Default to explicit medium reasoning for 5.1 (#6593)

codex-rs/core/tests/suite/client.rs

@@ -21,6 +21,7 @@ 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::ReasoningEffort;
 use codex_protocol::config_types::Verbosity;
 use codex_protocol::models::ReasoningItemContent;
 use codex_protocol::models::ReasoningItemReasoningSummary;
@@ -625,6 +626,121 @@ async fn includes_user_instructions_message_in_request() {
     assert_message_ends_with(&request_body["input"][1], "</environment_context>");
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn includes_configured_effort_in_request() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+    let server = MockServer::start().await;
+
+    let resp_mock =
+        responses::mount_sse_once_match(&server, path("/v1/responses"), sse_completed("resp1"))
+            .await;
+    let TestCodex { codex, .. } = test_codex()
+        .with_model("gpt-5.1-codex")
+        .with_config(|config| {
+            config.model_reasoning_effort = Some(ReasoningEffort::Medium);
+        })
+        .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();
+
+    assert_eq!(
+        request_body
+            .get("reasoning")
+            .and_then(|t| t.get("effort"))
+            .and_then(|v| v.as_str()),
+        Some("medium")
+    );
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn includes_no_effort_in_request() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+    let server = MockServer::start().await;
+
+    let resp_mock =
+        responses::mount_sse_once_match(&server, path("/v1/responses"), sse_completed("resp1"))
+            .await;
+    let TestCodex { codex, .. } = test_codex()
+        .with_model("gpt-5.1-codex")
+        .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();
+
+    assert_eq!(
+        request_body
+            .get("reasoning")
+            .and_then(|t| t.get("effort"))
+            .and_then(|v| v.as_str()),
+        None
+    );
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn includes_default_reasoning_effort_in_request_when_defined_by_model_family()
+-> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+    let server = MockServer::start().await;
+
+    let resp_mock =
+        responses::mount_sse_once_match(&server, path("/v1/responses"), sse_completed("resp1"))
+            .await;
+    let TestCodex { codex, .. } = test_codex().with_model("gpt-5.1").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();
+
+    assert_eq!(
+        request_body
+            .get("reasoning")
+            .and_then(|t| t.get("effort"))
+            .and_then(|v| v.as_str()),
+        Some("medium")
+    );
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn includes_default_verbosity_in_request() -> anyhow::Result<()> {
     skip_if_no_network!(Ok(()));