Terminate Windows non-TTY processes on interrupt (#35655)

## Why

Windows non-TTY exec sessions reported interrupts as unsupported, so sending
Ctrl-C through `write_stdin` did not stop the running process.

## What changed

- Route interrupt requests for Windows non-TTY processes through their existing
  termination callback, including pipe-backed processes.
- Track whether driver-backed Windows sessions use a TTY so PTY interrupts keep
  their existing behavior.
- Consume the terminator after a successful interrupt to avoid invoking it again
  when the process handle is dropped.

## Testing

Added coverage for local and remote exec-server sessions, unified exec, pipe
fallbacks, and legacy Windows sandbox processes.

GitOrigin-RevId: 34504d01f091ef57bb961e98ad5a8d9f1acee4ee

codex-rs/core/tests/suite/unified_exec.rs

@@ -2199,9 +2199,14 @@ async fn assert_write_stdin_ctrl_c_interrupts_non_tty_session(
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-#[cfg_attr(not(windows), ignore = "Windows-only unified exec interrupt test")]
+async fn write_stdin_ctrl_c_terminates_non_tty_session_on_windows() -> Result<()> {
-async fn write_stdin_ctrl_c_reports_unsupported_interrupt_to_model_on_windows() -> Result<()> {
+    if core_test_support::test_target_os() != core_test_support::TestTargetOs::Windows {
-    skip_if_no_network!(Ok(()));
+        return Ok(());
+    }
+    skip_if_wine_exec!(
+        Ok(()),
+        "Wine exits Windows non-TTY shell processes immediately"
+    );
     skip_if_sandbox!(Ok(()));
 
     let server = start_mock_server().await;
@@ -2218,8 +2223,7 @@ async fn write_stdin_ctrl_c_reports_unsupported_interrupt_to_model_on_windows()
     let interrupt_call_id = "uexec-windows-interrupt";
 
     let start_args = serde_json::json!({
-        "shell": "cmd",
+        "cmd": "Start-Sleep -Seconds 30",
-        "cmd": "echo READY && ping -n 30 127.0.0.1 >NUL",
         "yield_time_ms": 250,
         "tty": false,
     });
@@ -2277,23 +2281,15 @@ async fn write_stdin_ctrl_c_reports_unsupported_interrupt_to_model_on_windows()
         Some("1000"),
         "exec_command should leave a running non-TTY session"
     );
-    assert!(
-        start_output.output.contains("READY"),
-        "start output should include command readiness marker, got {:?}",
-        start_output.output
-    );
-
     let interrupt_output = request_log
         .function_call_output_text(interrupt_call_id)
         .expect("missing interrupt output for write_stdin");
+    let interrupt_output = parse_unified_exec_output(&interrupt_output)?;
     assert!(
-        interrupt_output.contains("write_stdin failed"),
+        interrupt_output.process_id.is_none(),
-        "model-visible write_stdin output should report failure, got {interrupt_output:?}"
+        "interrupted process should be cleared from the session map"
-    );
-    assert!(
-        interrupt_output.contains("process interrupt is not supported by this process backend"),
-        "model-visible write_stdin output should explain unsupported interrupt, got {interrupt_output:?}"
     );
+    assert_eq!(interrupt_output.exit_code, Some(1));
 
     Ok(())
 }

codex-rs/exec-server/src/local_process.rs

@@ -1764,6 +1764,8 @@ mod tests {
             terminator: None,
             writer_handle: None,
             resizer: None,
+            #[cfg(windows)]
+            tty: false,
         })
         .session
     }

codex-rs/exec-server/tests/exec_process.rs

@@ -932,7 +932,7 @@ async fn assert_exec_process_signal_interrupts_process(use_remote: bool) -> Resu
     Ok(())
 }
 
-async fn assert_exec_process_signal_reports_unsupported_on_windows(use_remote: bool) -> Result<()> {
+async fn assert_exec_process_signal_terminates_on_windows(use_remote: bool) -> Result<()> {
     let context = create_process_context(use_remote).await?;
     let session = context
         .backend
@@ -956,21 +956,13 @@ async fn assert_exec_process_signal_reports_unsupported_on_windows(use_remote: b
         })
         .await?;
 
-    let err = match session.process.signal(ProcessSignal::Interrupt).await {
+    let StartedExecProcess { process, .. } = session;
-        Ok(()) => anyhow::bail!("Windows non-TTY signal should report unsupported"),
+    let wake_rx = process.subscribe_wake();
-        Err(err) => err,
+    process.signal(ProcessSignal::Interrupt).await?;
-    };
+    let (_output, exit_code, closed) = collect_process_output_from_reads(process, wake_rx).await?;
-    let message = err.to_string();
-    assert!(
-        message.contains("failed to signal process"),
-        "unexpected signal error: {message}"
-    );
-    assert!(
-        message.contains("process interrupt is not supported by this process backend"),
-        "unexpected signal error: {message}"
-    );
 
-    session.process.terminate().await?;
+    assert_eq!(exit_code, Some(1));
+    assert!(closed);
     Ok(())
 }
 
@@ -1268,8 +1260,8 @@ async fn exec_process_signal_interrupts_process(use_remote: bool) -> Result<()>
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 // Serialize tests that launch a real exec-server process through the full CLI.
 #[serial_test::serial(remote_exec_server)]
-async fn exec_process_signal_reports_unsupported_on_windows(use_remote: bool) -> Result<()> {
+async fn exec_process_signal_terminates_on_windows(use_remote: bool) -> Result<()> {
-    assert_exec_process_signal_reports_unsupported_on_windows(use_remote).await
+    assert_exec_process_signal_terminates_on_windows(use_remote).await
 }
 
 #[test_case(false ; "local")]

codex-rs/utils/pty/src/pipe.rs

@@ -48,7 +48,12 @@ impl ChildTerminator for PipeChildTerminator {
                     crate::process_group::interrupt_process_group(self.process_group_id)
                 }
 
-                #[cfg(not(unix))]
+                #[cfg(windows)]
+                {
+                    self.kill()
+                }
+
+                #[cfg(not(any(unix, windows)))]
                 {
                     Err(crate::process::unsupported_signal(signal))
                 }

codex-rs/utils/pty/src/pipe_tests.rs

@@ -1,7 +1,7 @@
 use super::*;
 
 #[test]
-fn process_fallback_terminates_root() -> anyhow::Result<()> {
+fn process_fallback_interrupt_terminates_root() -> anyhow::Result<()> {
     let mut child = std::process::Command::new("ping.exe")
         .args(["-n", "60", "127.0.0.1"])
         .stdin(Stdio::null())
@@ -12,7 +12,7 @@ fn process_fallback_terminates_root() -> anyhow::Result<()> {
         windows: WindowsChildTerminator::Process(child.id()),
     };
 
-    terminator.kill()?;
+    terminator.signal(ProcessSignal::Interrupt)?;
 
     assert!(!child.wait()?.success());
     Ok(())

codex-rs/utils/pty/src/process.rs

@@ -234,7 +234,12 @@ impl ProcessHandle {
             return Ok(());
         };
 
-        killer.signal(signal)
+        let result = killer.signal(signal);
+        #[cfg(windows)]
+        if result.is_ok() {
+            killer_opt.take();
+        }
+        result
     }
 
     /// Attempts to kill the child and abort helper tasks.
@@ -273,10 +278,17 @@ impl Drop for ProcessHandle {
 /// Adapts a closure into a `ChildTerminator` implementation.
 struct ClosureTerminator {
     inner: Option<Box<dyn FnMut() + Send + Sync>>,
+    #[cfg(windows)]
+    interrupt_terminates: bool,
 }
 
 impl ChildTerminator for ClosureTerminator {
     fn signal(&mut self, signal: ProcessSignal) -> io::Result<()> {
+        #[cfg(windows)]
+        if self.interrupt_terminates {
+            return self.kill();
+        }
+
         Err(unsupported_signal(signal))
     }
 
@@ -356,6 +368,9 @@ pub struct ProcessDriver {
     pub terminator: Option<Box<dyn FnMut() + Send + Sync>>,
     pub writer_handle: Option<JoinHandle<()>>,
     pub resizer: Option<ResizeFn>,
+    /// Whether this Windows process is attached to a pseudo-console.
+    #[cfg(windows)]
+    pub tty: bool,
 }
 
 /// Build a `SpawnedProcess` from a driver that supplies stdin/output/exit channels.
@@ -368,8 +383,13 @@ pub fn spawn_from_driver(driver: ProcessDriver) -> SpawnedProcess {
         terminator,
         writer_handle,
         resizer,
+        #[cfg(windows)]
+        tty,
     } = driver;
 
+    #[cfg(windows)]
+    let interrupt_terminates = terminator.is_some() && !tty;
+
     let (stdout_tx, stdout_rx) = mpsc::channel::<Vec<u8>>(256);
     let (stderr_tx, stderr_rx) = mpsc::channel::<Vec<u8>>(256);
     let (exit_seen_tx, exit_seen_rx) = watch::channel(false);
@@ -433,7 +453,11 @@ pub fn spawn_from_driver(driver: ProcessDriver) -> SpawnedProcess {
 
     let handle = ProcessHandle::new(
         writer_tx,
-        Box::new(ClosureTerminator { inner: terminator }),
+        Box::new(ClosureTerminator {
+            inner: terminator,
+            #[cfg(windows)]
+            interrupt_terminates,
+        }),
         reader_handle,
         stderr_reader_handle
             .map(|handle| handle.abort_handle())

codex-rs/utils/pty/src/tests.rs

@@ -4,6 +4,7 @@ use std::path::Path;
 use pretty_assertions::assert_eq;
 
 use crate::ProcessDriver;
+use crate::ProcessSignal;
 use crate::SpawnedProcess;
 use crate::TerminalSize;
 use crate::combine_output_receivers;
@@ -614,7 +615,14 @@ async fn driver_backed_process_can_expose_split_stdout_and_stderr() -> anyhow::R
         terminator: None,
         writer_handle: None,
         resizer: None,
+        #[cfg(windows)]
+        tty: false,
     });
+    let error = spawned
+        .session
+        .signal(ProcessSignal::Interrupt)
+        .expect_err("interrupting a driver without a terminator should remain unsupported");
+    assert_eq!(error.kind(), std::io::ErrorKind::Unsupported);
 
     let SpawnedProcess {
         session: _session,
@@ -650,6 +658,37 @@ async fn driver_backed_process_can_expose_split_stdout_and_stderr() -> anyhow::R
     Ok(())
 }
 
+#[cfg(windows)]
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn driver_backed_interrupt_terminates_once() {
+    let terminations = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
+    let callback_terminations = std::sync::Arc::clone(&terminations);
+    let (writer_tx, _writer_rx) = tokio::sync::mpsc::channel::<Vec<u8>>(1);
+    let (_stdout_tx, stdout_rx) = tokio::sync::broadcast::channel::<Vec<u8>>(1);
+    let (_exit_tx, exit_rx) = tokio::sync::oneshot::channel::<i32>();
+    let spawned = spawn_from_driver(ProcessDriver {
+        writer_tx,
+        stdout_rx,
+        stderr_rx: None,
+        exit_rx,
+        terminator: Some(Box::new(move || {
+            callback_terminations.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+        })),
+        writer_handle: None,
+        resizer: None,
+        #[cfg(windows)]
+        tty: false,
+    });
+
+    spawned
+        .session
+        .signal(ProcessSignal::Interrupt)
+        .expect("interrupt should terminate the driver-backed process");
+    drop(spawned.session);
+
+    assert_eq!(terminations.load(std::sync::atomic::Ordering::SeqCst), 1);
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn driver_backed_process_can_resize_via_resizer_hook() -> anyhow::Result<()> {
     let (writer_tx, _writer_rx) = tokio::sync::mpsc::channel::<Vec<u8>>(1);
@@ -663,7 +702,7 @@ async fn driver_backed_process_can_resize_via_resizer_hook() -> anyhow::Result<(
         stdout_rx: stdout_driver_rx,
         stderr_rx: None,
         exit_rx,
-        terminator: None,
+        terminator: Some(Box::new(|| {})),
         writer_handle: None,
         resizer: Some(Box::new(move |size| {
             if let Ok(mut guard) = size_tx.lock()
@@ -673,8 +712,16 @@ async fn driver_backed_process_can_resize_via_resizer_hook() -> anyhow::Result<(
             }
             Ok(())
         })),
+        #[cfg(windows)]
+        tty: true,
     });
 
+    let error = spawned
+        .session
+        .signal(ProcessSignal::Interrupt)
+        .expect_err("interrupting a PTY-backed driver should remain unsupported");
+    assert_eq!(error.kind(), std::io::ErrorKind::Unsupported);
+
     spawned.session.resize(TerminalSize {
         rows: 40,
         cols: 120,
@@ -711,6 +758,8 @@ async fn driver_backed_process_drains_output_that_arrives_after_exit_signal() ->
         terminator: None,
         writer_handle: None,
         resizer: None,
+        #[cfg(windows)]
+        tty: false,
     });
 
     let SpawnedProcess {

codex-rs/windows-sandbox-rs/src/unified_exec/backends/elevated.rs

@@ -232,6 +232,7 @@ pub(crate) async fn spawn_windows_sandbox_session_elevated_for_permission_profil
             } else {
                 None
             },
+            tty,
         },
         stdin_open,
     ))

codex-rs/windows-sandbox-rs/src/unified_exec/backends/legacy.rs

@@ -470,6 +470,7 @@ pub(crate) async fn spawn_windows_sandbox_session_legacy(
             Box::new(move |size| resize_conpty_handle(&hpc, size))
                 as Box<dyn FnMut(TerminalSize) -> Result<()> + Send>
         }),
+        tty,
     };
 
     Ok(finish_driver_spawn(driver, stdin_open))

codex-rs/windows-sandbox-rs/src/unified_exec/tests.rs

@@ -12,6 +12,7 @@ use base64::engine::general_purpose::STANDARD as BASE64;
 use codex_protocol::models::PermissionProfile;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_pty::ProcessDriver;
+use codex_utils_pty::ProcessSignal;
 use pretty_assertions::assert_eq;
 use std::collections::HashMap;
 use std::fs;
@@ -345,7 +346,7 @@ fn legacy_non_tty_cmd_rejects_deny_read_overrides() {
 }
 
 #[test]
-fn legacy_non_tty_powershell_emits_output() {
+fn legacy_non_tty_powershell_interrupt_terminates_process() {
     let Some(pwsh) = pwsh_path() else {
         return;
     };
@@ -364,11 +365,11 @@ fn legacy_non_tty_powershell_emits_output() {
                 pwsh.display().to_string(),
                 "-NoProfile".to_string(),
                 "-Command".to_string(),
-                "Write-Output LEGACY-NONTTY-DIRECT".to_string(),
+                "Write-Output LEGACY-NONTTY-DIRECT; [System.Threading.ManualResetEvent]::new($false).WaitOne()".to_string(),
             ],
             cwd.as_path(),
             HashMap::new(),
-            Some(5_000),
+            /*timeout_ms*/ None,
             &[],
             &[],
             /*tty*/ false,
@@ -378,12 +379,41 @@ fn legacy_non_tty_powershell_emits_output() {
         .await
         .expect("spawn legacy non-tty powershell session");
         println!("pwsh spawn returned");
-        let (stdout, exit_code) =
+        let codex_utils_pty::SpawnedProcess {
-            collect_stdout_and_exit(spawned, codex_home.path(), Duration::from_secs(10)).await;
+            session,
-        println!("pwsh collect returned exit_code={exit_code}");
+            mut stdout_rx,
-        let stdout = String::from_utf8_lossy(&stdout);
+            stderr_rx: _stderr_rx,
-        assert_eq!(exit_code, 0, "stdout={stdout:?}");
+            exit_rx,
-        assert!(stdout.contains("LEGACY-NONTTY-DIRECT"), "stdout={stdout:?}");
+        } = spawned;
+        timeout(Duration::from_secs(5), async {
+            let mut stdout = Vec::new();
+            while let Some(chunk) = stdout_rx.recv().await {
+                stdout.extend(chunk);
+                if String::from_utf8_lossy(&stdout).contains("LEGACY-NONTTY-DIRECT") {
+                    return;
+                }
+            }
+            panic!(
+                "PowerShell exited before emitting its readiness marker\n{}",
+                sandbox_log(codex_home.path())
+            );
+        })
+        .await
+        .unwrap_or_else(|_| {
+            panic!(
+                "timed out waiting for PowerShell readiness marker\n{}",
+                sandbox_log(codex_home.path())
+            )
+        });
+
+        session
+            .signal(ProcessSignal::Interrupt)
+            .expect("interrupt should terminate the restricted-token process job");
+        let exit_code = timeout(Duration::from_secs(5), exit_rx)
+            .await
+            .unwrap_or_else(|_| panic!("timed out waiting for exit\n{}", sandbox_log(codex_home.path())))
+            .expect("interrupted process should report an exit code");
+        assert_eq!(exit_code, 1);
     });
 }
 
@@ -405,6 +435,7 @@ fn finish_driver_spawn_keeps_stdin_open_when_requested() {
                 terminator: None,
                 writer_handle: None,
                 resizer: None,
+                tty: false,
             },
             /*stdin_open*/ true,
         );
@@ -437,6 +468,7 @@ fn finish_driver_spawn_closes_stdin_when_not_requested() {
                 terminator: None,
                 writer_handle: None,
                 resizer: None,
+                tty: false,
             },
             /*stdin_open*/ false,
         );