feat(x): inline charts in chat via a charts skill

The chat's markdown fence override now renders ```chart blocks
(the same ChartBlockSchema notes use) as interactive recharts inline —
the mermaid pattern. A new ChartRenderer handles line/bar/pie with
multi-series support, light/dark theming, and a quiet placeholder
while the fence body is still streaming.

ChartBlockSchema.y widens to string | string[] for multi-series
charts (notes chart block updated to map series too), with a
chartSeries() helper in shared.

A new 'charts' skill teaches the model the fence format, form
selection (line/bar/pie, no mixed scales), and data honesty rules;
loaded on demand like any skill.

apps/x/apps/renderer/src/components/ai-elements/markdown-code-override.tsx

@@ -1,6 +1,7 @@
 import { isValidElement, type JSX } from 'react'
 import { FilePathCard } from './file-path-card'
 import { MermaidRenderer } from '@/components/mermaid-renderer'
+import { ChartRenderer } from '@/components/chart-renderer'
 
 export function MarkdownPreOverride(props: JSX.IntrinsicElements['pre']) {
   const { children, ...rest } = props
@@ -31,6 +32,17 @@ export function MarkdownPreOverride(props: JSX.IntrinsicElements['pre']) {
         return <MermaidRenderer source={text} />
       }
     }
+    if (
+      typeof childProps.className === 'string' &&
+      childProps.className.includes('language-chart')
+    ) {
+      const text = typeof childProps.children === 'string'
+        ? childProps.children.trim()
+        : ''
+      if (text) {
+        return <ChartRenderer source={text} />
+      }
+    }
   }
 
   // Passthrough for all other code blocks - return children directly

apps/x/apps/renderer/src/components/chart-renderer.tsx

@@ -0,0 +1,147 @@
+import { useMemo } from 'react'
+import { BarChart3 } from 'lucide-react'
+import { blocks } from '@x/shared'
+import { useTheme } from '@/contexts/theme-context'
+import {
+  LineChart, Line,
+  BarChart, Bar,
+  PieChart, Pie, Cell,
+  XAxis, YAxis, CartesianGrid, Tooltip, ResponsiveContainer, Legend,
+} from 'recharts'
+
+// Categorical palettes validated for CVD separation and surface contrast on
+// each mode's chart surface (dataviz six-checks validator). Slots are
+// assigned to series in fixed order — the dark column is the same hues
+// re-stepped for the dark surface, not a different palette.
+const SERIES_COLORS_LIGHT = ['#2a78d6', '#008300', '#e87ba4', '#eda100', '#1baf7a', '#eb6834']
+const SERIES_COLORS_DARK = ['#3987e5', '#008300', '#d55181', '#c98500', '#199e70', '#d95926']
+
+interface ChartRendererProps {
+  /** Raw contents of a ```chart fence: ChartBlockSchema JSON. */
+  source: string
+}
+
+/**
+ * Inline chart for chat messages: renders a ```chart fenced block (same
+ * ChartBlockSchema the notes chart block uses) via recharts. Invalid or
+ * still-streaming JSON renders as a quiet placeholder rather than an error —
+ * the fence body arrives token by token while the model writes it.
+ */
+export function ChartRenderer({ source }: ChartRendererProps) {
+  const { resolvedTheme } = useTheme()
+  const colors = resolvedTheme === 'dark' ? SERIES_COLORS_DARK : SERIES_COLORS_LIGHT
+  const gridStroke = resolvedTheme === 'dark' ? '#3a3a38' : '#e4e4e0'
+  const textColor = resolvedTheme === 'dark' ? '#c3c2b7' : '#52514e'
+
+  const config = useMemo(() => {
+    try {
+      return blocks.ChartBlockSchema.parse(JSON.parse(source))
+    } catch {
+      return null
+    }
+  }, [source])
+
+  if (!config || !config.data || config.data.length === 0) {
+    return (
+      <div className="my-2 flex h-24 items-center justify-center gap-2 rounded-md border border-border bg-muted/30 text-xs text-muted-foreground">
+        <BarChart3 className="size-3.5" />
+        Preparing chart…
+      </div>
+    )
+  }
+
+  const data = config.data
+  const series = blocks.chartSeries(config)
+  const axisProps = {
+    stroke: textColor,
+    tick: { fill: textColor, fontSize: 11 },
+    tickLine: false,
+  }
+
+  return (
+    <div className="my-2 rounded-md border border-border bg-card p-3">
+      {config.title && (
+        <div className="mb-2 text-sm font-medium text-foreground">{config.title}</div>
+      )}
+      <ResponsiveContainer width="100%" height={260}>
+        {config.chart === 'line' ? (
+          <LineChart data={data}>
+            <CartesianGrid strokeDasharray="3 3" stroke={gridStroke} vertical={false} />
+            <XAxis dataKey={config.x} {...axisProps} />
+            <YAxis {...axisProps} width={44} />
+            <Tooltip
+              contentStyle={{
+                backgroundColor: resolvedTheme === 'dark' ? '#1a1a19' : '#fcfcfb',
+                border: `1px solid ${gridStroke}`,
+                borderRadius: 6,
+                fontSize: 12,
+              }}
+            />
+            {series.length > 1 && <Legend wrapperStyle={{ fontSize: 12 }} />}
+            {series.map((key, i) => (
+              <Line
+                key={key}
+                type="monotone"
+                dataKey={key}
+                stroke={colors[i % colors.length]}
+                strokeWidth={2}
+                dot={{ r: 2.5 }}
+              />
+            ))}
+          </LineChart>
+        ) : config.chart === 'bar' ? (
+          <BarChart data={data}>
+            <CartesianGrid strokeDasharray="3 3" stroke={gridStroke} vertical={false} />
+            <XAxis dataKey={config.x} {...axisProps} />
+            <YAxis {...axisProps} width={44} />
+            <Tooltip
+              cursor={{ fill: resolvedTheme === 'dark' ? '#ffffff14' : '#00000009' }}
+              contentStyle={{
+                backgroundColor: resolvedTheme === 'dark' ? '#1a1a19' : '#fcfcfb',
+                border: `1px solid ${gridStroke}`,
+                borderRadius: 6,
+                fontSize: 12,
+              }}
+            />
+            {series.length > 1 && <Legend wrapperStyle={{ fontSize: 12 }} />}
+            {series.map((key, i) => (
+              <Bar
+                key={key}
+                dataKey={key}
+                fill={colors[i % colors.length]}
+                radius={[4, 4, 0, 0]}
+                maxBarSize={48}
+              />
+            ))}
+          </BarChart>
+        ) : (
+          <PieChart>
+            <Tooltip
+              contentStyle={{
+                backgroundColor: resolvedTheme === 'dark' ? '#1a1a19' : '#fcfcfb',
+                border: `1px solid ${gridStroke}`,
+                borderRadius: 6,
+                fontSize: 12,
+              }}
+            />
+            <Legend wrapperStyle={{ fontSize: 12 }} />
+            <Pie
+              data={data}
+              dataKey={series[0]}
+              nameKey={config.x}
+              cx="50%"
+              cy="50%"
+              outerRadius={90}
+              stroke={resolvedTheme === 'dark' ? '#1a1a19' : '#fcfcfb'}
+              strokeWidth={2}
+            >
+              {data.map((_, i) => (
+                <Cell key={i} fill={colors[i % colors.length]} />
+              ))}
+            </Pie>
+          </PieChart>
+        )}
+      </ResponsiveContainer>
+    </div>
+  )
+}

apps/x/apps/renderer/src/extensions/chart-block.tsx

@@ -64,6 +64,7 @@ function ChartBlockView({ node, deleteNode }: { node: { attrs: Record<string, un
     if (error) return <div className="chart-block-error-msg">{error}</div>
     if (!data || data.length === 0) return <div className="chart-block-empty">No data</div>
 
+    const series = blocks.chartSeries(config!)
     return (
       <ResponsiveContainer width="100%" height={250}>
         {config!.chart === 'line' ? (
@@ -73,7 +74,9 @@ function ChartBlockView({ node, deleteNode }: { node: { attrs: Record<string, un
             <YAxis />
             <Tooltip />
             <Legend />
-            <Line type="monotone" dataKey={config!.y} stroke="#8884d8" />
+            {series.map((key, index) => (
+              <Line key={key} type="monotone" dataKey={key} stroke={CHART_COLORS[index % CHART_COLORS.length]} />
+            ))}
           </LineChart>
         ) : config!.chart === 'bar' ? (
           <BarChart data={data}>
@@ -82,13 +85,15 @@ function ChartBlockView({ node, deleteNode }: { node: { attrs: Record<string, un
             <YAxis />
             <Tooltip />
             <Legend />
-            <Bar dataKey={config!.y} fill="#8884d8" />
+            {series.map((key, index) => (
+              <Bar key={key} dataKey={key} fill={CHART_COLORS[index % CHART_COLORS.length]} />
+            ))}
           </BarChart>
         ) : (
           <PieChart>
             <Tooltip />
             <Legend />
-            <Pie data={data} dataKey={config!.y} nameKey={config!.x} cx="50%" cy="50%" outerRadius={80} label>
+            <Pie data={data} dataKey={series[0]} nameKey={config!.x} cx="50%" cy="50%" outerRadius={80} label>
               {data.map((_, index) => (
                 <Cell key={`cell-${index}`} fill={CHART_COLORS[index % CHART_COLORS.length]} />
               ))}

apps/x/packages/core/src/runtime/assembly/skills/charts/skill.ts

@@ -0,0 +1,74 @@
+export const skill = String.raw`
+# Charts
+
+Load this skill when the user asks for a chart, graph, plot, trend, comparison, or "visualize" — or when data you've gathered (prices over time, counts per category, proportions) would land better as a picture than a table.
+
+## How it works
+
+Emit a fenced code block with language \`chart\` anywhere in your reply. The app renders it as an interactive chart inline (tooltips, legend, light/dark theming are handled for you — never pick colors yourself). Everything outside the fence is normal markdown.
+
+\`\`\`\`
+\`\`\`chart
+{ ...JSON config... }
+\`\`\`
+\`\`\`\`
+
+## Config schema
+
+- **\`chart\`** (required): \`"line"\` | \`"bar"\` | \`"pie"\`
+- **\`data\`** (required): array of flat objects — the rows to plot. Put REAL values you gathered this turn here; never invent numbers.
+- **\`x\`** (required): key of the label/category field in each row
+- **\`y\`** (required): key of the value field — a string for one series, or an array of keys for several series on one chart
+- **\`title\`** (optional): short heading shown above the chart
+
+## Picking the form
+
+- **line** — change over time (prices, counts by date). X is the time field.
+- **bar** — compare magnitudes across categories (issues per label, revenue per region).
+- **pie** — proportions of a whole; only with ≤ 6 slices, otherwise use a bar.
+- Two measures with very different scales (e.g. a $600 stock vs a $5 one): do NOT mix them on one chart — either normalize to % change and say so in the title, or emit two chart blocks.
+
+## Examples
+
+Multi-series line (comparison over time, normalized):
+
+\`\`\`chart
+{
+  "chart": "line",
+  "title": "5-Day % Change",
+  "x": "date",
+  "y": ["AAPL", "NVDA", "SPY"],
+  "data": [
+    { "date": "Jul 15", "AAPL": 0, "NVDA": 0, "SPY": 0 },
+    { "date": "Jul 16", "AAPL": -0.4, "NVDA": 1.2, "SPY": 0.1 },
+    { "date": "Jul 17", "AAPL": -1.1, "NVDA": 0.8, "SPY": -0.3 }
+  ]
+}
+\`\`\`
+
+Single-series bar:
+
+\`\`\`chart
+{
+  "chart": "bar",
+  "title": "Open issues by area",
+  "x": "area",
+  "y": "count",
+  "data": [
+    { "area": "sync", "count": 14 },
+    { "area": "editor", "count": 9 },
+    { "area": "billing", "count": 3 }
+  ]
+}
+\`\`\`
+
+## Rules
+
+- Data must come from what you actually fetched or computed this turn — never fabricate points to make a chart possible. Too little real data? Say so instead of charting.
+- Keep it readable: ≤ ~30 rows per chart, ≤ 6 series. Round values sensibly.
+- Numbers must be JSON numbers, not strings ("3.1", "5%" won't plot).
+- Follow the chart with one sentence of takeaway — what the reader should see in it.
+- One chart per distinct question; don't emit several variants of the same data.
+`;
+
+export default skill;

apps/x/packages/core/src/runtime/assembly/skills/index.ts

@@ -29,6 +29,7 @@ import backgroundTaskSkill from "./background-task/skill.js";
 import notifyUserSkill from "./notify-user/skill.js";
 import appsSkill from "./apps/skill.js";
 import slackSkill from "./slack/skill.js";
+import chartsSkill from "./charts/skill.js";
 
 const CURRENT_DIR = path.dirname(fileURLToPath(import.meta.url));
 const CATALOG_PREFIX = "src/runtime/assembly/skills";
@@ -77,6 +78,12 @@ const definitions: SkillDefinition[] = [
     summary: "Prepare for meetings by gathering context about attendees from the knowledge base.",
     content: meetingPrepSkill,
   },
+  {
+    id: "charts",
+    title: "Charts",
+    summary: "Render interactive charts (line, bar, pie) inline in the chat reply. Use when the user asks for a chart/graph/visualization or when gathered data is clearer as a picture.",
+    content: chartsSkill,
+  },
   {
     id: "organize-files",
     title: "Organize Files",

apps/x/packages/shared/src/blocks.ts

@@ -47,11 +47,18 @@ export const ChartBlockSchema = z.object({
   data: z.array(z.record(z.string(), z.unknown())).optional(),
   source: z.string().optional(),
   x: z.string(),
-  y: z.string(),
+  // One series (string) or several (array of data keys). Pie ignores all
+  // but the first.
+  y: z.union([z.string(), z.array(z.string()).min(1)]),
 });
 
 export type ChartBlock = z.infer<typeof ChartBlockSchema>;
 
+/** The y series list regardless of which form the block used. */
+export function chartSeries(block: ChartBlock): string[] {
+  return Array.isArray(block.y) ? block.y : [block.y];
+}
+
 export const TableBlockSchema = z.object({
   columns: z.array(z.string()),
   data: z.array(z.record(z.string(), z.unknown())),