diff --git a/codex-rs/cli/src/debug_sandbox.rs b/codex-rs/cli/src/debug_sandbox.rs
index 06c133394b..513dccfa10 100644
--- a/codex-rs/cli/src/debug_sandbox.rs
+++ b/codex-rs/cli/src/debug_sandbox.rs
@@ -380,7 +380,7 @@ async fn run_command_under_sandbox(
         SandboxType::Seatbelt => {
             let (file_system_sandbox_policy, network_sandbox_policy) =
                 runtime_permission_profile.to_runtime_permissions();
-            let args = create_seatbelt_command_args(CreateSeatbeltCommandArgsParams {
+            let mut args = create_seatbelt_command_args(CreateSeatbeltCommandArgsParams {
                 command,
                 file_system_sandbox_policy: &file_system_sandbox_policy,
                 network_sandbox_policy,
@@ -392,6 +392,15 @@ async fn run_command_under_sandbox(
                 extra_allow_unix_sockets: allow_unix_sockets,
             })
             .map_err(|err| anyhow::anyhow!(err))?;
+            // This CLI inherits the user's controlling terminal. Keep this deny
+            // after every shared policy allowance so the child cannot queue input
+            // for the unsandboxed shell that resumes when Codex exits.
+            match args.as_mut_slice() {
+                [flag, policy, ..] if flag.as_str() == "-p" => {
+                    policy.push_str("\n(deny file-ioctl (ioctl-command TIOCSTI))");
+                }
+                _ => anyhow::bail!("Seatbelt command is missing its generated policy"),
+            }
             spawn_debug_sandbox_child(
                 PathBuf::from("/usr/bin/sandbox-exec"),
                 args,
diff --git a/codex-rs/cli/tests/sandbox_tty.rs b/codex-rs/cli/tests/sandbox_tty.rs
new file mode 100644
index 0000000000..730ae9173a
--- /dev/null
+++ b/codex-rs/cli/tests/sandbox_tty.rs
@@ -0,0 +1,132 @@
+//! Exercises the public macOS sandbox runner with a disposable controlling terminal.
+
+#![cfg(target_os = "macos")]
+
+use std::collections::HashMap;
+use std::path::Path;
+use std::process::Command;
+use std::time::Duration;
+
+use anyhow::Context as _;
+use codex_utils_pty::SpawnedProcess;
+use codex_utils_pty::TerminalSize;
+use codex_utils_pty::spawn_pty_process;
+use pretty_assertions::assert_eq;
+use tempfile::TempDir;
+
+const PROBE: &str = r#"
+import errno, fcntl, os, select, signal, struct, sys, termios, tty
+
+signal.alarm(15)
+assert os.isatty(0)
+assert os.tcgetpgrp(0) == os.getpgrp()
+assert struct.unpack("HHHH", fcntl.ioctl(0, termios.TIOCGWINSZ, b"\0" * 8))[:2] == (24, 80)
+original = termios.tcgetattr(0)
+try:
+    tty.setraw(0)
+    print("__ready__", flush=True)
+    assert os.read(0, 1) == b"k"
+    try:
+        fcntl.ioctl(0, termios.TIOCSTI, b"x")
+    except OSError as error:
+        assert sys.argv[1] == "deny", error
+        assert error.errno == errno.EPERM, error
+        assert not select.select([0], [], [], 0)[0]
+    else:
+        assert os.read(0, 1) == b"x"
+        assert sys.argv[1] == "allow", "TIOCSTI unexpectedly succeeded"
+finally:
+    termios.tcsetattr(0, termios.TCSANOW, original)
+print("__passed__", flush=True)
+"#;
+
+#[tokio::test]
+async fn sandbox_blocks_terminal_input_injection() -> anyhow::Result<()> {
+    let availability = Command::new("/usr/bin/sandbox-exec")
+        .args(["-p", "(version 1)(allow default)", "/usr/bin/true"])
+        .output()?;
+    if !availability.status.success()
+        && String::from_utf8_lossy(&availability.stderr)
+            .contains("sandbox-exec: sandbox_apply: Operation not permitted")
+    {
+        eprintln!("skipping terminal injection test: nested Seatbelt is unavailable");
+        return Ok(());
+    }
+    assert!(availability.status.success(), "{availability:?}");
+
+    let codex_home = TempDir::new()?;
+    let mut env: HashMap<String, String> = std::env::vars().collect();
+    env.insert(
+        "CODEX_HOME".to_string(),
+        codex_home.path().to_string_lossy().into_owned(),
+    );
+
+    // The control proves this is a readable, foreground controlling terminal on
+    // which TIOCSTI would otherwise work. All injected input stays in this PTY.
+    run_probe(
+        "/usr/bin/python3",
+        vec!["-c".to_string(), PROBE.to_string(), "allow".to_string()],
+        codex_home.path(),
+        &env,
+    )
+    .await?;
+
+    let codex = codex_utils_cargo_bin::cargo_bin("codex")?;
+    run_probe(
+        &codex.to_string_lossy(),
+        vec![
+            "sandbox".to_string(),
+            "-P".to_string(),
+            ":read-only".to_string(),
+            "--".to_string(),
+            "/usr/bin/python3".to_string(),
+            "-c".to_string(),
+            PROBE.to_string(),
+            "deny".to_string(),
+        ],
+        codex_home.path(),
+        &env,
+    )
+    .await
+}
+
+async fn run_probe(
+    program: &str,
+    args: Vec<String>,
+    cwd: &Path,
+    env: &HashMap<String, String>,
+) -> anyhow::Result<()> {
+    let SpawnedProcess {
+        session,
+        mut stdout_rx,
+        exit_rx,
+        ..
+    } = spawn_pty_process(
+        program,
+        &args,
+        cwd,
+        env,
+        /*arg0*/ &None,
+        TerminalSize::default(),
+        &[],
+    )
+    .await?;
+    let mut output = Vec::new();
+    let mut sent_input = false;
+    let code = tokio::time::timeout(Duration::from_secs(30), async {
+        while let Some(bytes) = stdout_rx.recv().await {
+            output.extend_from_slice(&bytes);
+            if !sent_input && String::from_utf8_lossy(&output).contains("__ready__") {
+                session.writer_sender().send(b"k".to_vec()).await?;
+                sent_input = true;
+            }
+        }
+        Ok::<_, anyhow::Error>(exit_rx.await?)
+    })
+    .await
+    .context("terminal probe timed out")??;
+    let output = String::from_utf8_lossy(&output);
+    assert_eq!(code, 0, "terminal probe failed: {output}");
+    assert!(output.contains("__passed__"), "{output}");
+    Ok(())
+}