diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index 72c23a3ea..9659b1090 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -206,7 +206,11 @@ impl ModelClient {
         let reasoning = if model_family.supports_reasoning_summaries {
             Some(Reasoning {
                 effort: self.effort.or(model_family.default_reasoning_effort),
-                summary: Some(self.summary),
+                summary: if self.summary == ReasoningSummaryConfig::None {
+                    None
+                } else {
+                    Some(self.summary)
+                },
             })
         } else {
             None
diff --git a/codex-rs/core/tests/suite/client.rs b/codex-rs/core/tests/suite/client.rs
index faa9801f8..4d47c9f21 100644
--- a/codex-rs/core/tests/suite/client.rs
+++ b/codex-rs/core/tests/suite/client.rs
@@ -22,6 +22,7 @@ use codex_core::protocol::Op;
 use codex_core::protocol::SessionSource;
 use codex_otel::otel_event_manager::OtelEventManager;
 use codex_protocol::ConversationId;
+use codex_protocol::config_types::ReasoningSummary;
 use codex_protocol::config_types::Verbosity;
 use codex_protocol::models::ReasoningItemContent;
 use codex_protocol::models::ReasoningItemReasoningSummary;
@@ -823,6 +824,81 @@ async fn includes_default_reasoning_effort_in_request_when_defined_by_model_fami
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn configured_reasoning_summary_is_sent() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+    let server = MockServer::start().await;
+
+    let resp_mock = mount_sse_once(&server, sse_completed("resp1")).await;
+    let TestCodex { codex, .. } = test_codex()
+        .with_config(|config| {
+            config.model_reasoning_summary = ReasoningSummary::Concise;
+        })
+        .build(&server)
+        .await?;
+
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "hello".into(),
+            }],
+        })
+        .await
+        .unwrap();
+
+    wait_for_event(&codex, |ev| matches!(ev, EventMsg::TaskComplete(_))).await;
+
+    let request = resp_mock.single_request();
+    let request_body = request.body_json();
+
+    pretty_assertions::assert_eq!(
+        request_body
+            .get("reasoning")
+            .and_then(|reasoning| reasoning.get("summary"))
+            .and_then(|value| value.as_str()),
+        Some("concise")
+    );
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn reasoning_summary_is_omitted_when_disabled() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+    let server = MockServer::start().await;
+
+    let resp_mock = mount_sse_once(&server, sse_completed("resp1")).await;
+    let TestCodex { codex, .. } = test_codex()
+        .with_config(|config| {
+            config.model_reasoning_summary = ReasoningSummary::None;
+        })
+        .build(&server)
+        .await?;
+
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "hello".into(),
+            }],
+        })
+        .await
+        .unwrap();
+
+    wait_for_event(&codex, |ev| matches!(ev, EventMsg::TaskComplete(_))).await;
+
+    let request = resp_mock.single_request();
+    let request_body = request.body_json();
+
+    pretty_assertions::assert_eq!(
+        request_body
+            .get("reasoning")
+            .and_then(|reasoning| reasoning.get("summary")),
+        None
+    );
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn includes_default_verbosity_in_request() -> anyhow::Result<()> {
     skip_if_no_network!(Ok(()));