trying

codex-rs/config.md

@@ -483,6 +483,19 @@ Setting `hide_agent_reasoning` to `true` suppresses these events in **both** the
 hide_agent_reasoning = true   # defaults to false
 ```
 
+## show_raw_agent_reasoning
+
+Surfaces the model’s raw chain-of-thought ("raw reasoning content") when available.
+
+Notes:
+- Only takes effect if the selected model/provider actually emits raw reasoning content. Many models do not. When unsupported, this option has no visible effect.
+- Raw reasoning may include intermediate thoughts or sensitive context. Enable only if acceptable for your workflow.
+
+Example:
+```toml
+show_raw_agent_reasoning = true  # defaults to false
+```
+
 ## model_context_window
 
 The size of the context window for the model, in tokens.

codex-rs/core/src/chat_completions.rs

@@ -207,6 +207,7 @@ async fn process_chat_sse<S>(
     }
 
     let mut fn_call_state = FunctionCallState::default();
+    let mut assistant_text = String::new();
 
     loop {
         let sse = match timeout(idle_timeout, stream.next()).await {
@@ -254,26 +255,31 @@ async fn process_chat_sse<S>(
         let choice_opt = chunk.get("choices").and_then(|c| c.get(0));
 
         if let Some(choice) = choice_opt {
-            // Handle assistant content tokens.
+            // Handle assistant content tokens as streaming deltas.
             if let Some(content) = choice
                 .get("delta")
                 .and_then(|d| d.get("content"))
                 .and_then(|c| c.as_str())
             {
-                // Emit a delta so downstream consumers can stream text live.
+                if !content.is_empty() {
+                    assistant_text.push_str(content);
+                    let _ = tx_event
+                        .send(Ok(ResponseEvent::OutputTextDelta(content.to_string())))
+                        .await;
+                }
+            }
+
+            // Forward any reasoning/thinking deltas if present.
+            if let Some(reasoning) = choice
+                .get("delta")
+                .and_then(|d| d.get("reasoning"))
+                .and_then(|c| c.as_str())
+            {
                 let _ = tx_event
-                    .send(Ok(ResponseEvent::OutputTextDelta(content.to_string())))
+                    .send(Ok(ResponseEvent::ReasoningContentDelta(
+                        reasoning.to_string(),
+                    )))
                     .await;
-
-                let item = ResponseItem::Message {
-                    role: "assistant".to_string(),
-                    content: vec![ContentItem::OutputText {
-                        text: content.to_string(),
-                    }],
-                    id: None,
-                };
-
-                let _ = tx_event.send(Ok(ResponseEvent::OutputItemDone(item))).await;
             }
 
             // Handle streaming function / tool calls.
@@ -322,7 +328,18 @@ async fn process_chat_sse<S>(
                         let _ = tx_event.send(Ok(ResponseEvent::OutputItemDone(item))).await;
                     }
                     "stop" => {
-                        // Regular turn without tool-call.
+                        // Regular turn without tool-call. Emit the final assistant message
+                        // as a single OutputItemDone so non-delta consumers see the result.
+                        if !assistant_text.is_empty() {
+                            let item = ResponseItem::Message {
+                                role: "assistant".to_string(),
+                                content: vec![ContentItem::OutputText {
+                                    text: std::mem::take(&mut assistant_text),
+                                }],
+                                id: None,
+                            };
+                            let _ = tx_event.send(Ok(ResponseEvent::OutputItemDone(item))).await;
+                        }
                     }
                     _ => {}
                 }
@@ -360,10 +377,17 @@ async fn process_chat_sse<S>(
 /// The adapter is intentionally *lossless*: callers who do **not** opt in via
 /// [`AggregateStreamExt::aggregate()`] keep receiving the original unmodified
 /// events.
+#[derive(Copy, Clone, Eq, PartialEq)]
+enum AggregateMode {
+    AggregatedOnly,
+    Streaming,
+}
 pub(crate) struct AggregatedChatStream<S> {
     inner: S,
     cumulative: String,
-    pending_completed: Option<ResponseEvent>,
+    cumulative_reasoning: String,
+    pending: std::collections::VecDeque<ResponseEvent>,
+    mode: AggregateMode,
 }
 
 impl<S> Stream for AggregatedChatStream<S>
@@ -375,8 +399,8 @@ where
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         let this = self.get_mut();
 
-        // First, flush any buffered Completed event from the previous call.
-        if let Some(ev) = this.pending_completed.take() {
+        // First, flush any buffered events from the previous call.
+        if let Some(ev) = this.pending.pop_front() {
             return Poll::Ready(Some(Ok(ev)));
         }
 
@@ -393,16 +417,21 @@ where
                     let is_assistant_delta = matches!(&item, crate::models::ResponseItem::Message { role, .. } if role == "assistant");
 
                     if is_assistant_delta {
-                        if let crate::models::ResponseItem::Message { content, .. } = &item {
-                            if let Some(text) = content.iter().find_map(|c| match c {
-                                crate::models::ContentItem::OutputText { text } => Some(text),
-                                _ => None,
-                            }) {
-                                this.cumulative.push_str(text);
+                        // Only use the final assistant message if we have not
+                        // seen any deltas; otherwise, deltas already built the
+                        // cumulative text and this would duplicate it.
+                        if this.cumulative.is_empty() {
+                            if let crate::models::ResponseItem::Message { content, .. } = &item {
+                                if let Some(text) = content.iter().find_map(|c| match c {
+                                    crate::models::ContentItem::OutputText { text } => Some(text),
+                                    _ => None,
+                                }) {
+                                    this.cumulative.push_str(text);
+                                }
                             }
                         }
 
-                        // Swallow partial assistant chunk; keep polling.
+                        // Swallow assistant message here; emit on Completed.
                         continue;
                     }
 
@@ -413,24 +442,48 @@ where
                     response_id,
                     token_usage,
                 }))) => {
+                    // Build any aggregated items in the correct order: Reasoning first, then Message.
+                    let mut emitted_any = false;
+
+                    if !this.cumulative_reasoning.is_empty() {
+                        let aggregated_reasoning = crate::models::ResponseItem::Reasoning {
+                            id: String::new(),
+                            summary: vec![
+                                crate::models::ReasoningItemReasoningSummary::SummaryText {
+                                    text: std::mem::take(&mut this.cumulative_reasoning),
+                                },
+                            ],
+                            content: None,
+                            encrypted_content: None,
+                        };
+                        this.pending
+                            .push_back(ResponseEvent::OutputItemDone(aggregated_reasoning));
+                        emitted_any = true;
+                    }
+
                     if !this.cumulative.is_empty() {
-                        let aggregated_item = crate::models::ResponseItem::Message {
+                        let aggregated_message = crate::models::ResponseItem::Message {
                             id: None,
                             role: "assistant".to_string(),
                             content: vec![crate::models::ContentItem::OutputText {
                                 text: std::mem::take(&mut this.cumulative),
                             }],
                         };
+                        this.pending
+                            .push_back(ResponseEvent::OutputItemDone(aggregated_message));
+                        emitted_any = true;
+                    }
 
-                        // Buffer Completed so it is returned *after* the aggregated message.
-                        this.pending_completed = Some(ResponseEvent::Completed {
-                            response_id,
-                            token_usage,
+                    // Always emit Completed last when anything was aggregated.
+                    if emitted_any {
+                        this.pending.push_back(ResponseEvent::Completed {
+                            response_id: response_id.clone(),
+                            token_usage: token_usage.clone(),
                         });
-
-                        return Poll::Ready(Some(Ok(ResponseEvent::OutputItemDone(
-                            aggregated_item,
-                        ))));
+                        // Return the first pending event now.
+                        if let Some(ev) = this.pending.pop_front() {
+                            return Poll::Ready(Some(Ok(ev)));
+                        }
                     }
 
                     // Nothing aggregated – forward Completed directly.
@@ -445,13 +498,27 @@ where
                     continue;
                 }
                 Poll::Ready(Some(Ok(ResponseEvent::OutputTextDelta(delta)))) => {
-                    // Forward deltas unchanged so callers can stream text
-                    // live while still receiving a single aggregated
-                    // OutputItemDone at the end of the turn.
-                    return Poll::Ready(Some(Ok(ResponseEvent::OutputTextDelta(delta))));
+                    // Always accumulate deltas so we can emit a final OutputItemDone at Completed.
+                    this.cumulative.push_str(&delta);
+                    if matches!(this.mode, AggregateMode::Streaming) {
+                        // In streaming mode, also forward the delta immediately.
+                        return Poll::Ready(Some(Ok(ResponseEvent::OutputTextDelta(delta))));
+                    } else {
+                        continue;
+                    }
                 }
-                Poll::Ready(Some(Ok(ResponseEvent::ReasoningSummaryDelta(delta)))) => {
-                    return Poll::Ready(Some(Ok(ResponseEvent::ReasoningSummaryDelta(delta))));
+                Poll::Ready(Some(Ok(ResponseEvent::ReasoningContentDelta(delta)))) => {
+                    // Always accumulate reasoning deltas so we can emit a final Reasoning item at Completed.
+                    this.cumulative_reasoning.push_str(&delta);
+                    if matches!(this.mode, AggregateMode::Streaming) {
+                        // In streaming mode, also forward the delta immediately.
+                        return Poll::Ready(Some(Ok(ResponseEvent::ReasoningContentDelta(delta))));
+                    } else {
+                        continue;
+                    }
+                }
+                Poll::Ready(Some(Ok(ResponseEvent::ReasoningSummaryDelta(_)))) => {
+                    continue;
                 }
             }
         }
@@ -480,12 +547,24 @@ pub(crate) trait AggregateStreamExt: Stream<Item = Result<ResponseEvent>> + Size
     /// }
     /// ```
     fn aggregate(self) -> AggregatedChatStream<Self> {
-        AggregatedChatStream {
-            inner: self,
-            cumulative: String::new(),
-            pending_completed: None,
-        }
+        AggregatedChatStream::new(self, AggregateMode::AggregatedOnly)
     }
 }
 
 impl<T> AggregateStreamExt for T where T: Stream<Item = Result<ResponseEvent>> + Sized {}
+
+impl<S> AggregatedChatStream<S> {
+    fn new(inner: S, mode: AggregateMode) -> Self {
+        AggregatedChatStream {
+            inner,
+            cumulative: String::new(),
+            cumulative_reasoning: String::new(),
+            pending: std::collections::VecDeque::new(),
+            mode,
+        }
+    }
+
+    pub(crate) fn streaming_mode(inner: S) -> Self {
+        Self::new(inner, AggregateMode::Streaming)
+    }
+}

codex-rs/core/src/client.rs

@@ -92,7 +92,11 @@ impl ModelClient {
                 // Wrap it with the aggregation adapter so callers see *only*
                 // the final assistant message per turn (matching the
                 // behaviour of the Responses API).
-                let mut aggregated = response_stream.aggregate();
+                let mut aggregated = if self.config.show_raw_agent_reasoning {
+                    crate::chat_completions::AggregatedChatStream::streaming_mode(response_stream)
+                } else {
+                    response_stream.aggregate()
+                };
 
                 // Bridge the aggregated stream back into a standard
                 // `ResponseStream` by forwarding events through a channel.
@@ -433,6 +437,14 @@ async fn process_sse<S>(
                     }
                 }
             }
+            "response.reasoning_text.delta" => {
+                if let Some(delta) = event.delta {
+                    let event = ResponseEvent::ReasoningContentDelta(delta);
+                    if tx_event.send(Ok(event)).await.is_err() {
+                        return;
+                    }
+                }
+            }
             "response.created" => {
                 if event.response.is_some() {
                     let _ = tx_event.send(Ok(ResponseEvent::Created {})).await;

codex-rs/core/src/client_common.rs

@@ -71,6 +71,7 @@ pub enum ResponseEvent {
     },
     OutputTextDelta(String),
     ReasoningSummaryDelta(String),
+    ReasoningContentDelta(String),
 }
 
 #[derive(Debug, Serialize)]

codex-rs/core/src/codex.rs

@@ -56,6 +56,7 @@ use crate::mcp_tool_call::handle_mcp_tool_call;
 use crate::models::ContentItem;
 use crate::models::FunctionCallOutputPayload;
 use crate::models::LocalShellAction;
+use crate::models::ReasoningItemContent;
 use crate::models::ReasoningItemReasoningSummary;
 use crate::models::ResponseInputItem;
 use crate::models::ResponseItem;
@@ -66,6 +67,8 @@ use crate::protocol::AgentMessageDeltaEvent;
 use crate::protocol::AgentMessageEvent;
 use crate::protocol::AgentReasoningDeltaEvent;
 use crate::protocol::AgentReasoningEvent;
+use crate::protocol::AgentReasoningRawContentDeltaEvent;
+use crate::protocol::AgentReasoningRawContentEvent;
 use crate::protocol::ApplyPatchApprovalRequestEvent;
 use crate::protocol::AskForApproval;
 use crate::protocol::BackgroundEventEvent;
@@ -227,6 +230,7 @@ pub(crate) struct Session {
     state: Mutex<State>,
     codex_linux_sandbox_exe: Option<PathBuf>,
     user_shell: shell::Shell,
+    show_raw_agent_reasoning: bool,
 }
 
 impl Session {
@@ -822,6 +826,7 @@ async fn submission_loop(
                     codex_linux_sandbox_exe: config.codex_linux_sandbox_exe.clone(),
                     disable_response_storage,
                     user_shell: default_shell,
+                    show_raw_agent_reasoning: config.show_raw_agent_reasoning,
                 }));
 
                 // Patch restored state into the newly created session.
@@ -1132,6 +1137,7 @@ async fn run_task(sess: Arc<Session>, sub_id: String, input: Vec<InputItem>) {
                             ResponseItem::Reasoning {
                                 id,
                                 summary,
+                                content,
                                 encrypted_content,
                             },
                             None,
@@ -1139,6 +1145,7 @@ async fn run_task(sess: Arc<Session>, sub_id: String, input: Vec<InputItem>) {
                             items_to_record_in_conversation_history.push(ResponseItem::Reasoning {
                                 id: id.clone(),
                                 summary: summary.clone(),
+                                content: content.clone(),
                                 encrypted_content: encrypted_content.clone(),
                             });
                         }
@@ -1392,6 +1399,17 @@ async fn try_run_turn(
                 };
                 sess.tx_event.send(event).await.ok();
             }
+            ResponseEvent::ReasoningContentDelta(delta) => {
+                if sess.show_raw_agent_reasoning {
+                    let event = Event {
+                        id: sub_id.to_string(),
+                        msg: EventMsg::AgentReasoningRawContentDelta(
+                            AgentReasoningRawContentDeltaEvent { delta },
+                        ),
+                    };
+                    sess.tx_event.send(event).await.ok();
+                }
+            }
         }
     }
 }
@@ -1498,7 +1516,12 @@ async fn handle_response_item(
             }
             None
         }
-        ResponseItem::Reasoning { summary, .. } => {
+        ResponseItem::Reasoning {
+            id: _,
+            summary,
+            content,
+            encrypted_content: _,
+        } => {
             for item in summary {
                 let text = match item {
                     ReasoningItemReasoningSummary::SummaryText { text } => text,
@@ -1509,6 +1532,21 @@ async fn handle_response_item(
                 };
                 sess.tx_event.send(event).await.ok();
             }
+            if sess.show_raw_agent_reasoning && content.is_some() {
+                let content = content.unwrap();
+                for item in content {
+                    let text = match item {
+                        ReasoningItemContent::ReasoningText { text } => text,
+                    };
+                    let event = Event {
+                        id: sub_id.to_string(),
+                        msg: EventMsg::AgentReasoningRawContent(AgentReasoningRawContentEvent {
+                            text,
+                        }),
+                    };
+                    sess.tx_event.send(event).await.ok();
+                }
+            }
             None
         }
         ResponseItem::FunctionCall {

codex-rs/core/src/config.rs

@@ -57,6 +57,10 @@ pub struct Config {
     /// users are only interested in the final agent responses.
     pub hide_agent_reasoning: bool,
 
+    /// When set to `true`, `AgentReasoningRawContentEvent` events will be shown in the UI/output.
+    /// Defaults to `false`.
+    pub show_raw_agent_reasoning: bool,
+
     /// Disable server-side response storage (sends the full conversation
     /// context with every request). Currently necessary for OpenAI customers
     /// who have opted into Zero Data Retention (ZDR).
@@ -325,6 +329,10 @@ pub struct ConfigToml {
     /// UI/output. Defaults to `false`.
     pub hide_agent_reasoning: Option<bool>,
 
+    /// When set to `true`, `AgentReasoningRawContentEvent` events will be shown in the UI/output.
+    /// Defaults to `false`.
+    pub show_raw_agent_reasoning: Option<bool>,
+
     pub model_reasoning_effort: Option<ReasoningEffort>,
     pub model_reasoning_summary: Option<ReasoningSummary>,
 
@@ -518,6 +526,7 @@ impl Config {
             codex_linux_sandbox_exe,
 
             hide_agent_reasoning: cfg.hide_agent_reasoning.unwrap_or(false),
+            show_raw_agent_reasoning: cfg.show_raw_agent_reasoning.unwrap_or(false),
             model_reasoning_effort: config_profile
                 .model_reasoning_effort
                 .or(cfg.model_reasoning_effort)
@@ -891,6 +900,7 @@ disable_response_storage = true
                 tui: Tui::default(),
                 codex_linux_sandbox_exe: None,
                 hide_agent_reasoning: false,
+                show_raw_agent_reasoning: false,
                 model_reasoning_effort: ReasoningEffort::High,
                 model_reasoning_summary: ReasoningSummary::Detailed,
                 model_supports_reasoning_summaries: false,
@@ -941,6 +951,7 @@ disable_response_storage = true
             tui: Tui::default(),
             codex_linux_sandbox_exe: None,
             hide_agent_reasoning: false,
+            show_raw_agent_reasoning: false,
             model_reasoning_effort: ReasoningEffort::default(),
             model_reasoning_summary: ReasoningSummary::default(),
             model_supports_reasoning_summaries: false,
@@ -1006,6 +1017,7 @@ disable_response_storage = true
             tui: Tui::default(),
             codex_linux_sandbox_exe: None,
             hide_agent_reasoning: false,
+            show_raw_agent_reasoning: false,
             model_reasoning_effort: ReasoningEffort::default(),
             model_reasoning_summary: ReasoningSummary::default(),
             model_supports_reasoning_summaries: false,

codex-rs/core/src/models.rs

@@ -45,6 +45,8 @@ pub enum ResponseItem {
     Reasoning {
         id: String,
         summary: Vec<ReasoningItemReasoningSummary>,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        content: Option<Vec<ReasoningItemContent>>,
         encrypted_content: Option<String>,
     },
     LocalShellCall {
@@ -136,6 +138,12 @@ pub enum ReasoningItemReasoningSummary {
     SummaryText { text: String },
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum ReasoningItemContent {
+    ReasoningText { text: String },
+}
+
 impl From<Vec<InputItem>> for ResponseInputItem {
     fn from(items: Vec<InputItem>) -> Self {
         Self::Message {

codex-rs/core/src/protocol.rs

@@ -359,6 +359,12 @@ pub enum EventMsg {
     /// Agent reasoning delta event from agent.
     AgentReasoningDelta(AgentReasoningDeltaEvent),
 
+    /// Raw chain-of-thought from agent.
+    AgentReasoningRawContent(AgentReasoningRawContentEvent),
+
+    /// Agent reasoning content delta event from agent.
+    AgentReasoningRawContentDelta(AgentReasoningRawContentDeltaEvent),
+
     /// Ack the client's configure message.
     SessionConfigured(SessionConfiguredEvent),
 
@@ -464,6 +470,16 @@ pub struct AgentReasoningEvent {
     pub text: String,
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct AgentReasoningRawContentEvent {
+    pub text: String,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct AgentReasoningRawContentDeltaEvent {
+    pub delta: String,
+}
+
 #[derive(Debug, Clone, Deserialize, Serialize)]
 pub struct AgentReasoningDeltaEvent {
     pub delta: String,

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

@@ -27,9 +27,13 @@ pub fn load_default_config_for_test(codex_home: &TempDir) -> Config {
 /// makes it trivial to extend the fixtures as OpenAI adds new event kinds or
 /// fields.
 pub fn load_sse_fixture(path: impl AsRef<std::path::Path>) -> String {
-    let events: Vec<serde_json::Value> =
-        serde_json::from_reader(std::fs::File::open(path).expect("read fixture"))
-            .expect("parse JSON fixture");
+    // Resolve relative to this crate's root so tests are independent of the
+    // current working directory used by the test runner.
+    let path = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(path);
+    let events: Vec<serde_json::Value> = serde_json::from_reader(
+        std::fs::File::open(path).expect("read fixture"),
+    )
+    .expect("parse JSON fixture");
     events
         .into_iter()
         .map(|e| {
@@ -51,6 +55,9 @@ pub fn load_sse_fixture(path: impl AsRef<std::path::Path>) -> String {
 /// single JSON template be reused by multiple tests that each need a unique
 /// `response_id`.
 pub fn load_sse_fixture_with_id(path: impl AsRef<std::path::Path>, id: &str) -> String {
+    // Resolve relative to this crate's root so tests are independent of the
+    // current working directory used by the test runner.
+    let path = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(path);
     let raw = std::fs::read_to_string(path).expect("read fixture template");
     let replaced = raw.replace("__ID__", id);
     let events: Vec<serde_json::Value> =

codex-rs/exec/src/event_processor_with_human_output.rs

@@ -5,6 +5,8 @@ use codex_core::plan_tool::UpdatePlanArgs;
 use codex_core::protocol::AgentMessageDeltaEvent;
 use codex_core::protocol::AgentMessageEvent;
 use codex_core::protocol::AgentReasoningDeltaEvent;
+use codex_core::protocol::AgentReasoningRawContentDeltaEvent;
+use codex_core::protocol::AgentReasoningRawContentEvent;
 use codex_core::protocol::BackgroundEventEvent;
 use codex_core::protocol::ErrorEvent;
 use codex_core::protocol::Event;
@@ -55,8 +57,10 @@ pub(crate) struct EventProcessorWithHumanOutput {
 
     /// Whether to include `AgentReasoning` events in the output.
     show_agent_reasoning: bool,
+    show_raw_agent_reasoning: bool,
     answer_started: bool,
     reasoning_started: bool,
+    raw_reasoning_started: bool,
     last_message_path: Option<PathBuf>,
 }
 
@@ -81,8 +85,10 @@ impl EventProcessorWithHumanOutput {
                 green: Style::new().green(),
                 cyan: Style::new().cyan(),
                 show_agent_reasoning: !config.hide_agent_reasoning,
+                show_raw_agent_reasoning: config.show_raw_agent_reasoning,
                 answer_started: false,
                 reasoning_started: false,
+                raw_reasoning_started: false,
                 last_message_path,
             }
         } else {
@@ -97,8 +103,10 @@ impl EventProcessorWithHumanOutput {
                 green: Style::new(),
                 cyan: Style::new(),
                 show_agent_reasoning: !config.hide_agent_reasoning,
+                show_raw_agent_reasoning: config.show_raw_agent_reasoning,
                 answer_started: false,
                 reasoning_started: false,
+                raw_reasoning_started: false,
                 last_message_path,
             }
         }
@@ -203,6 +211,32 @@ impl EventProcessor for EventProcessorWithHumanOutput {
                 #[allow(clippy::expect_used)]
                 std::io::stdout().flush().expect("could not flush stdout");
             }
+            EventMsg::AgentReasoningRawContent(AgentReasoningRawContentEvent { text }) => {
+                if !self.show_raw_agent_reasoning {
+                    return CodexStatus::Running;
+                }
+                if !self.raw_reasoning_started {
+                    print!("{text}");
+                    #[allow(clippy::expect_used)]
+                    std::io::stdout().flush().expect("could not flush stdout");
+                } else {
+                    println!();
+                    self.raw_reasoning_started = false;
+                }
+            }
+            EventMsg::AgentReasoningRawContentDelta(AgentReasoningRawContentDeltaEvent {
+                delta,
+            }) => {
+                if !self.show_raw_agent_reasoning {
+                    return CodexStatus::Running;
+                }
+                if !self.raw_reasoning_started {
+                    self.raw_reasoning_started = true;
+                }
+                print!("{delta}");
+                #[allow(clippy::expect_used)]
+                std::io::stdout().flush().expect("could not flush stdout");
+            }
             EventMsg::AgentMessage(AgentMessageEvent { message }) => {
                 // if answer_started is false, this means we haven't received any
                 // delta. Thus, we need to print the message as a new answer.

codex-rs/mcp-server/src/codex_tool_runner.rs

@@ -252,7 +252,9 @@ async fn run_codex_tool_session_inner(
                     EventMsg::AgentMessage(AgentMessageEvent { .. }) => {
                         // TODO: think how we want to support this in the MCP
                     }
-                    EventMsg::TaskStarted
+                    EventMsg::AgentReasoningRawContent(_)
+                    | EventMsg::AgentReasoningRawContentDelta(_)
+                    | EventMsg::TaskStarted
                     | EventMsg::TokenCount(_)
                     | EventMsg::AgentReasoning(_)
                     | EventMsg::McpToolCallBegin(_)

codex-rs/mcp-server/src/conversation_loop.rs

@@ -90,7 +90,9 @@ pub async fn run_conversation_loop(
                     EventMsg::AgentMessage(AgentMessageEvent { .. }) => {
                         // TODO: think how we want to support this in the MCP
                     }
-                    EventMsg::TaskStarted
+                    EventMsg::AgentReasoningRawContent(_)
+                    | EventMsg::AgentReasoningRawContentDelta(_)
+                    | EventMsg::TaskStarted
                     | EventMsg::TokenCount(_)
                     | EventMsg::AgentReasoning(_)
                     | EventMsg::McpToolCallBegin(_)

codex-rs/tui/src/chatwidget.rs

@@ -9,6 +9,8 @@ use codex_core::protocol::AgentMessageDeltaEvent;
 use codex_core::protocol::AgentMessageEvent;
 use codex_core::protocol::AgentReasoningDeltaEvent;
 use codex_core::protocol::AgentReasoningEvent;
+use codex_core::protocol::AgentReasoningRawContentDeltaEvent;
+use codex_core::protocol::AgentReasoningRawContentEvent;
 use codex_core::protocol::ApplyPatchApprovalRequestEvent;
 use codex_core::protocol::ErrorEvent;
 use codex_core::protocol::Event;
@@ -61,6 +63,7 @@ pub(crate) struct ChatWidget<'a> {
     initial_user_message: Option<UserMessage>,
     token_usage: TokenUsage,
     reasoning_buffer: String,
+    content_buffer: String,
     // Buffer for streaming assistant answer text; we do not surface partial
     // We wait for the final AgentMessage event and then emit the full text
     // at once into scrollback so the history contains a single message.
@@ -161,6 +164,7 @@ impl ChatWidget<'_> {
             ),
             token_usage: TokenUsage::default(),
             reasoning_buffer: String::new(),
+            content_buffer: String::new(),
             answer_buffer: String::new(),
             running_commands: HashMap::new(),
             live_builder: RowBuilder::new(80),
@@ -276,6 +280,23 @@ impl ChatWidget<'_> {
                 self.finalize_stream(StreamKind::Reasoning);
                 self.request_redraw();
             }
+            EventMsg::AgentReasoningRawContentDelta(AgentReasoningRawContentDeltaEvent {
+                delta,
+            }) => {
+                self.content_buffer.push_str(&delta);
+            }
+            EventMsg::AgentReasoningRawContent(AgentReasoningRawContentEvent { text }) => {
+                let full = if text.is_empty() {
+                    std::mem::take(&mut self.content_buffer)
+                } else {
+                    self.content_buffer.clear();
+                    text
+                };
+                if !full.is_empty() {
+                    self.add_to_history(HistoryCell::new_agent_reasoning(&self.config, full));
+                }
+                self.request_redraw();
+            }
             EventMsg::TaskStarted => {
                 self.bottom_pane.clear_ctrl_c_quit_hint();
                 self.bottom_pane.set_task_running(true);
@@ -480,6 +501,7 @@ impl ChatWidget<'_> {
             self.submit_op(Op::Interrupt);
             self.answer_buffer.clear();
             self.reasoning_buffer.clear();
+            self.content_buffer.clear();
             CancellationEvent::Ignored
         } else if self.bottom_pane.ctrl_c_quit_hint_visible() {
             self.submit_op(Op::Shutdown);

codex-rs/tui/src/history_cell.rs

@@ -455,6 +455,22 @@ impl HistoryCell {
         }
     }
 
+    /// Render a block with the model's raw reasoning content.
+    /// This mirrors the streaming "thinking" header used during deltas and
+    /// commits the final content to history once available.
+    pub(crate) fn new_agent_reasoning(config: &Config, text: String) -> Self {
+        let mut lines: Vec<Line<'static>> = Vec::new();
+        // Header
+        lines.push(Line::from("thinking".magenta().italic()));
+        // Body (markdown-aware so citations and formatting render nicely)
+        crate::markdown::append_markdown(&text, &mut lines, config);
+        // Spacer
+        lines.push(Line::from(""));
+        HistoryCell::BackgroundEvent {
+            view: TextBlock::new(lines),
+        }
+    }
+
     /// Render a user‑friendly plan update with colourful status icons and a
     /// simple progress indicator so users can follow along.
     pub(crate) fn new_plan_update(update: UpdatePlanArgs) -> Self {