Show idle state in the top tab bar

Each agent tab now prefixes its label with the same one-rune idle
indicator the sidebar uses (✕ error, ? permission, ◐ thinking, ○ idle,
● working), so the state of every open agent is visible without
opening or focusing each tab. Tab redraws now fire on idle-state
changes in addition to sidebar redraws.

CHANGELOG.md

@@ -6,6 +6,12 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Added
+- The top tab bar now prefixes each agent tab's label with its
+  idle-state glyph (✕ error, ? permission, ◐ thinking, ○ idle, ●
+  working), matching the sidebar's vocabulary so the state of every
+  open agent is visible without opening or focusing each tab.
+
 ### Changed
 - Built-in agent presets (`claude`, `codex`, `opencode`) now live in
   memory and user preset files merge over them by name instead of

TODO.md

@@ -1 +0,0 @@
-- [ ] We should show idle state in the top tab bar as well

internal/app/app.go

@@ -829,11 +829,11 @@ func (st *uiState) OnChildSpawned(c *Child) {
 	st.drawStatusLine()
 }
 
-// OnChildStateChanged repaints the sidebar whenever a child's
-// idle-state badge flips. Cheap — the badge is the only chrome that
-// reflects state today, and drawSidebar bails when the cached frame
-// hasn't changed.
+// OnChildStateChanged repaints the sidebar and tab bar whenever a
+// child's idle-state badge flips. Cheap — both draws bail when the
+// cached frame hasn't changed.
 func (st *uiState) OnChildStateChanged(string, IdleState) {
+	st.drawTabBar()
 	st.drawSidebar()
 }
 

internal/app/tabbar.go

@@ -62,6 +62,8 @@ func (st *uiState) drawTabBar() {
 		startCol   int
 		width      int
 		label      string
+		glyph      string
+		glyphStyle string
 		active     bool
 	}
 	activeTab := -1
@@ -115,9 +117,16 @@ func (st *uiState) drawTabBar() {
 			if i < extra {
 				w++
 			}
+			active := c.ID == focus
+			glyph, glyphStyle := tabIdleGlyph(c.IdleState(), active)
 			label := c.DisplayName()
 			labelW := utf8.RuneCountInString(label)
-			maxLabelW := w - 2 // one pad on each side
+			// Reserve room for the glyph + its trailing space when present
+			// (1 + 1 runes), on top of the one-cell pad on each side.
+			maxLabelW := w - 2
+			if glyph != "" {
+				maxLabelW -= 2
+			}
 			if maxLabelW < 1 {
 				maxLabelW = 1
 			}
@@ -133,7 +142,9 @@ func (st *uiState) drawTabBar() {
 				startCol:   col,
 				width:      w,
 				label:      label,
-				active:   c.ID == focus,
+				glyph:      glyph,
+				glyphStyle: glyphStyle,
+				active:     active,
 			})
 			if tabs[len(tabs)-1].active {
 				activeTab = len(tabs) - 1
@@ -155,23 +166,37 @@ func (st *uiState) drawTabBar() {
 	fmt.Fprintf(&b, "\x1b[3;1H\x1b[%dX", width)
 
 	for _, t := range tabs {
-		// Row 1: centre-ish label inside the tab cell.
+		// Row 1: centre-ish glyph+label inside the tab cell.
 		labelW := utf8.RuneCountInString(t.label)
-		leftPad := (t.width - labelW) / 2
+		visibleW := labelW
+		if t.glyph != "" {
+			visibleW += 2 // glyph + separator space
+		}
+		leftPad := (t.width - visibleW) / 2
 		if leftPad < 1 {
 			leftPad = 1
 		}
-		rightPad := t.width - labelW - leftPad
+		rightPad := t.width - visibleW - leftPad
 		if rightPad < 0 {
 			rightPad = 0
 		}
-		fmt.Fprintf(&b, "\x1b[1;%dH", t.startCol)
+		cellStyle := styleHint
 		if t.active {
-			b.WriteString(styleActive)
-		} else {
-			b.WriteString(styleHint)
+			cellStyle = styleActive
 		}
+		fmt.Fprintf(&b, "\x1b[1;%dH", t.startCol)
+		b.WriteString(cellStyle)
 		b.WriteString(strings.Repeat(" ", leftPad))
+		if t.glyph != "" {
+			// Glyph uses its own colour so error/permission states pop
+			// regardless of tab focus, matching the sidebar's vocabulary.
+			b.WriteString(styleReset)
+			b.WriteString(t.glyphStyle)
+			b.WriteString(t.glyph)
+			b.WriteString(styleReset)
+			b.WriteString(cellStyle)
+			b.WriteString(" ")
+		}
 		b.WriteString(t.label)
 		b.WriteString(strings.Repeat(" ", rightPad))
 		b.WriteString(styleReset)
@@ -226,3 +251,29 @@ func (st *uiState) drawTabBar() {
 	defer st.outMu.Unlock()
 	fmt.Fprintf(os.Stdout, "\x1b7%s\x1b8", frame)
 }
+
+// tabIdleGlyph returns the one-rune state indicator (and its SGR style)
+// to render before a tab's label. Mirrors the sidebar's vocabulary so
+// users learn the symbols in one place: ✕ error, ? permission, ◐
+// thinking, ○ idle, ● working. Returns ("", "") for StateUnknown so the
+// first frame after spawn doesn't show a misleading badge.
+func tabIdleGlyph(state IdleState, active bool) (string, string) {
+	base := styleHint
+	if active {
+		base = styleAccent
+	}
+	switch state {
+	case StateError:
+		return "✕", styleError
+	case StatePermission:
+		return "?", styleAccent
+	case StateThinking:
+		return "◐", base
+	case StateIdle:
+		return "○", base
+	case StateWorking:
+		return "●", base
+	default:
+		return "", ""
+	}
+}