Add item streaming events (#5546)

Adds AgentMessageContentDelta, ReasoningContentDelta,
ReasoningRawContentDelta item streaming events while maintaining
compatibility for old events.

---------

Co-authored-by: Owen Lin <owen@openai.com>

codex-rs/core/tests/chat_completions_sse.rs

@@ -171,19 +171,24 @@ async fn streams_text_without_reasoning() {
     );
 
     let events = run_stream(sse).await;
-    assert_eq!(events.len(), 3, "unexpected events: {events:?}");
+    assert_eq!(events.len(), 4, "unexpected events: {events:?}");
 
     match &events[0] {
+        ResponseEvent::OutputItemAdded(ResponseItem::Message { .. }) => {}
+        other => panic!("expected initial assistant item, got {other:?}"),
+    }
+
+    match &events[1] {
         ResponseEvent::OutputTextDelta(text) => assert_eq!(text, "hi"),
         other => panic!("expected text delta, got {other:?}"),
     }
 
-    match &events[1] {
+    match &events[2] {
         ResponseEvent::OutputItemDone(item) => assert_message(item, "hi"),
         other => panic!("expected terminal message, got {other:?}"),
     }
 
-    assert_matches!(events[2], ResponseEvent::Completed { .. });
+    assert_matches!(events[3], ResponseEvent::Completed { .. });
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
@@ -202,29 +207,39 @@ async fn streams_reasoning_from_string_delta() {
     );
 
     let events = run_stream(sse).await;
-    assert_eq!(events.len(), 5, "unexpected events: {events:?}");
+    assert_eq!(events.len(), 7, "unexpected events: {events:?}");
 
     match &events[0] {
+        ResponseEvent::OutputItemAdded(ResponseItem::Reasoning { .. }) => {}
+        other => panic!("expected initial reasoning item, got {other:?}"),
+    }
+
+    match &events[1] {
         ResponseEvent::ReasoningContentDelta(text) => assert_eq!(text, "think1"),
         other => panic!("expected reasoning delta, got {other:?}"),
     }
 
-    match &events[1] {
+    match &events[2] {
+        ResponseEvent::OutputItemAdded(ResponseItem::Message { .. }) => {}
+        other => panic!("expected initial message item, got {other:?}"),
+    }
+
+    match &events[3] {
         ResponseEvent::OutputTextDelta(text) => assert_eq!(text, "ok"),
         other => panic!("expected text delta, got {other:?}"),
     }
 
-    match &events[2] {
+    match &events[4] {
         ResponseEvent::OutputItemDone(item) => assert_reasoning(item, "think1"),
-        other => panic!("expected reasoning item, got {other:?}"),
+        other => panic!("expected terminal reasoning, got {other:?}"),
     }
 
-    match &events[3] {
+    match &events[5] {
         ResponseEvent::OutputItemDone(item) => assert_message(item, "ok"),
-        other => panic!("expected message item, got {other:?}"),
+        other => panic!("expected terminal message, got {other:?}"),
     }
 
-    assert_matches!(events[4], ResponseEvent::Completed { .. });
+    assert_matches!(events[6], ResponseEvent::Completed { .. });
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
@@ -244,34 +259,44 @@ async fn streams_reasoning_from_object_delta() {
     );
 
     let events = run_stream(sse).await;
-    assert_eq!(events.len(), 6, "unexpected events: {events:?}");
+    assert_eq!(events.len(), 8, "unexpected events: {events:?}");
 
     match &events[0] {
+        ResponseEvent::OutputItemAdded(ResponseItem::Reasoning { .. }) => {}
+        other => panic!("expected initial reasoning item, got {other:?}"),
+    }
+
+    match &events[1] {
         ResponseEvent::ReasoningContentDelta(text) => assert_eq!(text, "partA"),
         other => panic!("expected reasoning delta, got {other:?}"),
     }
 
-    match &events[1] {
+    match &events[2] {
         ResponseEvent::ReasoningContentDelta(text) => assert_eq!(text, "partB"),
         other => panic!("expected reasoning delta, got {other:?}"),
     }
 
-    match &events[2] {
+    match &events[3] {
+        ResponseEvent::OutputItemAdded(ResponseItem::Message { .. }) => {}
+        other => panic!("expected initial message item, got {other:?}"),
+    }
+
+    match &events[4] {
         ResponseEvent::OutputTextDelta(text) => assert_eq!(text, "answer"),
         other => panic!("expected text delta, got {other:?}"),
     }
 
-    match &events[3] {
+    match &events[5] {
         ResponseEvent::OutputItemDone(item) => assert_reasoning(item, "partApartB"),
-        other => panic!("expected reasoning item, got {other:?}"),
+        other => panic!("expected terminal reasoning, got {other:?}"),
     }
 
-    match &events[4] {
+    match &events[6] {
         ResponseEvent::OutputItemDone(item) => assert_message(item, "answer"),
-        other => panic!("expected message item, got {other:?}"),
+        other => panic!("expected terminal message, got {other:?}"),
     }
 
-    assert_matches!(events[5], ResponseEvent::Completed { .. });
+    assert_matches!(events[7], ResponseEvent::Completed { .. });
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
@@ -286,19 +311,24 @@ async fn streams_reasoning_from_final_message() {
     let sse = "data: {\"choices\":[{\"message\":{\"reasoning\":\"final-cot\"},\"finish_reason\":\"stop\"}]}\n\n";
 
     let events = run_stream(sse).await;
-    assert_eq!(events.len(), 3, "unexpected events: {events:?}");
+    assert_eq!(events.len(), 4, "unexpected events: {events:?}");
 
     match &events[0] {
+        ResponseEvent::OutputItemAdded(ResponseItem::Reasoning { .. }) => {}
+        other => panic!("expected initial reasoning item, got {other:?}"),
+    }
+
+    match &events[1] {
         ResponseEvent::ReasoningContentDelta(text) => assert_eq!(text, "final-cot"),
         other => panic!("expected reasoning delta, got {other:?}"),
     }
 
-    match &events[1] {
+    match &events[2] {
         ResponseEvent::OutputItemDone(item) => assert_reasoning(item, "final-cot"),
         other => panic!("expected reasoning item, got {other:?}"),
     }
 
-    assert_matches!(events[2], ResponseEvent::Completed { .. });
+    assert_matches!(events[3], ResponseEvent::Completed { .. });
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
@@ -316,19 +346,24 @@ async fn streams_reasoning_before_tool_call() {
     );
 
     let events = run_stream(sse).await;
-    assert_eq!(events.len(), 4, "unexpected events: {events:?}");
+    assert_eq!(events.len(), 5, "unexpected events: {events:?}");
 
     match &events[0] {
+        ResponseEvent::OutputItemAdded(ResponseItem::Reasoning { .. }) => {}
+        other => panic!("expected initial reasoning item, got {other:?}"),
+    }
+
+    match &events[1] {
         ResponseEvent::ReasoningContentDelta(text) => assert_eq!(text, "pre-tool"),
         other => panic!("expected reasoning delta, got {other:?}"),
     }
 
-    match &events[1] {
+    match &events[2] {
         ResponseEvent::OutputItemDone(item) => assert_reasoning(item, "pre-tool"),
         other => panic!("expected reasoning item, got {other:?}"),
     }
 
-    match &events[2] {
+    match &events[3] {
         ResponseEvent::OutputItemDone(ResponseItem::FunctionCall {
             name,
             arguments,
@@ -342,7 +377,7 @@ async fn streams_reasoning_before_tool_call() {
         other => panic!("expected function call, got {other:?}"),
     }
 
-    assert_matches!(events[3], ResponseEvent::Completed { .. });
+    assert_matches!(events[4], ResponseEvent::Completed { .. });
 }
 
 #[tokio::test]

codex-rs/core/tests/common/responses.rs

@@ -217,6 +217,25 @@ pub fn ev_assistant_message(id: &str, text: &str) -> Value {
     })
 }
 
+pub fn ev_message_item_added(id: &str, text: &str) -> Value {
+    serde_json::json!({
+        "type": "response.output_item.added",
+        "item": {
+            "type": "message",
+            "role": "assistant",
+            "id": id,
+            "content": [{"type": "output_text", "text": text}]
+        }
+    })
+}
+
+pub fn ev_output_text_delta(delta: &str) -> Value {
+    serde_json::json!({
+        "type": "response.output_text.delta",
+        "delta": delta,
+    })
+}
+
 pub fn ev_reasoning_item(id: &str, summary: &[&str], raw_content: &[&str]) -> Value {
     let summary_entries: Vec<Value> = summary
         .iter()
@@ -243,6 +262,36 @@ pub fn ev_reasoning_item(id: &str, summary: &[&str], raw_content: &[&str]) -> Va
     event
 }
 
+pub fn ev_reasoning_item_added(id: &str, summary: &[&str]) -> Value {
+    let summary_entries: Vec<Value> = summary
+        .iter()
+        .map(|text| serde_json::json!({"type": "summary_text", "text": text}))
+        .collect();
+
+    serde_json::json!({
+        "type": "response.output_item.added",
+        "item": {
+            "type": "reasoning",
+            "id": id,
+            "summary": summary_entries,
+        }
+    })
+}
+
+pub fn ev_reasoning_summary_text_delta(delta: &str) -> Value {
+    serde_json::json!({
+        "type": "response.reasoning_summary_text.delta",
+        "delta": delta,
+    })
+}
+
+pub fn ev_reasoning_text_delta(delta: &str) -> Value {
+    serde_json::json!({
+        "type": "response.reasoning_text.delta",
+        "delta": delta,
+    })
+}
+
 pub fn ev_web_search_call_added(id: &str, status: &str, query: &str) -> Value {
     serde_json::json!({
         "type": "response.output_item.added",

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

@@ -1262,6 +1262,10 @@ async fn history_dedupes_streamed_and_final_messages_across_turns() {
     // Build a small SSE stream with deltas and a final assistant message.
     // We emit the same body for all 3 turns; ids vary but are unused by assertions.
     let sse_raw = r##"[
+        {"type":"response.output_item.added", "item":{
+            "type":"message", "role":"assistant",
+            "content":[{"type":"output_text","text":""}]
+        }},
         {"type":"response.output_text.delta", "delta":"Hey "},
         {"type":"response.output_text.delta", "delta":"there"},
         {"type":"response.output_text.delta", "delta":"!\n"},

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

@@ -9,7 +9,12 @@ use codex_protocol::items::TurnItem;
 use codex_protocol::user_input::UserInput;
 use core_test_support::responses::ev_assistant_message;
 use core_test_support::responses::ev_completed;
+use core_test_support::responses::ev_message_item_added;
+use core_test_support::responses::ev_output_text_delta;
 use core_test_support::responses::ev_reasoning_item;
+use core_test_support::responses::ev_reasoning_item_added;
+use core_test_support::responses::ev_reasoning_summary_text_delta;
+use core_test_support::responses::ev_reasoning_text_delta;
 use core_test_support::responses::ev_response_created;
 use core_test_support::responses::ev_web_search_call_added;
 use core_test_support::responses::ev_web_search_call_done;
@@ -234,3 +239,181 @@ async fn web_search_item_is_emitted() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn agent_message_content_delta_has_item_metadata() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+
+    let TestCodex {
+        codex,
+        session_configured,
+        ..
+    } = test_codex().build(&server).await?;
+
+    let stream = sse(vec![
+        ev_response_created("resp-1"),
+        ev_message_item_added("msg-1", ""),
+        ev_output_text_delta("streamed response"),
+        ev_assistant_message("msg-1", "streamed response"),
+        ev_completed("resp-1"),
+    ]);
+    mount_sse_once_match(&server, any(), stream).await;
+
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "please stream text".into(),
+            }],
+        })
+        .await?;
+
+    let (started_turn_id, started_item) = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::ItemStarted(ItemStartedEvent {
+            turn_id,
+            item: TurnItem::AgentMessage(item),
+            ..
+        }) => Some((turn_id.clone(), item.clone())),
+        _ => None,
+    })
+    .await;
+
+    let delta_event = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::AgentMessageContentDelta(event) => Some(event.clone()),
+        _ => None,
+    })
+    .await;
+    let legacy_delta = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::AgentMessageDelta(event) => Some(event.clone()),
+        _ => None,
+    })
+    .await;
+    let completed_item = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::ItemCompleted(ItemCompletedEvent {
+            item: TurnItem::AgentMessage(item),
+            ..
+        }) => Some(item.clone()),
+        _ => None,
+    })
+    .await;
+
+    let session_id = session_configured.session_id.to_string();
+    assert_eq!(delta_event.thread_id, session_id);
+    assert_eq!(delta_event.turn_id, started_turn_id);
+    assert_eq!(delta_event.item_id, started_item.id);
+    assert_eq!(delta_event.delta, "streamed response");
+    assert_eq!(legacy_delta.delta, "streamed response");
+    assert_eq!(completed_item.id, started_item.id);
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn reasoning_content_delta_has_item_metadata() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+
+    let TestCodex { codex, .. } = test_codex().build(&server).await?;
+
+    let stream = sse(vec![
+        ev_response_created("resp-1"),
+        ev_reasoning_item_added("reasoning-1", &[""]),
+        ev_reasoning_summary_text_delta("step one"),
+        ev_reasoning_item("reasoning-1", &["step one"], &[]),
+        ev_completed("resp-1"),
+    ]);
+    mount_sse_once_match(&server, any(), stream).await;
+
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "reason through it".into(),
+            }],
+        })
+        .await?;
+
+    let reasoning_item = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::ItemStarted(ItemStartedEvent {
+            item: TurnItem::Reasoning(item),
+            ..
+        }) => Some(item.clone()),
+        _ => None,
+    })
+    .await;
+
+    let delta_event = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::ReasoningContentDelta(event) => Some(event.clone()),
+        _ => None,
+    })
+    .await;
+    let legacy_delta = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::AgentReasoningDelta(event) => Some(event.clone()),
+        _ => None,
+    })
+    .await;
+
+    assert_eq!(delta_event.item_id, reasoning_item.id);
+    assert_eq!(delta_event.delta, "step one");
+    assert_eq!(legacy_delta.delta, "step one");
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn reasoning_raw_content_delta_respects_flag() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+
+    let TestCodex { codex, .. } = test_codex()
+        .with_config(|config| {
+            config.show_raw_agent_reasoning = true;
+        })
+        .build(&server)
+        .await?;
+
+    let stream = sse(vec![
+        ev_response_created("resp-1"),
+        ev_reasoning_item_added("reasoning-raw", &[""]),
+        ev_reasoning_text_delta("raw detail"),
+        ev_reasoning_item("reasoning-raw", &["complete"], &["raw detail"]),
+        ev_completed("resp-1"),
+    ]);
+    mount_sse_once_match(&server, any(), stream).await;
+
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: "show raw reasoning".into(),
+            }],
+        })
+        .await?;
+
+    let reasoning_item = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::ItemStarted(ItemStartedEvent {
+            item: TurnItem::Reasoning(item),
+            ..
+        }) => Some(item.clone()),
+        _ => None,
+    })
+    .await;
+
+    let delta_event = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::ReasoningRawContentDelta(event) => Some(event.clone()),
+        _ => None,
+    })
+    .await;
+    let legacy_delta = wait_for_event_match(&codex, |ev| match ev {
+        EventMsg::AgentReasoningRawContentDelta(event) => Some(event.clone()),
+        _ => None,
+    })
+    .await;
+
+    assert_eq!(delta_event.item_id, reasoning_item.id);
+    assert_eq!(delta_event.delta, "raw detail");
+    assert_eq!(legacy_delta.delta, "raw detail");
+
+    Ok(())
+}