diff --git a/app/api/related/route.test.ts b/app/api/related/route.test.ts
new file mode 100644
index 0000000..2315a71
--- /dev/null
+++ b/app/api/related/route.test.ts
@@ -0,0 +1,65 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { GET } from './route'
+import { getSupabaseAdmin } from '@/lib/supabaseAdmin'
+
+vi.mock('@/lib/supabaseAdmin', () => ({
+  getSupabaseAdmin: vi.fn(),
+}))
+
+describe('GET /api/related', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('falls back to the category when no tag matches exist', async () => {
+    const primaryQuery = {
+      select: vi.fn().mockReturnThis(),
+      eq: vi.fn().mockReturnThis(),
+      neq: vi.fn().mockReturnThis(),
+      limit: vi.fn().mockReturnThis(),
+      overlaps: vi.fn().mockReturnThis(),
+      order: vi.fn().mockResolvedValue({ data: [], error: null }),
+    }
+
+    const categoryResult = [
+      {
+        id: 'category-match',
+        title: 'Category Match',
+        description: 'A fallback result',
+        logo: null,
+        category: 'Productivity',
+        tier: 'free',
+        upvotes: 3,
+      },
+    ]
+    const categoryQuery = {
+      select: vi.fn().mockReturnThis(),
+      eq: vi.fn().mockReturnThis(),
+      neq: vi.fn().mockReturnThis(),
+      not: vi.fn(),
+      order: vi.fn().mockReturnThis(),
+      limit: vi.fn().mockResolvedValue({ data: categoryResult, error: null }),
+    }
+    categoryQuery.not.mockImplementation((_column, _operator, value) => {
+      if (value === '()') {
+        throw new Error('invalid empty in filter')
+      }
+      return categoryQuery
+    })
+
+    const from = vi.fn()
+      .mockReturnValueOnce(primaryQuery)
+      .mockReturnValueOnce(categoryQuery)
+    vi.mocked(getSupabaseAdmin).mockReturnValue({ from } as never)
+
+    const response = await GET(
+      new Request(
+        'http://localhost/api/related?id=current&category=Productivity&tags=missing',
+      ),
+    )
+
+    expect(response.status).toBe(200)
+    await expect(response.json()).resolves.toEqual({ data: categoryResult })
+    expect(categoryQuery.not).not.toHaveBeenCalled()
+  })
+})
diff --git a/app/api/related/route.ts b/app/api/related/route.ts
index 5c248be..f631ac0 100644
--- a/app/api/related/route.ts
+++ b/app/api/related/route.ts
@@ -31,13 +31,18 @@ export async function GET(req: Request) {
     let result = data ?? []
 
     if (data && data.length < 3 && tags.length > 0) {
-      const { data: categoryData, error: catError } = await supabase
+      let categoryQuery = supabase
         .from('software_submissions')
         .select(columns)
         .eq('status', 'approved')
         .eq('category', category)
         .neq('id', currentId)
-        .not('id', 'in', `(${data.map((d) => d.id).join(',')})`)
+
+      if (data.length > 0) {
+        categoryQuery = categoryQuery.not('id', 'in', `(${data.map((d) => d.id).join(',')})`)
+      }
+
+      const { data: categoryData, error: catError } = await categoryQuery
         .order('upvotes', { ascending: false })
         .limit(6 - data.length)