diff --git a/apps/storybook/stories/ProbeTheme.stories.tsx b/apps/storybook/stories/ProbeTheme.stories.tsx
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+// Copyright (c) Meta Platforms, Inc. and affiliates.
+
+/**
+ * @file ProbeTheme.stories.tsx
+ * @input The active Storybook theme selected in the toolbar
+ * @output A visual reference for every top-level defineTheme axis
+ * @position Core/Themes — theme-system verification, not a component demo
+ *
+ * Do not wrap these stories in <Theme>. The toolbar and visual gate must own
+ * the active theme, otherwise the probe theme cannot be selected or tested.
+ */
+
+import * as React from 'react';
+import type {Meta, StoryObj} from '@storybook/react';
+import * as stylex from '@stylexjs/stylex';
+import {Badge} from '@astryxdesign/core/Badge';
+import {Button} from '@astryxdesign/core/Button';
+import {Card} from '@astryxdesign/core/Card';
+import {CheckboxInput} from '@astryxdesign/core/CheckboxInput';
+import {CodeBlock} from '@astryxdesign/core/CodeBlock';
+import {Icon} from '@astryxdesign/core/Icon';
+import {RadioList, RadioListItem} from '@astryxdesign/core/RadioList';
+import {Stack} from '@astryxdesign/core/Stack';
+import {Switch} from '@astryxdesign/core/Switch';
+import {Heading, Text} from '@astryxdesign/core/Text';
+import {useTheme} from '@astryxdesign/core/theme';
+
+const meta = {
+  title: 'Core/Themes/Probe Theme',
+  parameters: {
+    layout: 'fullscreen',
+  },
+} satisfies Meta;
+
+export default meta;
+type Story = StoryObj<typeof meta>;
+
+const iconNames = [
+  'close',
+  'check',
+  'success',
+  'warning',
+  'info',
+  'calendar',
+  'search',
+  'copy',
+] as const;
+
+const code = `type ThemeAxis =
+  | 'components'
+  | 'tokens'
+  | 'icons'
+  | 'indicators'
+  | 'fonts'
+  | 'syntax';
+
+export const covered = true;`;
+
+function AxisCard({
+  title,
+  children,
+}: {
+  title: string;
+  children: React.ReactNode;
+}) {
+  return (
+    <Card>
+      <div {...stylex.props(styles.axisCard)}>
+        <Heading level={3}>{title}</Heading>
+        {children}
+      </div>
+    </Card>
+  );
+}
+
+function TokenSwatches() {
+  const {token} = useTheme();
+  const tokens = [
+    ['accent', '--color-accent', styles.accent],
+    ['body', '--color-background-body', styles.body],
+    ['text', '--color-text-primary', styles.text],
+    ['border', '--color-border', styles.border],
+  ] as const;
+
+  return (
+    <div {...stylex.props(styles.swatchGrid)}>
+      {tokens.map(([label, name, swatch]) => (
+        <div key={name} {...stylex.props(styles.swatchItem)}>
+          <div {...stylex.props(styles.swatch, swatch)} />
+          <Text type="label">{label}</Text>
+          <Text type="supporting">{token(name)}</Text>
+        </div>
+      ))}
+    </div>
+  );
+}
+
+function RegistrySpecimen() {
+  const [checked, setChecked] = React.useState<boolean | 'indeterminate'>(true);
+  const [radio, setRadio] = React.useState('one');
+  const [enabled, setEnabled] = React.useState(true);
+
+  return (
+    <Stack direction="vertical" gap={5}>
+      <div {...stylex.props(styles.iconRow)}>
+        {iconNames.map(name => (
+          <div key={name} {...stylex.props(styles.iconCell)}>
+            <Icon icon={name} size="lg" label={name} />
+            <Text type="supporting">{name}</Text>
+          </div>
+        ))}
+      </div>
+
+      <div {...stylex.props(styles.controlGrid)}>
+        <CheckboxInput
+          label="Checkbox indicator"
+          value={checked}
+          onChange={setChecked}
+        />
+        <Switch label="Switch control" value={enabled} onChange={setEnabled} />
+        <RadioList label="Radio indicator" value={radio} onChange={setRadio}>
+          <RadioListItem label="First" value="one" />
+          <RadioListItem label="Second" value="two" />
+        </RadioList>
+      </div>
+    </Stack>
+  );
+}
+
+function ComponentSpecimen() {
+  return (
+    <Stack direction="vertical" gap={5}>
+      <div {...stylex.props(styles.row)}>
+        <Button label="Primary" variant="primary" />
+        <Button label="Secondary" variant="secondary" />
+        <Button label="Ghost" variant="ghost" />
+        <Button label="Destructive" variant="destructive" />
+      </div>
+      <div {...stylex.props(styles.row)}>
+        <Badge label="Neutral" variant="neutral" />
+        <Badge label="Info" variant="info" />
+        <Badge label="Success" variant="success" />
+        <Badge label="Warning" variant="warning" />
+        <Badge label="Error" variant="error" />
+      </div>
+    </Stack>
+  );
+}
+
+function AllAxesSheet() {
+  const {name, mode} = useTheme();
+
+  return (
+    <main {...stylex.props(styles.page)}>
+      <div {...stylex.props(styles.header)}>
+        <div>
+          <Heading level={1}>Probe theme — all axes</Heading>
+          <Text type="body">
+            Select <strong>Probe (test fixture)</strong> in the Theme toolbar.
+            Every axis should become unmistakably synthetic.
+          </Text>
+        </div>
+        <Badge
+          label={`${name} · ${mode}`}
+          variant={name === 'probe' ? 'success' : 'neutral'}
+        />
+      </div>
+
+      <div {...stylex.props(styles.grid)}>
+        <AxisCard title="1 · Component targets">
+          <ComponentSpecimen />
+        </AxisCard>
+
+        <AxisCard title="2 · Tokens">
+          <TokenSwatches />
+        </AxisCard>
+
+        <AxisCard title="3 + 4 · Icon and indicator registries">
+          <RegistrySpecimen />
+        </AxisCard>
+
+        <AxisCard title="5 · Typography">
+          <Stack direction="vertical" gap={2}>
+            <Heading level={2}>AstryxProbeFace heading</Heading>
+            <Text type="body">Body text inherits the probe font token.</Text>
+            <Text type="code">const fontAxis = 'covered';</Text>
+          </Stack>
+        </AxisCard>
+
+        <div {...stylex.props(styles.wide)}>
+          <AxisCard title="6 · Syntax">
+            <CodeBlock
+              code={code}
+              language="typescript"
+              title="theme-axes.ts"
+              hasLineNumbers
+            />
+          </AxisCard>
+        </div>
+      </div>
+    </main>
+  );
+}
+
+/**
+ * All six top-level defineTheme axes on one surface. Switch the Theme toolbar
+ * between Neutral and Probe; this story never pins its own theme.
+ */
+export const AllAxes: Story = {
+  name: 'All Axes',
+  render: () => <AllAxesSheet />,
+};
+
+/** Component targets only, for a compact pixel-diff surface. */
+export const ComponentTargets: Story = {
+  name: 'Component Targets',
+  render: () => (
+    <main {...stylex.props(styles.compactPage)}>
+      <ComponentSpecimen />
+    </main>
+  ),
+};
+
+/** Icon and indicator swaps, separated from CSS component overrides. */
+export const Registries: Story = {
+  render: () => (
+    <main {...stylex.props(styles.compactPage)}>
+      <RegistrySpecimen />
+    </main>
+  ),
+};
+
+const styles = stylex.create({
+  page: {
+    backgroundColor: 'var(--color-background-body)',
+    minHeight: '100vh',
+    padding: 32,
+  },
+  compactPage: {
+    backgroundColor: 'var(--color-background-surface)',
+    minHeight: '100vh',
+    padding: 32,
+  },
+  header: {
+    alignItems: 'flex-start',
+    display: 'flex',
+    gap: 24,
+    justifyContent: 'space-between',
+    marginBottom: 24,
+  },
+  grid: {
+    display: 'grid',
+    gap: 16,
+    gridTemplateColumns: 'repeat(2, minmax(0, 1fr))',
+  },
+  wide: {
+    gridColumn: '1 / -1',
+  },
+  axisCard: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: 16,
+    padding: 20,
+  },
+  row: {
+    alignItems: 'center',
+    display: 'flex',
+    flexWrap: 'wrap',
+    gap: 12,
+  },
+  iconRow: {
+    display: 'grid',
+    gap: 12,
+    gridTemplateColumns: 'repeat(4, minmax(0, 1fr))',
+  },
+  iconCell: {
+    alignItems: 'center',
+    display: 'flex',
+    flexDirection: 'column',
+    gap: 4,
+  },
+  controlGrid: {
+    display: 'grid',
+    gap: 16,
+    gridTemplateColumns: 'repeat(3, minmax(0, 1fr))',
+  },
+  swatchGrid: {
+    display: 'grid',
+    gap: 12,
+    gridTemplateColumns: 'repeat(4, minmax(0, 1fr))',
+  },
+  swatchItem: {
+    display: 'flex',
+    flexDirection: 'column',
+    gap: 4,
+    minWidth: 0,
+  },
+  swatch: {
+    borderColor: 'var(--color-border)',
+    borderRadius: 'var(--radius-element)',
+    borderStyle: 'solid',
+    borderWidth: 2,
+    height: 48,
+  },
+  accent: {
+    backgroundColor: 'var(--color-accent)',
+  },
+  body: {
+    backgroundColor: 'var(--color-background-body)',
+  },
+  text: {
+    backgroundColor: 'var(--color-text-primary)',
+  },
+  border: {
+    backgroundColor: 'var(--color-border)',
+  },
+});