diff --git a/.changeset/fix-nan-tree-rendering.md b/.changeset/fix-nan-tree-rendering.md
new file mode 100644
index 00000000..e4d79a01
--- /dev/null
+++ b/.changeset/fix-nan-tree-rendering.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/devtools-ui': patch
+---
+
+Fix `NaN` rendering in `JsonTree`, previously rendered null, now correctly displays `NaN`
diff --git a/packages/devtools-ui/src/components/tree.tsx b/packages/devtools-ui/src/components/tree.tsx
index bcbe7870..225b34a8 100644
--- a/packages/devtools-ui/src/components/tree.tsx
+++ b/packages/devtools-ui/src/components/tree.tsx
@@ -71,7 +71,9 @@ function JsonValue(props: {
         }
 
         if (typeof props.value === 'number') {
-          return <span class={styles().tree.valueNumber}>{props.value}</span>
+          return (
+            <span class={styles().tree.valueNumber}>{String(props.value)}</span>
+          )
         }
 
         if (typeof props.value === 'boolean') {
diff --git a/packages/devtools-ui/tests/tree.tsx b/packages/devtools-ui/tests/tree.tsx
new file mode 100644
index 00000000..7a7e14c0
--- /dev/null
+++ b/packages/devtools-ui/tests/tree.tsx
@@ -0,0 +1,237 @@
+/** @jsxImportSource solid-js */
+import { afterEach, describe, expect, it } from 'vitest'
+import { render } from 'solid-js/web'
+import { JsonTree } from '../src/components/tree'
+import { ThemeContextProvider } from '../src/components/theme'
+
+// types
+import type { CollapsiblePaths } from '../src/utils/deep-keys'
+
+let container: HTMLDivElement
+let dispose: () => void
+
+function renderTree<TData, TName extends CollapsiblePaths<TData>>(
+  value: any,
+  extraProps: {
+    defaultExpansionDepth?: number
+    collapsePaths?: Array<TName>
+    config?: { dateFormat?: string }
+    copyable?: boolean
+  } = {},
+) {
+  container = document.createElement('div')
+  document.body.appendChild(container)
+  dispose = render(
+    () => (
+      <ThemeContextProvider theme="dark">
+        <JsonTree value={value} {...extraProps} />
+      </ThemeContextProvider>
+    ),
+    container,
+  )
+  return container
+}
+
+afterEach(() => {
+  dispose()
+  container.remove()
+})
+
+describe('JsonTree', () => {
+  describe('string', () => {
+    it('renders a string value wrapped in quotes', () => {
+      const el = renderTree('hello world')
+      expect(el.textContent).toContain('"hello world"')
+    })
+
+    it('renders an empty string as ""', () => {
+      const el = renderTree('')
+      expect(el.textContent).toContain('""')
+    })
+
+    it('renders a string with special characters', () => {
+      const el = renderTree('foo & <bar>')
+      expect(el.textContent).toContain('foo & <bar>')
+    })
+  })
+
+  describe('number', () => {
+    it('renders a positive integer', () => {
+      const el = renderTree(42)
+      expect(el.textContent).toContain('42')
+    })
+
+    it('renders a negative number', () => {
+      const el = renderTree(-7.5)
+      expect(el.textContent).toContain('-7.5')
+    })
+
+    it('renders zero', () => {
+      const el = renderTree(0)
+      expect(el.textContent).toContain('0')
+    })
+
+    it('renders NaN as "NaN"', () => {
+      const el = renderTree(NaN)
+      expect(el.textContent).toContain('NaN')
+    })
+  })
+
+  describe('boolean', () => {
+    it('renders true as the string "true"', () => {
+      const el = renderTree(true)
+      expect(el.textContent).toContain('true')
+    })
+
+    it('renders false as the string "false"', () => {
+      const el = renderTree(false)
+      expect(el.textContent).toContain('false')
+    })
+  })
+
+  describe('null', () => {
+    it('renders null as the string "null"', () => {
+      const el = renderTree(null)
+      expect(el.textContent).toContain('null')
+    })
+  })
+
+  describe('undefined', () => {
+    it('renders undefined as the string "undefined"', () => {
+      const el = renderTree(undefined)
+      expect(el.textContent).toContain('undefined')
+    })
+  })
+
+  describe('function', () => {
+    it('renders a named function as its string representation', () => {
+      function myFunc() {
+        return 1
+      }
+      const el = renderTree(myFunc)
+      expect(el.textContent).toContain('myFunc')
+    })
+
+    it('renders an arrow function as its string representation', () => {
+      const arrow = () => 'result'
+      const el = renderTree(arrow)
+      expect(el.textContent).toContain('=>')
+    })
+  })
+
+  describe('array', () => {
+    it('renders an empty array as []', () => {
+      const el = renderTree([])
+      expect(el.textContent).toContain('[]')
+    })
+
+    it('renders an expanded array with its items visible', () => {
+      const el = renderTree([1, 2, 3])
+      expect(el.textContent).toContain('[')
+      expect(el.textContent).toContain(']')
+      expect(el.textContent).toContain('1')
+      expect(el.textContent).toContain('2')
+      expect(el.textContent).toContain('3')
+    })
+
+    it('renders an array of strings with quoted values', () => {
+      const el = renderTree(['alpha', 'beta'])
+      expect(el.textContent).toContain('"alpha"')
+      expect(el.textContent).toContain('"beta"')
+    })
+
+    it('shows item count when array is nested inside an object', () => {
+      const el = renderTree({ list: [1, 2, 3] })
+      expect(el.textContent).toContain('3 items')
+    })
+
+    it('renders a mixed-type array', () => {
+      const el = renderTree([1, 'two', true, null])
+      expect(el.textContent).toContain('1')
+      expect(el.textContent).toContain('"two"')
+      expect(el.textContent).toContain('true')
+      expect(el.textContent).toContain('null')
+    })
+  })
+
+  describe('object', () => {
+    it('renders an empty object as {}', () => {
+      const el = renderTree({})
+      expect(el.textContent).toContain('{}')
+    })
+
+    it('renders object keys and their values', () => {
+      const el = renderTree({ name: 'Alice', age: 30 })
+      expect(el.textContent).toContain('"name"')
+      expect(el.textContent).toContain('"Alice"')
+      expect(el.textContent).toContain('"age"')
+      expect(el.textContent).toContain('30')
+    })
+
+    it('renders nested objects when within expansion depth', () => {
+      const el = renderTree({ a: { b: 'deep' } }, { defaultExpansionDepth: 2 })
+      expect(el.textContent).toContain('"a"')
+      expect(el.textContent).toContain('"b"')
+      expect(el.textContent).toContain('"deep"')
+    })
+
+    it('shows item count for nested objects', () => {
+      const el = renderTree({ meta: { x: 1, y: 2 } })
+      expect(el.textContent).toContain('2 items')
+    })
+  })
+
+  describe('Date', () => {
+    it('renders a Date with the default DDMMMYY format', () => {
+      const date = new Date('2024-01-15T12:00:00Z')
+      const el = renderTree(date)
+      expect(el.textContent).toContain('Jan')
+    })
+
+    it('renders a Date with a custom dateFormat', () => {
+      const date = new Date('2024-06-20T00:00:00Z')
+      const el = renderTree(date, { config: { dateFormat: 'YYYY-MM-DD' } })
+      expect(el.textContent).toContain('2024-06-20')
+    })
+  })
+
+  describe('expansion depth', () => {
+    it('collapses deeply nested objects beyond defaultExpansionDepth', () => {
+      const el = renderTree(
+        { a: { b: { c: 'deep' } } },
+        { defaultExpansionDepth: 1 },
+      )
+      expect(el.textContent).not.toContain('"c"')
+      expect(el.textContent).not.toContain('"deep"')
+    })
+
+    it('expands all levels within defaultExpansionDepth', () => {
+      const el = renderTree({ a: { b: 'value' } }, { defaultExpansionDepth: 2 })
+      expect(el.textContent).toContain('"value"')
+    })
+
+    it('collapses paths listed in collapsePaths', () => {
+      const el = renderTree(
+        { user: { name: 'Bob', address: { city: 'NY' } } },
+        { defaultExpansionDepth: 3, collapsePaths: ['user.address'] as any },
+      )
+      expect(el.textContent).toContain('"name"')
+      expect(el.textContent).not.toContain('"city"')
+    })
+  })
+
+  describe('key rendering', () => {
+    it('renders quoted key names for primitive values', () => {
+      const el = renderTree({ count: 5, label: 'test' })
+      expect(el.textContent).toContain('"count"')
+      expect(el.textContent).toContain('"label"')
+    })
+
+    it('renders array brackets around array values', () => {
+      const el = renderTree([10, 20])
+      const text = String(el.textContent)
+      expect(text.indexOf('[')).toBeLessThan(text.indexOf('10'))
+      expect(text.indexOf('10')).toBeLessThan(text.indexOf(']'))
+    })
+  })
+})
diff --git a/packages/devtools-ui/vite.config.ts b/packages/devtools-ui/vite.config.ts
index 6f3f1659..72e16ea8 100644
--- a/packages/devtools-ui/vite.config.ts
+++ b/packages/devtools-ui/vite.config.ts
@@ -9,6 +9,8 @@ const config = defineConfig({
   test: {
     name: packageJson.name,
     dir: './',
+    include: ['tests/**/*.{ts,tsx}'],
+    exclude: ['tests/test-setup.ts', '**/node_modules/**'],
     watch: false,
     environment: 'jsdom',
     setupFiles: ['./tests/test-setup.ts'],