diff --git a/codex-rs/analytics/src/analytics_client_tests.rs b/codex-rs/analytics/src/analytics_client_tests.rs
index a76c4a278b..acf6dcf429 100644
--- a/codex-rs/analytics/src/analytics_client_tests.rs
+++ b/codex-rs/analytics/src/analytics_client_tests.rs
@@ -2228,32 +2228,6 @@ async fn thread_execution_environment_flows_to_thread_turn_and_steer_events() {
     );
     out.clear();
 
-    reducer
-        .ingest(
-            AnalyticsFact::Custom(CustomAnalyticsFact::SubAgentThreadStarted(
-                SubAgentThreadStartedInput {
-                    thread_id: "thread-subagent".to_string(),
-                    parent_thread_id: Some("thread-2".to_string()),
-                    product_client_id: "codex-tui".to_string(),
-                    client_name: "codex-tui".to_string(),
-                    client_version: "1.0.0".to_string(),
-                    model: "gpt-5".to_string(),
-                    ephemeral: false,
-                    subagent_source: SubAgentSource::Review,
-                    created_at: 123,
-                },
-            )),
-            &mut out,
-        )
-        .await;
-
-    let subagent_payload = serde_json::to_value(&out[0]).expect("serialize subagent thread event");
-    assert_eq!(
-        subagent_payload["event_params"]["execution_environment"],
-        json!("remote")
-    );
-    out.clear();
-
     ingest_turn_prerequisites(
         &mut reducer,
         &mut out,
diff --git a/codex-rs/analytics/src/reducer.rs b/codex-rs/analytics/src/reducer.rs
index 59b43f1923..d76e5f5d17 100644
--- a/codex-rs/analytics/src/reducer.rs
+++ b/codex-rs/analytics/src/reducer.rs
@@ -278,17 +278,9 @@ impl AnalyticsReducer {
         input: SubAgentThreadStartedInput,
         out: &mut Vec<TrackEventRequest>,
     ) {
-        let parent_thread_id = input
-            .parent_thread_id
-            .clone()
-            .or_else(|| subagent_parent_thread_id(&input.subagent_source));
-        let execution_environment = parent_thread_id
-            .as_ref()
-            .and_then(|parent_thread_id| self.thread_metadata.get(parent_thread_id))
-            .and_then(|thread_metadata| thread_metadata.execution_environment);
-        let mut event = subagent_thread_started_event_request(input);
-        event.event_params.execution_environment = execution_environment;
-        out.push(TrackEventRequest::ThreadInitialized(event));
+        out.push(TrackEventRequest::ThreadInitialized(
+            subagent_thread_started_event_request(input),
+        ));
     }
 
     fn ingest_guardian_review(