diff --git a/src/openhuman/socket/medulla/mod.rs b/src/openhuman/socket/medulla/mod.rs
index 4d902e9ca..1a961e4c4 100644
--- a/src/openhuman/socket/medulla/mod.rs
+++ b/src/openhuman/socket/medulla/mod.rs
@@ -27,8 +27,9 @@ use std::sync::atomic::{AtomicI64, Ordering};
 use std::sync::{Arc, OnceLock};
 
 use parking_lot::Mutex;
-use tokio::sync::{mpsc, Notify};
-use tokio::time::Duration;
+use tokio::sync::mpsc;
+use tokio::time::{Duration, Instant};
+use tokio_util::sync::CancellationToken;
 
 use crate::openhuman::agent::progress::AgentProgress;
 use crate::openhuman::agent::turn_origin::{with_origin, AgentTurnOrigin};
@@ -60,8 +61,12 @@ pub fn manager() -> &'static Arc<MedullaTaskManager> {
 
 /// One in-flight task: a cooperative abort signal and a steering input channel.
 struct RunningTask {
-    /// Fired by `medulla:task_abort` to cancel the in-flight turn.
-    abort: Arc<Notify>,
+    /// Fired by `medulla:task_abort` to cancel the task. A
+    /// [`CancellationToken`] *latches*: an abort that arrives before the run
+    /// path starts awaiting it (e.g. while the driver is still building the
+    /// agent) is still observed when the turn checks it, so no cancellation is
+    /// lost.
+    abort: CancellationToken,
     /// Mid-task steering input (`medulla:task_send`) delivered as follow-up
     /// turns on the same agent session.
     steer_tx: mpsc::UnboundedSender<String>,
@@ -93,12 +98,12 @@ impl MedullaTaskManager {
             return;
         }
 
-        let abort = Arc::new(Notify::new());
+        let abort = CancellationToken::new();
         let (steer_tx, steer_rx) = mpsc::unbounded_channel::<String>();
         self.tasks.lock().insert(
             task_id.clone(),
             RunningTask {
-                abort: Arc::clone(&abort),
+                abort: abort.clone(),
                 steer_tx,
             },
         );
@@ -132,7 +137,7 @@ impl MedullaTaskManager {
         match self.tasks.lock().get(&abort.task_id) {
             Some(task) => {
                 log::info!("[medulla] aborting task_id={}", abort.task_id);
-                task.abort.notify_waiters();
+                task.abort.cancel();
             }
             None => log::warn!(
                 "[medulla] task_abort for unknown task_id={} — dropping",
@@ -146,7 +151,7 @@ impl MedullaTaskManager {
         let tasks = self.tasks.lock();
         for (task_id, task) in tasks.iter() {
             log::debug!("[medulla] socket down — aborting task_id={task_id}");
-            task.abort.notify_waiters();
+            task.abort.cancel();
         }
     }
 
@@ -161,7 +166,7 @@ impl MedullaTaskManager {
     async fn drive(
         &self,
         run: payloads::TaskRun,
-        abort: Arc<Notify>,
+        abort: CancellationToken,
         mut steer_rx: mpsc::UnboundedReceiver<String>,
     ) {
         let task_id = run.task_id.clone();
@@ -174,7 +179,7 @@ impl MedullaTaskManager {
             .unwrap_or_else(|| DEFAULT_AGENT_ID.to_string());
         let seq = Arc::new(AtomicI64::new(0));
 
-        let mut agent = match build_agent(&agent_id, &task_id).await {
+        let mut agent = match build_agent(&agent_id, &task_id, &session_id).await {
             Ok(agent) => agent,
             Err(err) => {
                 log::error!("[medulla] task_id={task_id} failed to build agent: {err}");
@@ -194,11 +199,25 @@ impl MedullaTaskManager {
             }
         };
 
-        let deadline = (run.timeout_ms > 0).then(|| Duration::from_millis(run.timeout_ms));
+        // `timeout_ms` is a hard wall-clock budget for the WHOLE task, not
+        // per turn: anchor a single deadline now and charge every turn
+        // (initial + steering follow-ups) against the time remaining until it.
+        let deadline =
+            (run.timeout_ms > 0).then(|| Instant::now() + Duration::from_millis(run.timeout_ms));
         let mut next_input = run.instruction.clone();
         let result;
 
         'outer: loop {
+            // Charge this turn against the remaining task budget; if it's
+            // already spent, settle the whole task as timed out.
+            let remaining = match remaining_budget(deadline, Instant::now()) {
+                Ok(remaining) => remaining,
+                Err(()) => {
+                    result = timeout_result(&task_id, &session_id, &seq);
+                    break 'outer;
+                }
+            };
+
             let (progress_tx, progress_rx) = mpsc::channel::<AgentProgress>(256);
             agent.set_on_progress(Some(progress_tx));
             let forwarder = spawn_forwarder(
@@ -216,7 +235,7 @@ impl MedullaTaskManager {
             };
             let turn = Box::pin(with_origin(origin, agent.run_single(&next_input)));
 
-            let turn_result = run_with_optional_timeout(deadline, &abort, turn).await;
+            let turn_result = run_with_optional_timeout(remaining, &abort, turn).await;
             // The forwarder ends when `progress_tx` drops; make sure it's flushed.
             agent.set_on_progress(None);
             let _ = forwarder.await;
@@ -233,22 +252,7 @@ impl MedullaTaskManager {
                     break 'outer;
                 }
                 TurnOutcome::TimedOut => {
-                    emit_envelope(
-                        &task_id,
-                        envelope::error_envelope(
-                            &session_id,
-                            next_seq(&seq),
-                            "task timed out",
-                            true,
-                        ),
-                    );
-                    result = TaskResult {
-                        task_id: task_id.clone(),
-                        ok: false,
-                        reply: String::new(),
-                        usage: None,
-                        error: Some("timeout".to_string()),
-                    };
+                    result = timeout_result(&task_id, &session_id, &seq);
                     break 'outer;
                 }
                 TurnOutcome::Errored(err) => {
@@ -302,17 +306,22 @@ enum TurnOutcome {
     TimedOut,
 }
 
-/// Race the agent turn against the cooperative abort signal and an optional
-/// wall-clock deadline.
+/// Race the agent turn against the cooperative abort signal and the remaining
+/// slice of the task's wall-clock budget.
+///
+/// `abort` is a [`CancellationToken`], so a cancellation that landed *before*
+/// this call starts polling is not lost: `cancelled()` resolves immediately for
+/// an already-cancelled token, and the `biased` select settles the turn as
+/// [`TurnOutcome::Aborted`] before the agent future is ever polled.
 async fn run_with_optional_timeout(
-    deadline: Option<Duration>,
-    abort: &Arc<Notify>,
+    remaining: Option<Duration>,
+    abort: &CancellationToken,
     turn: std::pin::Pin<Box<impl std::future::Future<Output = anyhow::Result<String>>>>,
 ) -> TurnOutcome {
     let run = async {
         tokio::select! {
             biased;
-            _ = abort.notified() => TurnOutcome::Aborted,
+            _ = abort.cancelled() => TurnOutcome::Aborted,
             res = turn => match res {
                 Ok(reply) => TurnOutcome::Completed(reply),
                 Err(err) => TurnOutcome::Errored(err.to_string()),
@@ -320,7 +329,7 @@ async fn run_with_optional_timeout(
         }
     };
 
-    match deadline {
+    match remaining {
         Some(d) => match tokio::time::timeout(d, run).await {
             Ok(outcome) => outcome,
             Err(_) => TurnOutcome::TimedOut,
@@ -329,6 +338,35 @@ async fn run_with_optional_timeout(
     }
 }
 
+/// Remaining wall-clock budget until the task `deadline`.
+///
+/// `Ok(None)` = no deadline configured (run unbounded); `Ok(Some(d))` = `d`
+/// left before the deadline; `Err(())` = the deadline has already passed, so
+/// the caller must settle the task as timed out instead of starting a turn.
+fn remaining_budget(deadline: Option<Instant>, now: Instant) -> Result<Option<Duration>, ()> {
+    match deadline {
+        Some(d) if now >= d => Err(()),
+        Some(d) => Ok(Some(d - now)),
+        None => Ok(None),
+    }
+}
+
+/// Build the terminal timeout [`TaskResult`], emitting the fatal `error`
+/// envelope that bookends a timed-out task's stream.
+fn timeout_result(task_id: &str, session_id: &str, seq: &AtomicI64) -> TaskResult {
+    emit_envelope(
+        task_id,
+        envelope::error_envelope(session_id, next_seq(seq), "task timed out", true),
+    );
+    TaskResult {
+        task_id: task_id.to_string(),
+        ok: false,
+        reply: String::new(),
+        usage: None,
+        error: Some("timeout".to_string()),
+    }
+}
+
 /// Return queued steering input (if any) after briefly waiting for input that
 /// was sent while the turn was still in flight.
 async fn drain_steer(steer_rx: &mut mpsc::UnboundedReceiver<String>) -> Option<String> {
@@ -342,18 +380,38 @@ async fn drain_steer(steer_rx: &mut mpsc::UnboundedReceiver<String>) -> Option<S
 }
 
 /// Build (or resume) an agent session for a medulla task.
-async fn build_agent(agent_id: &str, task_id: &str) -> Result<Agent, String> {
+///
+/// The transcript identity is scoped by `session_id` (which the caller has
+/// already resolved to the medulla `sessionId`, falling back to the `taskId`),
+/// not the bare `agent_definition_name`. Without this, two `medulla:task_run`s
+/// on the same `agentId` would collide onto one shared transcript and the
+/// second would resume the first's history.
+async fn build_agent(agent_id: &str, task_id: &str, session_id: &str) -> Result<Agent, String> {
     let config = crate::openhuman::config::rpc::load_config_with_timeout().await?;
     crate::openhuman::agent::harness::AgentDefinitionRegistry::init_global(&config.workspace_dir)
         .map_err(|err| format!("failed to init agent definition registry: {err}"))?;
     let mut agent = Agent::from_config_for_agent(&config, agent_id)
         .map_err(|err| format!("failed to build agent `{agent_id}`: {err}"))?;
     agent.set_event_context(format!("medulla:{task_id}"), "medulla_harness");
+    // Scope the transcript/session key per medulla session so distinct sessions
+    // on the same agent get isolated history (mirrors the web channel's
+    // per-thread `set_agent_definition_name`).
+    agent.set_agent_definition_name(medulla_session_key(agent_id, session_id));
     agent.fetch_connected_integrations().await;
     let _ = agent.refresh_delegation_tools();
     Ok(agent)
 }
 
+/// Derive a per-session agent-definition (transcript) key from the medulla
+/// `session_id`, namespaced by `agent_id`. The session id is truncated on a
+/// char boundary to keep transcript filenames bounded; the underlying
+/// [`Agent::set_agent_definition_name`] sanitizes any remaining non-filename
+/// characters.
+fn medulla_session_key(agent_id: &str, session_id: &str) -> String {
+    let short: String = session_id.chars().take(32).collect();
+    format!("{agent_id}_{short}")
+}
+
 /// Spawn the per-turn progress → `medulla:task_envelope` forwarder. Returns its
 /// join handle so the driver can flush it before the next turn.
 fn spawn_forwarder(
@@ -473,7 +531,7 @@ mod tests {
         let mgr = Arc::new(MedullaTaskManager::new());
         // Manually seed a running task to simulate an in-flight run, then prove
         // a second registration under the same id is ignored.
-        let abort = Arc::new(Notify::new());
+        let abort = CancellationToken::new();
         let (steer_tx, _rx) = mpsc::unbounded_channel();
         mgr.tasks
             .lock()
@@ -490,4 +548,38 @@ mod tests {
         });
         assert_eq!(mgr.tasks.lock().len(), 1);
     }
+
+    #[test]
+    fn session_key_scopes_transcript_by_session_id() {
+        // Same agent id + distinct session ids => distinct transcript keys, so
+        // two medulla sessions can't collide onto one shared transcript.
+        let a = medulla_session_key("orchestrator", "sess-abc");
+        let b = medulla_session_key("orchestrator", "sess-xyz");
+        assert_ne!(a, b);
+        assert_eq!(a, "orchestrator_sess-abc");
+        assert!(a.starts_with("orchestrator_"));
+        // Overlong session ids are truncated on a char boundary.
+        let long = "x".repeat(100);
+        let key = medulla_session_key("orchestrator", &long);
+        assert_eq!(key, format!("orchestrator_{}", "x".repeat(32)));
+    }
+
+    #[test]
+    fn remaining_budget_reports_time_left_and_exhaustion() {
+        let now = Instant::now();
+        // No deadline configured => unbounded.
+        assert_eq!(remaining_budget(None, now), Ok(None));
+        // Deadline in the future => remaining time until it.
+        let future = now + Duration::from_secs(10);
+        match remaining_budget(Some(future), now) {
+            Ok(Some(d)) => assert!(d <= Duration::from_secs(10) && d > Duration::from_secs(9)),
+            other => panic!("expected some remaining budget, got {other:?}"),
+        }
+        // Deadline already reached / passed => exhausted.
+        assert_eq!(remaining_budget(Some(now), now), Err(()));
+        assert_eq!(
+            remaining_budget(Some(now), now + Duration::from_secs(1)),
+            Err(())
+        );
+    }
 }