diff --git a/packages/ui/src/App.tsx b/packages/ui/src/App.tsx
index 1929683e..ad4bc2f4 100644
--- a/packages/ui/src/App.tsx
+++ b/packages/ui/src/App.tsx
@@ -209,6 +209,11 @@ const EmbeddedSessionChatContent: React.FC<{
       <OpenCodeUpdateToast />
       <ChatView
         active={embeddedBackgroundWorkEnabled}
+        // Always subscribe to message history in the mounted session-chat
+        // iframe. Visibility still gates composer focus and background work so
+        // a boot-inactive / lost-handshake race cannot leave a busy subagent
+        // showing only its status row (#2903 / #2892).
+        messagesEnabled={true}
         readOnly={embeddedSessionChat.readOnly}
         initialAllowPromptingSubagentSessions={embeddedSessionChat.allowPromptingSubagentSessions}
       />
diff --git a/packages/ui/src/components/chat/ChatContainer.tsx b/packages/ui/src/components/chat/ChatContainer.tsx
index ff38aeba..8f0c2114 100644
--- a/packages/ui/src/components/chat/ChatContainer.tsx
+++ b/packages/ui/src/components/chat/ChatContainer.tsx
@@ -533,12 +533,26 @@ const DraftWelcome: React.FC = () => {
 
 type ChatContainerProps = {
     active?: boolean;
+    /**
+     * When set, controls `useSessionMessageRecords` independently of `active`.
+     * Defaults to `active`. Embedded session-chat panels pass `true` so a
+     * delayed/lost visibility handshake cannot hide an already-materialized
+     * transcript (leaving only the working-status row — issue #2903).
+     */
+    messagesEnabled?: boolean;
     autoOpenDraft?: boolean;
     readOnly?: boolean;
     initialAllowPromptingSubagentSessions?: boolean;
 };
 
-export const ChatContainer: React.FC<ChatContainerProps> = ({ active = true, autoOpenDraft = true, readOnly = false, initialAllowPromptingSubagentSessions }) => {
+export const ChatContainer: React.FC<ChatContainerProps> = ({
+    active = true,
+    messagesEnabled: messagesEnabledProp,
+    autoOpenDraft = true,
+    readOnly = false,
+    initialAllowPromptingSubagentSessions,
+}) => {
+    const messagesEnabled = messagesEnabledProp ?? active;
     const { t } = useI18n();
     // Session UI state
     const currentSessionId = useSessionUIStore((s) => s.currentSessionId);
@@ -591,9 +605,11 @@ export const ChatContainer: React.FC<ChatContainerProps> = ({ active = true, aut
     );
     const sessionMessageCount = useSessionMessageCount(currentSessionId ?? '', effectiveSessionDirectory);
     const hasRenderableSessionSnapshot = useSessionRenderable(currentSessionId ?? '', effectiveSessionDirectory);
-    // Messages from sync system
+    // Messages from sync system. Keep this gated by `messagesEnabled`, not
+    // `active`, so embedded panels can show history while the composer stays
+    // inactive until the parent confirms visibility.
     const sessionMessageRecords = useSessionMessageRecords(currentSessionId ?? '', effectiveSessionDirectory, {
-        enabled: active,
+        enabled: messagesEnabled,
         suspendPartUpdates: Boolean(streamingMessageId),
         suspendPartUpdatesForMessageId: streamingMessageId,
     });
diff --git a/packages/ui/src/components/chat/__tests__/issue-2903-subagent-status-line-only.test.tsx b/packages/ui/src/components/chat/__tests__/issue-2903-subagent-status-line-only.test.tsx
new file mode 100644
index 00000000..8823e267
--- /dev/null
+++ b/packages/ui/src/components/chat/__tests__/issue-2903-subagent-status-line-only.test.tsx
@@ -0,0 +1,143 @@
+/**
+ * Regression coverage for https://github.com/openchamber/openchamber/issues/2903
+ *
+ * Busy embedded session-chat panels were rendering only the working-status row
+ * ("…is running command") because ChatContainer gated message reads on the
+ * same visibility flag used to keep the composer from stealing focus. When the
+ * iframe booted inactive (or a visibility postMessage was lost),
+ * useSessionMessageRecords returned [] while session status stayed busy — so
+ * the empty-state branch was skipped and the transcript showed status only.
+ *
+ * Idle sessions hit the empty state instead (#2892). Same root cause.
+ *
+ * Fix: embedded session-chat keeps `messagesEnabled={true}` so history stays
+ * subscribed while `active={embeddedBackgroundWorkEnabled}` still gates
+ * composer focus and background work.
+ */
+import { describe, expect, test } from 'bun:test';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import type { Message, Part } from '@opencode-ai/sdk/v2/client';
+
+import { getSessionMaterializationStatus, materializeSessionSnapshots } from '@/sync/materialization';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const appSource = readFileSync(join(__dirname, '..', '..', '..', 'App.tsx'), 'utf-8');
+const chatContainerSource = readFileSync(join(__dirname, '..', 'ChatContainer.tsx'), 'utf-8');
+const chatViewSource = readFileSync(join(__dirname, '..', '..', 'views', 'ChatView.tsx'), 'utf-8');
+const syncContextSource = readFileSync(join(__dirname, '..', '..', '..', 'sync', 'sync-context.tsx'), 'utf-8');
+
+const SESSION_ID = 'ses_subagent_2903';
+
+const createRecord = (id: string, role: 'user' | 'assistant', created: number) => ({
+  info: {
+    id,
+    sessionID: SESSION_ID,
+    role,
+    time: { created },
+    ...(role === 'assistant'
+      ? { parentID: `u_${created}`, providerID: 'deepseek', modelID: 'deepseek-v4-flash' }
+      : {}),
+  } as Message,
+  parts: [{
+    id: `prt_${id}`,
+    messageID: id,
+    sessionID: SESSION_ID,
+    type: 'text',
+    text: role === 'user' ? `prompt ${created}` : `output ${created}`,
+  }] as Part[],
+});
+
+/** 14-message subagent transcript, matching the issue reproduction fixture. */
+const buildFourteenMessageSnapshot = () => {
+  const records = Array.from({ length: 14 }, (_, index) => {
+    const n = index + 1;
+    return createRecord(
+      n % 2 === 1 ? `u_${n}` : `a_${n}`,
+      n % 2 === 1 ? 'user' : 'assistant',
+      n,
+    );
+  });
+  return materializeSessionSnapshots({ message: {}, part: {} }, SESSION_ID, records);
+};
+
+/**
+ * Mirrors the cold-start branch of useSessionMessageRecords when
+ * `options.enabled === false` and no prior snapshot exists for the session.
+ */
+const readRecordsThroughEnabledGate = (
+  storeMessages: Message[] | undefined,
+  enabled: boolean,
+): Message[] => {
+  if (enabled === false) {
+    // Cold iframe: snapshotRef is empty / wrong session → EMPTY records.
+    return [];
+  }
+  return storeMessages ?? [];
+};
+
+describe('issue #2903 busy embedded subagent status-line-only', () => {
+  test('materialized 14-message subagent is renderable', () => {
+    const snapshot = buildFourteenMessageSnapshot();
+    expect(snapshot.message[SESSION_ID]).toHaveLength(14);
+    expect(getSessionMaterializationStatus(snapshot, SESSION_ID)).toEqual({
+      hasMessages: true,
+      renderable: true,
+      missingPartMessageIDs: [],
+    });
+  });
+
+  test('inactive enabled:false hides a fully-renderable session (0 records)', () => {
+    const snapshot = buildFourteenMessageSnapshot();
+    expect(getSessionMaterializationStatus(snapshot, SESSION_ID).renderable).toBe(true);
+    expect(readRecordsThroughEnabledGate(snapshot.message[SESSION_ID], false)).toHaveLength(0);
+  });
+
+  test('enabled:true reveals all 14 materialized records', () => {
+    const snapshot = buildFourteenMessageSnapshot();
+    expect(readRecordsThroughEnabledGate(snapshot.message[SESSION_ID], true)).toHaveLength(14);
+  });
+
+  test('sync gate still returns empty on cold disabled reads', () => {
+    // Mutation check: the real hook still has the enabled===false early return
+    // that produced the bug when ChatContainer passed enabled: active.
+    expect(syncContextSource).toContain('if (options?.enabled === false)');
+    expect(syncContextSource).toContain('EMPTY_SESSION_MESSAGE_RECORDS');
+  });
+
+  test('embedded session-chat keeps message history enabled while visibility gates active', () => {
+    expect(appSource).toContain('messagesEnabled={true}');
+    expect(appSource).toContain('active={embeddedBackgroundWorkEnabled}');
+    expect(appSource).toContain('const [isEmbeddedVisible, setIsEmbeddedVisible] = React.useState(false);');
+    expect(chatViewSource).toContain('messagesEnabled?: boolean');
+    expect(chatContainerSource).toContain('messagesEnabled: messagesEnabledProp');
+    expect(chatContainerSource).toContain('const messagesEnabled = messagesEnabledProp ?? active;');
+    expect(chatContainerSource).toContain('enabled: messagesEnabled');
+    expect(chatContainerSource.includes('enabled: active')).toBe(false);
+  });
+
+  test('empty+busy branch skips empty state so StatusRowContainer can stand alone', () => {
+    // Busy + zero messages skips ChatEmptyState and falls through to the full
+    // ChatViewport, whose transcript always includes StatusRowContainer — the
+    // "one status line, no history" symptom when records stay empty.
+    expect(chatContainerSource).toContain('if (sessionMessages.length === 0 && !sessionIsWorking)');
+    expect(chatContainerSource).toContain('<ChatEmptyState');
+    expect(chatContainerSource).toContain('<StatusRowContainer />');
+
+    const emptyBusyGuard = 'if (sessionMessages.length === 0 && !sessionIsWorking)';
+    const emptyStateReturn = chatContainerSource.indexOf(emptyBusyGuard);
+    expect(emptyStateReturn).toBeGreaterThan(-1);
+    const emptyStateBlock = chatContainerSource.slice(
+      emptyStateReturn,
+      emptyStateReturn + 1600,
+    );
+    expect(emptyStateBlock).toContain('<ChatEmptyState');
+    expect(emptyStateBlock).not.toContain('<StatusRowContainer />');
+  });
+
+  test('visibility handshake remains as defense-in-depth for background work', () => {
+    expect(appSource).toContain('requestEmbeddedSessionVisibility();');
+    expect(appSource).toContain('EMBEDDED_VISIBILITY_UPDATE');
+  });
+});
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
index ccb2fea0..619a8cd2 100644
--- a/packages/ui/src/components/layout/__tests__/issue-2815-sessionChatIframesMountAllTabs.test.ts
+++ b/packages/ui/src/components/layout/__tests__/issue-2815-sessionChatIframesMountAllTabs.test.ts
@@ -147,11 +147,12 @@ describe('issue #2815 active-only chat iframe source guard', () => {
     expect(requestIndex).toBeGreaterThan(listenerIndex);
   });
 
-  test('gates embedded chat subscriptions and background work on visibility', () => {
+  test('gates embedded chat background work on visibility but keeps message history enabled', () => {
     expect(appSource).toContain(
       'const embeddedBackgroundWorkEnabled = !embeddedSessionChat || isEmbeddedVisible;',
     );
     expect(appSource).toContain('active={embeddedBackgroundWorkEnabled}');
+    expect(appSource).toContain('messagesEnabled={true}');
     expect(appSource).toContain(
       'useWebNotificationStream({ enabled: embeddedBackgroundWorkEnabled });',
     );
diff --git a/packages/ui/src/components/views/ChatView.tsx b/packages/ui/src/components/views/ChatView.tsx
index bcba8dc7..29d83cff 100644
--- a/packages/ui/src/components/views/ChatView.tsx
+++ b/packages/ui/src/components/views/ChatView.tsx
@@ -5,17 +5,29 @@ import { useSessionUIStore } from '@/sync/session-ui-store';
 
 type ChatViewProps = {
     active?: boolean;
+    /**
+     * Controls message-history subscription independently of `active`.
+     * Embedded session-chat panels keep this true so history stays visible
+     * while composer focus / background work remain gated by visibility.
+     */
+    messagesEnabled?: boolean;
     readOnly?: boolean;
     initialAllowPromptingSubagentSessions?: boolean;
 };
 
-export const ChatView: React.FC<ChatViewProps> = ({ active = true, readOnly = false, initialAllowPromptingSubagentSessions }) => {
+export const ChatView: React.FC<ChatViewProps> = ({
+    active = true,
+    messagesEnabled,
+    readOnly = false,
+    initialAllowPromptingSubagentSessions,
+}) => {
     const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
 
     return (
         <ChatErrorBoundary sessionId={currentSessionId || undefined}>
             <ChatContainer
                 active={active}
+                messagesEnabled={messagesEnabled}
                 readOnly={readOnly}
                 initialAllowPromptingSubagentSessions={initialAllowPromptingSubagentSessions}
             />
diff --git a/packages/ui/src/stores/DOCUMENTATION.md b/packages/ui/src/stores/DOCUMENTATION.md
index 14df83a7..4f17d6e4 100644
--- a/packages/ui/src/stores/DOCUMENTATION.md
+++ b/packages/ui/src/stores/DOCUMENTATION.md
@@ -45,7 +45,10 @@ its message listener, the iframe requests its authoritative visibility from the
 parent. The parent accepts requests only from a currently mounted chat frame and
 answers from the current active tab. Do not rely only on a parent `onLoad`
 notification: it can arrive before the iframe listener exists and leave a
-visible chat with background work and message subscriptions disabled.
+visible chat with background work disabled. Message-history subscriptions in the
+mounted session-chat iframe stay enabled independently of that visibility flag
+so a delayed or lost handshake cannot hide an already-materialized transcript
+(busy subagents would otherwise show only the working-status row).
 
 ### Session / project coordination stores