diff --git a/ui/src/e2e/chat-flow.sidebar-presentation.e2e.test.ts b/ui/src/e2e/chat-flow.sidebar-presentation.e2e.test.ts
index 707991a52632..edee17cdfc59 100644
--- a/ui/src/e2e/chat-flow.sidebar-presentation.e2e.test.ts
+++ b/ui/src/e2e/chat-flow.sidebar-presentation.e2e.test.ts
@@ -162,6 +162,12 @@ suite.define(() => {
     });
     const key = "agent:main:session-a";
     const runId = "run-sidebar-metadata";
+    const rosterPeer = {
+      key: "agent:main:roster-peer",
+      kind: "direct",
+      label: "Roster peer",
+      updatedAt: 1,
+    };
     const running = chatSessionListResponse([
       {
         key,
@@ -180,6 +186,7 @@ suite.define(() => {
           revision: 1,
         },
       },
+      rosterPeer,
     ]);
     const completed = chatSessionListResponse([
       {
@@ -200,8 +207,10 @@ suite.define(() => {
           revision: 2,
         },
       },
+      rosterPeer,
     ]);
     const gateway = await installMockGateway(page, {
+      deferredMethods: ["chat.startup"],
       methodResponses: { "sessions.list": running },
       sessionKey: key,
     });
@@ -210,6 +219,11 @@ suite.define(() => {
       await page.goto(controlUiSessionUrl(suite.server.baseUrl, key));
       const row = page.locator(`.sidebar-recent-session[data-session-key="${key}"]`);
       await row.getByText("Implementing the repair").waitFor();
+      // A descriptor can render the selected row before startup releases the roster.
+      // Wait for a roster-only row before measuring event-triggered list reads.
+      await gateway.waitForRequest("chat.startup");
+      await gateway.resolveDeferred("chat.startup");
+      await page.locator(`.sidebar-recent-session[data-session-key="${rosterPeer.key}"]`).waitFor();
       if (captureUiProofEnabled) {
         await writeFile(
           path.join(