diff --git a/frontend/src-tauri/src/extension_container.rs b/frontend/src-tauri/src/extension_container.rs
index ee02d27..b737f75 100644
--- a/frontend/src-tauri/src/extension_container.rs
+++ b/frontend/src-tauri/src/extension_container.rs
@@ -707,12 +707,51 @@ mod tests {
                 .code,
             "EXTENSION_PROCESS_WAIT_INVALID"
         );
-        running.terminate().unwrap();
+        let completed = running.start_tool_call().unwrap();
+        completed.finish().unwrap();
+        assert_eq!(running.wait(std::time::Duration::ZERO).unwrap(), None);
+        let deadline = running
+            .start_test_tool_call(std::time::Duration::from_millis(100))
+            .unwrap();
+        // No check() or finish() drives expiration; wait only on the OS process.
+        assert!(running
+            .wait(std::time::Duration::from_secs(5))
+            .unwrap()
+            .is_some());
+        assert_eq!(
+            deadline.finish().unwrap_err().code,
+            "EXTENSION_TOOL_DEADLINE_EXCEEDED"
+        );
         assert!(running
             .wait(std::time::Duration::from_secs(5))
             .unwrap()
             .is_some());
         drop(running);
+        for explicit_cancel in [false, true] {
+            let data = crate::extension_launch_data::LaunchData::new(
+                &executable,
+                &["wait".to_owned()],
+                &system,
+                &folder,
+                &folder.join("Temp"),
+                &std::collections::BTreeMap::new(),
+            )
+            .unwrap();
+            let suspended =
+                crate::extension_process::Suspended::create(&profile, &executable, data).unwrap();
+            let running = unsafe { suspended.resume().unwrap() };
+            let deadline = running.start_tool_call().unwrap();
+            assert_eq!(running.wait(std::time::Duration::ZERO).unwrap(), None);
+            if explicit_cancel {
+                deadline.cancel().unwrap();
+            } else {
+                drop(deadline);
+            }
+            assert!(running
+                .wait(std::time::Duration::from_secs(5))
+                .unwrap()
+                .is_some());
+        }
         for ip in ["127.0.0.1:0", "[::1]:0"] {
             let tcp = TcpListener::bind(ip).unwrap();
             let udp = UdpSocket::bind(ip).unwrap();
diff --git a/frontend/src-tauri/src/extension_deadline.rs b/frontend/src-tauri/src/extension_deadline.rs
new file mode 100644
index 0000000..300a1f2
--- /dev/null
+++ b/frontend/src-tauri/src/extension_deadline.rs
@@ -0,0 +1,158 @@
+//! Per-tool-call deadline. A persistent server does not have a 60-second lifetime.
+use crate::{
+    extension_job::Job,
+    workspace::{HostError, Result},
+};
+use std::{
+    sync::{
+        atomic::{AtomicU8, Ordering},
+        Arc, Condvar, Mutex,
+    },
+    thread::JoinHandle,
+    time::{Duration, Instant},
+};
+
+pub const TOOL_BUDGET: Duration = Duration::from_secs(60);
+struct State {
+    cancelled: Mutex<bool>,
+    wake: Condvar,
+    outcome: AtomicU8,
+}
+/// Host-owned guard, created before dispatching a tool call. Finish it only when
+/// the call completes. Expiration kills the entire instance group even if the
+/// caller never polls. Dropping without finish aborts the instance; only explicit
+/// successful completion cancels the timer while preserving the server.
+pub struct ToolDeadline {
+    state: Arc<State>,
+    job: Arc<Job>,
+    expires: Instant,
+    worker: Option<JoinHandle<()>>,
+}
+impl ToolDeadline {
+    pub(crate) fn arm(job: &Job) -> Result<Self> {
+        Self::with_budget(job, TOOL_BUDGET)
+    }
+    fn with_budget(job: &Job, budget: Duration) -> Result<Self> {
+        if budget.is_zero() || budget > TOOL_BUDGET {
+            return Err(HostError::new("EXTENSION_TOOL_BUDGET_INVALID"));
+        }
+        let expires = Instant::now() + budget;
+        let job = Arc::new(job.clone_for_deadline()?);
+        let state = Arc::new(State {
+            cancelled: Mutex::new(false),
+            wake: Condvar::new(),
+            outcome: AtomicU8::new(0),
+        });
+        let thread_job = Arc::clone(&job);
+        let thread_state = Arc::clone(&state);
+        let worker = std::thread::Builder::new()
+            .name("extension-tool-deadline".into())
+            .spawn(move || {
+                let mut cancelled = thread_state
+                    .cancelled
+                    .lock()
+                    .unwrap_or_else(|e| e.into_inner());
+                loop {
+                    if *cancelled {
+                        return;
+                    }
+                    let remaining = expires.saturating_duration_since(Instant::now());
+                    if remaining.is_zero() {
+                        break;
+                    }
+                    cancelled = thread_state
+                        .wake
+                        .wait_timeout(cancelled, remaining)
+                        .unwrap_or_else(|e| e.into_inner())
+                        .0;
+                }
+                thread_state.outcome.store(1, Ordering::Release);
+                drop(cancelled);
+                if thread_job.terminate().is_err() {
+                    thread_state.outcome.store(2, Ordering::Release);
+                }
+            })
+            .map_err(|_| HostError::new("EXTENSION_TOOL_WATCHDOG_UNAVAILABLE"))?;
+        Ok(Self {
+            state,
+            job,
+            expires,
+            worker: Some(worker),
+        })
+    }
+    pub fn check(&self) -> Result<()> {
+        match self.state.outcome.load(Ordering::Acquire) {
+            2 => Err(HostError::new("EXTENSION_RESOURCE_TERMINATE_FAILED")),
+            3 => Err(HostError::new("EXTENSION_TOOL_WATCHDOG_FAILED")),
+            1 => Err(HostError::new("EXTENSION_TOOL_DEADLINE_EXCEEDED")),
+            _ if Instant::now() >= self.expires => {
+                Err(HostError::new("EXTENSION_TOOL_DEADLINE_EXCEEDED"))
+            }
+            _ => Ok(()),
+        }
+    }
+    /// Completion cannot cancel an already elapsed budget, even if the timer
+    /// thread has not yet been scheduled to observe expiration.
+    pub fn finish(mut self) -> Result<()> {
+        self.stop();
+        match self.state.outcome.load(Ordering::Acquire) {
+            0 => Ok(()),
+            2 => Err(HostError::new("EXTENSION_RESOURCE_TERMINATE_FAILED")),
+            3 => Err(HostError::new("EXTENSION_TOOL_WATCHDOG_FAILED")),
+            _ => Err(HostError::new("EXTENSION_TOOL_DEADLINE_EXCEEDED")),
+        }
+    }
+    /// Explicit abandonment terminates the instance and reports kill failures.
+    pub fn cancel(mut self) -> Result<()> {
+        let result = self.job.terminate();
+        self.stop();
+        result
+    }
+    fn stop(&mut self) {
+        if self.worker.is_none() {
+            return;
+        }
+        let mut cancelled = self
+            .state
+            .cancelled
+            .lock()
+            .unwrap_or_else(|e| e.into_inner());
+        if Instant::now() < self.expires {
+            *cancelled = true;
+        }
+        self.state.wake.notify_all();
+        drop(cancelled);
+        if self.worker.take().unwrap().join().is_err() {
+            let _ = self.job.terminate();
+            self.state.outcome.store(3, Ordering::Release);
+        }
+    }
+    #[cfg(test)]
+    pub(crate) fn arm_test(job: &Job, budget: Duration) -> Result<Self> {
+        Self::with_budget(job, budget)
+    }
+}
+impl Drop for ToolDeadline {
+    fn drop(&mut self) {
+        if self.worker.is_some() {
+            let _ = self.job.terminate();
+            self.stop();
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn rejects_invalid_budgets_and_finishes_without_waiting_for_full_budget() {
+        let job = Job::new().unwrap();
+        assert!(ToolDeadline::with_budget(&job, Duration::ZERO).is_err());
+        assert!(ToolDeadline::with_budget(&job, Duration::from_secs(61)).is_err());
+        let deadline = ToolDeadline::arm(&job).unwrap();
+        assert!(deadline.check().is_ok());
+        let start = Instant::now();
+        deadline.finish().unwrap();
+        assert!(start.elapsed() < Duration::from_secs(5));
+    }
+}
diff --git a/frontend/src-tauri/src/extension_job.rs b/frontend/src-tauri/src/extension_job.rs
index 7bcb6c9..989e4ec 100644
--- a/frontend/src-tauri/src/extension_job.rs
+++ b/frontend/src-tauri/src/extension_job.rs
@@ -13,6 +13,14 @@ pub struct Job {
     handle: OwnedHandle,
 }
 impl Job {
+    pub(crate) fn clone_for_deadline(&self) -> Result<Self> {
+        Ok(Self {
+            handle: self
+                .handle
+                .try_clone()
+                .map_err(|_| HostError::new("EXTENSION_RESOURCE_UNAVAILABLE"))?,
+        })
+    }
     pub fn new() -> Result<Self> {
         Self::with_process_limit(16)
     }
diff --git a/frontend/src-tauri/src/extension_process.rs b/frontend/src-tauri/src/extension_process.rs
index 6f8a6c0..59c34a6 100644
--- a/frontend/src-tauri/src/extension_process.rs
+++ b/frontend/src-tauri/src/extension_process.rs
@@ -175,6 +175,18 @@ impl<'a> Suspended<'a> {
     }
 }
 impl Running<'_> {
+    /// Arm before dispatching a tool request; finish after receiving its result.
+    /// Failure to arm must prevent dispatch. This does not time server lifetime.
+    pub fn start_tool_call(&self) -> Result<crate::extension_deadline::ToolDeadline> {
+        crate::extension_deadline::ToolDeadline::arm(&self.0.job)
+    }
+    #[cfg(test)]
+    pub(crate) fn start_test_tool_call(
+        &self,
+        budget: Duration,
+    ) -> Result<crate::extension_deadline::ToolDeadline> {
+        crate::extension_deadline::ToolDeadline::arm_test(&self.0.job, budget)
+    }
     /// A bounded observation only. The runtime must enforce the tool deadline.
     pub fn wait(&self, timeout: Duration) -> Result<Option<u32>> {
         let milliseconds = u32::try_from(timeout.as_millis())
diff --git a/frontend/src-tauri/src/lib.rs b/frontend/src-tauri/src/lib.rs
index 4dedfea..c0f8ef9 100644
--- a/frontend/src-tauri/src/lib.rs
+++ b/frontend/src-tauri/src/lib.rs
@@ -63,3 +63,6 @@ pub mod extension_launch_data;
 
 #[cfg(windows)]
 pub mod extension_process;
+
+#[cfg(windows)]
+pub mod extension_deadline;