fix: WebviewUrl::App hash fragment bug — tool windows loading empty page

ROOT CAUSE FOUND: WebviewUrl::App takes a PathBuf, not a URL.
Passing "index.html#/tool/ping?sessionId=abc" treated the ENTIRE
string including # and ? as a file path. Tauri looked for a file
literally named "index.html#/tool/ping?sessionId=abc" which doesn't
exist. The webview loaded an empty/404 page and WKWebView killed
the content process, closing the window instantly.

Fix:
- Rust: split URL at '#' — pass only "index.html" to WebviewUrl::App,
  then set the hash fragment via window.eval() after build()
- Vue: App.vue now listens for 'hashchange' event in addition to
  checking hash on mount, so the eval-injected hash triggers the
  correct tool/detached mode

This was NEVER a CSP issue, focus issue, crossorigin issue, or
async chunk loading issue. It was always a bad file path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/src/commands/window_commands.rs

@@ -2,9 +2,12 @@ use tauri::AppHandle;
 use tauri::WebviewWindowBuilder;
 
 /// Open a child window from the Rust side using WebviewWindowBuilder.
-/// This is more reliable than JS-side WebviewWindow on macOS WKWebView.
+///
+/// The `url` parameter supports hash fragments (e.g. "index.html#/tool/ping?sessionId=abc").
+/// WebviewUrl::App takes a PathBuf and cannot handle hash/query — so we load plain
+/// index.html and set the hash via JS after the window is created.
 #[tauri::command]
-pub async fn open_child_window(
+pub fn open_child_window(
     app_handle: AppHandle,
     label: String,
     title: String,
@@ -12,13 +15,26 @@ pub async fn open_child_window(
     width: f64,
     height: f64,
 ) -> Result<(), String> {
-    let webview_url = tauri::WebviewUrl::App(url.into());
-    WebviewWindowBuilder::new(&app_handle, &label, webview_url)
+    // Split "index.html#/tool/ping?sessionId=abc" into path and fragment
+    let (path, hash) = match url.split_once('#') {
+        Some((p, h)) => (p.to_string(), Some(format!("#{}", h))),
+        None => (url.clone(), None),
+    };
+
+    let webview_url = tauri::WebviewUrl::App(path.into());
+    let window = WebviewWindowBuilder::new(&app_handle, &label, webview_url)
         .title(&title)
         .inner_size(width, height)
         .resizable(true)
         .center()
         .build()
         .map_err(|e| format!("Failed to create window '{}': {}", label, e))?;
+
+    // Set the hash fragment after the window loads — this triggers App.vue's
+    // onMounted hash detection to render the correct tool/detached component.
+    if let Some(hash) = hash {
+        let _ = window.eval(&format!("window.location.hash = '{}';", hash));
+    }
+
     Ok(())
 }

src/App.vue

@@ -16,7 +16,6 @@ const DetachedSession = defineAsyncComponent({
 const app = useAppStore();
 const appError = ref<string | null>(null);
 
-// Tool window mode — detected from URL hash: #/tool/network-scanner?sessionId=abc
 const isToolMode = ref(false);
 const isDetachedMode = ref(false);
 const toolName = ref("");
@@ -28,32 +27,39 @@ onErrorCaptured((err) => {
   return false;
 });
 
-onMounted(async () => {
-  const hash = window.location.hash;
+/** Parse hash and set mode flags. Called on mount and on hashchange. */
+function applyHash(hash: string): void {
   if (hash.startsWith("#/tool/")) {
     isToolMode.value = true;
-    const rest = hash.substring(7); // after "#/tool/"
+    const rest = hash.substring(7);
     const [name, query] = rest.split("?");
     toolName.value = name;
     toolSessionId.value = new URLSearchParams(query || "").get("sessionId") || "";
   } else if (hash.startsWith("#/detached-session")) {
     isDetachedMode.value = true;
-  } else {
+  }
+}
+
+onMounted(async () => {
+  // Check hash at load time (present if JS-side WebviewWindow set it in the URL)
+  applyHash(window.location.hash);
+
+  // Also listen for hash changes (Rust-side window sets hash via eval after load)
+  window.addEventListener("hashchange", () => applyHash(window.location.hash));
+
+  // Only init vault for the main app window (no hash)
+  if (!isToolMode.value && !isDetachedMode.value) {
     await app.checkVaultState();
   }
 });
 </script>
 
 <template>
-  <!-- Error display for debugging -->
   <div v-if="appError" class="fixed inset-0 z-50 flex items-center justify-center bg-[#0d1117] text-red-400 p-8 text-sm font-mono whitespace-pre-wrap">
     {{ appError }}
   </div>
-  <!-- Detached session window mode -->
   <DetachedSession v-else-if="isDetachedMode" />
-  <!-- Tool popup window mode -->
   <ToolWindow v-else-if="isToolMode" :tool="toolName" :session-id="toolSessionId" />
-  <!-- Normal app mode -->
   <div v-else class="app-root">
     <UnlockLayout v-if="!app.isUnlocked" />
     <MainLayout v-else />