apps/gateway/src/chat/chat.gateway.ts

@@ -668,7 +668,18 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
     );
     const actorId = binding && resolveDiscordInteractionActorId(binding, ingress.userId);
     const agentName = process.env['MOSAIC_AGENT_NAME']?.trim();
-    if (!actorId || !agentName || binding.instanceId !== agentName) return;
+    if (!actorId || !agentName || binding.instanceId !== agentName) {
+      this.logger.warn(
+        `Rejected Discord approval without a matching runtime agent from ${client.id}`,
+      );
+      client.emit('discord:approval', {
+        correlationId: ingress.correlationId,
+        success: false,
+        approvalId: undefined,
+        expiresAt: undefined,
+      });
+      return;
+    }
     const providerId = actionParts[1]!;
     const sessionId = actionParts[2]!;
     const approval = await this.commandAuthorization.createRuntimeTerminationApproval({

apps/gateway/src/plugin/discord-ingress.security.spec.ts

@@ -271,6 +271,24 @@ describe('Discord ingress security', () => {
     ]);
   });
 
+  it('rejects approval when the binding targets a different runtime agent', async () => {
+    configureDiscordEnv();
+    process.env['MOSAIC_AGENT_NAME'] = 'Other';
+    const { gateway, client } = discordGateway('admin');
+
+    await gateway.handleDiscordApproval(
+      client as never,
+      ingressEnvelope('/approve fleet runtime-1', 'mismatched-agent-approve'),
+    );
+
+    expect(client.emit).toHaveBeenCalledWith('discord:approval', {
+      correlationId: 'correlation-001',
+      success: false,
+      approvalId: undefined,
+      expiresAt: undefined,
+    });
+  });
+
   it('rejects unpaired and non-admin Discord users for approval and stop', async () => {
     configureDiscordEnv();
     const { gateway, client } = discordGateway('member');