chore: import upstream snapshot with attribution

tests/content-utils.test.ts

@@ -0,0 +1,43 @@
+import { describe, it, expect } from 'vitest'
+import { normalizeContentBlocks } from '../src/content-utils.js'
+
+describe('normalizeContentBlocks', () => {
+  it('passes an array of blocks through unchanged', () => {
+    const blocks = [{ type: 'text', text: 'hi' }, { type: 'tool_use', text: '' }]
+    expect(normalizeContentBlocks(blocks)).toBe(blocks)
+  })
+
+  it('wraps a string as a single text block (the issue #441 case)', () => {
+    expect(normalizeContentBlocks('hello world')).toEqual([{ type: 'text', text: 'hello world' }])
+  })
+
+  it('returns an empty array for null / undefined', () => {
+    expect(normalizeContentBlocks(null)).toEqual([])
+    expect(normalizeContentBlocks(undefined)).toEqual([])
+  })
+
+  it('returns an empty array for other non-array values', () => {
+    // Defensive against corrupt records: a number/object content must not throw downstream.
+    expect(normalizeContentBlocks(42 as unknown as string)).toEqual([])
+    expect(normalizeContentBlocks({ type: 'text' } as unknown as string)).toEqual([])
+  })
+
+  it('drops null/undefined elements inside an array (avoids the same crash one level down)', () => {
+    const dirty = [{ type: 'text', text: 'ok' }, null, undefined, { type: 'tool_use' }] as unknown as Array<{ type?: string }>
+    const out = normalizeContentBlocks(dirty)
+    expect(out).toEqual([{ type: 'text', text: 'ok' }, { type: 'tool_use' }])
+    expect(() => out.filter(b => b.type === 'text')).not.toThrow()
+  })
+
+  it('returns the same reference for a clean array (no copy)', () => {
+    const clean = [{ type: 'text', text: 'a' }, { type: 'tool_use' }]
+    expect(normalizeContentBlocks(clean)).toBe(clean)
+  })
+
+  it('the result is always safe to .filter/.some over', () => {
+    const inputs = ['a string', null, undefined, [{ type: 'text' }], [{ type: 'text' }, null]] as const
+    for (const input of inputs) {
+      expect(() => normalizeContentBlocks(input as never).filter(b => b.type === 'text')).not.toThrow()
+    }
+  })
+})