From 2b3d776403aca47ec522601df573bb3e6480dc75 Mon Sep 17 00:00:00 2001
From: Gustavo Madeira Santana <gumadeiras@gmail.com>
Date: Mon, 30 Mar 2026 03:04:43 -0400
Subject: [PATCH] Matrix: ignore stale history after room eviction

---
 .../src/matrix/monitor/room-history.test.ts   | 25 +++++++++++++++++++
 .../matrix/src/matrix/monitor/room-history.ts |  8 +++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/extensions/matrix/src/matrix/monitor/room-history.test.ts b/extensions/matrix/src/matrix/monitor/room-history.test.ts
index c8bf4303143..cb0f0243021 100644
--- a/extensions/matrix/src/matrix/monitor/room-history.test.ts
+++ b/extensions/matrix/src/matrix/monitor/room-history.test.ts
@@ -125,4 +125,29 @@ describe("createRoomHistoryTracker — roomQueues eviction", () => {
     expect(history).toHaveLength(1);
     expect(history[0]?.body).toBe("new msg in room1");
   });
+
+  it("ignores late consumeHistory calls after the room queue was evicted", () => {
+    const tracker = createRoomHistoryTracker(200, 1);
+    const room1 = "!room1:test";
+    const room2 = "!room2:test";
+
+    tracker.recordPending(room1, entry("old msg in room1"));
+    const prepared = tracker.prepareTrigger(AGENT, room1, 100, {
+      sender: "user",
+      body: "trigger in room1",
+      messageId: "$trigger",
+    });
+
+    // room2 creation evicts room1 (maxRoomQueues=1) while the trigger is still in flight.
+    tracker.recordPending(room2, entry("msg in room2"));
+
+    // Late completion for the evicted room must not recreate a stale watermark.
+    tracker.consumeHistory(AGENT, room1, prepared.snapshotIdx, "$trigger");
+
+    // Recreate room1 and add fresh content.
+    tracker.recordPending(room1, entry("new msg in room1"));
+    const history = tracker.getPendingHistory(AGENT, room1, 100);
+    expect(history).toHaveLength(1);
+    expect(history[0]?.body).toBe("new msg in room1");
+  });
 });
diff --git a/extensions/matrix/src/matrix/monitor/room-history.ts b/extensions/matrix/src/matrix/monitor/room-history.ts
index ecf12ded142..80c77a3a116 100644
--- a/extensions/matrix/src/matrix/monitor/room-history.ts
+++ b/extensions/matrix/src/matrix/monitor/room-history.ts
@@ -198,11 +198,17 @@ export function createRoomHistoryTracker(
 
     consumeHistory(agentId, roomId, snapshotIdx, messageId) {
       const key = wmKey(agentId, roomId);
+      const queue = roomQueues.get(roomId);
+      if (!queue) {
+        // The room was evicted while this trigger was in flight. Keep eviction authoritative
+        // so a late completion cannot recreate a stale watermark against a fresh queue.
+        agentWatermarks.delete(key);
+        return;
+      }
       // Monotone write: never regress an already-advanced watermark.
       // Guards against out-of-order completion when two triggers for the same
       // (agentId, roomId) are in-flight concurrently.
       agentWatermarks.set(key, Math.max(agentWatermarks.get(key) ?? 0, snapshotIdx));
-      const queue = roomQueues.get(roomId);
       const retryKey = preparedTriggerKey(agentId, messageId);
       if (queue && retryKey) {
         queue.preparedTriggers.delete(retryKey);