feat(cortex-tui): subagent navigation and improved tool summaries (#540)

* feat(cortex-tui): add subagent conversation navigation

- Add SubagentConversation(String) variant to AppView enum for viewing subagent conversations
- Add viewing_subagent: Option<String> field to AppState to track current subagent
- Add view_subagent_conversation(), return_to_main_conversation(), is_viewing_subagent(), get_viewing_subagent() methods
- Add SubagentView context to HintContext with hints for Esc (back to main) and scroll
- Add render_back_to_main_hint() function for displaying back navigation hint
- Update match expressions to handle new SubagentConversation variant

* fix(cortex-tui): improve tool result summary formatting

- Use '↳' prefix consistently across all tool summaries
- LS tool shows 'items' instead of generic 'lines'
- Glob/Grep show 'Found N files/matches' for clarity
- Add specific handling for Create, MultiEdit, TodoWrite, Task tools
- Default fallback shows 'items' instead of 'lines'
- Add unit tests for new summary formats

* feat(cortex-tui): add ESC key handler for subagent view navigation

- ESC key returns from subagent conversation to main conversation
- Display '← Back to main (Esc)' hint when viewing subagent
- Add SubagentView context for appropriate key hints

Author: echobt

src/cortex-tui/src/app/methods.rs

@@ -457,6 +457,28 @@ impl AppState {
             .filter(|t| !t.status.is_terminal())
             .count()
     }
+
+    /// Enter subagent conversation view
+    pub fn view_subagent_conversation(&mut self, session_id: String) {
+        self.viewing_subagent = Some(session_id.clone());
+        self.set_view(AppView::SubagentConversation(session_id));
+    }
+
+    /// Return to main conversation from subagent view
+    pub fn return_to_main_conversation(&mut self) {
+        self.viewing_subagent = None;
+        self.set_view(AppView::Session);
+    }
+
+    /// Check if viewing a subagent conversation
+    pub fn is_viewing_subagent(&self) -> bool {
+        self.viewing_subagent.is_some()
+    }
+
+    /// Get the currently viewed subagent session ID
+    pub fn get_viewing_subagent(&self) -> Option<&String> {
+        self.viewing_subagent.as_ref()
+    }
 }
 
 // ============================================================================

src/cortex-tui/src/app/state.rs

@@ -88,6 +88,8 @@ pub struct AppState {
     pub message_queue: VecDeque<String>,
     /// Active subagent tasks being displayed.
     pub active_subagents: Vec<SubagentTaskDisplay>,
+    /// Currently viewed subagent session ID (for SubagentConversation view)
+    pub viewing_subagent: Option<String>,
     /// MCP servers list for management
     pub mcp_servers: Vec<crate::modal::mcp_manager::McpServerInfo>,
     /// Context files added to the session
@@ -220,6 +222,7 @@ impl AppState {
             question_hovered_tab: None,
             message_queue: VecDeque::new(),
             active_subagents: Vec::new(),
+            viewing_subagent: None,
             mcp_servers: Vec::new(),
             context_files: Vec::new(),
             log_level: String::from("info"),
@@ -299,7 +302,7 @@ impl Default for AppState {
 impl AppState {
     /// Set the current view
     pub fn set_view(&mut self, view: AppView) {
-        self.previous_view = Some(self.view);
+        self.previous_view = Some(self.view.clone());
         self.view = view;
     }
 

src/cortex-tui/src/app/types.rs

@@ -5,14 +5,16 @@ use cortex_core::widgets::DisplayMode;
 pub type OperationMode = DisplayMode;
 
 /// The current view/screen being displayed
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
 pub enum AppView {
     #[default]
     Session,
     Approval,
     Questions,
     Settings,
     Help,
+    /// Viewing a subagent's conversation (stores the subagent session_id)
+    SubagentConversation(String),
 }
 
 /// Which UI element currently has focus

src/cortex-tui/src/runner/event_loop/input.rs

@@ -367,6 +367,13 @@ impl EventLoop {
 
     /// Handle ESC key with double-tap to quit
     fn handle_esc(&mut self, terminal: &mut CortexTerminal) -> Result<()> {
+        // Priority 1: If viewing a subagent conversation, return to main conversation
+        if self.app_state.is_viewing_subagent() {
+            self.app_state.return_to_main_conversation();
+            self.render(terminal)?;
+            return Ok(());
+        }
+
         // Check if app is idle (nothing active that ESC should cancel)
         let is_idle = !self.app_state.streaming.is_streaming
             && self.app_state.pending_approval.is_none()

src/cortex-tui/src/runner/event_loop/rendering.rs

@@ -35,7 +35,7 @@ impl EventLoop {
         terminal.draw(|frame| {
             let area = frame.area();
 
-            match self.app_state.view {
+            match &self.app_state.view {
                 AppView::Session => {
                     let view = crate::views::MinimalSessionView::new(&self.app_state);
                     frame.render_widget(view, area);
@@ -63,6 +63,12 @@ impl EventLoop {
                     let view = crate::views::MinimalSessionView::new(&self.app_state);
                     frame.render_widget(view, area);
                 }
+
+                AppView::SubagentConversation(_session_id) => {
+                    // Render the subagent conversation view (same as session for now)
+                    let view = crate::views::MinimalSessionView::new(&self.app_state);
+                    frame.render_widget(view, area);
+                }
             }
 
             // Render modal overlays (legacy)
@@ -162,12 +168,13 @@ impl EventLoop {
         let (width, height) = self.app_state.terminal_size;
         let area = Rect::new(0, 0, width, height);
 
-        match self.app_state.view {
+        match &self.app_state.view {
             AppView::Session
             | AppView::Approval
             | AppView::Questions
             | AppView::Settings
-            | AppView::Help => {
+            | AppView::Help
+            | AppView::SubagentConversation(_) => {
                 let input_height: u16 = 1;
                 let hints_height: u16 = 1;
                 let status_height: u16 = if self.app_state.streaming.is_streaming {
@@ -263,7 +270,6 @@ impl EventLoop {
             use std::cell::RefCell;
             let selected_lines: RefCell<Vec<String>> = RefCell::new(Vec::new());
 
-            let view = self.app_state.view;
             let active_modal = self.app_state.active_modal.clone();
             let card_active = self.card_handler.is_active();
 
@@ -273,7 +279,7 @@ impl EventLoop {
                 let screen_height = area.height;
 
                 // Full render
-                match view {
+                match &self.app_state.view {
                     AppView::Session => {
                         let widget = crate::views::MinimalSessionView::new(&self.app_state);
                         frame.render_widget(widget, area);
@@ -298,6 +304,10 @@ impl EventLoop {
                         let widget = crate::views::MinimalSessionView::new(&self.app_state);
                         frame.render_widget(widget, area);
                     }
+                    AppView::SubagentConversation(_session_id) => {
+                        let widget = crate::views::MinimalSessionView::new(&self.app_state);
+                        frame.render_widget(widget, area);
+                    }
                 }
 
                 // Render modals

src/cortex-tui/src/views/minimal_session/rendering.rs

@@ -20,6 +20,15 @@ use crate::views::tool_call::{ContentSegment, ToolCallDisplay, ToolStatus};
 use super::text_utils::wrap_text;
 use super::VERSION;
 
+/// Renders the "← Back to main conversation" hint when viewing a subagent.
+/// Displays in the top-left area of the screen.
+pub fn render_back_to_main_hint(area: Rect, buf: &mut Buffer, colors: &AdaptiveColors) {
+    let hint = "← Back to main (Esc)";
+    let style = Style::default().fg(colors.text_dim);
+    // Render at the start of the area with 1 character padding
+    buf.set_string(area.x + 1, area.y, hint, style);
+}
+
 /// Renders a single message to lines.
 pub fn render_message(
     msg: &Message,

src/cortex-tui/src/views/minimal_session/view.rs

@@ -630,7 +630,9 @@ impl<'a> Widget for MinimalSessionView<'a> {
         // 8. Key hints - only show when NOT in interactive mode
         if !self.app_state.is_interactive_mode() {
             let hints_area = Rect::new(area.x, next_y, area.width, hints_height);
-            let context = if is_task_running {
+            let context = if self.app_state.is_viewing_subagent() {
+                HintContext::SubagentView
+            } else if is_task_running {
                 HintContext::TaskRunning
             } else {
                 HintContext::Idle
@@ -642,6 +644,15 @@ impl<'a> Widget for MinimalSessionView<'a> {
                 hints = hints.with_thinking_budget(budget);
             }
             hints.render(hints_area, buf);
+
+            // Render "← Back to main (Esc)" hint when viewing a subagent
+            if self.app_state.is_viewing_subagent() {
+                crate::views::minimal_session::rendering::render_back_to_main_hint(
+                    hints_area,
+                    buf,
+                    &self.colors,
+                );
+            }
         }
     }
 }

src/cortex-tui/src/views/tool_call.rs

@@ -182,54 +182,74 @@ pub fn format_tool_summary(name: &str, args: &Value) -> String {
 
 /// Format a result summary based on tool name and output
 ///
-/// Returns a short summary like "Read 450 lines" or "Error: file not found"
+/// Returns a short summary like "↳ Read 450 lines" or "↳ Error: file not found"
+/// Uses '↳' prefix consistently across all tools for visual consistency.
 pub fn format_result_summary(name: &str, output: &str, success: bool) -> String {
     if !success {
         // Extract first line of error, truncated
         let first_line = output.lines().next().unwrap_or("unknown error");
         let truncated = truncate_str(first_line, 50);
-        return format!("Error: {truncated}");
+        return format!("↳ Error: {truncated}");
     }
 
     match name.to_lowercase().as_str() {
         "read" => {
             let line_count = output.lines().count();
-            format!("Read {line_count} lines")
+            format!("↳ Read {line_count} lines")
         }
-        "edit" => "Applied edit".to_string(),
+        "edit" | "multiedit" => "↳ Applied edit".to_string(),
+        "create" => "↳ File created".to_string(),
         "execute" | "bash" => {
             let line_count = output.lines().count();
             if line_count == 0 {
-                "Completed".to_string()
+                "↳ Completed".to_string()
             } else if line_count == 1 {
-                truncate_str(output.trim(), 60)
+                format!("↳ {}", truncate_str(output.trim(), 60))
             } else {
-                format!("{line_count} lines of output")
+                format!("↳ {line_count} lines of output")
             }
         }
         "glob" => {
             let file_count = output.lines().count();
             match file_count {
-                0 => "No matches".to_string(),
-                1 => "1 file".to_string(),
-                n => format!("{n} files"),
+                0 => "↳ No matches".to_string(),
+                1 => "↳ Found 1 file".to_string(),
+                n => format!("↳ Found {n} files"),
             }
         }
-        "websearch" | "codesearch" => {
+        "grep" => {
+            let match_count = output.lines().count();
+            match match_count {
+                0 => "↳ No matches".to_string(),
+                1 => "↳ Found 1 match".to_string(),
+                n => format!("↳ Found {n} matches"),
+            }
+        }
+        "ls" => {
+            let item_count = output.lines().count();
+            match item_count {
+                0 => "↳ Empty directory".to_string(),
+                1 => "↳ Listed 1 item".to_string(),
+                n => format!("↳ Listed {n} items"),
+            }
+        }
+        "websearch" | "codesearch" | "fetchurl" => {
             let char_count = output.len();
             if char_count > 1000 {
-                format!("Retrieved ~{} chars", char_count)
+                format!("↳ Retrieved ~{} chars", char_count)
             } else {
-                "Retrieved results".to_string()
+                "↳ Retrieved results".to_string()
             }
         }
-        "write" => "File written".to_string(),
+        "write" => "↳ File written".to_string(),
+        "todowrite" => "↳ Todos updated".to_string(),
+        "task" => "↳ Task completed".to_string(),
         _ => {
             let line_count = output.lines().count();
             if line_count == 0 {
-                "Completed".to_string()
+                "↳ Completed".to_string()
             } else {
-                format!("{line_count} lines")
+                format!("↳ {line_count} items")
             }
         }
     }
@@ -376,21 +396,49 @@ mod tests {
     fn test_format_result_summary_read() {
         let output = "line1\nline2\nline3\nline4\nline5";
         let summary = format_result_summary("read", output, true);
-        assert_eq!(summary, "Read 5 lines");
+        assert_eq!(summary, "↳ Read 5 lines");
     }
 
     #[test]
     fn test_format_result_summary_error() {
         let output = "file not found";
         let summary = format_result_summary("read", output, false);
-        assert_eq!(summary, "Error: file not found");
+        assert_eq!(summary, "↳ Error: file not found");
     }
 
     #[test]
     fn test_format_result_summary_glob() {
         let output = "file1.rs\nfile2.rs\nfile3.rs";
         let summary = format_result_summary("glob", output, true);
-        assert_eq!(summary, "3 files");
+        assert_eq!(summary, "↳ Found 3 files");
+    }
+
+    #[test]
+    fn test_format_result_summary_ls() {
+        let output = "file1.rs\nfile2.rs\ndir1";
+        let summary = format_result_summary("ls", output, true);
+        assert_eq!(summary, "↳ Listed 3 items");
+    }
+
+    #[test]
+    fn test_format_result_summary_grep() {
+        let output = "match1\nmatch2";
+        let summary = format_result_summary("grep", output, true);
+        assert_eq!(summary, "↳ Found 2 matches");
+    }
+
+    #[test]
+    fn test_format_result_summary_execute_multiline() {
+        let output = "line1\nline2\nline3";
+        let summary = format_result_summary("execute", output, true);
+        assert_eq!(summary, "↳ 3 lines of output");
+    }
+
+    #[test]
+    fn test_format_result_summary_default() {
+        let output = "item1\nitem2\nitem3\nitem4";
+        let summary = format_result_summary("unknown_tool", output, true);
+        assert_eq!(summary, "↳ 4 items");
     }
 
     #[test]

src/cortex-tui/src/widgets/key_hints.rs

@@ -30,6 +30,8 @@ pub enum HintContext {
     Approval,
     /// Selection list is focused
     Selection,
+    /// Viewing a subagent's conversation
+    SubagentView,
 }
 
 impl HintContext {
@@ -53,6 +55,10 @@ impl HintContext {
                 ("Esc", "close"),
                 ("/", "filter"),
             ],
+            HintContext::SubagentView => vec![
+                ("Esc", "back to main"),
+                ("↑/↓", "scroll"),
+            ],
         }
     }
 }