diff --git a/.gitignore b/.gitignore
index 301135b5e..d8d27a7ae 100644
--- a/.gitignore
+++ b/.gitignore
@@ -67,3 +67,4 @@ docs/pr-session-notes-*.md
 
 .cursor/
 .pnpm-store/
+package-lock.json
diff --git a/src/stores/chat.ts b/src/stores/chat.ts
index 2d9ae4c86..0d1e7bf34 100644
--- a/src/stores/chat.ts
+++ b/src/stores/chat.ts
@@ -777,6 +777,16 @@ function isToolResultRole(role: unknown): boolean {
   return normalized === 'toolresult' || normalized === 'tool_result';
 }
 
+/** True for internal plumbing messages that should never be shown in the UI. */
+function isInternalMessage(msg: { role?: unknown; content?: unknown }): boolean {
+  if (msg.role === 'system') return true;
+  if (msg.role === 'assistant') {
+    const text = getMessageText(msg.content);
+    if (/^(HEARTBEAT_OK|NO_REPLY)\s*$/.test(text)) return true;
+  }
+  return false;
+}
+
 function extractTextFromContent(content: unknown): string {
   if (typeof content === 'string') return content;
   if (!Array.isArray(content)) return '';
@@ -1314,7 +1324,7 @@ export const useChatStore = create<ChatState>((set, get) => ({
 
       // Before filtering: attach images/files from tool_result messages to the next assistant message
       const messagesWithToolImages = enrichWithToolResultFiles(rawMessages);
-      const filteredMessages = messagesWithToolImages.filter((msg) => !isToolResultRole(msg.role));
+      const filteredMessages = messagesWithToolImages.filter((msg) => !isToolResultRole(msg.role) && !isInternalMessage(msg));
       // Restore file attachments for user/assistant messages (from cache + text patterns)
       const enrichedMessages = enrichWithCachedImages(filteredMessages);
 
diff --git a/src/stores/chat/helpers.ts b/src/stores/chat/helpers.ts
index b2d9bb83b..75441c703 100644
--- a/src/stores/chat/helpers.ts
+++ b/src/stores/chat/helpers.ts
@@ -598,6 +598,16 @@ function isToolResultRole(role: unknown): boolean {
   return normalized === 'toolresult' || normalized === 'tool_result';
 }
 
+/** True for internal plumbing messages that should never be shown in the UI. */
+function isInternalMessage(msg: { role?: unknown; content?: unknown }): boolean {
+  if (msg.role === 'system') return true;
+  if (msg.role === 'assistant') {
+    const text = getMessageText(msg.content);
+    if (/^(HEARTBEAT_OK|NO_REPLY)\s*$/.test(text)) return true;
+  }
+  return false;
+}
+
 function extractTextFromContent(content: unknown): string {
   if (typeof content === 'string') return content;
   if (!Array.isArray(content)) return '';
@@ -824,6 +834,7 @@ export {
   extractRawFilePaths,
   makeAttachedFile,
   enrichWithToolResultFiles,
+  isInternalMessage,
   isToolResultRole,
   enrichWithCachedImages,
   loadMissingPreviews,
diff --git a/src/stores/chat/history-actions.ts b/src/stores/chat/history-actions.ts
index 0dbeca465..5770a0397 100644
--- a/src/stores/chat/history-actions.ts
+++ b/src/stores/chat/history-actions.ts
@@ -6,6 +6,7 @@ import {
   enrichWithToolResultFiles,
   getMessageText,
   hasNonToolAssistantContent,
+  isInternalMessage,
   isToolResultRole,
   loadMissingPreviews,
   toMs,
@@ -39,7 +40,7 @@ export function createHistoryActions(
       const applyLoadedMessages = (rawMessages: RawMessage[], thinkingLevel: string | null) => {
         // Before filtering: attach images/files from tool_result messages to the next assistant message
         const messagesWithToolImages = enrichWithToolResultFiles(rawMessages);
-        const filteredMessages = messagesWithToolImages.filter((msg) => !isToolResultRole(msg.role));
+        const filteredMessages = messagesWithToolImages.filter((msg) => !isToolResultRole(msg.role) && !isInternalMessage(msg));
         // Restore file attachments for user/assistant messages (from cache + text patterns)
         const enrichedMessages = enrichWithCachedImages(filteredMessages);
 
diff --git a/tests/unit/chat-history-actions.test.ts b/tests/unit/chat-history-actions.test.ts
index eb03c62bb..01645b11f 100644
--- a/tests/unit/chat-history-actions.test.ts
+++ b/tests/unit/chat-history-actions.test.ts
@@ -11,6 +11,14 @@ const hasNonToolAssistantContent = vi.fn((message: { content?: unknown } | undef
   return typeof message.content === 'string' ? message.content.trim().length > 0 : true;
 });
 const isToolResultRole = vi.fn((role: unknown) => role === 'toolresult' || role === 'tool_result');
+const isInternalMessage = vi.fn((msg: { role?: unknown; content?: unknown }) => {
+  if (msg.role === 'system') return true;
+  if (msg.role === 'assistant') {
+    const text = typeof msg.content === 'string' ? msg.content : '';
+    if (/^(HEARTBEAT_OK|NO_REPLY)\s*$/.test(text)) return true;
+  }
+  return false;
+});
 const loadMissingPreviews = vi.fn(async () => false);
 const toMs = vi.fn((ts: number) => ts < 1e12 ? ts * 1000 : ts);
 
@@ -28,6 +36,7 @@ vi.mock('@/stores/chat/helpers', () => ({
   enrichWithToolResultFiles: (...args: unknown[]) => enrichWithToolResultFiles(...args),
   getMessageText: (...args: unknown[]) => getMessageText(...args),
   hasNonToolAssistantContent: (...args: unknown[]) => hasNonToolAssistantContent(...args),
+  isInternalMessage: (...args: unknown[]) => isInternalMessage(...args),
   isToolResultRole: (...args: unknown[]) => isToolResultRole(...args),
   loadMissingPreviews: (...args: unknown[]) => loadMissingPreviews(...args),
   toMs: (...args: unknown[]) => toMs(...args as Parameters<typeof toMs>),
@@ -108,7 +117,6 @@ describe('chat history actions', () => {
       '/api/cron/session-history?sessionKey=agent%3Amain%3Acron%3Ajob-1&limit=200',
     );
     expect(h.read().messages.map((message) => message.content)).toEqual([
-      'Scheduled task: Drink water',
       'Drink water 💧',
     ]);
     expect(h.read().sessionLastActivity['agent:main:cron:job-1']).toBe(1773281732751);
@@ -128,4 +136,99 @@ describe('chat history actions', () => {
     expect(h.read().messages).toEqual([]);
     expect(h.read().loading).toBe(false);
   });
+
+  it('filters out system messages from loaded history', async () => {
+    const { createHistoryActions } = await import('@/stores/chat/history-actions');
+    const h = makeHarness();
+    const actions = createHistoryActions(h.set as never, h.get as never);
+
+    invokeIpcMock.mockResolvedValueOnce({
+      success: true,
+      result: {
+        messages: [
+          { role: 'user', content: 'Hello', timestamp: 1000 },
+          { role: 'system', content: 'Gateway restarted', timestamp: 1001 },
+          { role: 'assistant', content: 'Hi there!', timestamp: 1002 },
+        ],
+      },
+    });
+
+    await actions.loadHistory();
+
+    expect(h.read().messages.map((m) => m.content)).toEqual([
+      'Hello',
+      'Hi there!',
+    ]);
+  });
+
+  it('filters out HEARTBEAT_OK assistant messages', async () => {
+    const { createHistoryActions } = await import('@/stores/chat/history-actions');
+    const h = makeHarness();
+    const actions = createHistoryActions(h.set as never, h.get as never);
+
+    invokeIpcMock.mockResolvedValueOnce({
+      success: true,
+      result: {
+        messages: [
+          { role: 'user', content: 'Hello', timestamp: 1000 },
+          { role: 'assistant', content: 'HEARTBEAT_OK', timestamp: 1001 },
+          { role: 'assistant', content: 'Real response', timestamp: 1002 },
+        ],
+      },
+    });
+
+    await actions.loadHistory();
+
+    expect(h.read().messages.map((m) => m.content)).toEqual([
+      'Hello',
+      'Real response',
+    ]);
+  });
+
+  it('filters out NO_REPLY assistant messages', async () => {
+    const { createHistoryActions } = await import('@/stores/chat/history-actions');
+    const h = makeHarness();
+    const actions = createHistoryActions(h.set as never, h.get as never);
+
+    invokeIpcMock.mockResolvedValueOnce({
+      success: true,
+      result: {
+        messages: [
+          { role: 'user', content: 'Hello', timestamp: 1000 },
+          { role: 'assistant', content: 'NO_REPLY', timestamp: 1001 },
+          { role: 'assistant', content: 'Actual answer', timestamp: 1002 },
+        ],
+      },
+    });
+
+    await actions.loadHistory();
+
+    expect(h.read().messages.map((m) => m.content)).toEqual([
+      'Hello',
+      'Actual answer',
+    ]);
+  });
+
+  it('keeps normal assistant messages that contain HEARTBEAT_OK as substring', async () => {
+    const { createHistoryActions } = await import('@/stores/chat/history-actions');
+    const h = makeHarness();
+    const actions = createHistoryActions(h.set as never, h.get as never);
+
+    invokeIpcMock.mockResolvedValueOnce({
+      success: true,
+      result: {
+        messages: [
+          { role: 'user', content: 'What is HEARTBEAT_OK?', timestamp: 1000 },
+          { role: 'assistant', content: 'HEARTBEAT_OK is a status code', timestamp: 1001 },
+        ],
+      },
+    });
+
+    await actions.loadHistory();
+
+    expect(h.read().messages.map((m) => m.content)).toEqual([
+      'What is HEARTBEAT_OK?',
+      'HEARTBEAT_OK is a status code',
+    ]);
+  });
 });