fix(app): hydrate timeline message parents (#35269)

packages/app/e2e/performance/unit/mock-server.test.ts

@@ -0,0 +1,46 @@
+import { expect, test } from "bun:test"
+import type { Page, Route } from "@playwright/test"
+import { mockOpenCodeServer } from "../../utils/mock-server"
+
+test("applies message latency after a list response gate is released", async () => {
+  const events: string[] = []
+  const gate = Promise.withResolvers<void>()
+  let handler: ((route: Route) => Promise<void>) | undefined
+  const page = {
+    route: (_url: string, callback: (route: Route) => Promise<void>) => {
+      handler = callback
+      return Promise.resolve()
+    },
+  } as unknown as Page
+  await mockOpenCodeServer(page, {
+    provider: {},
+    directory: "C:/OpenCode",
+    project: {},
+    sessions: [{ id: "session" }],
+    messageDelay: 25,
+    beforeMessagesResponse: () => {
+      events.push("before")
+      return gate.promise
+    },
+    onMessages: (request) => events.push(request.phase),
+    pageMessages: () => {
+      events.push("page")
+      return { items: [] }
+    },
+  })
+
+  const response = handler!({
+    request: () => ({ url: () => "http://127.0.0.1:4096/session/session/message" }),
+    fulfill: () => {
+      events.push("fulfill")
+      return Promise.resolve()
+    },
+  } as unknown as Route)
+  expect(events).toEqual(["start", "before"])
+
+  const released = performance.now()
+  gate.resolve()
+  await response
+  expect(performance.now() - released).toBeGreaterThanOrEqual(20)
+  expect(events).toEqual(["start", "before", "page", "end", "fulfill"])
+})