Show the context fill grade as a pie chart

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/app/view.rs

@@ -845,6 +845,51 @@ fn sidebar_style(_: &Theme) -> container::Style {
     container::Style::default().background(Color::from_rgb8(23, 23, 25))
 }
 
+/// Fill grade from which the context pie warns that compaction is near.
+const CONTEXT_WARN: f32 = 0.8;
+
+/// Draws the context fill grade as a pie the size of an icon; the exact token
+/// counts live in a tooltip so the composer row stays compact.
+fn context_pie<'a>(fraction: f32, size: u16) -> Svg<'a> {
+    svg(svg::Handle::from_memory(
+        context_pie_svg(fraction).into_bytes(),
+    ))
+    .width(size as f32)
+    .height(size as f32)
+}
+
+fn context_pie_svg(fraction: f32) -> String {
+    let fraction = fraction.clamp(0.0, 1.0);
+    let palette = app_theme().palette();
+    let fill = hex(if fraction >= CONTEXT_WARN {
+        Color::from_rgb8(224, 140, 58)
+    } else {
+        palette.primary
+    });
+    let track = hex(muted_text());
+    let wedge = if fraction >= 1.0 {
+        format!(r#"<circle cx="10" cy="10" r="8" fill="{fill}"/>"#)
+    } else {
+        let angle = fraction * std::f32::consts::TAU;
+        let (x, y) = (10.0 + 8.0 * angle.sin(), 10.0 - 8.0 * angle.cos());
+        let large = u8::from(fraction > 0.5);
+        format!(r#"<path d="M10 10 L10 2 A8 8 0 {large} 1 {x:.2} {y:.2} Z" fill="{fill}"/>"#)
+    };
+    format!(
+        r#"<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 20 20"><circle cx="10" cy="10" r="8.5" fill="none" stroke="{track}" stroke-width="1.5" stroke-opacity="0.5"/>{wedge}</svg>"#
+    )
+}
+
+fn hex(color: Color) -> String {
+    let channel = |value: f32| (value.clamp(0.0, 1.0) * 255.0).round() as u8;
+    format!(
+        "#{:02x}{:02x}{:02x}",
+        channel(color.r),
+        channel(color.g),
+        channel(color.b)
+    )
+}
+
 // The lifetime is free: the handle owns its bytes and the style closure is
 // 'static, so an icon can join a row that borrows shorter-lived data.
 fn icon<'a>(data: &'static [u8], size: u16) -> Svg<'a> {
@@ -860,6 +905,17 @@ fn icon<'a>(data: &'static [u8], size: u16) -> Svg<'a> {
 mod tests {
     use super::*;
 
+    #[test]
+    fn context_pie_wedge_follows_the_fill_grade() {
+        assert!(context_pie_svg(0.0).contains(r#"A8 8 0 0 1 10.00 2.00"#));
+        assert!(context_pie_svg(0.25).contains(r#"A8 8 0 0 1 18.00 10.00"#));
+        assert!(context_pie_svg(0.75).contains(r#"A8 8 0 1 1 2.00 10.00"#));
+        assert!(context_pie_svg(1.5).contains("<circle cx=\"10\" cy=\"10\" r=\"8\""));
+        let warning = hex(Color::from_rgb8(224, 140, 58));
+        assert!(!context_pie_svg(CONTEXT_WARN - 0.01).contains(&warning));
+        assert!(context_pie_svg(CONTEXT_WARN).contains(&warning));
+    }
+
     #[test]
     fn raised_surfaces_stay_dark() {
         let theme = app_theme();

src/app/view/chat.rs

@@ -159,18 +159,27 @@ impl App {
                 container(
                     column![
                         composer,
-                        progress_bar(0.0..=1.0, context_fraction).height(3),
                         row![
                             icon(ICON_PAPERCLIP, 19),
-                            text(format!(
-                                "{} / {} tokens ({:.0}%) • {}",
-                                self.context_used,
-                                self.context_limit,
-                                context_fraction * 100.0,
-                                self.tokens_per_second.map_or_else(
-                                    || "— tok/s".to_owned(),
-                                    |speed| format!("{speed:.1} tok/s")
+                            tooltip(
+                                context_pie(context_fraction, 19),
+                                container(
+                                    text(format!(
+                                        "{} / {} tokens ({:.0}%)",
+                                        self.context_used,
+                                        self.context_limit,
+                                        context_fraction * 100.0
+                                    ))
+                                    .size(12)
                                 )
+                                .padding(10)
+                                .style(preference_group_style),
+                                tooltip::Position::Top,
+                            )
+                            .gap(6),
+                            text(self.tokens_per_second.map_or_else(
+                                || "— tok/s".to_owned(),
+                                |speed| format!("{speed:.1} tok/s")
                             ))
                             .size(11)
                             .color(muted_text()),
@@ -184,6 +193,7 @@ impl App {
                             .size(12),
                             action,
                         ]
+                        .spacing(6)
                         .align_y(Alignment::Center),
                     ]
                     .spacing(8),