diff --git a/packages/ui/src/components/layout/ContextPanel.tsx b/packages/ui/src/components/layout/ContextPanel.tsx
index a8d5b159..6b173209 100644
--- a/packages/ui/src/components/layout/ContextPanel.tsx
+++ b/packages/ui/src/components/layout/ContextPanel.tsx
@@ -45,6 +45,7 @@ import { invokeDesktopCommand } from '@/lib/desktopNative';
 import {
   EMBEDDED_RUNTIME_BOOTSTRAP_REQUEST,
   EMBEDDED_RUNTIME_BOOTSTRAP_RESPONSE,
+  getActiveEmbeddedSessionChatTab,
   getOrCreateEmbeddedSessionChatURL,
   type EmbeddedSessionChatURLCacheEntry,
   type EmbeddedSessionRuntimeBootstrap,
@@ -2483,8 +2484,13 @@ export const ContextPanel: React.FC = () => {
 
   }, [activeTab, directoryKey, setSelectedFilePath]);
 
-  const activeChatTabID = activeTab?.mode === 'chat' ? activeTab.id : null;
-  const activeChatSessionID = activeTab?.mode === 'chat' ? getSessionIDFromDedupeKey(activeTab.dedupeKey) : null;
+  const chatTabs = React.useMemo(
+    () => tabs.filter((tab) => tab.mode === 'chat'),
+    [tabs],
+  );
+  const activeChatTabID = isOpen && activeTab?.mode === 'chat' ? activeTab.id : null;
+  const activeChatSessionID = isOpen && activeTab?.mode === 'chat' ? getSessionIDFromDedupeKey(activeTab.dedupeKey) : null;
+  const activeChatTab = getActiveEmbeddedSessionChatTab(chatTabs, activeChatTabID);
 
   React.useEffect(() => {
     if (!isOpen || !directoryKey || !activeChatSessionID || typeof window === 'undefined') {
@@ -2525,6 +2531,10 @@ export const ContextPanel: React.FC = () => {
     });
   }, [currentTheme, darkThemeId, directoryKey, lightThemeId, themeMode]);
 
+  const activeChatSrc = activeChatTab && activeChatSessionID
+    ? getEmbeddedChatSrc(activeChatTab.id, activeChatSessionID, activeChatTab.readOnly)
+    : null;
+
   React.useEffect(() => {
     const liveTabIDs = new Set(tabs.map((tab) => tab.id));
     for (const tabID of chatFrameSrcByTabIDRef.current.keys()) {
@@ -2721,10 +2731,6 @@ export const ContextPanel: React.FC = () => {
                   </div>
                 );
 
-  const chatTabs = React.useMemo(
-    () => tabs.filter((tab) => tab.mode === 'chat'),
-    [tabs],
-  );
   const browserTabs = React.useMemo(
     () => tabs.filter((tab) => tab.mode === 'browser'),
     [tabs],
@@ -2934,41 +2940,26 @@ export const ContextPanel: React.FC = () => {
             <EditorTreeColumn visible={contextEditorTreeVisible} />
           </div>
         ) : null}
-        {chatTabs.map((tab) => {
-          const sessionID = getSessionIDFromDedupeKey(tab.dedupeKey);
-          if (!sessionID) {
-            return null;
-          }
-
-          const src = getEmbeddedChatSrc(tab.id, sessionID, tab.readOnly);
-          if (!src) {
-            return null;
-          }
-
-          return (
-            <iframe
-              key={tab.id}
-              ref={(node) => {
-                if (!node) {
-                  chatFrameRefs.current.delete(tab.id);
-                  return;
-                }
-                chatFrameRefs.current.set(tab.id, node);
-              }}
-              src={src}
-              title={t('contextPanel.iframe.sessionChatTitle', { sessionID })}
-              className={cn(
-                'absolute inset-0 h-full w-full border-0 bg-background',
-                activeChatTabID === tab.id ? 'block' : 'hidden'
-              )}
-              onLoad={() => {
-                postThemeSyncToEmbeddedChat();
-                postChatSettingsSyncToEmbeddedChat();
-                postEmbeddedVisibilityToChats();
-              }}
-            />
-          );
-        })}
+        {activeChatTab && activeChatSessionID && activeChatSrc ? (
+          <iframe
+            key={activeChatTab.id}
+            ref={(node) => {
+              if (!node) {
+                chatFrameRefs.current.delete(activeChatTab.id);
+                return;
+              }
+              chatFrameRefs.current.set(activeChatTab.id, node);
+            }}
+            src={activeChatSrc}
+            title={t('contextPanel.iframe.sessionChatTitle', { sessionID: activeChatSessionID })}
+            className="absolute inset-0 h-full w-full border-0 bg-background"
+            onLoad={() => {
+              postThemeSyncToEmbeddedChat();
+              postChatSettingsSyncToEmbeddedChat();
+              postEmbeddedVisibilityToChats();
+            }}
+          />
+        ) : null}
         {browserTabs.map((tab) => (
           <div
             key={tab.id}
diff --git a/packages/ui/src/components/layout/__tests__/issue-2815-sessionChatIframesMountAllTabs.test.ts b/packages/ui/src/components/layout/__tests__/issue-2815-sessionChatIframesMountAllTabs.test.ts
new file mode 100644
index 00000000..d540f359
--- /dev/null
+++ b/packages/ui/src/components/layout/__tests__/issue-2815-sessionChatIframesMountAllTabs.test.ts
@@ -0,0 +1,183 @@
+/**
+ * Regression coverage for https://github.com/openchamber/openchamber/issues/2815
+ *
+ * A full ContextPanel mount is not available in bun test because its import
+ * graph includes a Vite worker URL. This test follows the source-level guard
+ * pattern in contextPanelEscapeClosesTerminal.test.ts and uses the real store.
+ */
+import { afterAll, beforeEach, describe, expect, test } from 'bun:test';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+import { getDefaultTheme } from '@/lib/theme/themes';
+import { useUIStore } from '@/stores/useUIStore';
+import {
+  buildEmbeddedSessionChatURL,
+  getActiveEmbeddedSessionChatTab,
+  resetEmbeddedSessionChatCache,
+} from '../contextPanelEmbeddedChat';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const contextPanelSource = readFileSync(join(__dirname, '..', 'ContextPanel.tsx'), 'utf-8');
+
+type FixtureTab = {
+  id: string;
+  mode: 'chat' | 'git' | 'diff' | 'plan';
+  targetPath: string | null;
+  dedupeKey: string;
+  label: string | null;
+  sessionTitleFallback: string | null;
+  readOnly: boolean;
+  stagedDiff: boolean;
+  diffScope: 'working';
+  touchedAt: number;
+};
+
+const DIRECTORY = '/path/to/repository';
+const originalWindow = globalThis.window;
+
+const installWindowLocation = () => {
+  const url = new URL('http://127.0.0.1:3000/');
+  Object.defineProperty(globalThis, 'window', {
+    configurable: true,
+    value: {
+      location: {
+        href: url.toString(),
+        origin: url.origin,
+        pathname: url.pathname,
+        search: url.search,
+      },
+    },
+  });
+};
+
+const buildTab = (mode: FixtureTab['mode'], id: string): FixtureTab => ({
+  id: mode === 'chat' ? `chat:session:${id}` : id,
+  mode,
+  targetPath: null,
+  dedupeKey: mode === 'chat' ? `session:${id}` : id,
+  label: mode === 'chat' ? `Session ${id}` : null,
+  sessionTitleFallback: null,
+  readOnly: mode === 'chat',
+  stagedDiff: false,
+  diffScope: 'working',
+  touchedAt: Date.now(),
+});
+
+const sessionChatTabs = Array.from({ length: 8 }, (_, index) => buildTab('chat', `ses_${index + 1}`));
+const issueScenarioTabs = [
+  ...sessionChatTabs,
+  buildTab('git', 'git'),
+  buildTab('diff', 'diff'),
+  buildTab('plan', 'plan'),
+];
+
+const installIssueScenario = () => {
+  useUIStore.setState({
+    contextPanelByDirectory: {
+      [DIRECTORY]: {
+        isOpen: true,
+        expanded: false,
+        tabs: issueScenarioTabs,
+        activeTabId: sessionChatTabs[0].id,
+        widthByMode: {},
+        touchedAt: Date.now(),
+      },
+    } as never,
+  });
+};
+
+beforeEach(() => {
+  installWindowLocation();
+  resetEmbeddedSessionChatCache();
+  useUIStore.setState({ contextPanelByDirectory: {}, contextRailOrder: [] });
+  installIssueScenario();
+});
+
+afterAll(() => {
+  Object.defineProperty(globalThis, 'window', {
+    configurable: true,
+    value: originalWindow,
+  });
+});
+
+describe('issue #2815 active-only chat iframe source guard', () => {
+  test('does not map persisted chat tabs to iframe elements', () => {
+    expect(contextPanelSource).not.toContain('{chatTabs.map((tab) => {');
+  });
+
+  test('renders the iframe only when an active chat has a session and URL', () => {
+    const start = contextPanelSource.indexOf('{activeChatTab && activeChatSessionID && activeChatSrc ? (');
+    expect(start).toBeGreaterThan(-1);
+    const end = contextPanelSource.indexOf(') : null}', start);
+    expect(end).toBeGreaterThan(start);
+    const block = contextPanelSource.slice(start, end);
+
+    expect(block).toContain('<iframe');
+    expect(block).toContain('key={activeChatTab.id}');
+    expect(block).toContain('src={activeChatSrc}');
+    expect(block).not.toContain("'block' : 'hidden'");
+  });
+
+  test('does not select a chat iframe when the context panel is closed', () => {
+    expect(contextPanelSource).toContain(
+      "const activeChatTabID = isOpen && activeTab?.mode === 'chat' ? activeTab.id : null;",
+    );
+    expect(contextPanelSource).toContain(
+      "const activeChatSessionID = isOpen && activeTab?.mode === 'chat'",
+    );
+  });
+});
+
+describe('issue #2815 persisted scenario', () => {
+  test('keeps all tab records but selects one chat for mounting', () => {
+    const panel = useUIStore.getState().contextPanelByDirectory[DIRECTORY];
+    const chatTabs = panel.tabs.filter((tab) => tab.mode === 'chat');
+    const activeTab = getActiveEmbeddedSessionChatTab(chatTabs, panel.activeTabId);
+
+    expect(panel.tabs).toHaveLength(11);
+    expect(chatTabs).toHaveLength(8);
+    expect(activeTab?.id).toBe(sessionChatTabs[0].id);
+  });
+
+  test('produces one live embedded URL for eight persisted chats', () => {
+    const panel = useUIStore.getState().contextPanelByDirectory[DIRECTORY];
+    const chatTabs = panel.tabs.filter((tab) => tab.mode === 'chat');
+    const activeTab = getActiveEmbeddedSessionChatTab(chatTabs, panel.activeTabId);
+    const frames = activeTab ? [buildEmbeddedSessionChatURL('ses_1', DIRECTORY, activeTab.readOnly, {
+      mode: 'system',
+      lightThemeId: 'light',
+      darkThemeId: 'dark',
+      currentTheme: getDefaultTheme(true),
+    })] : [];
+
+    expect(frames).toHaveLength(1);
+    const url = new URL(frames[0]);
+    expect(url.searchParams.get('ocPanel')).toBe('session-chat');
+    expect(url.searchParams.get('sessionId')).toBe('ses_1');
+    expect(url.searchParams.get('readOnly')).toBe('1');
+  });
+
+  test('selects another single chat after a tab switch', () => {
+    useUIStore.getState().setActiveContextPanelTab(DIRECTORY, sessionChatTabs[6].id);
+
+    const panel = useUIStore.getState().contextPanelByDirectory[DIRECTORY];
+    const chatTabs = panel.tabs.filter((tab) => tab.mode === 'chat');
+    const activeTab = getActiveEmbeddedSessionChatTab(chatTabs, panel.activeTabId);
+
+    expect(activeTab?.id).toBe(sessionChatTabs[6].id);
+    expect(chatTabs.filter((tab) => tab.id === activeTab?.id)).toHaveLength(1);
+  });
+
+  test('selects no chat after the panel closes', () => {
+    useUIStore.getState().closeContextPanel(DIRECTORY);
+
+    const panel = useUIStore.getState().contextPanelByDirectory[DIRECTORY];
+    const chatTabs = panel.tabs.filter((tab) => tab.mode === 'chat');
+    const activeTabID = panel.isOpen ? panel.activeTabId : null;
+
+    expect(panel.isOpen).toBe(false);
+    expect(getActiveEmbeddedSessionChatTab(chatTabs, activeTabID)).toBeNull();
+  });
+});
diff --git a/packages/ui/src/components/layout/contextPanelEmbeddedChat.test.ts b/packages/ui/src/components/layout/contextPanelEmbeddedChat.test.ts
index 33cf7ef6..08992565 100644
--- a/packages/ui/src/components/layout/contextPanelEmbeddedChat.test.ts
+++ b/packages/ui/src/components/layout/contextPanelEmbeddedChat.test.ts
@@ -6,6 +6,7 @@ import {
   EMBEDDED_RUNTIME_BOOTSTRAP_REQUEST,
   EMBEDDED_RUNTIME_BOOTSTRAP_RESPONSE,
   getOrCreateEmbeddedSessionChatURL,
+  getActiveEmbeddedSessionChatTab,
   getEmbeddedSessionChatOriginSessionId,
   isEmbeddedSessionChat,
   requestEmbeddedSessionRuntimeBootstrap,
@@ -145,6 +146,22 @@ describe('embedded session chat URL', () => {
   });
 });
 
+describe('active embedded session chat', () => {
+  const tabs = Array.from({ length: 8 }, (_, index) => ({
+    id: `chat-${index + 1}`,
+    sessionID: `ses_${index + 1}`,
+  }));
+
+  test('selects one tab from persisted chat tabs', () => {
+    expect(getActiveEmbeddedSessionChatTab(tabs, 'chat-5')).toEqual(tabs[4]);
+  });
+
+  test('selects no tab when a chat is not active', () => {
+    expect(getActiveEmbeddedSessionChatTab(tabs, null)).toBeNull();
+    expect(getActiveEmbeddedSessionChatTab(tabs, 'missing-chat')).toBeNull();
+  });
+});
+
 describe('isEmbeddedSessionChat', () => {
   test('is true only for the session-chat panel search param', () => {
     installWindowLocation('http://127.0.0.1:5173/app?ocPanel=session-chat&sessionId=ses_1');
diff --git a/packages/ui/src/components/layout/contextPanelEmbeddedChat.ts b/packages/ui/src/components/layout/contextPanelEmbeddedChat.ts
index 14890478..57789111 100644
--- a/packages/ui/src/components/layout/contextPanelEmbeddedChat.ts
+++ b/packages/ui/src/components/layout/contextPanelEmbeddedChat.ts
@@ -158,6 +158,17 @@ export const getOrCreateEmbeddedSessionChatURL = (
   return src;
 };
 
+export const getActiveEmbeddedSessionChatTab = <T extends { id: string }>(
+  tabs: T[],
+  activeTabID: string | null,
+): T | null => {
+  if (!activeTabID) {
+    return null;
+  }
+
+  return tabs.find((tab) => tab.id === activeTabID) ?? null;
+};
+
 /**
  * True when the current document is the embedded session-chat iframe
  * (`?ocPanel=session-chat`). Used to distinguish the embedded iframe from
diff --git a/packages/ui/src/lib/surfaces/DOCUMENTATION.md b/packages/ui/src/lib/surfaces/DOCUMENTATION.md
index 4c5fb57f..0fa50263 100644
--- a/packages/ui/src/lib/surfaces/DOCUMENTATION.md
+++ b/packages/ui/src/lib/surfaces/DOCUMENTATION.md
@@ -44,11 +44,13 @@ the `openContext*` actions in `useUIStore`.
 
 - Opening a surface must never require a control outside the rail, the
   command palette, or an in-content link.
-- Multi-instance and session-holding surfaces (file/editor, chat, diff,
-  browser, terminal) are keep-alive panes in `ContextPanel.tsx`: switching
+- Multi-instance and session-holding surfaces (file/editor, diff, browser,
+  terminal) are keep-alive panes in `ContextPanel.tsx`. Switching these
   surfaces must not reset their state (open tabs, xterm session, scroll
-  positions). Singleton surfaces (git, pr, notes, plan, context) and preview
-  tabs intentionally remount on switch and must restore themselves from
-  their stores/snapshots instead.
+  positions). Chat tab records stay open, but only the active chat iframe is
+  mounted while the panel is open. A selected chat restores its state from
+  the session stores. A closed panel mounts no chat iframe.
+  Singleton surfaces (git, pr, notes, plan, context) and preview tabs remount
+  on switch. These surfaces must restore their state from stores or snapshots.
 - Runtime scope: desktop/web `MainLayout` only. VS Code and the dedicated
   mobile shell have their own layouts and do not consume this registry.