diff --git a/src/ws/dto/interaction-payload.dto.ts b/src/ws/dto/interaction-payload.dto.ts
new file mode 100644
index 0000000..76516bc
--- /dev/null
+++ b/src/ws/dto/interaction-payload.dto.ts
@@ -0,0 +1,7 @@
+export class InteractionPayloadDto {
+  senderUserId: string;
+  senderName: string;
+  content: string;
+  type: string;
+  timestamp: string;
+}
diff --git a/src/ws/dto/send-interaction.dto.ts b/src/ws/dto/send-interaction.dto.ts
new file mode 100644
index 0000000..90f793a
--- /dev/null
+++ b/src/ws/dto/send-interaction.dto.ts
@@ -0,0 +1,16 @@
+import { IsNotEmpty, IsString, IsUUID, MaxLength } from 'class-validator';
+
+export class SendInteractionDto {
+  @IsUUID()
+  @IsNotEmpty()
+  recipientUserId: string;
+
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(500)
+  content: string;
+
+  @IsString()
+  @IsNotEmpty()
+  type: string;
+}
diff --git a/src/ws/state/state.gateway.spec.ts b/src/ws/state/state.gateway.spec.ts
index 0ae5ac0..bb761bf 100644
--- a/src/ws/state/state.gateway.spec.ts
+++ b/src/ws/state/state.gateway.spec.ts
@@ -7,6 +7,8 @@ import { JwtVerificationService } from '../../auth/services/jwt-verification.ser
 import { PrismaService } from '../../database/prisma.service';
 import { UserSocketService } from './user-socket.service';
 import { WsNotificationService } from './ws-notification.service';
+import { SendInteractionDto } from '../dto/send-interaction.dto';
+import { WsException } from '@nestjs/websockets';
 
 interface MockSocket extends Partial<AuthenticatedSocket> {
   id: string;
@@ -472,4 +474,130 @@ describe('StateGateway', () => {
       ).rejects.toThrow('Unauthorized');
     });
   });
+
+  describe('handleSendInteraction', () => {
+    it('should send interaction to friend if online', async () => {
+      const mockClient: MockSocket = {
+        id: 'client1',
+        data: {
+          user: { keycloakSub: 'test-sub', name: 'TestUser' },
+          userId: 'user-1',
+          friends: new Set(['friend-1']),
+        },
+        emit: jest.fn(),
+      };
+
+      const data: SendInteractionDto = {
+        recipientUserId: 'friend-1',
+        content: 'hello',
+        type: 'text',
+      };
+
+      (mockUserSocketService.isUserOnline as jest.Mock).mockResolvedValue(true);
+
+      await gateway.handleSendInteraction(
+        mockClient as unknown as AuthenticatedSocket,
+        data,
+      );
+
+      expect(mockWsNotificationService.emitToUser).toHaveBeenCalledWith(
+        'friend-1',
+        'interaction-received',
+        expect.objectContaining({
+          senderUserId: 'user-1',
+          senderName: 'TestUser',
+          content: 'hello',
+          type: 'text',
+        }),
+      );
+    });
+
+    it('should fail if recipient is not a friend', async () => {
+      const mockClient: MockSocket = {
+        id: 'client1',
+        data: {
+          user: { keycloakSub: 'test-sub' },
+          userId: 'user-1',
+          friends: new Set(['friend-1']),
+        },
+        emit: jest.fn(),
+      };
+
+      const data: SendInteractionDto = {
+        recipientUserId: 'stranger-1',
+        content: 'hello',
+        type: 'text',
+      };
+
+      await gateway.handleSendInteraction(
+        mockClient as unknown as AuthenticatedSocket,
+        data,
+      );
+
+      expect(mockClient.emit).toHaveBeenCalledWith(
+        'interaction-delivery-failed',
+        expect.objectContaining({
+          reason: 'Recipient is not a friend',
+        }),
+      );
+      expect(mockWsNotificationService.emitToUser).not.toHaveBeenCalled();
+    });
+
+    it('should fail if recipient is offline', async () => {
+      const mockClient: MockSocket = {
+        id: 'client1',
+        data: {
+          user: { keycloakSub: 'test-sub' },
+          userId: 'user-1',
+          friends: new Set(['friend-1']),
+        },
+        emit: jest.fn(),
+      };
+
+      const data: SendInteractionDto = {
+        recipientUserId: 'friend-1',
+        content: 'hello',
+        type: 'text',
+      };
+
+      (mockUserSocketService.isUserOnline as jest.Mock).mockResolvedValue(
+        false,
+      );
+
+      await gateway.handleSendInteraction(
+        mockClient as unknown as AuthenticatedSocket,
+        data,
+      );
+
+      expect(mockClient.emit).toHaveBeenCalledWith(
+        'interaction-delivery-failed',
+        expect.objectContaining({
+          reason: 'Recipient is offline',
+        }),
+      );
+      expect(mockWsNotificationService.emitToUser).not.toHaveBeenCalled();
+    });
+
+    it('should throw Unauthorized if user not initialized', async () => {
+      const mockClient: MockSocket = {
+        id: 'client1',
+        data: {
+          // Missing user/userId
+        },
+      };
+
+      const data: SendInteractionDto = {
+        recipientUserId: 'friend-1',
+        content: 'hello',
+        type: 'text',
+      };
+
+      await expect(
+        gateway.handleSendInteraction(
+          mockClient as unknown as AuthenticatedSocket,
+          data,
+        ),
+      ).rejects.toThrow(WsException);
+    });
+  });
 });
diff --git a/src/ws/state/state.gateway.ts b/src/ws/state/state.gateway.ts
index a6c69d4..f678aa9 100644
--- a/src/ws/state/state.gateway.ts
+++ b/src/ws/state/state.gateway.ts
@@ -18,6 +18,8 @@ import type { AuthenticatedSocket } from '../../types/socket';
 import { AuthService } from '../../auth/auth.service';
 import { JwtVerificationService } from '../../auth/services/jwt-verification.service';
 import { CursorPositionDto } from '../dto/cursor-position.dto';
+import { SendInteractionDto } from '../dto/send-interaction.dto';
+import { InteractionPayloadDto } from '../dto/interaction-payload.dto';
 import { PrismaService } from '../../database/prisma.service';
 import { UserSocketService } from './user-socket.service';
 import { WsNotificationService } from './ws-notification.service';
@@ -336,4 +338,55 @@ export class StateGateway
       }
     }
   }
+
+  @SubscribeMessage(WS_EVENT.CLIENT_SEND_INTERACTION)
+  async handleSendInteraction(
+    client: AuthenticatedSocket,
+    data: SendInteractionDto,
+  ) {
+    const user = client.data.user;
+    const currentUserId = client.data.userId;
+
+    if (!user || !currentUserId) {
+      throw new WsException('Unauthorized: User not initialized');
+    }
+
+    // 1. Verify recipient is a friend
+    const friends = client.data.friends;
+    if (!friends || !friends.has(data.recipientUserId)) {
+      client.emit(WS_EVENT.INTERACTION_DELIVERY_FAILED, {
+        recipientUserId: data.recipientUserId,
+        reason: 'Recipient is not a friend',
+      });
+      return;
+    }
+
+    // 2. Check if recipient is online
+    const isOnline = await this.userSocketService.isUserOnline(
+      data.recipientUserId,
+    );
+    if (!isOnline) {
+      client.emit(WS_EVENT.INTERACTION_DELIVERY_FAILED, {
+        recipientUserId: data.recipientUserId,
+        reason: 'Recipient is offline',
+      });
+      return;
+    }
+
+    // 3. Construct payload
+    const payload: InteractionPayloadDto = {
+      senderUserId: currentUserId,
+      senderName: user.name || user.username || 'Unknown',
+      content: data.content,
+      type: data.type,
+      timestamp: new Date().toISOString(),
+    };
+
+    // 4. Send to recipient
+    await this.wsNotificationService.emitToUser(
+      data.recipientUserId,
+      WS_EVENT.INTERACTION_RECEIVED,
+      payload,
+    );
+  }
 }
diff --git a/src/ws/state/ws-events.ts b/src/ws/state/ws-events.ts
index 494f397..2d79a98 100644
--- a/src/ws/state/ws-events.ts
+++ b/src/ws/state/ws-events.ts
@@ -12,6 +12,9 @@ export const WS_EVENT = {
   FRIEND_DOLL_UPDATED: 'friend-doll-updated',
   FRIEND_DOLL_DELETED: 'friend-doll-deleted',
   FRIEND_ACTIVE_DOLL_CHANGED: 'friend-active-doll-changed',
+  CLIENT_SEND_INTERACTION: 'client-send-interaction',
+  INTERACTION_RECEIVED: 'interaction-received',
+  INTERACTION_DELIVERY_FAILED: 'interaction-delivery-failed',
 } as const;
 
 export const REDIS_CHANNEL = {