fix: normalize browser UNC file paths (#3750)

src/shared/browser-url.test.ts

@@ -42,6 +42,12 @@ describe('browser-url helpers', () => {
     expect(normalizeBrowserNavigationUrl('C:\\Users\\me\\Downloads\\Example.ipynb')).toBe(
       'file:///C:/Users/me/Downloads/Example.ipynb'
     )
+    expect(normalizeBrowserNavigationUrl('\\\\server\\share\\Example.ipynb')).toBe(
+      'file://server/share/Example.ipynb'
+    )
+    expect(
+      normalizeBrowserNavigationUrl('\\\\wsl.localhost\\Ubuntu\\home\\me\\Example.ipynb')
+    ).toBe('file://wsl.localhost/Ubuntu/home/me/Example.ipynb')
   })
 
   // Why: in-app preview is fine (sandboxed webview), but handing file:// to
@@ -49,6 +55,7 @@ describe('browser-url helpers', () => {
   // arbitrary paths. External-open paths must still refuse file://.
   it('rejects file:// for external opens even though it is allowed in-app', () => {
     expect(normalizeExternalBrowserUrl('file:///etc/passwd')).toBeNull()
+    expect(normalizeExternalBrowserUrl('\\\\server\\share\\Example.ipynb')).toBeNull()
   })
 
   it('returns null for non-URL input without search engine opt-in', () => {

src/shared/browser-url.ts

@@ -9,6 +9,7 @@ const LOCAL_ADDRESS_PATTERN =
 // a URL attempt, not a search query.
 const LOOKS_LIKE_URL_PATTERN = /^[^\s]+\.[a-z]{2,}(\/.*)?$/i
 const WINDOWS_ABSOLUTE_PATH_PATTERN = /^[A-Za-z]:[\\/][^\s]*$/
+const WINDOWS_UNC_PATH_PATTERN = /^\\\\[^\s\\/]+[\\/][^\\/]+(?:[\\/].*)?$/
 const UNIX_ABSOLUTE_PATH_PATTERN = /^\/[^\s]*$/
 
 export type SearchEngine = 'google' | 'duckduckgo' | 'bing' | 'kagi'
@@ -146,6 +147,12 @@ function absolutePathToFileUrl(filePath: string): string {
     : `file:///${segments.join('/')}`
 }
 
+function windowsUncPathToFileUrl(filePath: string): string {
+  const normalizedPath = filePath.replaceAll('\\', '/').replace(/^\/+/, '')
+  const [host, ...pathSegments] = normalizedPath.split('/')
+  return `file://${host}/${pathSegments.map(encodeURIComponent).join('/')}`
+}
+
 export function normalizeBrowserNavigationUrl(
   rawUrl: string,
   searchEngine?: SearchEngine | null,
@@ -164,6 +171,10 @@ export function normalizeBrowserNavigationUrl(
     }
   }
 
+  if (WINDOWS_UNC_PATH_PATTERN.test(trimmed)) {
+    return windowsUncPathToFileUrl(trimmed)
+  }
+
   if (UNIX_ABSOLUTE_PATH_PATTERN.test(trimmed) || WINDOWS_ABSOLUTE_PATH_PATTERN.test(trimmed)) {
     return absolutePathToFileUrl(trimmed)
   }