diff --git a/codex-rs/terminal-browser/src/process.rs b/codex-rs/terminal-browser/src/process.rs
index 4cc1898d9c..3c7154d4e4 100644
--- a/codex-rs/terminal-browser/src/process.rs
+++ b/codex-rs/terminal-browser/src/process.rs
@@ -137,6 +137,10 @@ impl Drop for StartupGuard<'_> {
 
 impl Inner {
     pub(crate) async fn ensure_session(self: &Arc<Self>, config: SessionConfig) -> Result<()> {
+        anyhow::ensure!(
+            !self.terminated.load(Ordering::SeqCst),
+            "terminal browser has been terminated"
+        );
         let expected_network_policy = config.network_policy.clone();
         let process_exited = self
             .process
@@ -190,6 +194,10 @@ impl Inner {
 
     async fn start_session(self: &Arc<Self>, config: SessionConfig) -> Result<()> {
         let binary = self.validated_binary().await?;
+        anyhow::ensure!(
+            !self.terminated.load(Ordering::SeqCst),
+            "terminal browser has been terminated"
+        );
         self.closing.store(/*val*/ false, Ordering::SeqCst);
         let persistent_profile = self.selected_profile_resources()?;
         let runtime =
@@ -278,6 +286,10 @@ impl Inner {
         });
         startup.set_exit_task(exit_task);
         let mut session_slot = self.session.lock().await;
+        anyhow::ensure!(
+            !self.terminated.load(Ordering::SeqCst),
+            "terminal browser has been terminated"
+        );
         let CommittedStartup {
             profile_lock,
             output_task,
@@ -296,11 +308,17 @@ impl Inner {
         });
         drop(session_slot);
         self.update_view(|view| {
-            view.status = BrowserStatus::Running;
-            if !target.title.is_empty() {
-                view.title = Some(target.title);
+            if !self.terminated.load(Ordering::SeqCst) {
+                view.status = BrowserStatus::Running;
+                if !target.title.is_empty() {
+                    view.title = Some(target.title);
+                }
             }
         });
+        if self.terminated.load(Ordering::SeqCst) {
+            self.close_session().await;
+            anyhow::bail!("terminal browser has been terminated");
+        }
         Ok(())
     }
 
@@ -377,6 +395,52 @@ impl Inner {
             view.human_control = false;
         });
     }
+
+    pub(crate) fn terminate_now(&self) {
+        self.terminated.store(/*val*/ true, Ordering::SeqCst);
+        self.closing.store(/*val*/ true, Ordering::SeqCst);
+        self.human_control.store(/*val*/ false, Ordering::SeqCst);
+        self.human_control_generation
+            .fetch_add(/*val*/ 1, Ordering::SeqCst);
+
+        if let Some(process) = self
+            .process
+            .lock()
+            .unwrap_or_else(PoisonError::into_inner)
+            .take()
+        {
+            process.terminate();
+        }
+        if let Ok(mut session) = self.session.try_lock()
+            && let Some(session) = session.take()
+        {
+            session.output_task.abort();
+            session.exit_task.abort();
+            session.navigation_policy_task.abort();
+        }
+
+        let status = if self
+            .binary
+            .read()
+            .unwrap_or_else(PoisonError::into_inner)
+            .is_some()
+        {
+            BrowserStatus::Idle
+        } else {
+            self.view
+                .read()
+                .unwrap_or_else(PoisonError::into_inner)
+                .status
+                .clone()
+        };
+        self.update_view(|view| {
+            view.status = status;
+            view.visible = false;
+            view.title = None;
+            view.url = None;
+            view.human_control = false;
+        });
+    }
 }
 
 fn spawn_screen_task(
diff --git a/codex-rs/terminal-browser/src/session.rs b/codex-rs/terminal-browser/src/session.rs
index a98ed75776..008e36270f 100644
--- a/codex-rs/terminal-browser/src/session.rs
+++ b/codex-rs/terminal-browser/src/session.rs
@@ -51,6 +51,7 @@ pub(crate) struct Inner {
     pub(crate) process: Mutex<Option<Arc<ProcessHandle>>>,
     pub(crate) resize_tx: watch::Sender<TerminalSize>,
     pub(crate) closing: AtomicBool,
+    pub(crate) terminated: AtomicBool,
     pub(crate) human_control: AtomicBool,
     pub(crate) human_control_transition: AtomicBool,
     pub(crate) human_control_generation: AtomicU64,
@@ -112,6 +113,7 @@ impl TerminalBrowser {
                 process: Mutex::new(/*t*/ None),
                 resize_tx,
                 closing: AtomicBool::new(/*v*/ false),
+                terminated: AtomicBool::new(/*v*/ false),
                 human_control: AtomicBool::new(/*v*/ false),
                 human_control_transition: AtomicBool::new(/*v*/ false),
                 human_control_generation: AtomicU64::new(/*v*/ 0),
@@ -235,6 +237,13 @@ impl TerminalBrowser {
         let _operation = self.inner.operation.lock().await;
         self.inner.close_session().await;
     }
+
+    /// Immediately terminates the browser process during application teardown.
+    ///
+    /// Normal lifecycle paths should prefer [`Self::close`] so Carbonyl can exit gracefully.
+    pub fn terminate(&self) {
+        self.inner.terminate_now();
+    }
 }
 
 impl Inner {
diff --git a/codex-rs/terminal-browser/src/terminal_browser_tests.rs b/codex-rs/terminal-browser/src/terminal_browser_tests.rs
index eee0d44e17..b5870abd53 100644
--- a/codex-rs/terminal-browser/src/terminal_browser_tests.rs
+++ b/codex-rs/terminal-browser/src/terminal_browser_tests.rs
@@ -33,6 +33,26 @@ async fn open_requires_network_enabled_by_the_active_permission_profile() {
     );
 }
 
+#[tokio::test]
+async fn emergency_termination_prevents_future_browser_startup() {
+    let browser = TerminalBrowser::discover();
+    browser
+        .set_network_policy(BrowserNetworkPolicy::Direct)
+        .await;
+
+    browser.terminate();
+
+    let error = browser
+        .execute(
+            "test-session",
+            "open",
+            serde_json::json!({ "url": "https://example.com" }),
+        )
+        .await
+        .expect_err("terminated browser should reject startup");
+    assert_eq!(error.to_string(), "terminal browser has been terminated");
+}
+
 #[tokio::test]
 async fn model_actions_are_rejected_during_human_control() {
     let browser = TerminalBrowser::discover();