diff --git a/codex-rs/core/src/state/turn.rs b/codex-rs/core/src/state/turn.rs
index ddc9efafea..7a5fa64afa 100644
--- a/codex-rs/core/src/state/turn.rs
+++ b/codex-rs/core/src/state/turn.rs
@@ -3,6 +3,7 @@
 use indexmap::IndexMap;
 use std::collections::HashMap;
 use std::sync::Arc;
+use std::time::Instant;
 use tokio::sync::Mutex;
 use tokio::sync::Notify;
 use tokio_util::sync::CancellationToken;
@@ -19,14 +20,12 @@ use crate::tasks::SessionTask;
 pub(crate) struct ActiveTurn {
     pub(crate) tasks: IndexMap<String, RunningTask>,
     pub(crate) turn_state: Arc<Mutex<TurnState>>,
+    pub(crate) started_at: Instant,
 }
 
 impl Default for ActiveTurn {
     fn default() -> Self {
-        Self {
-            tasks: IndexMap::new(),
-            turn_state: Arc::new(Mutex::new(TurnState::default())),
-        }
+        Self::new()
     }
 }
 
@@ -48,6 +47,14 @@ pub(crate) struct RunningTask {
 }
 
 impl ActiveTurn {
+    pub(crate) fn new() -> Self {
+        Self {
+            tasks: IndexMap::new(),
+            turn_state: Arc::new(Mutex::new(TurnState::default())),
+            started_at: Instant::now(),
+        }
+    }
+
     pub(crate) fn add_task(&mut self, task: RunningTask) {
         let sub_id = task.turn_context.sub_id.clone();
         self.tasks.insert(sub_id, task);
diff --git a/codex-rs/core/src/tasks/mod.rs b/codex-rs/core/src/tasks/mod.rs
index d6754c23c8..f589093540 100644
--- a/codex-rs/core/src/tasks/mod.rs
+++ b/codex-rs/core/src/tasks/mod.rs
@@ -168,9 +168,11 @@ impl Session {
         last_agent_message: Option<String>,
     ) {
         let mut active = self.active_turn.lock().await;
+        let mut completed_turn = None;
         let should_close_processes = if let Some(at) = active.as_mut()
             && at.remove_task(&turn_context.sub_id)
         {
+            completed_turn = Some(at.started_at);
             *active = None;
             true
         } else {
@@ -180,13 +182,20 @@ impl Session {
         if should_close_processes {
             self.close_unified_exec_processes().await;
         }
+        if let Some(started_at) = completed_turn {
+            self.services.otel_manager.record_duration(
+                "codex.turn.end_to_end_duration",
+                started_at.elapsed(),
+                &[],
+            );
+        }
         let event = EventMsg::TurnComplete(TurnCompleteEvent { last_agent_message });
         self.send_event(turn_context.as_ref(), event).await;
     }
 
     async fn register_new_active_task(&self, task: RunningTask) {
         let mut active = self.active_turn.lock().await;
-        let mut turn = ActiveTurn::default();
+        let mut turn = ActiveTurn::new();
         turn.add_task(task);
         *active = Some(turn);
     }
diff --git a/codex-rs/otel/tests/suite/manager_metrics.rs b/codex-rs/otel/tests/suite/manager_metrics.rs
index 1497a5f84c..501cebeefc 100644
--- a/codex-rs/otel/tests/suite/manager_metrics.rs
+++ b/codex-rs/otel/tests/suite/manager_metrics.rs
@@ -1,6 +1,7 @@
 use crate::harness::attributes_to_map;
 use crate::harness::build_metrics_with_defaults;
 use crate::harness::find_metric;
+use crate::harness::histogram_data;
 use crate::harness::latest_metrics;
 use codex_app_server_protocol::AuthMode;
 use codex_otel::OtelManager;
@@ -11,6 +12,7 @@ use opentelemetry_sdk::metrics::data::AggregatedMetrics;
 use opentelemetry_sdk::metrics::data::MetricData;
 use pretty_assertions::assert_eq;
 use std::collections::BTreeMap;
+use std::time::Duration;
 
 // Ensures OtelManager attaches metadata tags when forwarding metrics.
 #[test]
@@ -102,3 +104,62 @@ fn manager_allows_disabling_metadata_tags() -> Result<()> {
 
     Ok(())
 }
+
+// Ensures duration metrics from OtelManager emit histograms with metadata tags.
+#[test]
+fn manager_records_turn_end_to_end_duration_histogram() -> Result<()> {
+    let (metrics, exporter) = build_metrics_with_defaults(&[("service", "codex-cli")])?;
+    let manager = OtelManager::new(
+        ThreadId::new(),
+        "gpt-5.1",
+        "gpt-5.1",
+        Some("account-id".to_string()),
+        None,
+        Some(AuthMode::ApiKey),
+        true,
+        "tty".to_string(),
+        SessionSource::Cli,
+    )
+    .with_metrics(metrics);
+
+    manager.record_duration(
+        "codex.turn.end_to_end_duration",
+        Duration::from_millis(120),
+        &[],
+    );
+    manager.shutdown_metrics()?;
+
+    let resource_metrics = latest_metrics(&exporter);
+    let (_bounds, bucket_counts, sum, count) =
+        histogram_data(&resource_metrics, "codex.turn.end_to_end_duration");
+    assert_eq!(bucket_counts.iter().sum::<u64>(), 1);
+    assert_eq!(sum, 120.0);
+    assert_eq!(count, 1);
+
+    let metric = find_metric(&resource_metrics, "codex.turn.end_to_end_duration")
+        .expect("duration metric missing");
+    let attrs = match metric.data() {
+        AggregatedMetrics::F64(data) => match data {
+            MetricData::Histogram(histogram) => {
+                let points: Vec<_> = histogram.data_points().collect();
+                assert_eq!(points.len(), 1);
+                attributes_to_map(points[0].attributes())
+            }
+            _ => panic!("unexpected histogram aggregation"),
+        },
+        _ => panic!("unexpected metric data type"),
+    };
+
+    let expected = BTreeMap::from([
+        (
+            "app.version".to_string(),
+            env!("CARGO_PKG_VERSION").to_string(),
+        ),
+        ("auth_mode".to_string(), AuthMode::ApiKey.to_string()),
+        ("model".to_string(), "gpt-5.1".to_string()),
+        ("service".to_string(), "codex-cli".to_string()),
+    ]);
+    assert_eq!(attrs, expected);
+
+    Ok(())
+}