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"])
+})

packages/app/e2e/performance/unit/session-tab-switch-metrics.test.ts

@@ -52,3 +52,35 @@ test("reports missing correctness without throwing", () => {
   expect(result.firstCorrectObservedMs).toBeNull()
   expect(result.stableObservedMs).toBeNull()
 })
+
+test("requires an explicitly tracked part to be visible", () => {
+  const result = classifySessionSwitch([
+    {
+      observedAtMs: 16,
+      destination: ["destination"],
+      source: [],
+      hasVisibleRows: true,
+      last: true,
+      requiredPartVisible: false,
+      bottomErrorPx: 0,
+    },
+  ])
+
+  expect(result.firstCorrectObservedMs).toBeNull()
+})
+
+test("can measure content correctness without requiring a bottom anchor", () => {
+  const result = classifySessionSwitch([
+    {
+      observedAtMs: 16,
+      destination: ["destination"],
+      source: [],
+      hasVisibleRows: true,
+      last: true,
+      requiredPartVisible: true,
+      bottomAnchorRequired: false,
+    },
+  ])
+
+  expect(result.firstCorrectObservedMs).toBe(16)
+})

packages/app/e2e/performance/unit/session-tab-switch-probe.test.ts

@@ -0,0 +1,45 @@
+import { expect, test } from "bun:test"
+import type { Page } from "@playwright/test"
+import { measureSessionSwitch } from "../timeline/session-tab-switch-probe"
+
+function testPage(waitFailure?: Error) {
+  const stops: unknown[] = []
+  const page = {
+    evaluate: async (_callback: unknown, input?: unknown) => {
+      if (input) return
+      stops.push(undefined)
+    },
+    waitForFunction: async () => {
+      if (waitFailure) throw waitFailure
+    },
+  } as unknown as Page
+  return { page, stops }
+}
+
+function input(run: () => Promise<void>) {
+  return {
+    destinationIDs: ["destination"],
+    sourceIDs: ["source"],
+    lastID: "destination",
+    href: "/session/destination",
+    switch: run,
+  }
+}
+
+test("stops sampling when the session switch fails", async () => {
+  const failure = new Error("switch failed")
+  const context = testPage()
+
+  await expect(measureSessionSwitch(context.page, input(async () => Promise.reject(failure)))).rejects.toBe(failure)
+
+  expect(context.stops).toHaveLength(1)
+})
+
+test("stops sampling when the stable wait fails", async () => {
+  const failure = new Error("stable wait failed")
+  const context = testPage(failure)
+
+  await expect(measureSessionSwitch(context.page, input(async () => {}))).rejects.toBe(failure)
+
+  expect(context.stops).toHaveLength(1)
+})