diff --git a/src/base/common/downloadUtil.test.ts b/src/base/common/downloadUtil.test.ts
index 8684c8e1c..7ab107f39 100644
--- a/src/base/common/downloadUtil.test.ts
+++ b/src/base/common/downloadUtil.test.ts
@@ -1,6 +1,9 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
-import { downloadFile } from '@/base/common/downloadUtil'
+import {
+  downloadFile,
+  extractFilenameFromContentDisposition
+} from '@/base/common/downloadUtil'
 
 let mockIsCloud = false
 
@@ -155,10 +158,14 @@ describe('downloadUtil', () => {
       const testUrl = 'https://storage.googleapis.com/bucket/file.bin'
       const blob = new Blob(['test'])
       const blobFn = vi.fn().mockResolvedValue(blob)
+      const headersMock = {
+        get: vi.fn().mockReturnValue(null)
+      }
       fetchMock.mockResolvedValue({
         ok: true,
         status: 200,
-        blob: blobFn
+        blob: blobFn,
+        headers: headersMock
       } as unknown as Response)
 
       downloadFile(testUrl)
@@ -195,5 +202,147 @@ describe('downloadUtil', () => {
       expect(createObjectURLSpy).not.toHaveBeenCalled()
       consoleSpy.mockRestore()
     })
+
+    it('uses filename from Content-Disposition header in cloud mode', async () => {
+      mockIsCloud = true
+      const testUrl = 'https://storage.googleapis.com/bucket/abc123.png'
+      const blob = new Blob(['test'])
+      const blobFn = vi.fn().mockResolvedValue(blob)
+      const headersMock = {
+        get: vi.fn().mockReturnValue('attachment; filename="user-friendly.png"')
+      }
+      fetchMock.mockResolvedValue({
+        ok: true,
+        status: 200,
+        blob: blobFn,
+        headers: headersMock
+      } as unknown as Response)
+
+      downloadFile(testUrl)
+
+      expect(fetchMock).toHaveBeenCalledWith(testUrl)
+      const fetchPromise = fetchMock.mock.results[0].value as Promise<Response>
+      await fetchPromise
+      const blobPromise = blobFn.mock.results[0].value as Promise<Blob>
+      await blobPromise
+      await Promise.resolve()
+      expect(headersMock.get).toHaveBeenCalledWith('Content-Disposition')
+      expect(mockLink.download).toBe('user-friendly.png')
+    })
+
+    it('uses RFC 5987 filename from Content-Disposition header', async () => {
+      mockIsCloud = true
+      const testUrl = 'https://storage.googleapis.com/bucket/abc123.png'
+      const blob = new Blob(['test'])
+      const blobFn = vi.fn().mockResolvedValue(blob)
+      const headersMock = {
+        get: vi
+          .fn()
+          .mockReturnValue(
+            'attachment; filename="fallback.png"; filename*=UTF-8\'\'%E4%B8%AD%E6%96%87.png'
+          )
+      }
+      fetchMock.mockResolvedValue({
+        ok: true,
+        status: 200,
+        blob: blobFn,
+        headers: headersMock
+      } as unknown as Response)
+
+      downloadFile(testUrl)
+
+      const fetchPromise = fetchMock.mock.results[0].value as Promise<Response>
+      await fetchPromise
+      const blobPromise = blobFn.mock.results[0].value as Promise<Blob>
+      await blobPromise
+      await Promise.resolve()
+      expect(mockLink.download).toBe('中文.png')
+    })
+
+    it('falls back to provided filename when Content-Disposition is missing', async () => {
+      mockIsCloud = true
+      const testUrl = 'https://storage.googleapis.com/bucket/abc123.png'
+      const blob = new Blob(['test'])
+      const blobFn = vi.fn().mockResolvedValue(blob)
+      const headersMock = {
+        get: vi.fn().mockReturnValue(null)
+      }
+      fetchMock.mockResolvedValue({
+        ok: true,
+        status: 200,
+        blob: blobFn,
+        headers: headersMock
+      } as unknown as Response)
+
+      downloadFile(testUrl, 'my-fallback.png')
+
+      const fetchPromise = fetchMock.mock.results[0].value as Promise<Response>
+      await fetchPromise
+      const blobPromise = blobFn.mock.results[0].value as Promise<Blob>
+      await blobPromise
+      await Promise.resolve()
+      expect(mockLink.download).toBe('my-fallback.png')
+    })
+  })
+
+  describe('extractFilenameFromContentDisposition', () => {
+    it('returns null for null header', () => {
+      expect(extractFilenameFromContentDisposition(null)).toBeNull()
+    })
+
+    it('returns null for empty header', () => {
+      expect(extractFilenameFromContentDisposition('')).toBeNull()
+    })
+
+    it('extracts filename from simple quoted format', () => {
+      const header = 'attachment; filename="test-file.png"'
+      expect(extractFilenameFromContentDisposition(header)).toBe(
+        'test-file.png'
+      )
+    })
+
+    it('extracts filename from unquoted format', () => {
+      const header = 'attachment; filename=test-file.png'
+      expect(extractFilenameFromContentDisposition(header)).toBe(
+        'test-file.png'
+      )
+    })
+
+    it('extracts filename from RFC 5987 format', () => {
+      const header = "attachment; filename*=UTF-8''test%20file.png"
+      expect(extractFilenameFromContentDisposition(header)).toBe(
+        'test file.png'
+      )
+    })
+
+    it('prefers RFC 5987 format over simple format', () => {
+      const header =
+        'attachment; filename="fallback.png"; filename*=UTF-8\'\'preferred.png'
+      expect(extractFilenameFromContentDisposition(header)).toBe(
+        'preferred.png'
+      )
+    })
+
+    it('handles unicode characters in RFC 5987 format', () => {
+      const header =
+        "attachment; filename*=UTF-8''%E4%B8%AD%E6%96%87%E6%96%87%E4%BB%B6.png"
+      expect(extractFilenameFromContentDisposition(header)).toBe('中文文件.png')
+    })
+
+    it('falls back to simple format when RFC 5987 decoding fails', () => {
+      const header =
+        'attachment; filename="fallback.png"; filename*=UTF-8\'\'%invalid'
+      expect(extractFilenameFromContentDisposition(header)).toBe('fallback.png')
+    })
+
+    it('handles header with only attachment disposition', () => {
+      const header = 'attachment'
+      expect(extractFilenameFromContentDisposition(header)).toBeNull()
+    })
+
+    it('handles case-insensitive filename parameter', () => {
+      const header = 'attachment; FILENAME="test.png"'
+      expect(extractFilenameFromContentDisposition(header)).toBe('test.png')
+    })
   })
 })
diff --git a/src/base/common/downloadUtil.ts b/src/base/common/downloadUtil.ts
index 4462dd1a7..78bb1ca56 100644
--- a/src/base/common/downloadUtil.ts
+++ b/src/base/common/downloadUtil.ts
@@ -75,14 +75,57 @@ const extractFilenameFromUrl = (url: string): string | null => {
   }
 }
 
+/**
+ * Extract filename from Content-Disposition header
+ * Handles both simple format: attachment; filename="name.png"
+ * And RFC 5987 format: attachment; filename="fallback.png"; filename*=UTF-8''encoded%20name.png
+ * @param header - The Content-Disposition header value
+ * @returns The extracted filename or null if not found
+ */
+export function extractFilenameFromContentDisposition(
+  header: string | null
+): string | null {
+  if (!header) return null
+
+  // Try RFC 5987 extended format first (filename*=UTF-8''...)
+  const extendedMatch = header.match(/filename\*=UTF-8''([^;]+)/i)
+  if (extendedMatch?.[1]) {
+    try {
+      return decodeURIComponent(extendedMatch[1])
+    } catch {
+      // Fall through to simple format
+    }
+  }
+
+  // Try simple quoted format: filename="..."
+  const quotedMatch = header.match(/filename="([^"]+)"/i)
+  if (quotedMatch?.[1]) {
+    return quotedMatch[1]
+  }
+
+  // Try unquoted format: filename=...
+  const unquotedMatch = header.match(/filename=([^;\s]+)/i)
+  if (unquotedMatch?.[1]) {
+    return unquotedMatch[1]
+  }
+
+  return null
+}
+
 const downloadViaBlobFetch = async (
   href: string,
-  filename: string
+  fallbackFilename: string
 ): Promise<void> => {
   const response = await fetch(href)
   if (!response.ok) {
     throw new Error(`Failed to fetch ${href}: ${response.status}`)
   }
+
+  // Try to get filename from Content-Disposition header (set by backend)
+  const contentDisposition = response.headers.get('Content-Disposition')
+  const headerFilename =
+    extractFilenameFromContentDisposition(contentDisposition)
+
   const blob = await response.blob()
-  downloadBlob(filename, blob)
+  downloadBlob(headerFilename ?? fallbackFilename, blob)
 }