feat(tui): add support for reasoning in chat messages and update transcript handling

apps/interfaces/tui/src/action.rs

@@ -165,7 +165,10 @@ pub fn apply_action(state: &mut crate::state::AppStateRest, action: Action) {
                         ));
                     }
                     zesdex_infrastructure::TurnEvent::StreamToken(text) => {
-                        state.append_to_last_transcript(&text);
+                        state.append_to_last_transcript(&text, false);
+                    }
+                    zesdex_infrastructure::TurnEvent::StreamReasoning(text) => {
+                        state.append_to_last_transcript(&text, true);
                     }
                     zesdex_infrastructure::TurnEvent::StreamDone(_msg) => {
                         // The final message is already accumulated in the transcript.

apps/interfaces/tui/src/state.rs

@@ -32,6 +32,8 @@ pub struct ChatMessageDisplay {
     pub role: zesdex_domain::core::Role,
     /// Rendered text content (plain text, no markdown).
     pub content: String,
+    /// Model reasoning (e.g. from DeepSeek-R1 <think> block).
+    pub reasoning: String,
     /// Millisecond timestamp when this display entry was created.
     pub timestamp: i64,
 }
@@ -42,6 +44,7 @@ impl ChatMessageDisplay {
         ChatMessageDisplay {
             role,
             content,
+            reasoning: String::new(),
             timestamp: chrono::Utc::now().timestamp_millis(),
         }
     }
@@ -1009,10 +1012,14 @@ impl AppStateRest {
     }
 
     /// Append text to the last assistant message in the transcript, if one exists.
-    pub fn append_to_last_transcript(&mut self, text: &str) {
+    pub fn append_to_last_transcript(&mut self, text: &str, is_reasoning: bool) {
         if let Some(msg) = self.transcript_cache.messages.back_mut() {
             if msg.role == zesdex_domain::core::Role::Assistant {
-                msg.content.push_str(text);
+                if is_reasoning {
+                    msg.reasoning.push_str(text);
+                } else {
+                    msg.content.push_str(text);
+                }
                 self.transcript_cache.dirty = true;
                 self.dirty = true;
             }

apps/interfaces/tui/src/turn.rs

@@ -141,9 +141,12 @@ fn run_turn(
                     return false;
                 }
                 match event {
-                    zesdex_domain::core::StreamEvent::Token(s) | zesdex_domain::core::StreamEvent::Reasoning(s) => {
+                    zesdex_domain::core::StreamEvent::Token(s) => {
                         push_event(turn_events, TurnEvent::StreamToken(s.clone()));
                     }
+                    zesdex_domain::core::StreamEvent::Reasoning(s) => {
+                        push_event(turn_events, TurnEvent::StreamReasoning(s.clone()));
+                    }
                     _ => {}
                 }
                 true

apps/interfaces/tui/src/view/chat.rs

@@ -88,28 +88,73 @@ fn render_one_message(
         ),
     ];
 
+    let mut first_line_handled = false;
+
+    if !msg.reasoning.trim().is_empty() {
+        let reasoning_str = format!("[Thinking...]\n{}", msg.reasoning.trim());
+        let reasoning_spans = super::markdown::render_markdown(&reasoning_str, content_width, false);
+        // Dim the reasoning text
+        let dimmed_spans: Vec<Span> = reasoning_spans.into_iter().map(|mut s| {
+            s.style = s.style.fg(Theme::TEXT_DIM);
+            s
+        }).collect();
+        let reasoning_lines = split_spans_into_lines(dimmed_spans);
+        let mut lines_iter = reasoning_lines.into_iter();
+
+        if let Some(first) = lines_iter.next() {
+            let mut spans = header_prefix.clone();
+            spans.extend(first.spans);
+            lines.push(Line::from(spans));
+            first_line_handled = true;
+        }
+
+        for line in lines_iter {
+            let mut spans = vec![Span::raw(" ".repeat(PREFIX_WIDTH))];
+            spans.extend(line.spans);
+            lines.push(Line::from(spans));
+        }
+    }
+
     let content_str = if msg.content.trim().is_empty() {
-        "(tool execution)".to_string()
+        if msg.reasoning.trim().is_empty() {
+            "(tool execution)".to_string()
+        } else {
+            String::new()
+        }
     } else {
         msg.content.clone()
     };
 
-    let content_spans = super::markdown::render_markdown(&content_str, content_width, false);
-    let content_lines = split_spans_into_lines(content_spans);
-    let mut lines_iter = content_lines.into_iter();
+    if !content_str.is_empty() {
+        let content_spans = super::markdown::render_markdown(&content_str, content_width, false);
+        let content_lines = split_spans_into_lines(content_spans);
+        let mut lines_iter = content_lines.into_iter();
 
-    if let Some(first) = lines_iter.next() {
-        let mut spans = header_prefix;
-        spans.extend(first.spans);
-        lines.push(Line::from(spans));
-    } else {
-        lines.push(Line::from(header_prefix));
+        if !first_line_handled {
+            if let Some(first) = lines_iter.next() {
+                let mut spans = header_prefix.clone();
+                spans.extend(first.spans);
+                lines.push(Line::from(spans));
+                first_line_handled = true;
+            }
+        } else {
+            // Header already printed by reasoning, just indent
+            if let Some(first) = lines_iter.next() {
+                let mut spans = vec![Span::raw(" ".repeat(PREFIX_WIDTH))];
+                spans.extend(first.spans);
+                lines.push(Line::from(spans));
+            }
+        }
+
+        for line in lines_iter {
+            let mut spans = vec![Span::raw(" ".repeat(PREFIX_WIDTH))];
+            spans.extend(line.spans);
+            lines.push(Line::from(spans));
+        }
     }
-
-    for line in lines_iter {
-        let mut spans = vec![Span::raw(" ".repeat(PREFIX_WIDTH))];
-        spans.extend(line.spans);
-        lines.push(Line::from(spans));
+    
+    if !first_line_handled {
+        lines.push(Line::from(header_prefix));
     }
 
     lines