diff --git a/tests-js/scripts/mock-server.ts b/tests-js/scripts/mock-server.ts
index 6dffd2cf0f388..09c6de07d81b2 100644
--- a/tests-js/scripts/mock-server.ts
+++ b/tests-js/scripts/mock-server.ts
@@ -502,0 +503,15 @@ export function startMockServer(options: MockServerOptions = {}): Promise<MockSe
+          const dmMatch = userText.match(/E2E_DM\(([^)]+)\)\[([\s\S]*)\]/)
+          const lastUserIndex = messages.lastIndexOf(lastUserMsg)
+          if (dmMatch && !messages.slice(lastUserIndex + 1).some(m => m?.role === 'tool')) {
+            const turn: ScriptedTurn = {
+              text: '',
+              toolCalls: [{ name: 'message_agent', args: { target: dmMatch[1], message: dmMatch[2] } }],
+            }
+            if (stream) {
+              streamScriptedTurn(res, model, turn)
+            } else {
+              nonStreamingScriptedTurn(res, model, turn)
+            }
+            return
+          }
+