From b6f88b72e8a30e4e5b7bff53fc661bb9d01ab98b Mon Sep 17 00:00:00 2001
From: Gustavo Madeira Santana <gumadeiras@gmail.com>
Date: Mon, 30 Mar 2026 15:05:51 -0400
Subject: [PATCH] Matrix: limit ingress locking to room history

---
 .../monitor/handler.group-history.test.ts     | 40 +++++++++++++++
 .../matrix/src/matrix/monitor/handler.ts      | 50 +++++++++++++++----
 2 files changed, 80 insertions(+), 10 deletions(-)

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 fefd05a2692..5e854c64a8a 100644
--- a/extensions/matrix/src/matrix/monitor/handler.group-history.test.ts
+++ b/extensions/matrix/src/matrix/monitor/handler.group-history.test.ts
@@ -249,6 +249,46 @@ describe("matrix group chat history — scenario 1: basic accumulation", () => {
     }
   });
 
+  it("history-enabled rooms do not serialize DM ingress heavy work", async () => {
+    let resolveFirstName: (() => void) | undefined;
+    let nameLookupCalls = 0;
+    const getMemberDisplayName = vi.fn(async () => {
+      nameLookupCalls += 1;
+      if (nameLookupCalls === 1) {
+        await new Promise<void>((resolve) => {
+          resolveFirstName = resolve;
+        });
+      }
+      return "sender";
+    });
+
+    const { handler } = createMatrixHandlerTestHarness({
+      historyLimit: 20,
+      isDirectMessage: true,
+      getMemberDisplayName,
+      dispatchReplyFromConfig: async () => ({
+        queuedFinal: true,
+        counts: { final: 1, block: 0, tool: 0 },
+      }),
+    });
+
+    const first = handler(DEFAULT_ROOM, makeRoomPlainEvent({ eventId: "$dm-a", body: "first dm" }));
+    await vi.waitFor(() => {
+      expect(resolveFirstName).toBeTypeOf("function");
+    });
+
+    const second = handler(
+      DEFAULT_ROOM,
+      makeRoomPlainEvent({ eventId: "$dm-b", body: "second dm" }),
+    );
+    await vi.waitFor(() => {
+      expect(nameLookupCalls).toBe(2);
+    });
+
+    resolveFirstName?.();
+    await Promise.all([first, second]);
+  });
+
   it("includes skipped media-only room messages in next trigger history", 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 842b557ece0..5fba58af5c9 100644
--- a/extensions/matrix/src/matrix/monitor/handler.ts
+++ b/extensions/matrix/src/matrix/monitor/handler.ts
@@ -287,11 +287,6 @@ 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;
@@ -336,7 +331,7 @@ export function createMatrixRoomMessageHandler(params: MatrixMonitorHandlerParam
         await inboundDeduper.commitEvent({ roomId, eventId });
         claimedInboundEvent = false;
       };
-      const ingressResult = await runHistoryAwareRoomIngress(roomId, async () => {
+      const readIngressPrefix = async () => {
         const selfUserId = await client.getUserId();
         if (senderId === selfUserId) {
           return;
@@ -389,8 +384,18 @@ export function createMatrixRoomMessageHandler(params: MatrixMonitorHandlerParam
           senderId,
           selfUserId,
         });
+        return { content, isDirectMessage, locationPayload, selfUserId };
+      };
+      const continueIngress = async (params: {
+        content: RoomMessageEventContent;
+        isDirectMessage: boolean;
+        locationPayload: MatrixLocationPayload | null;
+        selfUserId: string;
+      }) => {
+        let content = params.content;
+        const isDirectMessage = params.isDirectMessage;
         const isRoom = !isDirectMessage;
-
+        const { locationPayload, selfUserId } = params;
         if (isRoom && groupPolicy === "disabled") {
           await commitInboundEventIfClaimed();
           return;
@@ -846,8 +851,33 @@ export function createMatrixRoomMessageHandler(params: MatrixMonitorHandlerParam
           triggerSnapshot,
           threadRootId: _threadRootId,
         };
-      });
-      if (!ingressResult) {
+      };
+      const ingressResult =
+        historyLimit > 0
+          ? await runRoomIngress(roomId, async () => {
+              const prefix = await readIngressPrefix();
+              if (!prefix) {
+                return;
+              }
+              if (prefix.isDirectMessage) {
+                return { deferredPrefix: prefix } as const;
+              }
+              return { ingressResult: await continueIngress(prefix) } as const;
+            })
+          : undefined;
+      const resolvedIngressResult =
+        historyLimit > 0
+          ? ingressResult?.deferredPrefix
+            ? await continueIngress(ingressResult.deferredPrefix)
+            : ingressResult?.ingressResult
+          : await (async () => {
+              const prefix = await readIngressPrefix();
+              if (!prefix) {
+                return;
+              }
+              return await continueIngress(prefix);
+            })();
+      if (!resolvedIngressResult) {
         return;
       }
 
@@ -869,7 +899,7 @@ export function createMatrixRoomMessageHandler(params: MatrixMonitorHandlerParam
         messageId: _messageId,
         triggerSnapshot,
         threadRootId: _threadRootId,
-      } = ingressResult;
+      } = resolvedIngressResult;
 
       // Keep the per-room ingress gate focused on ordering-sensitive state updates.
       // Prompt/session enrichment below can run concurrently after the history snapshot is fixed.