Manage the KV cache disc usage from preferences and stats

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

src/app/view/stats.rs

@@ -319,6 +319,7 @@ impl App {
             .spacing(9)
             .into(),
         );
+        let disc = stats_panel("KV CACHE DISC USAGE", self.cache_explorer());
         let server = stats_panel(
             "LOCAL SERVER",
             column![
@@ -353,6 +354,7 @@ impl App {
                     throughput,
                     kv_io,
                     requests,
+                    disc,
                     row![model, runtime].spacing(10),
                     row![cache, server].spacing(10),
                     text("Counters are published by the runtime with relaxed atomics and sampled by the UI every 200 ms.")
@@ -368,4 +370,135 @@ impl App {
         .height(Length::Fill)
         .into()
     }
+
+    /// Disc usage of both cache buckets, split by age. The bar is the age
+    /// distribution of what is stored; the budget governs the transient store
+    /// only and is reported on its own row.
+    fn cache_explorer(&self) -> Element<'_, Message> {
+        let usage = &self.kv_cache_report;
+        let total = usage.total_bytes();
+        let capacity = total.max(1);
+        let mut bar = row![].height(14).spacing(2);
+        let mut legend = column![].spacing(6);
+        for (index, (label, _)) in crate::metrics::CACHE_AGE_BUCKETS.iter().enumerate() {
+            let bytes = usage.age_bytes[index];
+            if bytes == 0 {
+                continue;
+            }
+            let color = AGE_COLORS[index];
+            bar = bar.push(
+                container(Space::new(Length::Fill, Length::Fill))
+                    .width(Length::FillPortion(portion(bytes, capacity)))
+                    .style(move |_| chart_bar_style(color)),
+            );
+            legend = legend.push(
+                row![
+                    container(Space::new(9, 9)).style(move |_| chart_bar_style(color)),
+                    text(*label).size(12).color(muted_text()),
+                    Space::with_width(Length::Fill),
+                    text(format!(
+                        "{} · {:.0}%",
+                        format_bytes(bytes),
+                        bytes as f32 / total.max(1) as f32 * 100.0
+                    ))
+                    .size(12),
+                ]
+                .spacing(8)
+                .align_y(Alignment::Center),
+            );
+        }
+        if total == 0 {
+            bar = bar.push(
+                container(Space::new(Length::Fill, Length::Fill))
+                    .style(|_| chart_bar_style(muted_text().scale_alpha(0.25))),
+            );
+        }
+
+        let mut rows = column![].spacing(7);
+        for entry in &usage.entries {
+            let path = entry.path.clone();
+            rows = rows.push(
+                row![
+                    text(entry.name.clone()).size(12),
+                    Space::with_width(Length::Fill),
+                    text(format!(
+                        "{} · {} old",
+                        format_bytes(entry.bytes),
+                        format_duration(entry.age_seconds as f64)
+                    ))
+                    .size(12)
+                    .color(muted_text()),
+                    action_button(text("Discard").size(12))
+                        .on_press(Message::DiscardCacheEntry(path)),
+                ]
+                .spacing(10)
+                .align_y(Alignment::Center),
+            );
+        }
+
+        column![
+            metric_row(
+                "Stored",
+                format!(
+                    "{} · {} files",
+                    format_bytes(total),
+                    usage.session_files + usage.transient_files
+                ),
+            ),
+            container(bar).height(14).width(Length::Fill),
+            legend,
+            metric_row(
+                "Sessions",
+                format!(
+                    "{} · {} files · not evicted",
+                    format_bytes(usage.session_bytes),
+                    usage.session_files
+                ),
+            ),
+            metric_row(
+                "Transient",
+                format!(
+                    "{} of {} budget · {} files · {:.0}% full",
+                    format_bytes(usage.transient_bytes),
+                    format_bytes(usage.budget_bytes),
+                    usage.transient_files,
+                    usage.transient_bytes as f32 / usage.budget_bytes.max(1) as f32 * 100.0,
+                ),
+            ),
+            Space::with_height(2),
+            text(if usage.entries.is_empty() {
+                "No checkpoints stored yet."
+            } else {
+                "OLDEST CHECKPOINTS"
+            })
+            .size(10)
+            .color(muted_text()),
+            rows,
+            row![
+                text("Discarding a checkpoint costs one prefill to rebuild it.")
+                    .size(11)
+                    .color(muted_text()),
+                Space::with_width(Length::Fill),
+                action_button(text("Clear transient cache").size(12))
+                    .on_press(Message::ClearTransientCache),
+            ]
+            .spacing(10)
+            .align_y(Alignment::Center),
+        ]
+        .spacing(9)
+        .into()
+    }
+}
+
+/// Age buckets from green (fresh) to grey (past every hit half-life).
+const AGE_COLORS: [Color; 5] = [
+    Color::from_rgb(0.28, 0.69, 0.44),
+    Color::from_rgb(0.33, 0.67, 1.0),
+    Color::from_rgb(0.62, 0.47, 1.0),
+    Color::from_rgb(0.94, 0.71, 0.27),
+    Color::from_rgb(0.45, 0.45, 0.48),
+];
+
+fn portion(bytes: u64, capacity: u64) -> u16 {
+    ((bytes.saturating_mul(1000) / capacity.max(1)) as u16).max(1)
 }