fix(desktop): allow Obsidian deep links in openExternal

apps/desktop/electron/external-url.test.ts

@@ -0,0 +1,51 @@
+import assert from 'node:assert/strict'
+
+import { test } from 'vitest'
+
+import { isAllowedShellOpenExternalUrl, SHELL_OPEN_EXTERNAL_PROTOCOLS } from './external-url'
+
+test('allowlist keeps the original web + mail schemes', () => {
+  assert.equal(SHELL_OPEN_EXTERNAL_PROTOCOLS.has('http:'), true)
+  assert.equal(SHELL_OPEN_EXTERNAL_PROTOCOLS.has('https:'), true)
+  assert.equal(SHELL_OPEN_EXTERNAL_PROTOCOLS.has('mailto:'), true)
+})
+
+test('isAllowedShellOpenExternalUrl accepts http(s) and mailto', () => {
+  assert.equal(isAllowedShellOpenExternalUrl('https://example.com/path'), true)
+  assert.equal(isAllowedShellOpenExternalUrl('http://127.0.0.1:5174/'), true)
+  assert.equal(isAllowedShellOpenExternalUrl('mailto:user@example.com'), true)
+})
+
+test('isAllowedShellOpenExternalUrl accepts Obsidian vault deep links', () => {
+  // Regression: Desktop chat previously threw "Invalid external URL" for
+  // obsidian:// because openExternalUrl only allowed http/https/mailto.
+  const vaultLink =
+    'obsidian://open?vault=b9dec633969aa228&file=Policy%2FExample.md'
+
+  assert.equal(isAllowedShellOpenExternalUrl(vaultLink), true)
+  assert.equal(isAllowedShellOpenExternalUrl('obsidian://open?vault=Lead%20Maine'), true)
+  assert.equal(isAllowedShellOpenExternalUrl('OBSIDIAN://open?vault=x'), true)
+})
+
+test('isAllowedShellOpenExternalUrl rejects empty and unparseable input', () => {
+  assert.equal(isAllowedShellOpenExternalUrl(''), false)
+  assert.equal(isAllowedShellOpenExternalUrl('   '), false)
+  assert.equal(isAllowedShellOpenExternalUrl(null), false)
+  assert.equal(isAllowedShellOpenExternalUrl(undefined), false)
+  assert.equal(isAllowedShellOpenExternalUrl('not a url'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('/relative/path.md'), false)
+})
+
+test('isAllowedShellOpenExternalUrl rejects dangerous or unlisted schemes', () => {
+  // file: is handled via openPath, not this allowlist
+  assert.equal(isAllowedShellOpenExternalUrl('file:///C:/Users/x/note.md'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('javascript:alert(1)'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('data:text/html,hi'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('vbscript:msgbox(1)'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('chrome://settings'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('about:blank'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('ms-settings:bluetooth'), false)
+  // Not yet allowlisted — add deliberately if a product surface needs them
+  assert.equal(isAllowedShellOpenExternalUrl('vscode://file/tmp/x'), false)
+  assert.equal(isAllowedShellOpenExternalUrl('cursor://file/tmp/x'), false)
+})

apps/desktop/electron/external-url.ts

@@ -0,0 +1,36 @@
+// Protocols that Desktop may hand to the OS via shell.openExternal (or the
+// WSL→Windows `cmd /c start` path). Kept as an explicit allowlist so chat
+// markdown can't drive arbitrary custom handlers (javascript:, data:, ms-*,
+// etc.). `file:` is intentionally NOT here — openExternalUrl routes it through
+// shell.openPath after path hardening instead.
+//
+// App deep-link schemes go here only when:
+//   1. a real product surface wants them clickable in chat, and
+//   2. the handler is a known local desktop app (not a web navigation).
+// Obsidian vault deep links (`obsidian://open?vault=…&file=…`) are the first.
+
+export const SHELL_OPEN_EXTERNAL_PROTOCOLS = new Set([
+  'http:',
+  'https:',
+  'mailto:',
+  'obsidian:'
+])
+
+/** True when `rawUrl` parses and its protocol is on the shell-open allowlist. */
+export function isAllowedShellOpenExternalUrl(rawUrl: unknown): boolean {
+  const raw = String(rawUrl ?? '').trim()
+
+  if (!raw) {
+    return false
+  }
+
+  let parsed: URL
+
+  try {
+    parsed = new URL(raw)
+  } catch {
+    return false
+  }
+
+  return SHELL_OPEN_EXTERNAL_PROTOCOLS.has(parsed.protocol.toLowerCase())
+}

apps/desktop/electron/main.ts

@@ -91,6 +91,7 @@ import {
 import { describeDevCdpDecision, resolveDevCdpPort } from './dev-cdp'
 import { installEmbedReferer } from './embed-referer'
 import { createEventDeduper } from './event-dedupe'
+import { isAllowedShellOpenExternalUrl } from './external-url'
 import { findGitBash as _findGitBash } from './find-git-bash'
 import { installFoundInPageForwarder, performFind, stopFind } from './find-in-page'
 import { createFirstRunSetupGate } from './first-run-setup-gate'
@@ -1350,7 +1351,9 @@ function openExternalUrl(rawUrl) {
     return true
   }
 
-  if (!['http:', 'https:', 'mailto:'].includes(parsed.protocol)) {
+  // Explicit scheme allowlist (http/https/mailto + known local app deep
+  // links like obsidian://). See electron/external-url.ts.
+  if (!isAllowedShellOpenExternalUrl(parsed.toString())) {
     return false
   }