diff --git a/extensions/matrix/src/matrix/monitor/handler.group-history.test.ts b/extensions/matrix/src/matrix/monitor/handler.group-history.test.ts
index e5dd7e94682..691eeb641ab 100644
--- a/extensions/matrix/src/matrix/monitor/handler.group-history.test.ts
+++ b/extensions/matrix/src/matrix/monitor/handler.group-history.test.ts
@@ -60,6 +60,14 @@ beforeEach(() => {
   installMatrixMonitorTestRuntime();
 });
 
+function deferred<T>() {
+  let resolve!: (value: T | PromiseLike<T>) => void;
+  const promise = new Promise<T>((res) => {
+    resolve = res;
+  });
+  return { promise, resolve };
+}
+
 describe("matrix group chat history — scenario 1: basic accumulation", () => {
   it("pending messages appear in InboundHistory; trigger itself does not", async () => {
     const finalizeInboundContext = vi.fn((ctx: unknown) => ctx);
@@ -185,6 +193,39 @@ describe("matrix group chat history — scenario 1: basic accumulation", () => {
     expect(history ?? []).toHaveLength(0);
   });
 
+  it("historyLimit=0 does not serialize same-room ingress", async () => {
+    const firstUserId = deferred<string>();
+    let getUserIdCalls = 0;
+    const { handler } = createMatrixHandlerTestHarness({
+      historyLimit: 0,
+      groupPolicy: "open",
+      isDirectMessage: false,
+      client: {
+        getUserId: async () => {
+          getUserIdCalls += 1;
+          if (getUserIdCalls === 1) {
+            return await firstUserId.promise;
+          }
+          return "@bot:example.org";
+        },
+      },
+      dispatchReplyFromConfig: async () => ({
+        queuedFinal: true,
+        counts: { final: 1, block: 0, tool: 0 },
+      }),
+    });
+
+    const first = handler(DEFAULT_ROOM, makeRoomTriggerEvent({ eventId: "$a", body: "first" }));
+    await Promise.resolve();
+    const second = handler(DEFAULT_ROOM, makeRoomTriggerEvent({ eventId: "$b", body: "second" }));
+    await Promise.resolve();
+
+    expect(getUserIdCalls).toBe(2);
+
+    firstUserId.resolve("@bot:example.org");
+    await Promise.all([first, second]);
+  });
+
   it("DMs do not accumulate history (group chat only)", async () => {
     const finalizeInboundContext = vi.fn((ctx: unknown) => ctx);
     const { handler } = createMatrixHandlerTestHarness({
diff --git a/extensions/matrix/src/matrix/monitor/handler.ts b/extensions/matrix/src/matrix/monitor/handler.ts
index 33941101272..838d86df1f8 100644
--- a/extensions/matrix/src/matrix/monitor/handler.ts
+++ b/extensions/matrix/src/matrix/monitor/handler.ts
@@ -287,6 +287,11 @@ export function createMatrixRoomMessageHandler(params: MatrixMonitorHandlerParam
     }
   };
 
+  const runHistoryAwareRoomIngress = async <T>(
+    roomId: string,
+    task: () => Promise<T>,
+  ): Promise<T> => (historyLimit > 0 ? runRoomIngress(roomId, task) : task());
+
   return async (roomId: string, event: MatrixRawEvent) => {
     const eventId = typeof event.event_id === "string" ? event.event_id.trim() : "";
     let claimedInboundEvent = false;
@@ -331,7 +336,7 @@ export function createMatrixRoomMessageHandler(params: MatrixMonitorHandlerParam
         await inboundDeduper.commitEvent({ roomId, eventId });
         claimedInboundEvent = false;
       };
-      const ingressResult = await runRoomIngress(roomId, async () => {
+      const ingressResult = await runHistoryAwareRoomIngress(roomId, async () => {
         const selfUserId = await client.getUserId();
         if (senderId === selfUserId) {
           return;
diff --git a/extensions/matrix/src/matrix/monitor/room-history.test.ts b/extensions/matrix/src/matrix/monitor/room-history.test.ts
index edf493ba0f1..cb0e909f6f5 100644
--- a/extensions/matrix/src/matrix/monitor/room-history.test.ts
+++ b/extensions/matrix/src/matrix/monitor/room-history.test.ts
@@ -91,6 +91,41 @@ describe("createRoomHistoryTracker — watermark monotonicity", () => {
     expect(room1History).toHaveLength(1);
     expect(room1History[0]?.body).toBe("new msg in room1");
   });
+
+  it("refreshes prepared-trigger recency before capped eviction on retry hits", () => {
+    const tracker = createRoomHistoryTracker(200, 10, 5000, 2);
+    const room1 = "!room1:test";
+
+    tracker.prepareTrigger(AGENT, room1, 100, {
+      sender: "user",
+      body: "trigger1",
+      messageId: "$trigger1",
+    });
+    tracker.prepareTrigger(AGENT, room1, 100, {
+      sender: "user",
+      body: "trigger2",
+      messageId: "$trigger2",
+    });
+
+    // Retry hit should refresh trigger1 so trigger2 becomes the stale entry.
+    const retried = tracker.prepareTrigger(AGENT, room1, 100, {
+      sender: "user",
+      body: "trigger1",
+      messageId: "$trigger1",
+    });
+    tracker.prepareTrigger(AGENT, room1, 100, {
+      sender: "user",
+      body: "trigger3",
+      messageId: "$trigger3",
+    });
+
+    const reused = tracker.prepareTrigger(AGENT, room1, 100, {
+      sender: "user",
+      body: "trigger1",
+      messageId: "$trigger1",
+    });
+    expect(reused.snapshotIdx).toBe(retried.snapshotIdx);
+  });
 });
 
 describe("createRoomHistoryTracker — roomQueues eviction", () => {
diff --git a/extensions/matrix/src/matrix/monitor/room-history.ts b/extensions/matrix/src/matrix/monitor/room-history.ts
index aabc535e422..079f291e512 100644
--- a/extensions/matrix/src/matrix/monitor/room-history.ts
+++ b/extensions/matrix/src/matrix/monitor/room-history.ts
@@ -86,6 +86,7 @@ export function createRoomHistoryTracker(
   maxQueueSize = DEFAULT_MAX_QUEUE_SIZE,
   maxRoomQueues = DEFAULT_MAX_ROOM_QUEUES,
   maxWatermarkEntries = MAX_WATERMARK_ENTRIES,
+  maxPreparedTriggerEntries = MAX_PREPARED_TRIGGER_ENTRIES,
 ): RoomHistoryTracker {
   const roomQueues = new Map<string, RoomQueue>();
   /** Maps `${agentId}:${roomId}` → absolute consumed-up-to index */
@@ -153,6 +154,25 @@ export function createRoomHistoryTracker(
     }
   }
 
+  function rememberPreparedTrigger(
+    queue: RoomQueue,
+    retryKey: string,
+    prepared: PreparedTriggerResult,
+  ): PreparedTriggerResult {
+    if (queue.preparedTriggers.has(retryKey)) {
+      // Refresh insertion order so capped eviction keeps actively retried events hot.
+      queue.preparedTriggers.delete(retryKey);
+    }
+    queue.preparedTriggers.set(retryKey, prepared);
+    if (queue.preparedTriggers.size > maxPreparedTriggerEntries) {
+      const oldest = queue.preparedTriggers.keys().next().value;
+      if (oldest !== undefined) {
+        queue.preparedTriggers.delete(oldest);
+      }
+    }
+    return prepared;
+  }
+
   function computePendingHistory(
     queue: RoomQueue,
     agentId: string,
@@ -193,7 +213,7 @@ export function createRoomHistoryTracker(
       if (retryKey) {
         const prepared = queue.preparedTriggers.get(retryKey);
         if (prepared) {
-          return prepared;
+          return rememberPreparedTrigger(queue, retryKey, prepared);
         }
       }
       const prepared = {
@@ -201,13 +221,7 @@ export function createRoomHistoryTracker(
         snapshotIdx: appendToQueue(queue, entry),
       };
       if (retryKey) {
-        queue.preparedTriggers.set(retryKey, prepared);
-        if (queue.preparedTriggers.size > MAX_PREPARED_TRIGGER_ENTRIES) {
-          const oldest = queue.preparedTriggers.keys().next().value;
-          if (oldest !== undefined) {
-            queue.preparedTriggers.delete(oldest);
-          }
-        }
+        return rememberPreparedTrigger(queue, retryKey, prepared);
       }
       return prepared;
     },