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

packages/app/e2e/performance/timeline/session-parent-hydration-benchmark.spec.ts

@@ -0,0 +1,146 @@
+import type { Page } from "@playwright/test"
+import { expectSessionTitle } from "../../utils/waits"
+import { mockOpenCodeServer } from "../../utils/mock-server"
+import { benchmark, expect, withBenchmarkPage } from "../benchmark"
+import { fixture } from "./session-timeline-stress.fixture"
+import { installStressSessionTabs, stressSessionHref } from "./timeline-test-helpers"
+import { measureSessionSwitch, waitForStableTimeline } from "./session-tab-switch-probe"
+
+type ParentHydrationBenchmarkMode = "natural" | "candidate"
+
+const mode = process.env.SESSION_PARENT_HYDRATION_BENCHMARK_MODE ?? "natural"
+if (mode !== "natural" && mode !== "candidate") throw new Error(`Unknown parent hydration benchmark mode: ${mode}`)
+const userID = "msg_parent_hydration_user"
+const user = {
+  ...fixture.messages[fixture.targetID][0]!,
+  info: { ...fixture.messages[fixture.targetID][0]!.info, id: userID, time: { created: 1700001000000 } },
+  parts: fixture.messages[fixture.targetID][0]!.parts.map((part, index) => ({
+    ...part,
+    id: `prt_parent_hydration_user_${index}`,
+    messageID: userID,
+  })),
+}
+const assistantSeed = fixture.messages[fixture.targetID][3]!
+const assistants = Array.from({ length: 14 }, (_, index) => {
+  const messageID = `msg_parent_hydration_${String(index).padStart(2, "0")}`
+  return {
+    ...assistantSeed,
+    info: {
+      ...assistantSeed.info,
+      id: messageID,
+      parentID: userID,
+      time: { created: 1700001001000 + index * 1_000, completed: 1700001001500 + index * 1_000 },
+    },
+    parts: assistantSeed.parts.map((part, partIndex) => ({
+      ...part,
+      id: `prt_parent_hydration_${String(index).padStart(2, "0")}_${partIndex}`,
+      messageID,
+    })),
+  }
+})
+const messages = [user, ...assistants]
+const target = fixture.sessions.find((session) => session.id === fixture.targetID)!
+const lastID = userID
+const lastPartID = assistants.at(-1)!.parts.at(-1)!.id
+
+benchmark("hydrates an orphaned latest turn after a cold session click", async ({ browser, report }, testInfo) => {
+  benchmark.setTimeout(180_000)
+  const results = [] as Awaited<ReturnType<typeof trial>>[]
+  for (let run = 0; run < 5; run++) {
+    results.push(
+      await withBenchmarkPage(browser, `session-parent-hydration-${mode}-${run}`, (page) => trial(page, mode), testInfo),
+    )
+  }
+  const timing = results.map((result) => result.metrics.firstCorrectObservedMs!).sort((a, b) => a - b)
+  report(
+    {
+      results: results.map((result) => ({ ...result.metrics, historyGateCount: result.historyGateCount })),
+      summary: {
+        firstCorrectObservedMs: { min: timing[0], median: timing[2], max: timing.at(-1) },
+        blankSamples: results.map((result) => result.metrics.blankSamples),
+        requestCounts: {
+          list: results.map((result) => result.requestCounts.list),
+          parent: results.map((result) => result.requestCounts.parent),
+        },
+        historyGateCount: results.map((result) => result.historyGateCount),
+      },
+    },
+    { mode },
+  )
+})
+
+async function trial(page: Page, mode: ParentHydrationBenchmarkMode) {
+  const requests: { type: "list" | "parent"; before?: string }[] = []
+  const history = mode === "candidate" ? Promise.withResolvers<void>() : undefined
+  let historyGates = 0
+  await mockOpenCodeServer(page, {
+    sessions: fixture.sessions.filter((session) => session.id === fixture.sourceID),
+    provider: fixture.provider,
+    directory: fixture.directory,
+    project: fixture.project,
+    messageDelay: 50,
+    onMessages: (request) => {
+      if (request.sessionID === fixture.targetID && request.phase === "start")
+        requests.push({ type: "list", before: request.before })
+    },
+    beforeMessagesResponse: (request) => {
+      if (mode !== "candidate" || request.sessionID !== fixture.targetID || !request.before) return Promise.resolve()
+      historyGates++
+      return history!.promise
+    },
+    onMessage: (request) => {
+      if (request.sessionID === fixture.targetID && request.messageID === userID) requests.push({ type: "parent" })
+    },
+    message: (sessionID, messageID) => {
+      if (sessionID !== fixture.targetID || messageID !== userID) return
+      return user
+    },
+    pageMessages: (sessionID, limit, before) => {
+      const items = sessionID === fixture.targetID ? messages : fixture.messages[fixture.sourceID]
+      const end = before ? items.findIndex((message) => message.info.id === before) : items.length
+      const start = Math.max(0, end - limit)
+      return { items: items.slice(start, end), cursor: start > 0 ? items[start]!.info.id : undefined }
+    },
+  })
+  await page.route(`**/session/${fixture.targetID}`, (route) =>
+    route.fulfill({ status: 200, contentType: "application/json", body: JSON.stringify(target) }),
+  )
+  await installStressSessionTabs(page, { sessionIDs: [fixture.sourceID] })
+  await page.goto(stressSessionHref(fixture.sourceID))
+  await expectSessionTitle(page, fixture.expected.sourceTitle)
+  await waitForStableTimeline(page, fixture.expected.sourceMessageIDs.at(-1)!)
+
+  const href = stressSessionHref(fixture.targetID)
+  await page.evaluate(
+    ({ href, title }) => {
+      const link = document.createElement("a")
+      link.id = "parent-hydration-target"
+      link.href = href
+      link.textContent = title
+      document.body.append(link)
+    },
+    { href, title: target.title },
+  )
+  const metrics = await measureSessionSwitch(page, {
+    destinationIDs: messages.map((message) => message.info.id),
+    sourceIDs: fixture.messages[fixture.sourceID].map((message) => message.info.id),
+    lastID,
+    requiredPartID: lastPartID,
+    requireBottomAnchor: false,
+    href,
+    switch: async () => {
+      await page.locator("#parent-hydration-target").click()
+      await expectSessionTitle(page, target.title)
+    },
+  }).finally(() => history?.resolve())
+  expect(metrics.firstCorrectObservedMs).not.toBeNull()
+  const requestCounts = {
+    list: requests.filter((request) => request.type === "list").length,
+    parent: requests.filter((request) => request.type === "parent").length,
+  }
+  if (mode === "candidate") {
+    expect(requestCounts.parent).toBe(1)
+    expect(historyGates).toBe(1)
+  }
+  return { metrics, requestCounts, historyGateCount: historyGates }
+}

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

@@ -4,6 +4,8 @@ export type SessionSwitchSample = {
   source: string[]
   hasVisibleRows: boolean
   last: boolean
+  requiredPartVisible?: boolean
+  bottomAnchorRequired?: boolean
   bottomErrorPx?: number
 }
 
@@ -31,7 +33,8 @@ export function isCorrectDestination(sample: SessionSwitchSample) {
     sample.destination.length > 0 &&
     sample.source.length === 0 &&
     sample.last &&
-    Math.abs(sample.bottomErrorPx ?? Infinity) <= 1
+    sample.requiredPartVisible !== false &&
+    (sample.bottomAnchorRequired === false || Math.abs(sample.bottomErrorPx ?? Infinity) <= 1)
   )
 }
 

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

@@ -8,19 +8,56 @@ type SessionSwitchProbe = {
 
 async function installSessionSwitchProbe(
   page: Page,
-  input: { destinationIDs: string[]; sourceIDs: string[]; lastID: string; href: string },
+  input: {
+    destinationIDs: string[]
+    sourceIDs: string[]
+    lastID: string
+    requiredPartID?: string
+    requireBottomAnchor?: boolean
+    href: string
+  },
 ) {
-  await page.evaluate(({ destinationIDs, sourceIDs, lastID, href }) => {
+  await page.evaluate(({ destinationIDs, sourceIDs, lastID, requiredPartID, requireBottomAnchor, href }) => {
     const destination = new Set(destinationIDs)
     const source = new Set(sourceIDs)
     const samples: SessionSwitchSample[] = []
     let started: number | undefined
     let running = true
+    const reviewLevels: Record<string, string> = {
+      panel: "#review-panel",
+      tabs: '#review-panel [data-component="tabs"]',
+      body: '#review-panel [data-slot="session-review-v2-body"]',
+      review: '#review-panel [data-component="session-review-v2"]',
+      preview: '#review-panel [data-slot="session-review-v2-preview"]',
+      scroll: '#review-panel [data-slot="session-review-v2-diff-scroll"]',
+      file: '#review-panel [data-component="file"][data-mode="diff"]',
+    }
+    const initialReviewNodes: Record<string, Element | null> = {}
     const sample = () => {
       if (!running || started === undefined) return
       setTimeout(() => {
         if (!running || started === undefined) return
         const observedAtMs = performance.now() - started
+        const reviewPanel = document.querySelector<HTMLElement>("#review-panel")
+        const reviewFile = reviewPanel?.querySelector('[data-component="file"][data-mode="diff"]')
+        const initialReviewFile = initialReviewNodes.file
+        const replacedLevels = Object.entries(reviewLevels).flatMap(([name, selector]) => {
+          const initial = initialReviewNodes[name]
+          if (!initial) return []
+          const current = document.querySelector(selector)
+          return current && current !== initial ? [name] : []
+        })
+        const review = reviewPanel
+          ? {
+              fileHost: !!reviewFile,
+              fileHostReplaced: !!initialReviewFile && !!reviewFile && reviewFile !== initialReviewFile,
+              header:
+                reviewPanel
+                  .querySelector<HTMLElement>('[data-slot="session-review-v2-file-header"]')
+                  ?.textContent?.trim() ?? "",
+              replacedLevels,
+            }
+          : undefined
         const root = [...document.querySelectorAll<HTMLElement>(".scroll-view__viewport")].find((element) =>
           element.querySelector("[data-timeline-row]"),
         )
@@ -36,17 +73,36 @@ async function installSessionSwitchProbe(
             const rect = element.getBoundingClientRect()
             return rect.bottom > view.top && rect.top < view.bottom
           })
+          const requiredPartVisible = requiredPartID
+            ? [...root.querySelectorAll<HTMLElement>("[data-timeline-part-id]")].some((element) => {
+                if (element.dataset.timelinePartId !== requiredPartID) return false
+                const rect = element.getBoundingClientRect()
+                return rect.width > 0 && rect.height > 0 && rect.bottom > view.top && rect.top < view.bottom
+              })
+            : undefined
           const spacer = root.querySelector<HTMLElement>('[data-timeline-row="bottom-spacer"]')?.getBoundingClientRect()
           samples.push({
             observedAtMs,
             destination: visible.filter((id) => destination.has(id)),
             source: visible.filter((id) => source.has(id)),
             hasVisibleRows,
             last: visible.includes(lastID),
+            requiredPartVisible,
+            bottomAnchorRequired: requireBottomAnchor !== false,
             bottomErrorPx: spacer ? spacer.bottom - view.bottom : undefined,
+            review,
           })
         } else {
-          samples.push({ observedAtMs, destination: [], source: [], hasVisibleRows: false, last: false })
+          samples.push({
+            observedAtMs,
+            destination: [],
+            source: [],
+            hasVisibleRows: false,
+            last: false,
+            requiredPartVisible: requiredPartID ? false : undefined,
+            bottomAnchorRequired: requireBottomAnchor !== false,
+            review,
+          })
         }
         requestAnimationFrame(sample)
       }, 0)
@@ -57,6 +113,9 @@ async function installSessionSwitchProbe(
         const link = event.target instanceof Element ? event.target.closest("a") : undefined
         if (link?.getAttribute("href") !== href) return
         started = performance.now()
+        for (const [name, selector] of Object.entries(reviewLevels)) {
+          initialReviewNodes[name] = document.querySelector(selector)
+        }
         requestAnimationFrame(sample)
       },
       { capture: true, once: true },
@@ -83,7 +142,8 @@ async function waitForStableSessionSwitch(page: Page) {
             sample.destination.length > 0 &&
             sample.source.length === 0 &&
             sample.last &&
-            Math.abs(sample.bottomErrorPx ?? Infinity) <= 1,
+            sample.requiredPartVisible !== false &&
+            (sample.bottomAnchorRequired === false || Math.abs(sample.bottomErrorPx ?? Infinity) <= 1),
         )
       )
     })
@@ -101,13 +161,27 @@ async function collectSessionSwitchResult(page: Page) {
 
 export async function measureSessionSwitch(
   page: Page,
-  input: { destinationIDs: string[]; sourceIDs: string[]; lastID: string; href: string; switch: () => Promise<void> },
+  input: {
+    destinationIDs: string[]
+    sourceIDs: string[]
+    lastID: string
+    requiredPartID?: string
+    requireBottomAnchor?: boolean
+    href: string
+    switch: () => Promise<void>
+  },
 ) {
   const { switch: run, ...probe } = input
   await installSessionSwitchProbe(page, probe)
-  await run()
-  await waitForStableSessionSwitch(page)
-  return collectSessionSwitchResult(page)
+  try {
+    await run()
+    await waitForStableSessionSwitch(page)
+    return await collectSessionSwitchResult(page)
+  } finally {
+    await page.evaluate(() => {
+      ;(window as Window & { __sessionSwitchProbe?: SessionSwitchProbe }).__sessionSwitchProbe?.stop()
+    })
+  }
 }
 
 export async function waitForStableTimeline(page: Page, lastID: string) {

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)
+})