diff --git a/AGENTS.md b/AGENTS.md
index e5a0cf5..e4497e0 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -154,7 +154,7 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - Taffy 0.13 collapses a child's vertical margin through a block parent with no padding or border on that side, and its size cache keeps only that block's size, so a box that measures it again leaves the margin out. A component moves a box with a relative offset, or with padding where what follows moves too, not with such a margin: `layout::Drawer` pulls and snaps its panel, and a fullscreen `overlays::Dialog` slides its card, with `top`; `motion::Stagger`, `Transition`, a centered Dialog and the palette's card rise with padding, so the box a scrim centers grows with them; the gallery's inspector sample is its probe's own child. A margin that stops at its parent is safe: a flex or grid item's own, or a child's of a flex item or of a box with padding or a border on that side. A flex wrapper stops the collapse but gives its items a definite height, so percent heights inside start to resolve (the Drawer's `max_h(relative(0.85))`).
 - Tiles in a picture's shape sit in flex rows of `flex_1` cells (`generative::GenerationGrid`). A cell's padding counts in its flex base, so a row of fewer cells gives each more width; cells that match across rows keep their inset on a box inside (`messaging::VideoCallGrid`).
 - Rise reads green and fall red unless a component's `red_up` swaps them, as markets in East Asia read. `finance::quotes::moves` picks the pair.
-- Charts lay out in `f32` pixels of their own box, tested without gpui, and paint through `charts::paint::at`: a canvas's paint gets window coordinates, and `with_element_offset` works only in prepaint. Their sizes come from `theme.chart()`.
+- Charts lay out in `f32` pixels of their own box, tested without gpui, and paint through `charts::paint::at`: a canvas's paint gets window coordinates, and `with_element_offset` works only in prepaint. Their sizes come from `theme.chart()`. A chart value is finite and within ±`charts::LIMIT` (1e30), so sums of values and their pixels stay inside `f32`; the builders refuse others, and a scale works in halves so a domain across the limit maps.
 - A label pinned to a point sits in a zero-size absolute box that centers it with flex (`charts::axes`), so no offset guesses at text size.
 - Tokens live in `src/theme`; the raw `px()` scan skips that folder only.
 - An owner's palette, edited or imported, reaches the theme per mode through `Theme::set_palette`, and `Theme::palette` names the one the shown mode fades to; high contrast strengthens Ely's own palettes alone. A color goes by its field's name through `token` and `token_mut`, on `Palette` and `Syntax` alike. Ely's palettes pass `tooling::A11yChecker`'s audit in both modes, with high contrast and without; a test holds them there.
diff --git a/src/charts/burndown.rs b/src/charts/burndown.rs
index 79da911..f77f4c6 100644
--- a/src/charts/burndown.rs
+++ b/src/charts/burndown.rs
@@ -11,6 +11,7 @@ use super::{
     parts::ChartTooltip,
     scale::{Linear, compact, nice},
     schedule::{days, marks},
+    series::drawable,
     tiles::{Tiles, tracked},
 };
 use crate::{
@@ -62,7 +63,10 @@ impl BurndownChart {
     /// A sprint from its first day through its last, with `scope` to do, in points or issues.
     pub fn new(id: impl Into<ElementId>, first: Date, last: Date, scope: f64) -> Self {
         assert!(last > first, "a sprint ends after its first day");
-        assert!(scope.is_finite() && scope > 0.0, "a sprint has work to do");
+        assert!(
+            drawable(scope) && scope > 0.0,
+            "a sprint has work to do, within charts::LIMIT"
+        );
         Self {
             base: div(),
             id: id.into(),
@@ -85,8 +89,8 @@ impl BurndownChart {
         assert!(
             self.left
                 .iter()
-                .all(|value| value.is_finite() && *value >= 0.0),
-            "work left is a count, zero or more"
+                .all(|value| drawable(*value) && *value >= 0.0),
+            "work left is a count, zero or more, within charts::LIMIT"
         );
         self
     }
diff --git a/src/charts/calendar.rs b/src/charts/calendar.rs
index d783cda..2d7ddd0 100644
--- a/src/charts/calendar.rs
+++ b/src/charts/calendar.rs
@@ -4,7 +4,10 @@ use gpui::{
     App, Div, ElementId, Entity, Hsla, InteractiveElement, IntoElement, ParentElement, Pixels,
     Refineable, RenderOnce, StyleRefinement, Styled, Window, canvas, div, fill,
 };
-use jiff::{Span, civil::Date};
+use jiff::{
+    Span,
+    civil::{Date, date},
+};
 
 use super::{
     axes::{anchored, beside},
@@ -14,6 +17,7 @@ use super::{
     parts::ChartTooltip,
     plot::Format,
     scale::compact,
+    series::drawable,
     tiles::{Tiles, key, tracked},
 };
 use crate::theme::{ActiveTheme, Radius, TextSize};
@@ -37,10 +41,13 @@ impl CalendarHeatmap {
     ) -> Self {
         let counts: Vec<f64> = counts.into_iter().collect();
         assert!(
-            counts
-                .iter()
-                .all(|count| count.is_finite() && *count >= 0.0),
-            "a calendar needs counts of zero or more"
+            counts.iter().all(|count| drawable(*count) && *count >= 0.0),
+            "a calendar needs counts of zero or more, within charts::LIMIT"
+        );
+        let span = Span::new().days(counts.len().saturating_sub(1) as i64);
+        assert!(
+            start.checked_add(span).is_ok(),
+            "a calendar's last day lies past the dates jiff holds"
         );
         Self {
             base: div(),
@@ -119,10 +126,7 @@ impl RenderOnce for CalendarHeatmap {
                     .child(text(day(ix).strftime("%b").to_string()))
             });
         let weekdays = [0usize, 2, 4].map(|weekday| {
-            let date = (0..7)
-                .map(day)
-                .find(|date| date.weekday().to_monday_zero_offset() as usize == weekday)
-                .expect("seven days hold every weekday");
+            let date = date(2024, 1, 1 + weekday as i8);
             beside(
                 top + side * (weekday as f32 + 0.5),
                 sizes.gutter.to_pixels(rem),
diff --git a/src/charts/cartesian.rs b/src/charts/cartesian.rs
index ae961e0..aab9af7 100644
--- a/src/charts/cartesian.rs
+++ b/src/charts/cartesian.rs
@@ -10,6 +10,7 @@ use super::{
     geometry::{Categories, Ink, Mark, categories, scatter},
     plot::{Format, Layout, Pick, Plot, Scene, Tips, plot},
     scale::compact,
+    series::drawable,
     series::{Points, Series, csv, points_csv},
 };
 use crate::theme::ActiveTheme;
@@ -173,18 +174,22 @@ macro_rules! category_chart {
 
             /// A dashed level across the chart with its label, as a target or a limit.
             pub fn rule(mut self, value: f64, label: impl Into<SharedString>) -> Self {
-                assert!(value.is_finite(), "a rule needs a finite value");
+                assert!(
+                    drawable(value),
+                    "a rule needs a value, within charts::LIMIT"
+                );
                 self.chart.rules.push((value, label.into()));
                 self
             }
 
             /// A mark at category `ix` with its label, as a release or an incident.
             pub fn note(mut self, ix: usize, label: impl Into<SharedString>) -> Self {
-                assert!(
-                    ix < self.chart.labels.len(),
-                    "note {ix} is past the last label"
-                );
-                self.chart.notes.push((ix, label.into()));
+                let label = label.into();
+                if ix >= self.chart.labels.len() {
+                    log::error!("chart: note {label} at {ix} is past the last label; skipped");
+                    return self;
+                }
+                self.chart.notes.push((ix, label));
                 self
             }
 
diff --git a/src/charts/distribution.rs b/src/charts/distribution.rs
index 97cf066..319fc63 100644
--- a/src/charts/distribution.rs
+++ b/src/charts/distribution.rs
@@ -11,6 +11,7 @@ use super::{
     plot::{Layout, Pick, Plot, Scene, Tips},
     scale::{Band, Linear, compact, nice},
     series::Series,
+    series::drawable,
     stats::{Step, bins, density, five, steps},
 };
 
@@ -77,8 +78,8 @@ impl Histogram {
     pub fn new(id: impl Into<ElementId>, values: impl IntoIterator<Item = f64>) -> Self {
         let values: Vec<f64> = values.into_iter().collect();
         assert!(
-            values.iter().all(|value| value.is_finite()),
-            "a histogram needs finite values"
+            values.iter().all(|value| drawable(*value)),
+            "a histogram needs values, within charts::LIMIT"
         );
         Self {
             base: div(),
@@ -130,7 +131,10 @@ impl WaterfallChart {
 
     /// A change, up or down, from the running total.
     pub fn step(mut self, label: impl Into<SharedString>, change: f64) -> Self {
-        assert!(change.is_finite(), "a step needs a finite change");
+        assert!(
+            drawable(change),
+            "a step needs a change, within charts::LIMIT"
+        );
         self.steps.push((label.into(), change, false));
         self
     }
@@ -257,8 +261,8 @@ macro_rules! grouped {
             ) -> Self {
                 let values: Vec<f64> = values.into_iter().collect();
                 assert!(
-                    values.len() >= 2 && values.iter().all(|value| value.is_finite()),
-                    "a group needs two finite values"
+                    values.len() >= 2 && values.iter().all(|value| drawable(*value)),
+                    "a group needs two values, within charts::LIMIT"
                 );
                 self.groups.push((label.into(), values));
                 self
diff --git a/src/charts/flow.rs b/src/charts/flow.rs
index 32b9880..ffea558 100644
--- a/src/charts/flow.rs
+++ b/src/charts/flow.rs
@@ -13,6 +13,7 @@ use super::{
     parts::ChartTooltip,
     plot::Format,
     scale::compact,
+    series::drawable,
 };
 use crate::{
     theme::{ActiveTheme, Radius, TextSize},
@@ -118,15 +119,18 @@ pub(crate) fn sankey(
     let columns = column.iter().max().map_or(1, |last| last + 1);
     let placed = &column;
     let members = |c: usize| (0..count).filter(move |ix| placed[*ix] == c);
+    let total = |c: usize| members(c).map(|ix| through[ix]).sum::<f64>();
+    let biggest = (0..columns).map(total).fold(0.0, f64::max);
     let scale = (0..columns)
         .map(|c| {
-            let (total, gaps) = (
-                members(c).map(|ix| through[ix]).sum::<f64>(),
-                members(c).count().saturating_sub(1),
-            );
-            (frame.h - padding * gaps as f32).max(0.0) / total.max(f64::EPSILON) as f32
+            let gaps = members(c).count().saturating_sub(1);
+            f64::from((frame.h - padding * gaps as f32).max(0.0)) / (total(c) / biggest)
         })
-        .fold(f32::MAX, f32::min);
+        .fold(f64::INFINITY, f64::min);
+    let height = |value: f64| match biggest > 0.0 {
+        true => (value / biggest * scale) as f32,
+        false => 0.0,
+    };
     let mut nodes = vec![Rect::default(); count];
     for c in 0..columns {
         let x = if columns > 1 {
@@ -134,7 +138,7 @@ pub(crate) fn sankey(
         } else {
             frame.x
         };
-        let tall: f32 = members(c).map(|ix| through[ix] as f32 * scale).sum::<f32>()
+        let tall: f32 = members(c).map(|ix| height(through[ix])).sum::<f32>()
             + padding * members(c).count().saturating_sub(1) as f32;
         let mut y = frame.y + (frame.h - tall) / 2.0;
         for ix in members(c) {
@@ -142,7 +146,7 @@ pub(crate) fn sankey(
                 x,
                 y,
                 w: node,
-                h: through[ix] as f32 * scale,
+                h: height(through[ix]),
             };
             y += nodes[ix].h + padding;
         }
@@ -152,7 +156,7 @@ pub(crate) fn sankey(
         .map(|link| Ribbon {
             from: (0.0, 0.0),
             to: (0.0, 0.0),
-            thick: link.2 as f32 * scale,
+            thick: height(link.2),
         })
         .collect();
     let mut order: Vec<usize> = (0..links.len()).collect();
@@ -200,13 +204,16 @@ impl SankeyChart {
 
     /// A flow of `value` from node `from` to node `to`, by their places in the list.
     pub fn link(mut self, from: usize, to: usize, value: f64) -> Self {
+        if from >= self.nodes.len() || to >= self.nodes.len() || from == to {
+            log::error!(
+                "sankey: a link {from} -> {to} among {} nodes; skipped",
+                self.nodes.len()
+            );
+            return self;
+        }
         assert!(
-            from < self.nodes.len() && to < self.nodes.len() && from != to,
-            "a link joins two known nodes"
-        );
-        assert!(
-            value.is_finite() && value > 0.0,
-            "a link carries a positive value"
+            drawable(value) && value > 0.0,
+            "a link carries a positive value, within charts::LIMIT"
         );
         self.links.push((from, to, value));
         self
@@ -243,6 +250,7 @@ impl RenderOnce for SankeyChart {
             w: (f32::from(bounds.size.width) - room * 2.0).max(0.0),
             h: (f32::from(bounds.size.height) - pixels(sizes.inset) * 2.0).max(0.0),
         };
+        let hover = hover.filter(|_| frame.w > 0.0);
         let (nodes, ribbons) = if frame.w > 0.0 {
             sankey(
                 self.nodes.len(),
diff --git a/src/charts/funnel.rs b/src/charts/funnel.rs
index 8d0978e..3f9c929 100644
--- a/src/charts/funnel.rs
+++ b/src/charts/funnel.rs
@@ -13,6 +13,7 @@ use super::{
     parts::ChartTooltip,
     plot::Format,
     scale::compact,
+    series::drawable,
     tiles::Tiles,
 };
 use crate::{
@@ -41,8 +42,8 @@ impl FunnelChart {
 
     pub fn stage(mut self, name: impl Into<SharedString>, value: f64) -> Self {
         assert!(
-            value.is_finite() && value >= 0.0,
-            "a stage needs a value of zero or more"
+            drawable(value) && value >= 0.0,
+            "a stage needs a value of zero or more, within charts::LIMIT"
         );
         self.stages.push((name.into(), value));
         self
diff --git a/src/charts/mod.rs b/src/charts/mod.rs
index 1643306..56506bc 100644
--- a/src/charts/mod.rs
+++ b/src/charts/mod.rs
@@ -43,6 +43,7 @@ pub use radar::RadarChart;
 pub use realtime::RealtimeChart;
 pub use relations::ChordDiagram;
 pub use schedule::{GanttChart, Task};
+pub use series::LIMIT;
 pub use series::{Points, Series};
 pub use sunburst::{Slice, Sunburst};
 pub use targets::{Bullet, BulletChart, ProgressChart};
diff --git a/src/charts/network.rs b/src/charts/network.rs
index 203dcbf..63920d2 100644
--- a/src/charts/network.rs
+++ b/src/charts/network.rs
@@ -129,10 +129,13 @@ impl NetworkGraph {
 
     /// An edge between two nodes, by their places in the list.
     pub fn edge(mut self, a: usize, b: usize) -> Self {
-        assert!(
-            a < self.nodes.len() && b < self.nodes.len() && a != b,
-            "an edge joins two known nodes"
-        );
+        if a >= self.nodes.len() || b >= self.nodes.len() || a == b {
+            log::error!(
+                "network: an edge {a} - {b} among {} nodes; skipped",
+                self.nodes.len()
+            );
+            return self;
+        }
         self.edges.push((a, b));
         self
     }
diff --git a/src/charts/parallel.rs b/src/charts/parallel.rs
index de50bd5..f4cf370 100644
--- a/src/charts/parallel.rs
+++ b/src/charts/parallel.rs
@@ -12,6 +12,7 @@ use super::{
     parts::ChartTooltip,
     plot::Format,
     scale::{Linear, compact, nice},
+    series::drawable,
     tiles::{Tiles, tracked},
 };
 use crate::theme::{ActiveTheme, TextSize};
@@ -109,8 +110,8 @@ impl ParallelCoordinates {
             "a record needs a value per axis"
         );
         assert!(
-            values.iter().all(|value| value.is_finite()),
-            "a record needs finite values"
+            values.iter().all(|value| drawable(*value)),
+            "a record needs values, within charts::LIMIT"
         );
         self.records.push((name.into(), values));
         self
diff --git a/src/charts/pie.rs b/src/charts/pie.rs
index c5fb330..b40b614 100644
--- a/src/charts/pie.rs
+++ b/src/charts/pie.rs
@@ -16,6 +16,7 @@ use super::{
     paint::{finish, measure, tint},
     parts::{ChartLegend, ChartTooltip},
     scale::compact,
+    series::drawable,
 };
 use crate::{
     motion,
@@ -191,8 +192,8 @@ impl PieChart {
 
     pub fn slice(mut self, name: impl Into<SharedString>, value: f64) -> Self {
         assert!(
-            value.is_finite() && value >= 0.0,
-            "a slice needs a value of zero or more"
+            drawable(value) && value >= 0.0,
+            "a slice needs a value of zero or more, within charts::LIMIT"
         );
         self.slices.push((name.into(), value));
         self
diff --git a/src/charts/realtime.rs b/src/charts/realtime.rs
index 3ad4103..58421f6 100644
--- a/src/charts/realtime.rs
+++ b/src/charts/realtime.rs
@@ -10,6 +10,7 @@ use super::{
     geometry::{Rect, frame},
     paint::{at, finish, measure, place, ring, tint, trace},
     scale::{Linear, compact, nice},
+    series::drawable,
 };
 use crate::{
     motion,
@@ -43,8 +44,8 @@ impl RealtimeChart {
     ) -> Self {
         let values: Vec<f64> = values.into_iter().collect();
         assert!(
-            values.iter().all(|value| value.is_finite()),
-            "a stream needs finite values"
+            values.iter().all(|value| drawable(*value)),
+            "a stream needs values, within charts::LIMIT"
         );
         Self {
             base: div(),
diff --git a/src/charts/relations.rs b/src/charts/relations.rs
index 01eb0b9..1337aad 100644
--- a/src/charts/relations.rs
+++ b/src/charts/relations.rs
@@ -15,6 +15,7 @@ use super::{
     pie::{bearing, toward, wedge},
     plot::Format,
     scale::compact,
+    series::drawable,
     tiles::{Tiles, tracked},
 };
 use crate::theme::{ActiveTheme, TextSize};
@@ -26,10 +27,9 @@ type Arcs = Vec<(f32, f32)>;
 pub(crate) fn chords(matrix: &[Vec<f64>], pad: f32) -> (Arcs, Vec<Arcs>) {
     let grand: f64 = matrix.iter().flatten().sum();
     let room = (TAU - pad * matrix.len() as f32).max(0.0);
-    let scale = if grand > 0.0 {
-        room / grand as f32
-    } else {
-        0.0
+    let share = |value: f64| match grand > 0.0 {
+        true => (value / grand * f64::from(room)) as f32,
+        false => 0.0,
     };
     let mut angle = -FRAC_PI_2 + pad / 2.0;
     let (mut groups, mut parts) = (Vec::new(), Vec::new());
@@ -38,7 +38,7 @@ pub(crate) fn chords(matrix: &[Vec<f64>], pad: f32) -> (Arcs, Vec<Arcs>) {
         parts.push(
             row.iter()
                 .map(|value| {
-                    let part = (angle, *value as f32 * scale);
+                    let part = (angle, share(*value));
                     angle += part.1;
                     part
                 })
@@ -126,8 +126,8 @@ impl ChordDiagram {
             matrix
                 .iter()
                 .flatten()
-                .all(|value| value.is_finite() && *value >= 0.0),
-            "flows are zero or more"
+                .all(|value| drawable(*value) && *value >= 0.0),
+            "flows are zero or more, within charts::LIMIT"
         );
         Self {
             base: div(),
diff --git a/src/charts/scale.rs b/src/charts/scale.rs
index 8c70d20..3be448a 100644
--- a/src/charts/scale.rs
+++ b/src/charts/scale.rs
@@ -1,3 +1,6 @@
+/// Shares past this many ranges lie off any screen; the bound keeps their pixels in `f32`.
+const FAR: f64 = 1e4;
+
 /// A linear map from a domain of values onto a range of pixels.
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub(crate) struct Linear {
@@ -22,16 +25,17 @@ impl Linear {
         } else {
             (f64::from(at) - f64::from(self.range.0)) / f64::from(span)
         };
-        self.domain.0 + (self.domain.1 - self.domain.0) * share
+        let (low, high) = (self.domain.0 / 2.0, self.domain.1 / 2.0);
+        (low + (high - low) * share) * 2.0
     }
 
-    /// Where `value` lands; a flat domain lands in the middle.
+    /// Where `value` lands; a flat domain lands in the middle. Halves keep wide domains finite.
     pub(crate) fn at(&self, value: f64) -> f32 {
-        let span = self.domain.1 - self.domain.0;
-        let share = if span == 0.0 {
+        let (low, high) = (self.domain.0 / 2.0, self.domain.1 / 2.0);
+        let share = if high == low {
             0.5
         } else {
-            (value - self.domain.0) / span
+            ((value / 2.0 - low) / (high - low)).clamp(-FAR, FAR)
         };
         self.range.0 + (self.range.1 - self.range.0) * share as f32
     }
@@ -62,12 +66,13 @@ pub(crate) fn nice(low: f64, high: f64, count: usize) -> ((f64, f64), Vec<f64>)
     let (low, high) = (low.min(high), low.max(high));
     let (low, high) = if high - low <= high.abs().max(low.abs()) * 1e-12 {
         let pad = (high.abs().max(low.abs()) * 0.1).max(1.0);
-        (low - pad, high + pad)
+        ((low - pad).max(f64::MIN), (high + pad).min(f64::MAX))
     } else {
         (low, high)
     };
     let step = nice_step(high - low, count);
-    let (start, end) = ((low / step).floor() * step, (high / step).ceil() * step);
+    let start = ((low / step).floor() * step).max(f64::MIN);
+    let end = ((high / step).ceil() * step).min(f64::MAX);
     let ticks = (0..count.max(1) * 4 + 4)
         .map(|ix| start + step * ix as f64)
         .take_while(|tick| *tick <= end + step * 1e-9)
diff --git a/src/charts/schedule.rs b/src/charts/schedule.rs
index 5e6f8d0..ff71bab 100644
--- a/src/charts/schedule.rs
+++ b/src/charts/schedule.rs
@@ -107,12 +107,15 @@ impl GanttChart {
     }
 
     /// A task; the ones it waits for come before it.
-    pub fn task(mut self, task: Task) -> Self {
-        assert!(
-            task.after.iter().all(|ix| *ix < self.tasks.len()),
-            "task {} waits for one not yet given",
-            task.name
-        );
+    pub fn task(mut self, mut task: Task) -> Self {
+        let known = self.tasks.len();
+        if task.after.iter().any(|ix| *ix >= known) {
+            log::error!(
+                "gantt: task {} waits for one not given; that wait is dropped",
+                task.name
+            );
+            task.after.retain(|ix| *ix < known);
+        }
         self.tasks.push(task);
         self
     }
diff --git a/src/charts/series.rs b/src/charts/series.rs
index 9cea4a9..8e1b6f5 100644
--- a/src/charts/series.rs
+++ b/src/charts/series.rs
@@ -7,12 +7,20 @@ pub struct Series {
     pub(crate) values: Vec<f64>,
 }
 
+/// The largest value a chart draws: sums and pixels of such values stay within `f32`.
+pub const LIMIT: f64 = 1e30;
+
+/// A value a chart can draw: finite and within ±`LIMIT`.
+pub(crate) fn drawable(value: f64) -> bool {
+    value.is_finite() && value.abs() <= LIMIT
+}
+
 impl Series {
     pub fn new(name: impl Into<SharedString>, values: impl IntoIterator<Item = f64>) -> Self {
         let values: Vec<f64> = values.into_iter().collect();
         assert!(
-            values.iter().all(|value| value.is_finite()),
-            "a series needs finite values"
+            values.iter().all(|value| drawable(*value)),
+            "a series needs values, within charts::LIMIT"
         );
         Self {
             name: name.into(),
@@ -36,8 +44,8 @@ impl Points {
     ) -> Self {
         let points: Vec<(f64, f64)> = points.into_iter().collect();
         assert!(
-            points.iter().all(|(x, y)| x.is_finite() && y.is_finite()),
-            "points need finite values"
+            points.iter().all(|(x, y)| drawable(*x) && drawable(*y)),
+            "points need values, within charts::LIMIT"
         );
         Self {
             name: name.into(),
@@ -55,8 +63,8 @@ impl Points {
             "a bubble needs a size for each point"
         );
         assert!(
-            sizes.iter().all(|size| size.is_finite() && *size >= 0.0),
-            "bubble sizes are not negative"
+            sizes.iter().all(|size| drawable(*size) && *size >= 0.0),
+            "bubble sizes are not negative, within charts::LIMIT"
         );
         self.sizes = Some(sizes);
         self
@@ -96,7 +104,7 @@ pub(crate) fn extent(values: impl Iterator<Item = f64>) -> (f64, f64) {
     })
 }
 
-/// Tangents for a smooth line through `points` that never overshoots between them (Fritsch–Carlson).
+/// Tangents for a smooth line through `points` that never overshoots between them (Fritsch–Carlson); points at one x rise straight.
 pub(crate) fn tangents(points: &[(f32, f32)]) -> Vec<f32> {
     let count = points.len();
     if count < 2 {
@@ -104,7 +112,10 @@ pub(crate) fn tangents(points: &[(f32, f32)]) -> Vec<f32> {
     }
     let slopes: Vec<f32> = points
         .windows(2)
-        .map(|pair| (pair[1].1 - pair[0].1) / (pair[1].0 - pair[0].0))
+        .map(|pair| {
+            let slope = (pair[1].1 - pair[0].1) / (pair[1].0 - pair[0].0);
+            if slope.is_finite() { slope } else { 0.0 }
+        })
         .collect();
     let mut tangents: Vec<f32> = (0..count)
         .map(|ix| match ix {
@@ -178,6 +189,16 @@ pub(crate) fn points_csv(clouds: &[Points]) -> String {
 mod tests {
     use super::*;
 
+    #[test]
+    fn points_at_one_x_rise_with_flat_tangents() {
+        let rising = tangents(&[(10.0, 0.0), (10.0, 5.0), (10.0, 9.0), (11.0, 9.5)]);
+        assert!(
+            rising.iter().all(|tangent| tangent.is_finite()),
+            "{rising:?}"
+        );
+        assert_eq!(&rising[..2], &[0.0, 0.0]);
+    }
+
     #[test]
     fn stacks_rise_from_zero_and_negatives_fall() {
         let stacks = stacked(&[&[2.0, -1.0], &[3.0, -2.0]]);
diff --git a/src/charts/stats.rs b/src/charts/stats.rs
index f4ec8a4..f2aaa11 100644
--- a/src/charts/stats.rs
+++ b/src/charts/stats.rs
@@ -45,7 +45,16 @@ pub(crate) struct Five {
 fn quantile(sorted: &[f64], share: f64) -> f64 {
     let at = share * (sorted.len() - 1) as f64;
     let (below, above) = (at.floor() as usize, at.ceil() as usize);
-    sorted[below] + (sorted[above] - sorted[below]) * (at - below as f64)
+    let (low, high, part) = (sorted[below], sorted[above], at - below as f64);
+    if low == high {
+        return low;
+    }
+    let lerp = low + (high - low) * part;
+    if lerp.is_finite() {
+        lerp
+    } else {
+        low * (1.0 - part) + high * part
+    }
 }
 
 pub(crate) fn five(values: &[f64]) -> Five {
@@ -149,6 +158,13 @@ pub(crate) fn steps(changes: &[(f64, bool)]) -> Vec<(f64, f64, Step)> {
 mod tests {
     use super::*;
 
+    #[test]
+    fn quartiles_across_all_of_f64_stay_finite() {
+        let spread = five(&[-f64::MAX, f64::MAX]);
+        assert!(spread.q1.is_finite() && spread.q3.is_finite());
+        assert_eq!((spread.low, spread.high), (-f64::MAX, f64::MAX));
+    }
+
     #[test]
     fn values_fall_into_equal_bins() {
         let bins = bins(&[1.0, 2.0, 2.5, 9.0, 10.0], 5);
diff --git a/src/charts/sunburst.rs b/src/charts/sunburst.rs
index e9a9003..e62b6b9 100644
--- a/src/charts/sunburst.rs
+++ b/src/charts/sunburst.rs
@@ -10,6 +10,7 @@ use super::{
     paint::{finish, measure, tint},
     pie::{bearing, wedge},
     scale::compact,
+    series::drawable,
     tiles::Tiles,
 };
 use crate::{
@@ -28,8 +29,8 @@ pub struct Slice {
 impl Slice {
     pub fn new(name: impl Into<SharedString>, value: f64) -> Self {
         assert!(
-            value.is_finite() && value >= 0.0,
-            "a slice needs a value of zero or more"
+            drawable(value) && value >= 0.0,
+            "a slice needs a value of zero or more, within charts::LIMIT"
         );
         Self {
             name: name.into(),
diff --git a/src/charts/targets.rs b/src/charts/targets.rs
index 7b94062..ed934aa 100644
--- a/src/charts/targets.rs
+++ b/src/charts/targets.rs
@@ -18,6 +18,7 @@ use super::{
     pie::{bearing, toward, wedge},
     plot::Format,
     scale::{compact, nice},
+    series::drawable,
     tiles::{Tiles, tracked},
 };
 use crate::{
@@ -38,8 +39,8 @@ pub struct Bullet {
 impl Bullet {
     pub fn new(label: impl Into<SharedString>, value: f64, target: f64) -> Self {
         assert!(
-            value.is_finite() && target.is_finite() && value >= 0.0 && target >= 0.0,
-            "a bullet reads values of zero or more"
+            drawable(value) && drawable(target) && value >= 0.0 && target >= 0.0,
+            "a bullet reads values of zero or more, within charts::LIMIT"
         );
         Self {
             label: label.into(),
@@ -54,8 +55,8 @@ impl Bullet {
         self.bands = ends.into_iter().collect();
         assert!(
             self.bands.windows(2).all(|pair| pair[0] < pair[1])
-                && self.bands.iter().all(|end| *end > 0.0),
-            "bands end in rising order"
+                && self.bands.iter().all(|end| *end > 0.0 && drawable(*end)),
+            "bands end in rising order, within charts::LIMIT"
         );
         self
     }
@@ -283,8 +284,8 @@ impl ProgressChart {
     /// A goal: how far it has come of its target.
     pub fn goal(mut self, name: impl Into<SharedString>, value: f64, target: f64) -> Self {
         assert!(
-            value.is_finite() && value >= 0.0 && target.is_finite() && target > 0.0,
-            "a goal has a positive target and a value of zero or more"
+            drawable(value) && value >= 0.0 && drawable(target) && target > 0.0,
+            "a goal has a positive target and a value of zero or more, within charts::LIMIT"
         );
         self.goals.push((name.into(), value, target));
         self
@@ -313,9 +314,10 @@ impl RenderOnce for ProgressChart {
             .iter()
             .map(|(_, value, target)| value / target)
             .collect();
+        let drawn: Vec<f64> = shares.iter().map(|share| share.min(1.0)).collect();
         let slow = motion::duration(motion::SLOW, cx);
         let (glided, moving) = glide.update(cx, |glide, _| {
-            glide.follow(std::slice::from_ref(&shares), slow)
+            glide.follow(std::slice::from_ref(&drawn), slow)
         });
         if moving {
             window.request_animation_frame();
diff --git a/src/charts/tests/limits.rs b/src/charts/tests/limits.rs
new file mode 100644
index 0000000..245c2ae
--- /dev/null
+++ b/src/charts/tests/limits.rs
@@ -0,0 +1,270 @@
+use std::{cell::Cell, rc::Rc};
+
+use gpui::{
+    AnyElement, Context, IntoElement, Modifiers, ParentElement, Render, Styled, TestAppContext,
+    Window, div, point, px,
+};
+use jiff::civil::date;
+
+use super::settle;
+use crate::{
+    charts::{
+        AreaChart, BarChart, BoxPlot, Bullet, BulletChart, CalendarHeatmap, ChordDiagram,
+        FunnelChart, HeatmapChart, Histogram, LIMIT, LineChart, ParallelCoordinates, PieChart,
+        ProgressChart, RadarChart, SankeyChart, Series, Slice, Sunburst, Treemap, ViolinPlot,
+        WaterfallChart,
+    },
+    theme::{ActiveTheme, Theme},
+};
+
+/// Every chart fed values at the edge of what it draws.
+struct Edge(u8);
+
+impl Render for Edge {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let top = Series::new("s", [LIMIT, LIMIT]);
+        let chart: AnyElement = match self.0 {
+            0 => SankeyChart::new("sankey", ["a", "b"])
+                .link(0, 1, LIMIT)
+                .into_any_element(),
+            1 => ChordDiagram::new("chord", ["a", "b"], vec![vec![0.0, LIMIT], vec![1.0, 0.0]])
+                .into_any_element(),
+            2 => Histogram::new("histogram", [-LIMIT, LIMIT]).into_any_element(),
+            3 => ViolinPlot::new("violin")
+                .group("s", [LIMIT, LIMIT])
+                .into_any_element(),
+            4 => AreaChart::new("stack", ["a", "b"])
+                .series(top.clone())
+                .series(Series::new("t", [LIMIT, LIMIT]))
+                .stacked()
+                .into_any_element(),
+            5 => WaterfallChart::new("waterfall")
+                .step("a", LIMIT)
+                .step("b", LIMIT)
+                .total("all")
+                .into_any_element(),
+            6 => Sunburst::new(
+                "sunburst",
+                [Slice::new("root", 0.0)
+                    .children([Slice::new("a", LIMIT), Slice::new("b", LIMIT)])],
+            )
+            .into_any_element(),
+            7 => Treemap::new("treemap")
+                .tile("a", LIMIT)
+                .tile("b", LIMIT)
+                .into_any_element(),
+            8 => RadarChart::new("radar", ["a", "b", "c"])
+                .series(Series::new("s", [LIMIT; 3]))
+                .into_any_element(),
+            9 => LineChart::new("rule", ["a", "b"])
+                .series(Series::new("s", [1.0, 2.0]))
+                .rule(LIMIT, "target")
+                .into_any_element(),
+            10 => BoxPlot::new("box")
+                .group("s", [-LIMIT, LIMIT])
+                .into_any_element(),
+            11 => CalendarHeatmap::new("calendar", date(9999, 12, 31), [1.0]).into_any_element(),
+            12 => ChordDiagram::new("tiny", ["a", "b"], vec![vec![0.0, 1e-40], vec![1e-40, 0.0]])
+                .into_any_element(),
+            13 => LineChart::new("far", ["a", "b"])
+                .series(Series::new("s", [1e-20, 2e-20]))
+                .rule(LIMIT, "target")
+                .into_any_element(),
+            14 => ChordDiagram::new(
+                "least",
+                ["a", "b"],
+                vec![vec![0.0, 1e-310], vec![1e-310, 0.0]],
+            )
+            .into_any_element(),
+            15 => Treemap::new("least-tiles")
+                .tile("a", 1e-310)
+                .tile("b", 1e-310)
+                .into_any_element(),
+            16 => SankeyChart::new("least-flow", ["a", "b", "c"])
+                .link(0, 1, 1e-310)
+                .link(1, 2, 1e-310)
+                .into_any_element(),
+            _ => LineChart::new("top", ["a", "b"])
+                .series(top)
+                .into_any_element(),
+        };
+        div().w(px(400.0)).h(px(240.0)).child(chart)
+    }
+}
+
+#[gpui::test]
+fn every_chart_draws_values_at_its_limit(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    for case in 0..=17 {
+        let (_, cx) = cx.add_window_view(move |_, _| Edge(case));
+        settle(cx);
+    }
+}
+
+/// A line that turns from the top limit to the bottom one, and a goal from far past its target back to twice it.
+struct Turning(Rc<Cell<bool>>);
+
+impl Render for Turning {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let turned = self.0.get();
+        let value = if turned { -LIMIT } else { LIMIT };
+        let (goal, target) = if turned { (2.0, 1.0) } else { (LIMIT, 1e-30) };
+        div()
+            .w(px(400.0))
+            .child(LineChart::new("line", ["a", "b"]).series(Series::new("s", [value, value])))
+            .child(ProgressChart::new("progress").goal("g", goal, target))
+    }
+}
+
+#[gpui::test]
+fn a_chart_glides_between_its_limits(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let turned = Rc::new(Cell::new(false));
+    let seen = turned.clone();
+    let (view, cx) = cx.add_window_view(|_, _| Turning(seen));
+    settle(cx);
+    turned.set(true);
+    view.update(cx, |_, cx| cx.notify());
+    settle(cx);
+}
+
+#[test]
+#[should_panic(expected = "within charts::LIMIT")]
+fn a_value_past_the_limit_is_refused() {
+    let _ = Series::new("s", [LIMIT * 10.0]);
+}
+
+#[test]
+#[should_panic(expected = "within charts::LIMIT")]
+fn a_band_past_the_limit_is_refused() {
+    let _ = Bullet::new("b", 1.0, 2.0).bands([LIMIT * 10.0]);
+}
+
+/// A smooth line in a box barely wider than its gutter.
+struct Sliver;
+
+impl Render for Sliver {
+    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let chart = cx.theme().chart();
+        let rem = window.rem_size();
+        let width = chart.gutter.to_pixels(rem) + chart.inset.to_pixels(rem) + px(0.000015);
+        div().w(width).h(px(240.0)).child(
+            LineChart::new("sliver", ["a", "b", "c", "d", "e"])
+                .series(Series::new("s", [1.0, 2.0, 3.0, 4.0, 5.0]))
+                .smooth(),
+        )
+    }
+}
+
+#[gpui::test]
+fn a_smooth_line_in_a_sliver_draws(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (_, cx) = cx.add_window_view(|_, _| Sliver);
+    settle(cx);
+}
+
+/// A centered sankey that shrinks under a resting pointer.
+struct Shrinking(Rc<Cell<bool>>);
+
+impl Render for Shrinking {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let width = if self.0.get() { 20.0 } else { 400.0 };
+        div()
+            .w(px(400.0))
+            .h(px(240.0))
+            .flex()
+            .flex_col()
+            .items_center()
+            .child(
+                SankeyChart::new("shrinking", ["a", "b"])
+                    .link(0, 1, 5.0)
+                    .w(px(width))
+                    .h(px(240.0)),
+            )
+    }
+}
+
+#[gpui::test]
+fn a_hovered_sankey_that_shrinks_drops_its_hover(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let shrunk = Rc::new(Cell::new(false));
+    let seen = shrunk.clone();
+    let (view, cx) = cx.add_window_view(|_, _| Shrinking(seen));
+    settle(cx);
+    cx.simulate_mouse_move(point(px(200.0), px(120.0)), None, Modifiers::none());
+    settle(cx);
+    shrunk.set(true);
+    view.update(cx, |_, cx| cx.notify());
+    settle(cx);
+}
+
+const LEAST: f64 = 1e-310;
+
+/// Every other chart fed the smallest values it takes.
+struct Least(u8);
+
+impl Render for Least {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let tiny = || Series::new("s", [LEAST, LEAST * 2.0, LEAST]);
+        let chart: AnyElement = match self.0 {
+            0 => PieChart::new("pie")
+                .slice("a", LEAST)
+                .slice("b", LEAST)
+                .into_any_element(),
+            1 => FunnelChart::new("funnel")
+                .stage("a", LEAST)
+                .stage("b", LEAST)
+                .into_any_element(),
+            2 => ParallelCoordinates::new("parallel", ["a", "b"])
+                .record("r", [LEAST, LEAST * 2.0])
+                .record("q", [LEAST * 2.0, LEAST])
+                .into_any_element(),
+            3 => BulletChart::new("bullets")
+                .bullet(Bullet::new("b", LEAST, LEAST * 2.0).bands([LEAST, LEAST * 3.0]))
+                .into_any_element(),
+            4 => ProgressChart::new("goals")
+                .goal("g", LEAST, LEAST)
+                .into_any_element(),
+            5 => HeatmapChart::new("heat", ["a", "b"])
+                .row("r", [LEAST, LEAST * 2.0])
+                .into_any_element(),
+            6 => Histogram::new("histogram", [LEAST, LEAST * 2.0, LEAST * 3.0]).into_any_element(),
+            7 => BoxPlot::new("box")
+                .group("s", [LEAST, LEAST * 2.0, LEAST * 4.0])
+                .into_any_element(),
+            8 => ViolinPlot::new("violin")
+                .group("s", [LEAST, LEAST * 2.0])
+                .into_any_element(),
+            9 => WaterfallChart::new("waterfall")
+                .step("a", LEAST)
+                .total("all")
+                .into_any_element(),
+            10 => RadarChart::new("radar", ["a", "b", "c"])
+                .series(tiny())
+                .into_any_element(),
+            11 => Sunburst::new(
+                "sunburst",
+                [Slice::new("root", LEAST).children([Slice::new("a", LEAST)])],
+            )
+            .into_any_element(),
+            12 => AreaChart::new("area", ["a", "b", "c"])
+                .series(tiny())
+                .stacked()
+                .into_any_element(),
+            _ => BarChart::new("bars", ["a", "b", "c"])
+                .series(tiny())
+                .horizontal()
+                .into_any_element(),
+        };
+        div().w(px(400.0)).h(px(240.0)).child(chart)
+    }
+}
+
+#[gpui::test]
+fn every_chart_draws_its_smallest_values(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    for case in 0..=13 {
+        let (_, cx) = cx.add_window_view(move |_, _| Least(case));
+        settle(cx);
+    }
+}
diff --git a/src/charts/tests.rs b/src/charts/tests/mod.rs
similarity index 92%
rename from src/charts/tests.rs
rename to src/charts/tests/mod.rs
index 88494ef..f160d4b 100644
--- a/src/charts/tests.rs
+++ b/src/charts/tests/mod.rs
@@ -1,3 +1,5 @@
+mod limits;
+
 use std::{
     cell::{Cell, RefCell},
     rc::Rc,
@@ -138,7 +140,7 @@ impl Render for Picked {
     }
 }
 
-fn settle(cx: &mut VisualTestContext) {
+pub(super) fn settle(cx: &mut VisualTestContext) {
     for _ in 0..3 {
         cx.run_until_parked();
         cx.update(|window, _| window.refresh());
@@ -373,3 +375,36 @@ fn a_long_band_name_widens_the_gutter_to_half_the_chart(cx: &mut TestAppContext)
         }
     }
 }
+
+/// A note, a link, an edge and a wait that name what their chart lacks.
+struct Dangling;
+
+impl Render for Dangling {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let line = LineChart::new("line", ["a", "b"])
+            .series(Series::new("s", [1.0, 2.0]))
+            .note(7, "late");
+        let sankey = SankeyChart::new("sankey", ["a", "b"])
+            .link(0, 9, 5.0)
+            .link(0, 1, 5.0);
+        let network = NetworkGraph::new("network")
+            .node("a", 0)
+            .node("b", 0)
+            .edge(0, 9);
+        let gantt = GanttChart::new("gantt")
+            .task(Task::new("t", date(2026, 3, 1), date(2026, 3, 9)).after(4));
+        div()
+            .w(px(400.0))
+            .child(line)
+            .child(sankey)
+            .child(network)
+            .child(gantt)
+    }
+}
+
+#[gpui::test]
+fn entries_past_their_lists_are_skipped(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (_, cx) = cx.add_window_view(|_, _| Dangling);
+    settle(cx);
+}
diff --git a/src/charts/tiles.rs b/src/charts/tiles.rs
index 8a92369..812b327 100644
--- a/src/charts/tiles.rs
+++ b/src/charts/tiles.rs
@@ -14,6 +14,7 @@ use super::{
     parts::ChartTooltip,
     plot::Format,
     scale::compact,
+    series::drawable,
 };
 use crate::{
     theme::{ActiveTheme, Radius, TextSize},
@@ -105,8 +106,8 @@ impl Treemap {
 
     pub fn tile(mut self, name: impl Into<SharedString>, value: f64) -> Self {
         assert!(
-            value.is_finite() && value >= 0.0,
-            "a tile needs a value of zero or more"
+            drawable(value) && value >= 0.0,
+            "a tile needs a value of zero or more, within charts::LIMIT"
         );
         self.tiles.push((name.into(), value));
         self
@@ -282,8 +283,8 @@ impl HeatmapChart {
             "a heatmap row needs a value per column"
         );
         assert!(
-            values.iter().all(|value| value.is_finite()),
-            "a heatmap needs finite values"
+            values.iter().all(|value| drawable(*value)),
+            "a heatmap needs values, within charts::LIMIT"
         );
         self.rows.push((label.into(), values));
         self
diff --git a/tasks/panics.md b/tasks/panics.md
index 3f33ed8..ca7c764 100644
--- a/tasks/panics.md
+++ b/tasks/panics.md
@@ -29,7 +29,7 @@ Each item reads every site in its folders, fixes what the rules name, updates ca
 - [x] P12 Data Display — `src/data_display`
 - [x] P13 Lists & Trees — `src/lists`
 - [x] P14 Tables — `src/tables`
-- [ ] P15 Charts — `src/charts`
+- [x] P15 Charts — `src/charts`
 - [ ] P16 Finance — `src/finance`
 - [ ] P17 Code Editor — `src/editor`
 - [ ] P18 Terminal — `src/terminal`
@@ -79,3 +79,4 @@ One line per item: what changed, what stayed and why, review rounds.
 - P12: a featured column past the columns features none; a gauge past its scale pegs; usage parts past the total fill it and repeat hues past eight; stars above max log and fill. Kept: one-value contracts, a comparison row's shape, construction. Review: 3 rounds (round 2 met an edit that had not applied).
 - P13: a directory listing's selected name gone from its entries picks none. Kept: one-value contracts; activation, folder split, single-select sections and tree rows hold by construction. Review: 1 round.
 - P14: a pivot field missing from its data draws an error line; a gone group-by column leaves the table ungrouped; a merge past the sheet is skipped; each logs. Kept: row shapes of one snapshot, one-value contracts, builder misuse, construction. Review: 1 round.
+- P15: chart values are finite and within ±`charts::LIMIT` (1e30), so sums and pixels stay in `f32`; scales work in halves and bound a share to ±1e4 ranges; chord and sankey size by shares; quartiles, weekday labels, flat tangents and a zero-width sankey's hover hold; notes, links, edges and waits past their lists are skipped. Review: 5 rounds, the cap; round 5's finding (points at one x) is fixed and tested, and P16's review checks it.