
+                #[cfg(windows)]
+                self.restore_windows_input_mode,
+            );
+        }
     }
 }
 
@@ -1281,7 +1300,7 @@ fn run_client_with_mode(
     let panic_restore_windows_input_mode = terminal_guard.restore_windows_input_mode;
     let original_hook = std::panic::take_hook();
     std::panic::set_hook(Box::new(move |info| {
-        restore_terminal_state(
+        let _ = restore_terminal_state(
             panic_resets_modify_other_keys,
             panic_resets_host_color_scheme_reports,
             #[cfg(windows)]
@@ -1323,19 +1342,22 @@ fn run_client_with_mode(
     });
 
     // Restore the terminal before printing any final status message.
-    drop(terminal_guard);
+    let terminal_restore_failed = terminal_guard.restore().is_err();
 
     if let Err(err) = result {
-        eprintln!("herdr: {err}");
+        let _ = writeln!(io::stderr(), "herdr: {err}");
         rt.shutdown_timeout(Duration::from_millis(100));
         crate::logging::shutdown("client");
 
-        if matches!(
-            err,
+        let detached = matches!(
+            &err,
             ClientError::ServerShutdown {
                 reason: Some(reason)
             } if reason == "detached"
-        ) {
+        );
+        let connection_lost_during_terminal_hangup =
+            terminal_restore_failed && matches!(&err, ClientError::ConnectionLost(_));
+        if detached || connection_lost_during_terminal_hangup {
             return Ok(());
         }
 

tests/client_mode.rs

@@ -1075,6 +1075,65 @@ fn read_until_client_attaches(client: &SpawnedHerdr) -> String {
     panic!("thin client must attach and render a frame; output: {output:?}");
 }
 
+#[test]
+fn client_exits_cleanly_when_terminal_and_transport_hang_up() {
+    let _lock = test_lock();
+    let base = unique_test_dir();
+    let config_home = base.join("config");
+    let runtime_dir = base.join("runtime");
+    let api_socket = runtime_dir.join("herdr.sock");
+    let client_socket = runtime_dir.join("herdr-client.sock");
+
+    let mut spawned_server = spawn_server(&config_home, &runtime_dir, &api_socket, &client_socket);
+    wait_for_socket(&api_socket, Duration::from_secs(10));
+    wait_for_socket(&client_socket, Duration::from_secs(10));
+
+    let mut thin_client = spawn_client_process(&config_home, &runtime_dir, &api_socket);
+    read_until_client_attaches(&thin_client);
+
+    // Freeze the client so the dead terminal and transport EOF are both
+    // observable when it resumes, making the `--remote` shutdown race deterministic.
+    let client_pid = thin_client.child.process_id().expect("thin client pid") as libc::pid_t;
+    assert_eq!(
+        unsafe { libc::kill(client_pid, libc::SIGSTOP) },
+        0,
+        "stop thin client"
+    );
+    let server_pid = spawned_server.child.process_id().expect("server pid") as libc::pid_t;
+    assert_eq!(
+        unsafe { libc::kill(server_pid, libc::SIGKILL) },
+        0,
+        "kill server transport"
+    );
+    spawned_server.close_master();
+    thin_client.close_master();
+    assert_eq!(
+        unsafe { libc::kill(client_pid, libc::SIGCONT) },
+        0,
+        "resume thin client"
+    );
+
+    let deadline = Instant::now() + Duration::from_secs(12);
+    let status = loop {
+        if let Some(status) = thin_client.child.try_wait().expect("poll thin client") {
+            break Some(status);
+        }
+        if Instant::now() >= deadline {
+            break None;
+        }
+        thread::sleep(Duration::from_millis(20));
+    };
+
+    drop(spawned_server);
+    cleanup_spawned_herdr(thin_client, base);
+
+    let status = status.expect("thin client should exit after terminal and transport hang up");
+    assert!(
+        status.success(),
+        "thin client should exit cleanly after terminal and transport hang up, got {status}"
+    );
+}
+
 #[test]
 fn client_exits_cleanly_when_terminal_hangs_up() {
     let _lock = test_lock();