feat(tui): search pane t-key opens TracePopup (fb-37)

crates/kebab-tui/src/app.rs

@@ -387,6 +387,8 @@ pub struct App {
     pub ask: Option<AskState>,
     /// Populated by p9-4.
     pub inspect: Option<InspectState>,
+    /// p9-fb-37: trace popup state, `Some` while open.
+    pub trace_popup: Option<crate::trace_popup::TracePopupState>,
     /// Populated by p9-fb-03 when the user kicks off an in-shell
     /// ingest (Library `r`). Cleared by the run loop a few seconds
     /// after the run reaches a terminal event.
@@ -461,6 +463,7 @@ impl App {
             search: None,
             ask: None,
             inspect: None,
+            trace_popup: None,
             ingest_state: None,
             error_overlay: None,
             should_quit: false,

crates/kebab-tui/src/cheatsheet.rs

@@ -80,6 +80,7 @@ pub fn render_cheatsheet(f: &mut Frame, area: Rect, app: &App) {
         ("Delete", "remove char at cursor"),
         ("g", "open hit's citation in $EDITOR (Normal)"),
         ("o", "inspect selected hit's chunk (Normal — was `i` pre-fb-21)"),
+        ("t", "open retrieval trace popup (Normal — p9-fb-37)"),
         ("i", "Normal → Insert (toggle back to typing)"),
         ("Esc", "back to Library"),
     ]);

crates/kebab-tui/src/lib.rs

@@ -27,6 +27,7 @@ mod run;
 mod search;
 mod terminal;
 mod theme;
+pub mod trace_popup;
 
 pub use input::{InputBuffer, display_width, place_cursor_x, truncate_to_display_width};
 pub use theme::{Palette, Role, Theme};

crates/kebab-tui/src/run.rs

@@ -130,6 +130,21 @@ pub(crate) fn run_loop(app: &mut App) -> Result<()> {
         if event::poll(POLL_INTERVAL)? {
             match event::read()? {
                 Event::Key(key) if key.kind == KeyEventKind::Press => {
+                    // p9-fb-37: trace popup eats keys while open.
+                    // Sits ahead of cheatsheet + mode + pane dispatch
+                    // so Esc / j / k / arrows route to the popup
+                    // instead of leaking through to the search pane.
+                    if app.trace_popup.is_some() {
+                        let close = if let Some(popup) = app.trace_popup.as_mut() {
+                            crate::trace_popup::handle_key_trace_popup(popup, key)
+                        } else {
+                            false
+                        };
+                        if close {
+                            app.trace_popup = None;
+                        }
+                        continue;
+                    }
                     // p9-fb-13: cheatsheet popup toggle takes
                     // precedence over both mode + pane dispatch.
                     // F1 toggles open/close. While visible, Esc
@@ -255,6 +270,12 @@ fn render_root(f: &mut Frame, app: &App) {
     }
     render_status_bar(f, outer[2], app);
     render_key_hints(f, outer[3], app);
+    // p9-fb-37: trace popup overlays on top of pane content but
+    // below the error overlay (errors are higher-priority modal).
+    if let Some(popup) = &app.trace_popup {
+        let popup_area = centered_rect(80, 80, f.area());
+        crate::trace_popup::render_trace_popup(f, popup_area, popup);
+    }
     if let Some(err) = &app.error_overlay {
         render_error_overlay(f, f.area(), err, &app.theme);
     }
@@ -263,6 +284,28 @@ fn render_root(f: &mut Frame, app: &App) {
     }
 }
 
+/// p9-fb-37: centered sub-rect helper for the trace popup. Returns
+/// a rect of `percent_x` × `percent_y` percent of `r`, centered.
+fn centered_rect(percent_x: u16, percent_y: u16, r: ratatui::layout::Rect) -> ratatui::layout::Rect {
+    use ratatui::layout::{Constraint, Direction, Layout};
+    let popup_layout = Layout::default()
+        .direction(Direction::Vertical)
+        .constraints([
+            Constraint::Percentage((100 - percent_y) / 2),
+            Constraint::Percentage(percent_y),
+            Constraint::Percentage((100 - percent_y) / 2),
+        ])
+        .split(r);
+    Layout::default()
+        .direction(Direction::Horizontal)
+        .constraints([
+            Constraint::Percentage((100 - percent_x) / 2),
+            Constraint::Percentage(percent_x),
+            Constraint::Percentage((100 - percent_x) / 2),
+        ])
+        .split(popup_layout[1])[1]
+}
+
 fn render_header(f: &mut Frame, area: Rect, app: &App) {
     let pane_label = match app.focus {
         Pane::Library => "Library",

crates/kebab-tui/src/search.rs

@@ -209,6 +209,49 @@ pub fn handle_key_search(state: &mut App, key: KeyEvent) -> KeyOutcome {
     // pre-fb-12 SHIFT/none heuristic).
     let is_normal = state.mode == crate::app::Mode::Normal;
 
+    // p9-fb-37: `t` opens the trace popup. Re-runs the last submitted
+    // query with SearchOpts.trace = true. Bypasses cache by going
+    // through `search_with_opts_with_config` (Task 5 wires opts.trace
+    // to skip the LRU cache).
+    if is_normal
+        && matches!(
+            (key.code, key.modifiers),
+            (KeyCode::Char('t'), KeyModifiers::NONE)
+        )
+    {
+        let (last_query, has_results) = {
+            let s = state.search.as_ref().unwrap();
+            (s.last_query.clone(), !s.hits.is_empty())
+        };
+        if !has_results {
+            return KeyOutcome::Continue;
+        }
+        if let Some((q_text, q_mode)) = last_query {
+            let q = kebab_core::SearchQuery {
+                text: q_text,
+                mode: q_mode,
+                k: state.config.search.default_k,
+                filters: kebab_core::SearchFilters::default(),
+            };
+            let opts = kebab_core::SearchOpts {
+                trace: true,
+                ..Default::default()
+            };
+            match kebab_app::search_with_opts_with_config(state.config.clone(), q, opts) {
+                Ok(resp) => {
+                    if let Some(t) = resp.trace {
+                        state.trace_popup = Some(crate::trace_popup::TracePopupState::new(t));
+                    }
+                }
+                Err(_) => {
+                    // Silent failure — trace is debug-only; user
+                    // can still see search hits without it.
+                }
+            }
+        }
+        return KeyOutcome::Continue;
+    }
+
     // p9-fb-21: chunk-inspect rebound from `i` to `o` (vim "open").
     // The `i` key is now the universal Normal→Insert toggle (handled
     // in `mode_intercept`), so it cannot also mean "inspect chunk"

crates/kebab-tui/src/trace_popup.rs

@@ -0,0 +1,139 @@
+//! p9-fb-37: TUI trace popup. Opens from Search pane via `t` key
+//! when results are visible. Re-runs the current query with
+//! `SearchOpts.trace = true` and displays the lex / vec / rrf union
+//! + per-stage timing as a single scroll list.
+
+use crossterm::event::{KeyCode, KeyEvent};
+use kebab_core::SearchTrace;
+use ratatui::Frame;
+use ratatui::layout::Rect;
+use ratatui::style::{Modifier, Style};
+use ratatui::text::{Line, Span};
+use ratatui::widgets::{Block, Borders, Paragraph, Wrap};
+
+#[derive(Debug, Clone)]
+pub struct TracePopupState {
+    pub trace: SearchTrace,
+    pub scroll: u16,
+}
+
+impl TracePopupState {
+    pub fn new(trace: SearchTrace) -> Self {
+        Self { trace, scroll: 0 }
+    }
+}
+
+pub fn render_trace_popup(f: &mut Frame, area: Rect, state: &TracePopupState) {
+    let mut lines: Vec<Line> = Vec::new();
+    let bold = Style::default().add_modifier(Modifier::BOLD);
+
+    lines.push(Line::from(Span::styled(
+        format!(
+            "Lexical ({} hits, {} ms)",
+            state.trace.lexical.len(),
+            state.trace.timing.lexical_ms,
+        ),
+        bold,
+    )));
+    for c in &state.trace.lexical {
+        lines.push(Line::from(format!(
+            "  #{:>2} score={:.4} chunk={}",
+            c.rank, c.score, c.chunk_id.0
+        )));
+    }
+    lines.push(Line::from(""));
+    lines.push(Line::from(Span::styled(
+        format!(
+            "Vector ({} hits, {} ms)",
+            state.trace.vector.len(),
+            state.trace.timing.vector_ms,
+        ),
+        bold,
+    )));
+    for c in &state.trace.vector {
+        lines.push(Line::from(format!(
+            "  #{:>2} score={:.4} chunk={}",
+            c.rank, c.score, c.chunk_id.0
+        )));
+    }
+    lines.push(Line::from(""));
+    lines.push(Line::from(Span::styled(
+        format!(
+            "RRF inputs ({} entries, {} ms fusion)",
+            state.trace.rrf_inputs.len(),
+            state.trace.timing.fusion_ms,
+        ),
+        bold,
+    )));
+    for e in &state.trace.rrf_inputs {
+        lines.push(Line::from(format!(
+            "  chunk={} lex={:?} vec={:?} fusion={:.4}",
+            e.chunk_id.0, e.lexical_rank, e.vector_rank, e.fusion_score
+        )));
+    }
+    lines.push(Line::from(""));
+    lines.push(Line::from(Span::styled(
+        format!("Total: {} ms", state.trace.timing.total_ms),
+        bold,
+    )));
+
+    let block = Block::default()
+        .title("Trace — Esc to close, j/k or ↑↓ to scroll")
+        .borders(Borders::ALL);
+    let p = Paragraph::new(lines)
+        .block(block)
+        .scroll((state.scroll, 0))
+        .wrap(Wrap { trim: false });
+    f.render_widget(p, area);
+}
+
+/// Handle keys while popup is open. Returns true if the popup should close.
+pub fn handle_key_trace_popup(state: &mut TracePopupState, key: KeyEvent) -> bool {
+    match key.code {
+        KeyCode::Esc => true,
+        KeyCode::Char('j') | KeyCode::Down => {
+            state.scroll = state.scroll.saturating_add(1);
+            false
+        }
+        KeyCode::Char('k') | KeyCode::Up => {
+            state.scroll = state.scroll.saturating_sub(1);
+            false
+        }
+        _ => false,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crossterm::event::KeyModifiers;
+    use kebab_core::TraceTiming;
+
+    fn dummy_state() -> TracePopupState {
+        TracePopupState::new(SearchTrace {
+            lexical: vec![],
+            vector: vec![],
+            rrf_inputs: vec![],
+            timing: TraceTiming::default(),
+        })
+    }
+
+    #[test]
+    fn esc_closes() {
+        let mut s = dummy_state();
+        assert!(handle_key_trace_popup(
+            &mut s,
+            KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE),
+        ));
+    }
+
+    #[test]
+    fn j_scrolls_down() {
+        let mut s = dummy_state();
+        assert!(!handle_key_trace_popup(
+            &mut s,
+            KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE),
+        ));
+        assert_eq!(s.scroll, 1);
+    }
+}