diff --git a/desktop/src/testing/e2eBridge.ts b/desktop/src/testing/e2eBridge.ts
index e4028f01716..29c7ff0427a 100644
--- a/desktop/src/testing/e2eBridge.ts
+++ b/desktop/src/testing/e2eBridge.ts
@@ -2370,6 +2370,28 @@ function resetMockRelayAgents(config?: E2eConfig) {
       respond_to: seed.respondTo ?? "owner-only",
       respond_to_allowlist: seed.respondToAllowlist ?? [],
     });
+
+    // A relay-agent seed that names real channels represents a bot that is
+    // an actual member of those channels — e.g. another identity's agent
+    // added as a bot member of a shared channel — not just a
+    // relay-directory listing. Mirror resetMockManagedAgents's membership
+    // push (below) so specs can exercise the cross-owner "bot member of a
+    // shared channel" case without also declaring the agent as locally
+    // managed.
+    for (const channel of channels) {
+      if (channel.members.some((member) => member.pubkey === seed.pubkey)) {
+        continue;
+      }
+      channel.members.push({
+        pubkey: seed.pubkey,
+        role: "bot",
+        is_agent: true,
+        joined_at: new Date().toISOString(),
+        display_name: seed.name,
+      });
+      syncMockChannel(channel);
+      touchMockChannel(channel);
+    }
   }
 }
 
@@ -3583,7 +3605,7 @@ function initializeMockHuddle(
 const openedExternalUrls: string[] = [];
 const defaultMockRelayAgents: RawRelayAgent[] = [
   {
-    pubkey: ALICE_PUBKEY,
+    pubkey: "5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a",
     name: "alice",
     agent_type: "goose",
     channels: ["general", "agents"],
@@ -3597,7 +3619,7 @@ const defaultMockRelayAgents: RawRelayAgent[] = [
     respond_to_allowlist: [],
   },
   {
-    pubkey: CHARLIE_PUBKEY,
+    pubkey: "5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c5c",
     name: "charlie",
     agent_type: "codex",
     channels: ["general"],
diff --git a/desktop/tests/e2e/mentions.spec.ts b/desktop/tests/e2e/mentions.spec.ts
index 25d73b28ca7..0154d6d5d61 100644
--- a/desktop/tests/e2e/mentions.spec.ts
+++ b/desktop/tests/e2e/mentions.spec.ts
@@ -1933,6 +1933,69 @@ test("shared agents wait for initial directory authorization", async ({
   });
 });
 
+test("bot agents owned by another identity are mentionable when added to a shared channel", async ({
+  page,
+}) => {
+  const OTHER_OWNER_BOT_PUBKEY =
+    "7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b7b";
+  await installMockBridge(page, {
+    relayAgents: [
+      {
+        pubkey: OTHER_OWNER_BOT_PUBKEY,
+        name: "scout",
+        respondTo: "anyone",
+        channelNames: ["general"],
+      },
+    ],
+  });
+  await page.goto("/");
+  await page.getByTestId("channel-general").click();
+  await expect(page.getByTestId("chat-title")).toHaveText("general");
+
+  const input = page.getByTestId("message-input");
+  await input.fill("@scout");
+
+  const dropdown = autocomplete(page);
+  await expect(dropdown.getByText("scout")).toBeVisible();
+  await expect(dropdown.getByText("agent")).toBeVisible();
+
+  await input.press("Enter");
+  await page.keyboard.type(" can you help?");
+  await page.getByTestId("send-message").click();
+
+  const mentionChip = page
+    .getByTestId("message-row")
+    .last()
+    .locator("[data-mention].agent-mention-highlight", { hasText: "scout" });
+  await expect(mentionChip).toBeVisible();
+});
+
+test("bot agents owned by another identity stay hidden when not added to a shared channel", async ({
+  page,
+}) => {
+  const OTHER_OWNER_BOT_PUBKEY =
+    "8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c8c";
+  await installMockBridge(page, {
+    relayAgents: [
+      {
+        pubkey: OTHER_OWNER_BOT_PUBKEY,
+        name: "ghost",
+        respondTo: "anyone",
+        // Deliberately not added to "general" — respondTo=anyone alone must
+        // not be enough; the fix requires real channel membership too.
+      },
+    ],
+  });
+  await page.goto("/");
+  await page.getByTestId("channel-general").click();
+  await expect(page.getByTestId("chat-title")).toHaveText("general");
+
+  const input = page.getByTestId("message-input");
+  await input.fill("@ghost");
+
+  await expect(autocomplete(page)).toHaveCount(0);
+});
+
 test("mentioning an in-channel stopped managed agent starts it before sending", async ({
   page,
 }) => {