diff --git a/src/dashboard/react-components/MessageList.tsx b/src/dashboard/react-components/MessageList.tsx
index 3aee9f1f..fd83ad7e 100644
--- a/src/dashboard/react-components/MessageList.tsx
+++ b/src/dashboard/react-components/MessageList.tsx
@@ -43,6 +43,7 @@ SyntaxHighlighter.registerLanguage('dockerfile', docker);
 import type { Message, Agent, Attachment } from '../types';
 import { MessageStatusIndicator } from './MessageStatusIndicator';
 import { ThinkingIndicator } from './ThinkingIndicator';
+import { deduplicateBroadcasts } from './hooks/useBroadcastDedup';
 
 // Provider icons and colors matching landing page
 const PROVIDER_CONFIG: Record<string, { icon: string; color: string }> = {
@@ -127,7 +128,7 @@ export function MessageList({
   const isScrollingRef = useRef(false);
 
   // Filter messages for current channel or current thread
-  const filteredMessages = messages.filter((msg) => {
+  const channelFilteredMessages = messages.filter((msg) => {
     // When a thread is selected, show messages related to that thread
     if (currentThread) {
       // Show the original message (id matches thread) or replies (thread field matches)
@@ -148,6 +149,14 @@ export function MessageList({
     return msg.from === currentChannel || msg.to === currentChannel;
   });
 
+  // Deduplicate broadcast messages in #general channel
+  // When a broadcast is sent to '*', the backend delivers it to each recipient separately,
+  // causing the same message to appear multiple times. Deduplication removes duplicates
+  // by grouping broadcasts with the same sender, content, and timestamp.
+  const filteredMessages = currentChannel === 'general'
+    ? deduplicateBroadcasts(channelFilteredMessages)
+    : channelFilteredMessages;
+
   // Populate latestMessageToAgent with the latest message from current user to each agent
   // Iterate in order (oldest to newest) so the last one wins
   for (const msg of filteredMessages) {
diff --git a/src/dashboard/react-components/hooks/useBroadcastDedup.test.ts b/src/dashboard/react-components/hooks/useBroadcastDedup.test.ts
new file mode 100644
index 00000000..579602f3
--- /dev/null
+++ b/src/dashboard/react-components/hooks/useBroadcastDedup.test.ts
@@ -0,0 +1,371 @@
+/**
+ * Tests for broadcast message deduplication in #general channel
+ *
+ * TDD approach: Write failing tests first, then fix the implementation.
+ *
+ * Problem: When a broadcast is sent (to='*'), the backend delivers it to each
+ * recipient separately. Each delivery gets a unique ID and is stored separately.
+ * In #general channel, this causes the same message to appear multiple times
+ * (once per recipient).
+ *
+ * Solution: Deduplicate broadcast messages by grouping those with the same
+ * sender, content, and approximate timestamp (within 1 second).
+ */
+
+import { describe, it, expect } from 'vitest';
+import type { Message } from '../../types';
+import { deduplicateBroadcasts, getBroadcastKey } from './useBroadcastDedup';
+
+// Helper to create test messages
+function createMessage(
+  from: string,
+  to: string,
+  content: string,
+  options?: {
+    id?: string;
+    isBroadcast?: boolean;
+    timestamp?: string;
+    channel?: string;
+  }
+): Message {
+  return {
+    id: options?.id || `msg-${Math.random().toString(36).slice(2)}`,
+    from,
+    to,
+    content,
+    timestamp: options?.timestamp || new Date().toISOString(),
+    isBroadcast: options?.isBroadcast,
+    channel: options?.channel,
+  };
+}
+
+describe('Broadcast Deduplication', () => {
+  describe('deduplicateBroadcasts', () => {
+    it('should show broadcast message only once when delivered to multiple recipients', () => {
+      const timestamp = '2026-01-08T12:00:00.000Z';
+
+      // Same broadcast delivered to 3 different recipients
+      const messages: Message[] = [
+        createMessage('Alice', 'Agent1', 'Hello everyone!', {
+          id: 'delivery-1',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent2', 'Hello everyone!', {
+          id: 'delivery-2',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent3', 'Hello everyone!', {
+          id: 'delivery-3',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      // Should only show one instance of the broadcast
+      expect(deduped).toHaveLength(1);
+      expect(deduped[0].content).toBe('Hello everyone!');
+      expect(deduped[0].from).toBe('Alice');
+    });
+
+    it('should preserve different broadcasts from the same sender', () => {
+      const timestamp1 = '2026-01-08T12:00:00.000Z';
+      const timestamp2 = '2026-01-08T12:01:00.000Z'; // 1 minute later
+
+      const messages: Message[] = [
+        // First broadcast delivered to 2 recipients
+        createMessage('Alice', 'Agent1', 'First message', {
+          id: 'delivery-1',
+          isBroadcast: true,
+          timestamp: timestamp1,
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent2', 'First message', {
+          id: 'delivery-2',
+          isBroadcast: true,
+          timestamp: timestamp1,
+          channel: 'general',
+        }),
+        // Second broadcast delivered to 2 recipients
+        createMessage('Alice', 'Agent1', 'Second message', {
+          id: 'delivery-3',
+          isBroadcast: true,
+          timestamp: timestamp2,
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent2', 'Second message', {
+          id: 'delivery-4',
+          isBroadcast: true,
+          timestamp: timestamp2,
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      // Should show both broadcasts, but only once each
+      expect(deduped).toHaveLength(2);
+      expect(deduped.map(m => m.content)).toContain('First message');
+      expect(deduped.map(m => m.content)).toContain('Second message');
+    });
+
+    it('should not deduplicate non-broadcast messages', () => {
+      const timestamp = '2026-01-08T12:00:00.000Z';
+
+      // Direct messages with same content should NOT be deduplicated
+      const messages: Message[] = [
+        createMessage('Alice', 'Bob', 'Hello!', {
+          id: 'dm-1',
+          isBroadcast: false,
+          timestamp,
+        }),
+        createMessage('Alice', 'Charlie', 'Hello!', {
+          id: 'dm-2',
+          isBroadcast: false,
+          timestamp,
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      // Both DMs should remain (they're intentionally separate messages)
+      expect(deduped).toHaveLength(2);
+    });
+
+    it('should preserve message order after deduplication', () => {
+      const messages: Message[] = [
+        createMessage('Alice', 'Agent1', 'First', {
+          id: 'msg-1',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:00.000Z',
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent2', 'First', {
+          id: 'msg-2',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:00.000Z',
+          channel: 'general',
+        }),
+        createMessage('Bob', 'Agent1', 'Second', {
+          id: 'msg-3',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:30.000Z',
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent1', 'Third', {
+          id: 'msg-4',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:01:00.000Z',
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      expect(deduped).toHaveLength(3);
+      expect(deduped[0].content).toBe('First');
+      expect(deduped[1].content).toBe('Second');
+      expect(deduped[2].content).toBe('Third');
+    });
+
+    it('should handle mixed broadcast and direct messages', () => {
+      const messages: Message[] = [
+        // Broadcast delivered to 2 recipients
+        createMessage('Alice', 'Agent1', 'Broadcast', {
+          id: 'broadcast-1',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:00.000Z',
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent2', 'Broadcast', {
+          id: 'broadcast-2',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:00.000Z',
+          channel: 'general',
+        }),
+        // Direct message
+        createMessage('Bob', 'Alice', 'DM to Alice', {
+          id: 'dm-1',
+          isBroadcast: false,
+          timestamp: '2026-01-08T12:00:30.000Z',
+        }),
+        // Another broadcast
+        createMessage('Charlie', 'Agent1', 'Another broadcast', {
+          id: 'broadcast-3',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:01:00.000Z',
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      expect(deduped).toHaveLength(3);
+      expect(deduped.map(m => m.content)).toEqual([
+        'Broadcast',
+        'DM to Alice',
+        'Another broadcast',
+      ]);
+    });
+
+    it('should keep first occurrence when deduplicating', () => {
+      const timestamp = '2026-01-08T12:00:00.000Z';
+
+      const messages: Message[] = [
+        createMessage('Alice', 'Agent1', 'Hello everyone!', {
+          id: 'first-delivery',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent2', 'Hello everyone!', {
+          id: 'second-delivery',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      // Should keep the first one (first-delivery)
+      expect(deduped).toHaveLength(1);
+      expect(deduped[0].id).toBe('first-delivery');
+    });
+
+    it('should handle empty message array', () => {
+      const deduped = deduplicateBroadcasts([]);
+      expect(deduped).toHaveLength(0);
+    });
+
+    it('should handle messages with to="*" as broadcasts even without isBroadcast flag', () => {
+      const timestamp = '2026-01-08T12:00:00.000Z';
+
+      // Messages with to='*' but no isBroadcast flag (legacy format)
+      const messages: Message[] = [
+        createMessage('Alice', '*', 'Broadcast message', {
+          id: 'delivery-1',
+          timestamp,
+          channel: 'general',
+        }),
+        // Same message delivered to specific agent with isBroadcast flag
+        createMessage('Alice', 'Agent1', 'Broadcast message', {
+          id: 'delivery-2',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      // Should deduplicate - both represent the same broadcast
+      expect(deduped).toHaveLength(1);
+    });
+
+    it('should differentiate broadcasts with same content but different senders', () => {
+      const timestamp = '2026-01-08T12:00:00.000Z';
+
+      const messages: Message[] = [
+        createMessage('Alice', 'Agent1', 'Hello!', {
+          id: 'alice-1',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+        createMessage('Bob', 'Agent1', 'Hello!', {
+          id: 'bob-1',
+          isBroadcast: true,
+          timestamp,
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      // Different senders, so both should appear
+      expect(deduped).toHaveLength(2);
+    });
+
+    it('should handle timestamps within 1 second as same broadcast', () => {
+      // Timestamps within 1 second should be grouped
+      const messages: Message[] = [
+        createMessage('Alice', 'Agent1', 'Quick message', {
+          id: 'delivery-1',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:00.100Z',
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent2', 'Quick message', {
+          id: 'delivery-2',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:00.500Z',
+          channel: 'general',
+        }),
+        createMessage('Alice', 'Agent3', 'Quick message', {
+          id: 'delivery-3',
+          isBroadcast: true,
+          timestamp: '2026-01-08T12:00:00.900Z',
+          channel: 'general',
+        }),
+      ];
+
+      const deduped = deduplicateBroadcasts(messages);
+
+      // All within 1 second, same sender/content - should be 1 message
+      expect(deduped).toHaveLength(1);
+    });
+  });
+
+  describe('getBroadcastKey', () => {
+    it('should generate consistent keys for same sender/content/timestamp', () => {
+      const msg1 = createMessage('Alice', 'Agent1', 'Hello', {
+        timestamp: '2026-01-08T12:00:00.000Z',
+      });
+      const msg2 = createMessage('Alice', 'Agent2', 'Hello', {
+        timestamp: '2026-01-08T12:00:00.500Z', // Same second
+      });
+
+      expect(getBroadcastKey(msg1)).toBe(getBroadcastKey(msg2));
+    });
+
+    it('should generate different keys for different senders', () => {
+      const msg1 = createMessage('Alice', 'Agent1', 'Hello', {
+        timestamp: '2026-01-08T12:00:00.000Z',
+      });
+      const msg2 = createMessage('Bob', 'Agent1', 'Hello', {
+        timestamp: '2026-01-08T12:00:00.000Z',
+      });
+
+      expect(getBroadcastKey(msg1)).not.toBe(getBroadcastKey(msg2));
+    });
+
+    it('should generate different keys for different content', () => {
+      const msg1 = createMessage('Alice', 'Agent1', 'Hello', {
+        timestamp: '2026-01-08T12:00:00.000Z',
+      });
+      const msg2 = createMessage('Alice', 'Agent1', 'Goodbye', {
+        timestamp: '2026-01-08T12:00:00.000Z',
+      });
+
+      expect(getBroadcastKey(msg1)).not.toBe(getBroadcastKey(msg2));
+    });
+
+    it('should generate different keys for timestamps more than 1 second apart', () => {
+      const msg1 = createMessage('Alice', 'Agent1', 'Hello', {
+        timestamp: '2026-01-08T12:00:00.000Z',
+      });
+      const msg2 = createMessage('Alice', 'Agent1', 'Hello', {
+        timestamp: '2026-01-08T12:00:02.000Z', // 2 seconds later
+      });
+
+      expect(getBroadcastKey(msg1)).not.toBe(getBroadcastKey(msg2));
+    });
+  });
+});
diff --git a/src/dashboard/react-components/hooks/useBroadcastDedup.ts b/src/dashboard/react-components/hooks/useBroadcastDedup.ts
new file mode 100644
index 00000000..8aad74f9
--- /dev/null
+++ b/src/dashboard/react-components/hooks/useBroadcastDedup.ts
@@ -0,0 +1,86 @@
+/**
+ * Broadcast message deduplication utilities
+ *
+ * When a broadcast is sent (to='*'), the backend delivers it to each
+ * recipient separately. Each delivery gets a unique ID and is stored separately.
+ * In #general channel, this causes the same message to appear multiple times
+ * (once per recipient).
+ *
+ * This module provides utilities to deduplicate broadcast messages by grouping
+ * those with the same sender, content, and approximate timestamp.
+ */
+
+import { useMemo } from 'react';
+import type { Message } from '../../types';
+
+/**
+ * Check if a message is a broadcast message.
+ * A message is considered a broadcast if:
+ * - isBroadcast flag is true, OR
+ * - to field is '*'
+ */
+function isBroadcastMessage(message: Message): boolean {
+  return message.isBroadcast === true || message.to === '*';
+}
+
+/**
+ * Generate a deduplication key for broadcast messages.
+ * Uses sender + content + timestamp bucket (1-second window).
+ *
+ * @param message The message to generate a key for
+ * @returns A string key for deduplication
+ */
+export function getBroadcastKey(message: Message): string {
+  const timestampBucket = Math.floor(new Date(message.timestamp).getTime() / 1000);
+  return `${message.from}:${timestampBucket}:${message.content}`;
+}
+
+/**
+ * Deduplicate broadcast messages.
+ *
+ * When a broadcast is sent, it gets delivered to each recipient separately,
+ * resulting in multiple stored messages with the same content. This function
+ * deduplicates them by grouping broadcasts with the same:
+ * - from (sender)
+ * - content (message body)
+ * - timestamp (within 1 second window)
+ *
+ * Non-broadcast messages (direct messages) are preserved unchanged.
+ * Message order is maintained, keeping the first occurrence of each broadcast.
+ *
+ * @param messages Array of messages to deduplicate
+ * @returns Deduplicated array with broadcast duplicates removed
+ */
+export function deduplicateBroadcasts(messages: Message[]): Message[] {
+  const seenBroadcastKeys = new Set<string>();
+  const result: Message[] = [];
+
+  for (const message of messages) {
+    // Non-broadcast messages pass through unchanged
+    if (!isBroadcastMessage(message)) {
+      result.push(message);
+      continue;
+    }
+
+    // For broadcasts, check if we've seen this key before
+    const key = getBroadcastKey(message);
+    if (!seenBroadcastKeys.has(key)) {
+      seenBroadcastKeys.add(key);
+      result.push(message);
+    }
+    // If key already seen, skip this duplicate
+  }
+
+  return result;
+}
+
+/**
+ * Hook for using broadcast deduplication with React state.
+ * Uses useMemo to prevent unnecessary recalculations when messages haven't changed.
+ *
+ * @param messages Array of messages to deduplicate
+ * @returns Deduplicated messages
+ */
+export function useBroadcastDedup(messages: Message[]): Message[] {
+  return useMemo(() => deduplicateBroadcasts(messages), [messages]);
+}