diff --git a/packages/browser/src/plugins/in-app-plugin/__tests__/inbox_messages.test.ts b/packages/browser/src/plugins/in-app-plugin/__tests__/inbox_messages.test.ts
new file mode 100644
index 000000000..474ae81e0
--- /dev/null
+++ b/packages/browser/src/plugins/in-app-plugin/__tests__/inbox_messages.test.ts
@@ -0,0 +1,158 @@
+import { Analytics } from '../../../core/analytics'
+import { createInboxAPI, GistInboxMessage } from '../inbox_messages'
+
+function makeMessage(
+  overrides: Partial<GistInboxMessage> = {}
+): GistInboxMessage {
+  return {
+    messageType: 'inline',
+    expiry: '',
+    priority: 0,
+    type: 'test',
+    properties: {},
+    queueId: `msg-${Math.random().toString(36).slice(2)}`,
+    userToken: 'user-1',
+    deliveryId: 'delivery-1',
+    sentAt: new Date().toISOString(),
+    opened: false,
+    ...overrides,
+  }
+}
+
+function createMockGist(messages: GistInboxMessage[]) {
+  const listeners: Record<string, Function[]> = {}
+  return {
+    getInboxMessages: jest.fn().mockResolvedValue(messages),
+    updateInboxMessageOpenState: jest.fn(),
+    removeInboxMessage: jest.fn(),
+    events: {
+      on: jest.fn((event: string, cb: Function) => {
+        if (!listeners[event]) listeners[event] = []
+        listeners[event].push(cb)
+      }),
+      off: jest.fn(),
+      emit: (event: string, data: any) => {
+        ;(listeners[event] || []).forEach((cb) => cb(data))
+      },
+    },
+  }
+}
+
+describe('Inbox _cio topic filtering', () => {
+  const analytics = { track: jest.fn() } as unknown as Analytics
+
+  const regularMessage = makeMessage({
+    queueId: 'regular',
+    topics: ['news'],
+  })
+  const noTopicMessage = makeMessage({
+    queueId: 'no-topic',
+    topics: [],
+  })
+  const cioMessage = makeMessage({
+    queueId: 'cio-msg',
+    topics: ['_cio_inbox_5'],
+  })
+  const mixedMessage = makeMessage({
+    queueId: 'mixed-msg',
+    topics: ['news', '_cio_feed'],
+  })
+
+  const allMessages = [regularMessage, noTopicMessage, cioMessage, mixedMessage]
+
+  describe('no topics specified', () => {
+    it('should return messages without _cio topics', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, [])
+
+      const messages = await inbox.messages()
+      const ids = messages.map((m) => m.messageId)
+
+      expect(ids).toContain('regular')
+      expect(ids).toContain('no-topic')
+      expect(ids).not.toContain('cio-msg')
+      expect(ids).not.toContain('mixed-msg')
+    })
+
+    it('should not count _cio messages in total', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, [])
+
+      expect(await inbox.total()).toBe(2)
+    })
+
+    it('should not count _cio messages in totalUnopened', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, [])
+
+      expect(await inbox.totalUnopened()).toBe(2)
+    })
+
+    it('should filter _cio messages in onUpdates', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, [])
+
+      const result = await new Promise<any[]>((resolve) => {
+        inbox.onUpdates((messages) => resolve(messages))
+        gist.events.emit('messageInboxUpdated', allMessages)
+      })
+
+      const ids = result.map((m) => m.messageId)
+      expect(ids).toContain('regular')
+      expect(ids).toContain('no-topic')
+      expect(ids).not.toContain('cio-msg')
+      expect(ids).not.toContain('mixed-msg')
+    })
+  })
+
+  describe('non-_cio topic specified', () => {
+    it('should return matching messages but exclude _cio messages', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, ['news'])
+
+      const messages = await inbox.messages()
+      const ids = messages.map((m) => m.messageId)
+
+      expect(ids).toContain('regular')
+      expect(ids).not.toContain('no-topic')
+      expect(ids).not.toContain('cio-msg')
+      // mixed-msg has 'news' but also has '_cio_feed', should be excluded
+      expect(ids).not.toContain('mixed-msg')
+    })
+
+    it('should not count _cio messages in total', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, ['news'])
+
+      expect(await inbox.total()).toBe(1)
+    })
+  })
+
+  describe('_cio topic explicitly specified', () => {
+    it('should return _cio messages when explicitly requested', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, ['_cio_inbox_5'])
+
+      const messages = await inbox.messages()
+      const ids = messages.map((m) => m.messageId)
+
+      expect(ids).toContain('cio-msg')
+      expect(ids).not.toContain('mixed-msg')
+      expect(ids).not.toContain('regular')
+      expect(ids).not.toContain('no-topic')
+    })
+
+    it('should return _cio messages when a _cio topic is requested alongside others', async () => {
+      const gist = createMockGist(allMessages)
+      const inbox = createInboxAPI(analytics, gist, ['news', '_cio_feed'])
+
+      const messages = await inbox.messages()
+      const ids = messages.map((m) => m.messageId)
+
+      expect(ids).toContain('regular')
+      expect(ids).toContain('mixed-msg')
+      expect(ids).not.toContain('no-topic')
+      expect(ids).not.toContain('cio-msg')
+    })
+  })
+})
diff --git a/packages/browser/src/plugins/in-app-plugin/inbox_messages.ts b/packages/browser/src/plugins/in-app-plugin/inbox_messages.ts
index d11fabd71..c4d464e86 100644
--- a/packages/browser/src/plugins/in-app-plugin/inbox_messages.ts
+++ b/packages/browser/src/plugins/in-app-plugin/inbox_messages.ts
@@ -1,6 +1,8 @@
 import { Analytics } from '../../core/analytics'
 import { JourneysEvents } from './events'
 
+const CIO_TOPIC_PREFIX = '_cio'
+
 export interface GistInboxMessage {
   messageType: string
   expiry: string
@@ -143,14 +145,25 @@ async function getFilteredMessages(
   })
 
   if (topics.length === 0) {
-    return allMessages
+    return allMessages.filter((message) => {
+      const messageTopics = message.topics
+      if (!messageTopics || messageTopics.length === 0) {
+        return true
+      }
+      return !messageTopics.some((topic) => topic.startsWith(CIO_TOPIC_PREFIX))
+    })
   }
 
+  const hasCioTopic = topics.some((topic) => topic.startsWith(CIO_TOPIC_PREFIX))
+
   return allMessages.filter((message) => {
     const messageTopics = message.topics
     if (!messageTopics || messageTopics.length === 0) {
       return false
     }
+    if (!hasCioTopic && messageTopics.some((topic) => topic.startsWith(CIO_TOPIC_PREFIX))) {
+      return false
+    }
     return messageTopics.some((messageTopic) => topics.includes(messageTopic))
   })
 }