diff --git a/src/__tests__/handbook.shape-invariants.test.ts b/src/__tests__/handbook.shape-invariants.test.ts
new file mode 100644
index 000000000..3dc6f8715
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+++ b/src/__tests__/handbook.shape-invariants.test.ts
@@ -0,0 +1,109 @@
+/**
+ * Shape-invariants for src/app/[locale]/contribute-handbook/handbook.ts.
+ *
+ * `handbookCards` is the data source rendered by the Community Handbook
+ * page (`src/app/[locale]/contribute-handbook/page.tsx`). It ships:
+ *
+ *   - a stable `id` used as a React key,
+ *   - an inline SVG `iconPath` fed into a shared icon component,
+ *   - bg/icon Tailwind color classes selected by design,
+ *   - a `link` that MUST resolve inside `/docs/contributing/` because that
+ *     is the shared-section route wired up in
+ *     `src/app/docs/page-map.ts::buildNavNodes`. A typo like
+ *     `"/docs/contribute/…"` or a missing leading slash would silently
+ *     dead-end the handbook cards — no compile error, no runtime error.
+ *
+ * Nothing in `src/__tests__/` imported this module before this file
+ * (companion invariants tests already exist for `programs/programs.ts`
+ * via versions.shape-invariants patterns). These tests are pure data
+ * checks — they run in milliseconds and catch every class of "someone
+ * edited the JSON and broke a card" regression the codebase has hit on
+ * peer data modules.
+ */
+import { describe, it, expect } from 'vitest'
+import { handbookCards, type HandbookCard } from '@/app/[locale]/contribute-handbook/handbook'
+
+describe('handbookCards — shape invariants', () => {
+  it('exports at least one card', () => {
+    expect(Array.isArray(handbookCards)).toBe(true)
+    expect(handbookCards.length).toBeGreaterThan(0)
+  })
+
+  it('each card has every required non-empty string field', () => {
+    const required: (keyof HandbookCard)[] = [
+      'id',
+      'iconType',
+      'iconPath',
+      'bgColor',
+      'iconColor',
+      'link',
+    ]
+    for (const card of handbookCards) {
+      for (const key of required) {
+        expect(typeof card[key]).toBe('string')
+        expect((card[key] as string).length).toBeGreaterThan(0)
+      }
+    }
+  })
+
+  it('card ids are unique (React key stability)', () => {
+    const ids = handbookCards.map(c => c.id)
+    expect(new Set(ids).size).toBe(ids.length)
+  })
+
+  it('every link starts with /docs/contributing/', () => {
+    // buildNavNodes in src/app/docs/page-map.ts routes shared-section
+    // pages under /docs/contributing/... — a typo here would silently
+    // 404 the handbook card.
+    for (const card of handbookCards) {
+      expect(card.link).toMatch(/^\/docs\/contributing\//)
+    }
+  })
+
+  it('no link contains a whitespace character', () => {
+    for (const card of handbookCards) {
+      expect(card.link).not.toMatch(/\s/)
+    }
+  })
+
+  it('links are unique', () => {
+    const links = handbookCards.map(c => c.link)
+    expect(new Set(links).size).toBe(links.length)
+  })
+
+  it('bgColor uses a Tailwind bg-*-500/20 or bg-*/20 rgba token', () => {
+    // Design system contract: opacity-20 background pill. A regression
+    // to solid bg-*-500 (no /20) would visually dominate the card.
+    for (const card of handbookCards) {
+      expect(card.bgColor).toMatch(/^bg-[a-z]+-\d{2,3}\/\d+$/)
+    }
+  })
+
+  it('iconColor uses a Tailwind text-*-400 token', () => {
+    // Design system contract: text-*-400 icon on the /20 background.
+    for (const card of handbookCards) {
+      expect(card.iconColor).toMatch(/^text-[a-z]+-\d{2,3}$/)
+    }
+  })
+
+  it('iconType is kebab-case (matches the shared icon lookup keys)', () => {
+    for (const card of handbookCards) {
+      expect(card.iconType).toMatch(/^[a-z][a-z0-9-]*[a-z0-9]$/)
+    }
+  })
+
+  it('iconPath contains only SVG path-data characters', () => {
+    // SVG `d=` attribute allowed chars: command letters, digits,
+    // decimal point, comma, whitespace, minus. Anything else would
+    // break the raw SVG the page inlines.
+    for (const card of handbookCards) {
+      expect(card.iconPath).toMatch(/^[MmLlHhVvCcSsQqTtAaZz0-9.,\s-]+$/)
+    }
+  })
+
+  it('iconPath begins with a valid SVG move-to command (M or m)', () => {
+    for (const card of handbookCards) {
+      expect(card.iconPath).toMatch(/^[Mm]/)
+    }
+  })
+})