diff --git a/packages/ui/src/components/layout/ContextPanel.tsx b/packages/ui/src/components/layout/ContextPanel.tsx
index ca1767cb..d45f993d 100644
--- a/packages/ui/src/components/layout/ContextPanel.tsx
+++ b/packages/ui/src/components/layout/ContextPanel.tsx
@@ -447,6 +447,21 @@ const stripPreviewTokenFromUrl = (value: string): string => {
     return value;
   }
 };
+
+const stripPreviewQueryParams = (value: string): string => {
+  if (!value) return value;
+  try {
+    const parsed = new URL(value);
+    parsed.searchParams.delete('ocPreview');
+    parsed.searchParams.delete('oc_preview_token');
+    parsed.searchParams.delete('oc_client_token');
+    parsed.searchParams.delete('oc_url_token');
+    return parsed.toString();
+  } catch {
+    return value;
+  }
+};
+
 const PreviewPane: React.FC<PreviewPaneProps> = ({ rawUrl, onNavigate }) => {
   const { t } = useI18n();
   const { currentTheme } = useThemeSystem();
@@ -593,6 +608,8 @@ const PreviewPane: React.FC<PreviewPaneProps> = ({ rawUrl, onNavigate }) => {
     ? (() => {
       const path = normalizedUrl.pathname || '/';
       const searchParams = new URLSearchParams(normalizedUrl.search);
+      searchParams.delete('oc_url_token');
+      searchParams.delete('oc_client_token');
       searchParams.set('ocPreview', String(reloadNonce));
       searchParams.set('oc_preview_token', proxyState.previewToken || '');
       const search = searchParams.toString();
@@ -1394,6 +1411,8 @@ const IframeBrowserPane: React.FC<DesktopBrowserPaneProps> = ({ initialUrl, dire
       const parsed = new URL(currentUrl);
       const path = parsed.pathname || '/';
       const searchParams = new URLSearchParams(parsed.search);
+      searchParams.delete('oc_url_token');
+      searchParams.delete('oc_client_token');
       searchParams.set('ocPreview', String(reloadNonce));
       searchParams.set('oc_preview_token', proxyState.previewToken || '');
       const search = searchParams.toString();
@@ -1418,7 +1437,7 @@ const IframeBrowserPane: React.FC<DesktopBrowserPaneProps> = ({ initialUrl, dire
 
       const rest = parsedFrameUrl.pathname.slice(proxyBasePath.length) || '/';
       const upstreamOrigin = new URL(currentUrl).origin;
-      return new URL(`${rest}${parsedFrameUrl.search}${parsedFrameUrl.hash}`, upstreamOrigin).toString();
+      return stripPreviewQueryParams(new URL(`${rest}${parsedFrameUrl.search}${parsedFrameUrl.hash}`, upstreamOrigin).toString());
     } catch {
       return '';
     }
@@ -1440,7 +1459,7 @@ const IframeBrowserPane: React.FC<DesktopBrowserPaneProps> = ({ initialUrl, dire
         return '';
       }
 
-      return new URL(`${parsedFrameUrl.pathname}${parsedFrameUrl.search}${parsedFrameUrl.hash}`, upstreamOrigin).toString();
+      return stripPreviewQueryParams(new URL(`${parsedFrameUrl.pathname}${parsedFrameUrl.search}${parsedFrameUrl.hash}`, upstreamOrigin).toString());
     } catch {
       return '';
     }
diff --git a/packages/ui/src/lib/runtime-url.test.ts b/packages/ui/src/lib/runtime-url.test.ts
index 631076cf..2b30836c 100644
--- a/packages/ui/src/lib/runtime-url.test.ts
+++ b/packages/ui/src/lib/runtime-url.test.ts
@@ -120,6 +120,19 @@ describe('createRuntimeUrlResolver', () => {
     }
   });
 
+  test('replaces existing short-lived URL auth query on relative authenticated URLs', () => {
+    setRuntimeUrlAuthToken('oc_url_secret', Date.now() + 60_000);
+    try {
+      const urls = createRuntimeUrlResolver();
+
+      expect(urls.authenticatedAsset('/api/preview/proxy/abc/?oc_url_token=stale&x=1#top')).toBe(
+        '/api/preview/proxy/abc/?oc_url_token=oc_url_secret&x=1#top',
+      );
+    } finally {
+      setRuntimeUrlAuthToken(null, null);
+    }
+  });
+
   test('does not put the long-lived client token in URLs', () => {
     setRuntimeBearerToken('oc_client_secret');
     try {
diff --git a/packages/ui/src/lib/runtime-url.ts b/packages/ui/src/lib/runtime-url.ts
index d1bc46ab..ba3797c0 100644
--- a/packages/ui/src/lib/runtime-url.ts
+++ b/packages/ui/src/lib/runtime-url.ts
@@ -91,14 +91,12 @@ const withUrlAuth = (urlValue: string): string => {
   const token = getRuntimeUrlAuthTokenSync();
   if (!token) return urlValue;
 
-  if (ABSOLUTE_URL_PATTERN.test(urlValue)) {
-    const url = new URL(urlValue);
-    url.searchParams.set('oc_url_token', token);
-    return url.toString();
-  }
-
-  const separator = urlValue.includes('?') ? '&' : '?';
-  return `${urlValue}${separator}oc_url_token=${encodeURIComponent(token)}`;
+  const url = ABSOLUTE_URL_PATTERN.test(urlValue)
+    ? new URL(urlValue)
+    : new URL(urlValue, 'http://openchamber.local');
+  url.searchParams.set('oc_url_token', token);
+  if (ABSOLUTE_URL_PATTERN.test(urlValue)) return url.toString();
+  return `${url.pathname}${url.search}${url.hash}`;
 };
 
 const toWebSocketUrl = (candidate: string, config: RuntimeUrlConfig): string => {