diff --git a/agentscope-harness/src/main/java/io/agentscope/harness/agent/gateway/WakeupDispatcher.java b/agentscope-harness/src/main/java/io/agentscope/harness/agent/gateway/WakeupDispatcher.java
index d102f9106..04218fb97 100644
--- a/agentscope-harness/src/main/java/io/agentscope/harness/agent/gateway/WakeupDispatcher.java
+++ b/agentscope-harness/src/main/java/io/agentscope/harness/agent/gateway/WakeupDispatcher.java
@@ -70,11 +70,10 @@ public WakeupDispatcher(MessageBus messageBus, WakeupTarget target) {
     }
 
     /**
-     * Starts the dispatcher: performs an initial drain of any queued wakeups (to pick up signals
-     * produced while this process was down), then subscribes to the live signal channel.
+     * Starts the dispatcher: subscribes to the live signal channel, then performs an initial drain
+     * of any queued wakeups produced while this process was down.
      */
     public void start() {
-        drainAndDispatch();
         subscription =
                 messageBus
                         .subscribeWakeup()
@@ -85,6 +84,7 @@ public void start() {
                                                 "WakeupDispatcher subscription error; "
                                                         + "dispatcher is dead",
                                                 err));
+        drainAndDispatch();
         log.info("WakeupDispatcher started");
     }
 
@@ -100,14 +100,20 @@ public void close() {
 
     private void drainAndDispatch() {
         try {
-            List<BusEntry> entries =
-                    messageBus.queueDrain("agentscope:wakeups", MAX_DRAIN_COUNT).block();
-            if (entries == null || entries.isEmpty()) {
-                return;
-            }
-
-            for (BusEntry entry : entries) {
-                dispatch(entry.payload());
+            while (true) {
+                List<BusEntry> entries =
+                        messageBus.queueDrain("agentscope:wakeups", MAX_DRAIN_COUNT).block();
+                if (entries == null || entries.isEmpty()) {
+                    return;
+                }
+
+                for (BusEntry entry : entries) {
+                    dispatch(entry.payload());
+                }
+
+                if (entries.size() < MAX_DRAIN_COUNT) {
+                    return;
+                }
             }
         } catch (Exception e) {
             log.warn("WakeupDispatcher: drainAndDispatch failed", e);
diff --git a/agentscope-harness/src/test/java/io/agentscope/harness/agent/gateway/WakeupDispatcherTest.java b/agentscope-harness/src/test/java/io/agentscope/harness/agent/gateway/WakeupDispatcherTest.java
index a5777ded3..20ddf2329 100644
--- a/agentscope-harness/src/test/java/io/agentscope/harness/agent/gateway/WakeupDispatcherTest.java
+++ b/agentscope-harness/src/test/java/io/agentscope/harness/agent/gateway/WakeupDispatcherTest.java
@@ -32,6 +32,7 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
+import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 class WakeupDispatcherTest {
@@ -115,6 +116,44 @@ void initialDrain_picksUpPreExisting() throws Exception {
         assertEquals("sess-pre", target.wokenSessions.get(0));
     }
 
+    @Test
+    @DisplayName("Startup drain processes all pre-existing wakeups across multiple batches")
+    void initialDrain_processesMoreThanOneBatch() {
+        int wakeupCount = 65;
+        for (int i = 0; i < wakeupCount; i++) {
+            String sessionId = "sess-pre-" + i;
+            target.addKnown(sessionId);
+            messageBus
+                    .queuePush(
+                            "agentscope:wakeups",
+                            Map.of(
+                                    "userId", "user-1",
+                                    "sessionId", sessionId,
+                                    "agentId", "agent-main"))
+                    .block();
+        }
+
+        dispatcher.start();
+
+        assertEquals(wakeupCount, target.wokenSessions.size());
+    }
+
+    @Test
+    @DisplayName("Startup subscribes before draining the durable wakeup queue")
+    void startup_subscribesBeforeInitialDrain() {
+        String sessionId = "sess-startup-race";
+        target.addKnown(sessionId);
+        messageBus =
+                new EnqueueOnSubscribeMessageBus(
+                        new LocalFilesystem(tmpDir, true, 10), "/bus", sessionId);
+        dispatcher = new WakeupDispatcher(messageBus, target);
+
+        dispatcher.start();
+
+        assertEquals(1, target.wokenSessions.size());
+        assertEquals(sessionId, target.wokenSessions.get(0));
+    }
+
     // ------------------------------------------------------------------
     //  Test double
     // ------------------------------------------------------------------
@@ -157,4 +196,30 @@ boolean awaitWakeup(int expected, long timeout, TimeUnit unit) throws Interrupte
             return wakeupLatch.await(timeout, unit);
         }
     }
+
+    private static final class EnqueueOnSubscribeMessageBus extends WorkspaceMessageBus {
+
+        private final String sessionId;
+
+        private EnqueueOnSubscribeMessageBus(
+                LocalFilesystem filesystem, String busRoot, String sessionId) {
+            super(filesystem, busRoot);
+            this.sessionId = sessionId;
+        }
+
+        @Override
+        public Flux<Map<String, Object>> subscribeWakeup() {
+            return Flux.defer(
+                    () -> {
+                        queuePush(
+                                        "agentscope:wakeups",
+                                        Map.of(
+                                                "userId", "user-1",
+                                                "sessionId", sessionId,
+                                                "agentId", "agent-main"))
+                                .block();
+                        return Flux.never();
+                    });
+        }
+    }
 }