diff --git a/CHANGELOG.md b/CHANGELOG.md
index fd021143..f03d79e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ All notable changes to this project will be documented in this file.
 - Chat: a "Follow new content while streaming" checkbox (Settings → Chat → Streaming, on by default) turns automatic following off entirely; with it off, the scroll-to-bottom pill now appears as soon as the reply grows past the visible area.
 - Command palette: rarely used commands (pin session, copy session ID, multi-run launcher, archived sessions, notes, todos, status, theme) are found by typing but stay off the first screen.
 - Mobile: narrowing a browser window past phone size switches into the mobile layout (and back when widened); the old/new mobile layout setting is gone.
+- Browser: an agent opening a page with the browser tool no longer pops the browser panel open (or switches the surface you're on) — the page loads in the background and the rail is where you peek at it.
 - Usage: the Command Code tile is gone — their official API exposes no usage data, so the tile could only fail.
 - Auth: an expired OpenChamber login is announced within seconds by a banner with a Log in button, instead of being discovered through failing actions. Sending pauses until login, and a conversation that failed to load reloads itself afterwards.
 - Chat: a failed send returns your typed prompt to the input — whatever the reason — instead of losing it to an error toast; a mid-send session switch lands it in that session's draft.
diff --git a/packages/ui/src/components/layout/ContextPanel.tsx b/packages/ui/src/components/layout/ContextPanel.tsx
index 8c24e134..aa52be5d 100644
--- a/packages/ui/src/components/layout/ContextPanel.tsx
+++ b/packages/ui/src/components/layout/ContextPanel.tsx
@@ -452,10 +452,13 @@ export const ContextPanel: React.FC = () => {
 
   // Lets an agent's browser.open create the tab it needs when none is open yet.
   // Registered from the panel because opening a tab is panel state, not
-  // something the browser view itself can do before it exists.
+  // something the browser view itself can do before it exists. Background on
+  // purpose: an agent working a page must not pop the panel open (or steal
+  // the active surface) under the user — the tab mounts invisibly, and the
+  // rail is where the user opens it when curious.
   React.useEffect(() => {
     if (!effectiveDirectory) return;
-    return registerBrowserOpener((url) => openContextBrowser(effectiveDirectory, url));
+    return registerBrowserOpener((url) => openContextBrowser(effectiveDirectory, url, { reveal: false }));
   }, [effectiveDirectory, openContextBrowser]);
   const reorderContextPanelTabs = useUIStore((state) => state.reorderContextPanelTabs);
   const setSelectedFilePath = useFilesViewTabsStore((state) => state.setSelectedPath);
diff --git a/packages/ui/src/stores/useUIStore.ts b/packages/ui/src/stores/useUIStore.ts
index b5254f2e..5eceb243 100644
--- a/packages/ui/src/stores/useUIStore.ts
+++ b/packages/ui/src/stores/useUIStore.ts
@@ -393,7 +393,9 @@ const touchContextPanelState = (prev?: ContextPanelDirectoryState): ContextPanel
 const upsertContextPanelTab = (
   current: ContextPanelDirectoryState,
   descriptor: ContextPanelTabDescriptor,
+  options?: { reveal?: boolean },
 ): ContextPanelDirectoryState => {
+  const reveal = options?.reveal !== false;
   const nextTab = createContextPanelTab(descriptor);
   // A real file tab replaces the empty editor placeholder ('file' with no
   // target) that the rail can open before any file is picked.
@@ -418,12 +420,18 @@ const upsertContextPanelTab = (
         }
       : tab));
 
-  const activeTabId = nextTab.id;
+  // A background upsert (an agent working a page) keeps the panel exactly as
+  // the user left it: closed stays closed, and whatever tab they were on
+  // stays active. The tab still exists — panes are kept mounted regardless of
+  // visibility — so agent control and a later manual open both find it.
+  const activeTabId = reveal
+    ? nextTab.id
+    : current.activeTabId ?? nextTab.id;
   const clampedTabs = clampContextPanelTabs(tabs, CONTEXT_PANEL_MAX_TABS, activeTabId);
 
   return {
     ...current,
-    isOpen: true,
+    isOpen: reveal ? true : current.isOpen,
     tabs: clampedTabs,
     activeTabId: resolveActiveContextPanelTabID(clampedTabs, activeTabId),
     touchedAt: Date.now(),
@@ -806,14 +814,14 @@ interface UIStore {
   toggleContextEditorTree: () => void;
   setContextEditorTreeWidth: (width: number) => void;
   openContextSurface: (directory: string, mode: ContextPanelMode) => void;
-  openContextPanelTab: (directory: string, tab: ContextPanelTabDescriptor) => void;
+  openContextPanelTab: (directory: string, tab: ContextPanelTabDescriptor, options?: { reveal?: boolean }) => void;
   openContextDiff: (directory: string, filePath: string, staged?: boolean, scope?: PendingDiffScope | null) => void;
   openContextFile: (directory: string, filePath: string) => void;
   openContextFileAtLine: (directory: string, filePath: string, line: number, column?: number) => void;
   openContextOverview: (directory: string) => void;
   openContextPlan: (directory: string) => void;
   openContextPreview: (directory: string, url: string) => void;
-  openContextBrowser: (directory: string, url?: string) => void;
+  openContextBrowser: (directory: string, url?: string, options?: { reveal?: boolean }) => void;
   openNewContextBrowserTab: (directory: string) => void;
   setContextPanelTabTargetPath: (directory: string, tabID: string, targetPath: string) => void;
   setActiveContextPanelTab: (directory: string, tabID: string) => void;
@@ -1239,7 +1247,7 @@ export const useUIStore = create<UIStore>()(
           state.openContextPanelTab(normalizedDirectory, { mode });
         },
 
-        openContextPanelTab: (directory, tab) => {
+        openContextPanelTab: (directory, tab, options) => {
           const normalizedDirectory = normalizeDirectoryPath((directory || '').trim());
           if (!normalizedDirectory) {
             return;
@@ -1250,7 +1258,7 @@ export const useUIStore = create<UIStore>()(
             const current = touchContextPanelState(prev);
             const byDirectory = {
               ...state.contextPanelByDirectory,
-              [normalizedDirectory]: upsertContextPanelTab(current, tab),
+              [normalizedDirectory]: upsertContextPanelTab(current, tab, options),
             };
 
             return { contextPanelByDirectory: clampContextPanelRoots(byDirectory, 20) };
@@ -1351,7 +1359,7 @@ export const useUIStore = create<UIStore>()(
             label: null,
           });
         },
-        openContextBrowser: (directory, url = '') => {
+        openContextBrowser: (directory, url = '', options) => {
           const normalizedDirectory = normalizeDirectoryPath((directory || '').trim());
           if (!normalizedDirectory || isVSCodeRuntime()) return;
           const targetUrl = typeof url === 'string' && url.trim().length > 0 ? url.trim() : '';
@@ -1360,7 +1368,7 @@ export const useUIStore = create<UIStore>()(
             targetPath: targetUrl,
             dedupeKey: targetUrl || 'browser',
             label: null,
-          });
+          }, options);
         },
 
         setContextPanelTabTargetPath: (directory, tabID, targetPath) => {