diff --git a/packages/agent/src/server/agent-server.test.ts b/packages/agent/src/server/agent-server.test.ts
index 99e0c67a9d..447ed9b43e 100644
--- a/packages/agent/src/server/agent-server.test.ts
+++ b/packages/agent/src/server/agent-server.test.ts
@@ -1905,6 +1905,46 @@ describe("AgentServer HTTP Mode", () => {
   });
 
   describe("POST /command", () => {
+    it("acknowledges an asynchronous user message before its turn completes", async () => {
+      const s = createServer();
+      await s.start();
+      let resolvePrompt!: (value: { stopReason: string }) => void;
+      const promptPending = new Promise<{ stopReason: string }>((resolve) => {
+        resolvePrompt = resolve;
+      });
+      const serverInternals = s as unknown as {
+        session: {
+          clientConnection: { prompt: () => Promise<{ stopReason: string }> };
+        };
+      };
+      serverInternals.session.clientConnection.prompt = () => promptPending;
+
+      const response = await fetch(`http://localhost:${port}/command`, {
+        method: "POST",
+        headers: {
+          Authorization: `Bearer ${createToken({ run_id: "test-run-id" })}`,
+          "Content-Type": "application/json",
+        },
+        body: JSON.stringify({
+          jsonrpc: "2.0",
+          id: "async-message",
+          method: "user_message",
+          params: {
+            content: "do the thing",
+            messageId: "message-1",
+            waitForCompletion: false,
+          },
+        }),
+      });
+
+      expect(await response.json()).toEqual({
+        jsonrpc: "2.0",
+        id: "async-message",
+        result: { accepted: true },
+      });
+      resolvePrompt({ stopReason: "end_turn" });
+    });
+
     it("returns 401 without authorization", async () => {
       await createServer().start();
 
diff --git a/packages/agent/src/server/agent-server.ts b/packages/agent/src/server/agent-server.ts
index 3a1853f7b9..5f5b2fe6fe 100644
--- a/packages/agent/src/server/agent-server.ts
+++ b/packages/agent/src/server/agent-server.ts
@@ -712,10 +712,28 @@ export class AgentServer {
       }
 
       try {
-        const result = await this.executeCommand(
+        const commandPromise = this.executeCommand(
           command.method,
           (command.params as Record<string, unknown>) || {},
         );
+        if (
+          (command.method === POSTHOG_NOTIFICATIONS.USER_MESSAGE ||
+            command.method === "user_message") &&
+          command.params?.waitForCompletion === false
+        ) {
+          void commandPromise.catch((error) =>
+            this.logger.error("Asynchronous user_message command failed", {
+              error,
+              messageId: command.params?.messageId,
+            }),
+          );
+          return c.json({
+            jsonrpc: "2.0",
+            id: command.id,
+            result: { accepted: true },
+          });
+        }
+        const result = await commandPromise;
         return c.json({
           jsonrpc: "2.0",
           id: command.id,
diff --git a/packages/agent/src/server/schemas.ts b/packages/agent/src/server/schemas.ts
index 56fa3b608b..596d39f692 100644
--- a/packages/agent/src/server/schemas.ts
+++ b/packages/agent/src/server/schemas.ts
@@ -69,6 +69,7 @@ export const userMessageParamsSchema = z
     artifacts: z.array(z.record(z.string(), z.unknown())).optional(),
     messageId: z.string().min(1).optional(),
     steer: z.boolean().optional(),
+    waitForCompletion: z.boolean().optional(),
   })
   .refine(
     (params) => {