Add streaming to exec and tui (#1594)

Added support for streaming in `tui`
Added support for streaming in `exec`


https://github.com/user-attachments/assets/4215892e-d940-452c-a1d0-416ed0cf14eb

codex-rs/tui/src/app.rs

@@ -297,6 +297,8 @@ impl<'a> App<'a> {
     }
 
     fn draw_next_frame(&mut self, terminal: &mut tui::Tui) -> Result<()> {
+        // TODO: add a throttle to avoid redrawing too often
+
         match &mut self.app_state {
             AppState::Chat { widget } => {
                 terminal.draw(|frame| frame.render_widget_ref(&**widget, frame.area()))?;

codex-rs/tui/src/chatwidget.rs

@@ -51,6 +51,8 @@ pub(crate) struct ChatWidget<'a> {
     config: Config,
     initial_user_message: Option<UserMessage>,
     token_usage: TokenUsage,
+    reasoning_buffer: String,
+    answer_buffer: String,
 }
 
 #[derive(Clone, Copy, Eq, PartialEq)]
@@ -137,6 +139,8 @@ impl ChatWidget<'_> {
                 initial_images,
             ),
             token_usage: TokenUsage::default(),
+            reasoning_buffer: String::new(),
+            answer_buffer: String::new(),
         }
     }
 
@@ -242,16 +246,51 @@ impl ChatWidget<'_> {
                 self.request_redraw();
             }
             EventMsg::AgentMessage(AgentMessageEvent { message }) => {
+                // if the answer buffer is empty, this means we haven't received any
+                // delta. Thus, we need to print the message as a new answer.
+                if self.answer_buffer.is_empty() {
+                    self.conversation_history
+                        .add_agent_message(&self.config, message);
+                } else {
+                    self.conversation_history
+                        .replace_prev_agent_message(&self.config, message);
+                }
+                self.answer_buffer.clear();
+                self.request_redraw();
+            }
+            EventMsg::AgentMessageDelta(AgentMessageDeltaEvent { delta }) => {
+                if self.answer_buffer.is_empty() {
+                    self.conversation_history
+                        .add_agent_message(&self.config, "".to_string());
+                }
+                self.answer_buffer.push_str(&delta.clone());
                 self.conversation_history
-                    .add_agent_message(&self.config, message);
+                    .replace_prev_agent_message(&self.config, self.answer_buffer.clone());
+                self.request_redraw();
+            }
+            EventMsg::AgentReasoningDelta(AgentReasoningDeltaEvent { delta }) => {
+                if self.reasoning_buffer.is_empty() {
+                    self.conversation_history
+                        .add_agent_reasoning(&self.config, "".to_string());
+                }
+                self.reasoning_buffer.push_str(&delta.clone());
+                self.conversation_history
+                    .replace_prev_agent_reasoning(&self.config, self.reasoning_buffer.clone());
                 self.request_redraw();
             }
             EventMsg::AgentReasoning(AgentReasoningEvent { text }) => {
-                if !self.config.hide_agent_reasoning {
+                // if the reasoning buffer is empty, this means we haven't received any
+                // delta. Thus, we need to print the message as a new reasoning.
+                if self.reasoning_buffer.is_empty() {
                     self.conversation_history
-                        .add_agent_reasoning(&self.config, text);
-                    self.request_redraw();
+                        .add_agent_reasoning(&self.config, "".to_string());
+                } else {
+                    // else, we rerender one last time.
+                    self.conversation_history
+                        .replace_prev_agent_reasoning(&self.config, text);
                 }
+                self.reasoning_buffer.clear();
+                self.request_redraw();
             }
             EventMsg::TaskStarted => {
                 self.bottom_pane.clear_ctrl_c_quit_hint();
@@ -377,12 +416,6 @@ impl ChatWidget<'_> {
                 self.bottom_pane
                     .on_history_entry_response(log_id, offset, entry.map(|e| e.text));
             }
-            EventMsg::AgentMessageDelta(AgentMessageDeltaEvent { delta: _ }) => {
-                // TODO: think how we want to support this in the TUI
-            }
-            EventMsg::AgentReasoningDelta(AgentReasoningDeltaEvent { delta: _ }) => {
-                // TODO: think how we want to support this in the TUI
-            }
             event => {
                 self.conversation_history
                     .add_background_event(format!("{event:?}"));

codex-rs/tui/src/conversation_history_widget.rs

@@ -202,6 +202,14 @@ impl ConversationHistoryWidget {
         self.add_to_history(HistoryCell::new_agent_reasoning(config, text));
     }
 
+    pub fn replace_prev_agent_reasoning(&mut self, config: &Config, text: String) {
+        self.replace_last_agent_reasoning(config, text);
+    }
+
+    pub fn replace_prev_agent_message(&mut self, config: &Config, text: String) {
+        self.replace_last_agent_message(config, text);
+    }
+
     pub fn add_background_event(&mut self, message: String) {
         self.add_to_history(HistoryCell::new_background_event(message));
     }
@@ -249,6 +257,42 @@ impl ConversationHistoryWidget {
         });
     }
 
+    pub fn replace_last_agent_reasoning(&mut self, config: &Config, text: String) {
+        if let Some(idx) = self
+            .entries
+            .iter()
+            .rposition(|entry| matches!(entry.cell, HistoryCell::AgentReasoning { .. }))
+        {
+            let width = self.cached_width.get();
+            let entry = &mut self.entries[idx];
+            entry.cell = HistoryCell::new_agent_reasoning(config, text);
+            let height = if width > 0 {
+                entry.cell.height(width)
+            } else {
+                0
+            };
+            entry.line_count.set(height);
+        }
+    }
+
+    pub fn replace_last_agent_message(&mut self, config: &Config, text: String) {
+        if let Some(idx) = self
+            .entries
+            .iter()
+            .rposition(|entry| matches!(entry.cell, HistoryCell::AgentMessage { .. }))
+        {
+            let width = self.cached_width.get();
+            let entry = &mut self.entries[idx];
+            entry.cell = HistoryCell::new_agent_message(config, text);
+            let height = if width > 0 {
+                entry.cell.height(width)
+            } else {
+                0
+            };
+            entry.line_count.set(height);
+        }
+    }
+
     pub fn record_completed_exec_command(
         &mut self,
         call_id: String,
@@ -454,7 +498,7 @@ impl WidgetRef for ConversationHistoryWidget {
 
         {
             // Choose a thumb color that stands out only when this pane has focus so that the
-            // user’s attention is naturally drawn to the active viewport. When unfocused we show
+            // user's attention is naturally drawn to the active viewport. When unfocused we show
             // a low-contrast thumb so the scrollbar fades into the background without becoming
             // invisible.
             let thumb_style = if self.has_input_focus {