From e50f182035199cdc8f3e6cf4a75b1881bf6a8bc7 Mon Sep 17 00:00:00 2001
From: Gustavo Madeira Santana <gumadeiras@gmail.com>
Date: Thu, 12 Mar 2026 08:22:00 +0000
Subject: [PATCH] Matrix: revalidate cached direct targets

---
 .../matrix/src/matrix/send/targets.test.ts    | 34 +++++++++++++++++++
 extensions/matrix/src/matrix/send/targets.ts  |  7 ++--
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/extensions/matrix/src/matrix/send/targets.test.ts b/extensions/matrix/src/matrix/send/targets.test.ts
index 280bf2a6005..bd3559c146c 100644
--- a/extensions/matrix/src/matrix/send/targets.test.ts
+++ b/extensions/matrix/src/matrix/send/targets.test.ts
@@ -166,6 +166,40 @@ describe("resolveMatrixRoomId", () => {
 
     await expect(resolveMatrixRoomId(client, userId)).resolves.toBe("!dm-room:example.org");
   });
+
+  it("revalidates cached direct rooms before reuse when membership changes", async () => {
+    const userId = "@shared:example.org";
+    const directRooms = ["!dm-room-1:example.org"];
+    const membersByRoom = new Map<string, string[]>([
+      ["!dm-room-1:example.org", ["@bot:example.org", userId]],
+      ["!dm-room-2:example.org", ["@bot:example.org", userId]],
+    ]);
+    const client = {
+      getAccountData: vi.fn().mockImplementation(async () => ({
+        [userId]: [...directRooms],
+      })),
+      getUserId: vi.fn().mockResolvedValue("@bot:example.org"),
+      getJoinedRooms: vi
+        .fn()
+        .mockResolvedValue(["!dm-room-1:example.org", "!dm-room-2:example.org"]),
+      getJoinedRoomMembers: vi
+        .fn()
+        .mockImplementation(async (roomId: string) => membersByRoom.get(roomId) ?? []),
+      setAccountData: vi.fn(),
+      resolveRoom: vi.fn(),
+    } as unknown as MatrixClient;
+
+    await expect(resolveMatrixRoomId(client, userId)).resolves.toBe("!dm-room-1:example.org");
+
+    directRooms.splice(0, directRooms.length, "!dm-room-1:example.org", "!dm-room-2:example.org");
+    membersByRoom.set("!dm-room-1:example.org", [
+      "@bot:example.org",
+      userId,
+      "@mallory:example.org",
+    ]);
+
+    await expect(resolveMatrixRoomId(client, userId)).resolves.toBe("!dm-room-2:example.org");
+  });
 });
 
 describe("normalizeThreadId", () => {
diff --git a/extensions/matrix/src/matrix/send/targets.ts b/extensions/matrix/src/matrix/send/targets.ts
index d7abb2c5006..e71da63117c 100644
--- a/extensions/matrix/src/matrix/send/targets.ts
+++ b/extensions/matrix/src/matrix/send/targets.ts
@@ -97,13 +97,16 @@ async function resolveDirectRoomId(client: MatrixClient, userId: string): Promis
   if (!isMatrixQualifiedUserId(trimmed)) {
     throw new Error(`Matrix user IDs must be fully qualified (got "${trimmed}")`);
   }
+  const selfUserId = (await client.getUserId().catch(() => null))?.trim() || null;
 
   const directRoomCache = resolveDirectRoomCache(client);
   const cached = directRoomCache.get(trimmed);
-  if (cached) {
+  if (cached && (await isStrictDirectRoom(client, cached, trimmed, selfUserId))) {
     return cached;
   }
-  const selfUserId = (await client.getUserId().catch(() => null))?.trim() || null;
+  if (cached) {
+    directRoomCache.delete(trimmed);
+  }
 
   // 1) Fast path: use account data (m.direct) for *this* logged-in user (the bot).
   try {