fix(desktop): tag and preview Windows absolute paths (C:\, UNC)

apps/desktop/src/components/assistant-ui/tool/fallback-model.test.ts

@@ -7,9 +7,11 @@ import {
   clampForDisplay,
   countDiffLineStats,
   inlineDiffFromResult,
+  isPreviewableTarget,
   MAX_TOOL_RENDER_CHARS,
   prettyJson,
-  type ToolPart
+  type ToolPart,
+  toolPreviewOutcome
 } from './fallback-model'
 
 const part = (overrides: Partial<ToolPart>): ToolPart => ({
@@ -464,6 +466,27 @@ describe('buildToolView title actions', () => {
   })
 })
 
+// #85132: Windows agents write `C:\\...` / UNC paths; those must get the same
+// artifact preview tag a POSIX `/Users/...` path gets.
+describe('Windows absolute preview targets', () => {
+  it.each(['C:\\Users\\me\\report.html', 'D:/work/report.htm', '\\\\server\\share\\report.html'])(
+    'tags a written %s as a previewable artifact',
+    path => {
+      const outcome = toolPreviewOutcome(
+        part({ args: { content: '<h1>hi</h1>', path }, result: { bytes_written: 11 }, toolName: 'write_file' })
+      )
+
+      expect(outcome.previewTarget).toBe(path)
+      expect(isPreviewableTarget(outcome.previewTarget)).toBe(true)
+    }
+  )
+
+  it('keeps non-HTML Windows files out of the preview tag, like POSIX ones', () => {
+    expect(isPreviewableTarget('C:\\Users\\me\\notes.txt')).toBe(isPreviewableTarget('/Users/me/notes.txt'))
+    expect(isPreviewableTarget('C:\\Users\\me\\notes.txt')).toBe(false)
+  })
+})
+
 describe('clampForDisplay', () => {
   it('passes short payloads through untouched', () => {
     expect(clampForDisplay('hello')).toBe('hello')

apps/desktop/src/components/assistant-ui/tool/fallback-model/targets.ts

@@ -1,3 +1,5 @@
+import { isWindowsAbsolutePath } from '@/lib/path-compare'
+
 import type { ToolPart } from './types'
 
 export function looksLikeUrl(value: string): boolean {
@@ -5,7 +7,7 @@ export function looksLikeUrl(value: string): boolean {
 }
 
 export function looksLikePath(value: string): boolean {
-  return /^file:\/\//i.test(value) || /^(?:\/|\.{1,2}\/|~\/).+/.test(value)
+  return /^file:\/\//i.test(value) || /^(?:\/|\.{1,2}\/|~\/).+/.test(value) || isWindowsAbsolutePath(value)
 }
 
 export function isPreviewableTarget(target: string): boolean {
@@ -17,7 +19,7 @@ export function isPreviewableTarget(target: string): boolean {
   return Boolean(
     target &&
     (/^file:\/\//i.test(target) ||
-      /^(?:\/|\.{1,2}\/|~\/).+\.html?$/i.test(target) ||
+      (looksLikePath(target) && /\.html?$/i.test(target)) ||
       /^https?:\/\/(?:localhost|127\.0\.0\.1|0\.0\.0\.0|\[::1\])/i.test(target))
   )
 }

apps/desktop/src/lib/local-preview.test.ts

@@ -148,6 +148,19 @@ describe('remote HTML previews', () => {
     expect(localPreviewTarget('/tmp/report\\draft.html')?.url).toBe('file:///tmp/report%5Cdraft.html')
   })
 
+  // #85132: a Windows absolute path is absolute; joining it onto cwd made
+  // `/repo/C:\\Users\\...` which no filesystem has.
+  it.each(['C:\\Users\\me\\report.html', 'C:/Users/me/report.html', '\\\\server\\share\\report.html'])(
+    'treats Windows absolute path %s as absolute instead of joining it onto cwd',
+    raw => {
+      expect(localPreviewTarget(raw, '/repo')).toMatchObject({ label: 'report.html', path: raw, previewKind: 'html' })
+    }
+  )
+
+  it('still joins relative paths onto cwd', () => {
+    expect(localPreviewTarget('out/report.html', '/repo')?.path).toBe('/repo/out/report.html')
+  })
+
   it('preserves POSIX double-slash file paths', () => {
     expect(localPreviewTarget('//srv/share/report #1?.html')?.url).toBe('file:////srv/share/report%20%231%3F.html')
   })

apps/desktop/src/lib/local-preview.ts

@@ -1,6 +1,7 @@
 import DOMPurify from 'dompurify'
 
 import { isDesktopFsRemoteMode, readDesktopFileDataUrl, readDesktopFileText } from '@/lib/desktop-fs'
+import { isWindowsAbsolutePath } from '@/lib/path-compare'
 import type { PreviewTarget } from '@/store/preview'
 
 const HTML_EXTENSIONS = new Set(['.htm', '.html'])
@@ -221,7 +222,7 @@ export function localPreviewTarget(rawTarget: string, cwd?: string | null): Prev
     } catch {
       path = raw.replace(/^file:\/\//i, '')
     }
-  } else if (!raw.startsWith('/') && cwd) {
+  } else if (!raw.startsWith('/') && !isWindowsAbsolutePath(raw) && cwd) {
     path = joinPath(cwd, raw)
   }
 

apps/desktop/src/lib/path-compare.test.ts

@@ -1,6 +1,16 @@
 import { describe, expect, it } from 'vitest'
 
-import { cleanPath, comparisonPath, isUnderPath } from './path-compare'
+import { cleanPath, comparisonPath, isUnderPath, isWindowsAbsolutePath } from './path-compare'
+
+describe('isWindowsAbsolutePath', () => {
+  it.each(['C:\\Users\\me', 'd:/work', '\\\\server\\share'])('accepts %s', path => {
+    expect(isWindowsAbsolutePath(path)).toBe(true)
+  })
+
+  it.each(['/home/me', './out', 'out\\report.html', 'C:relative', 'https://x.com'])('rejects %s', path => {
+    expect(isWindowsAbsolutePath(path)).toBe(false)
+  })
+})
 
 describe('cleanPath', () => {
   it('unifies separators and drops trailing slashes', () => {

apps/desktop/src/lib/path-compare.ts

@@ -5,6 +5,10 @@
  *  case. Compare through these rather than `===` / `startsWith`.
  */
 
+/** Windows drive (`C:\\`, `C:/`) or UNC (`\\\\server\\share`) absolute path.
+ *  Such a path never gets joined onto a cwd. */
+export const isWindowsAbsolutePath = (path: string): boolean => /^(?:[A-Za-z]:[\\/]|\\\\)/.test(path)
+
 /** POSIX-style spelling: one separator, no trailing slash. */
 export const cleanPath = (path: string): string => path.trim().replace(/\\/g, '/').replace(/\/+$/, '') || '/'
 

apps/desktop/src/lib/preview-targets.test.ts

@@ -1,6 +1,24 @@
 import { describe, expect, it } from 'vitest'
 
-import { extractPreviewTargets, previewTargetFromMarkdownHref, stripPreviewTargets } from './preview-targets'
+import {
+  extractPreviewTargets,
+  previewName,
+  previewTargetFromMarkdownHref,
+  stripPreviewTargets
+} from './preview-targets'
+
+describe('previewName', () => {
+  // #85132: `new URL('C:\\...')` parses the drive letter as a scheme, which
+  // labelled the tag with the whole backslash path.
+  it.each([
+    'C:\\Users\\me\\report.html',
+    'C:/Users/me/report.html',
+    '\\\\server\\share\\report.html',
+    '/Users/me/report.html'
+  ])('labels %s by its file name', target => {
+    expect(previewName(target)).toBe('report.html')
+  })
+})
 
 describe('preview target detection', () => {
   it('does not infer preview targets from raw paths or URLs', () => {

apps/desktop/src/lib/preview-targets.ts

@@ -1,3 +1,5 @@
+import { isWindowsAbsolutePath } from '@/lib/path-compare'
+
 const PREVIEW_MARKDOWN_RE = /\[Preview:[^\]]+\]\((?<href>#preview[:/][^)]+)\)/gi
 
 export function stripPreviewTargets(text: string): string {
@@ -37,6 +39,11 @@ export function previewTargetFromMarkdownHref(href?: string): string | null {
 }
 
 export function previewName(target: string): string {
+  // `new URL('C:\\...')` would read the drive letter as a URL scheme.
+  if (isWindowsAbsolutePath(target)) {
+    return target.split(/[\\/]/).filter(Boolean).pop() || target
+  }
+
   try {
     const url = new URL(target)