fix(app): make session navigation stable and fast

packages/app/e2e/performance/README.md

@@ -18,6 +18,8 @@ bun run test:bench
 The suite contains:
 
 - cold and hot session-tab timing
+- home-session click timing split between content and titlebar-tab paint
+- single-session tab close timing through stable home restoration
 - cached session repaint and mutation tracing
 - streaming timeline throughput, RAF-gap, long-task, geometry, and remount diagnostics
 

packages/app/e2e/performance/timeline/first-navigation-benchmark.spec.ts

@@ -0,0 +1,87 @@
+import { expectSessionTitle } from "../../utils/waits"
+import { benchmark, expect } from "../benchmark"
+import { measureFirstNavigation } from "./first-navigation-probe"
+import { fixture } from "./session-timeline-stress.fixture"
+import {
+  installStressSessionTabs,
+  installTimelineSettings,
+  mockStressTimeline,
+  stressDraftHref,
+  stressSessionHref,
+} from "./timeline-test-helpers"
+import { waitForStableTimeline } from "./session-tab-switch-probe"
+
+const contentSelector = '[data-message-id], [data-component="prompt-input"]'
+const draftID = "draft_first_navigation"
+
+benchmark.describe("performance: first navigation paint", () => {
+  benchmark("opens an unvisited session tab without a blank frame", async ({ page, report }) => {
+    await setup(page)
+    const href = stressSessionHref(fixture.targetID)
+    const result = await measureFirstNavigation(page, {
+      href,
+      destinationPath: href,
+      sourceSelector: messageSelector(fixture.expected.sourceMessageIDs.at(-1)!),
+      destinationSelector: messageSelector(fixture.expected.targetMessageIDs.at(-1)!),
+      contentSelector,
+      navigate: async () => {
+        await page.locator(`[data-slot="titlebar-tabs"] a[href="${href}"]`).first().click()
+        await expectSessionTitle(page, fixture.expected.targetTitle)
+      },
+    })
+    report(result)
+    expect(result.summary.blankSamples).toBe(0)
+    expect(result.summary.unknownSamples).toBe(0)
+  })
+
+  benchmark("opens the new session page before its lazy module is used", async ({ page, report }) => {
+    await setup(page, draftID)
+    const href = stressDraftHref(draftID)
+    const result = await measureFirstNavigation(page, {
+      href,
+      destinationPath: href,
+      sourceSelector: messageSelector(fixture.expected.sourceMessageIDs.at(-1)!),
+      destinationSelector: '[data-component="prompt-input"]',
+      contentSelector,
+      navigate: async () => {
+        await page.locator(`[data-slot="titlebar-tabs"] a[href="${href}"]`).first().click()
+        await expect(page.locator('[data-component="prompt-input"]')).toBeVisible()
+      },
+    })
+    report(result)
+    expect(result.summary.blankSamples).toBe(0)
+    expect(result.summary.unknownSamples).toBe(0)
+  })
+
+  benchmark("opens a child session without a blank frame", async ({ page, report }) => {
+    await setup(page)
+    const href = stressSessionHref(fixture.childID)
+    const result = await measureFirstNavigation(page, {
+      href,
+      destinationPath: href,
+      sourceSelector: messageSelector(fixture.expected.sourceMessageIDs.at(-1)!),
+      destinationSelector: messageSelector(fixture.expected.childMessageIDs.at(-1)!),
+      contentSelector,
+      navigate: async () => {
+        await page.locator(`a[href="${href}"]`, { has: page.locator('[data-component="task-tool-card"]') }).click()
+        await expectSessionTitle(page, fixture.expected.childTitle)
+      },
+    })
+    report(result)
+    expect(result.summary.blankSamples).toBe(0)
+    expect(result.summary.unknownSamples).toBe(0)
+  })
+})
+
+async function setup(page: Parameters<typeof mockStressTimeline>[0], draft?: string) {
+  await mockStressTimeline(page)
+  await installTimelineSettings(page)
+  await installStressSessionTabs(page, draft ? { draftID: draft } : undefined)
+  await page.goto(stressSessionHref(fixture.sourceID))
+  await expectSessionTitle(page, fixture.expected.sourceTitle)
+  await waitForStableTimeline(page, fixture.expected.sourceMessageIDs.at(-1)!)
+}
+
+function messageSelector(id: string) {
+  return `[data-message-id="${id}"]`
+}

packages/app/e2e/performance/timeline/first-navigation-metrics.ts

@@ -0,0 +1,34 @@
+export type FirstNavigationSample = {
+  observedAtMs: number
+  source: boolean
+  destination: boolean
+  content: boolean
+  pathname?: string
+  center?: string
+}
+
+function category(sample: FirstNavigationSample) {
+  if (sample.destination && !sample.source) return "destination"
+  if (sample.source && !sample.destination) return "source"
+  if (!sample.content) return "blank"
+  return "unknown"
+}
+
+export function summarizeFirstNavigation(samples: FirstNavigationSample[]) {
+  const categories = samples.map(category)
+  const stable = categories.findIndex(
+    (value, index) =>
+      value === "destination" &&
+      categories[index + 1] === "destination" &&
+      categories[index + 2] === "destination",
+  )
+  return {
+    samples: samples.length,
+    firstDestinationObservedMs: samples[categories.indexOf("destination")]?.observedAtMs ?? null,
+    stableDestinationObservedMs: stable === -1 ? null : samples[stable + 2]!.observedAtMs,
+    sourceSamples: categories.filter((value) => value === "source").length,
+    blankSamples: categories.filter((value) => value === "blank").length,
+    unknownSamples: categories.filter((value) => value === "unknown").length,
+    destinationSamples: categories.filter((value) => value === "destination").length,
+  }
+}

packages/app/e2e/performance/timeline/first-navigation-probe.ts

@@ -0,0 +1,85 @@
+import type { Page } from "@playwright/test"
+import { summarizeFirstNavigation, type FirstNavigationSample } from "./first-navigation-metrics"
+
+type FirstNavigationProbe = {
+  samples: FirstNavigationSample[]
+  stop: () => void
+}
+
+export async function measureFirstNavigation(
+  page: Page,
+  input: {
+    href: string
+    destinationPath: string
+    sourceSelector: string
+    destinationSelector: string
+    contentSelector: string
+    navigate: () => Promise<void>
+  },
+) {
+  await page.evaluate(
+    ({ href, destinationPath, sourceSelector, destinationSelector, contentSelector }) => {
+      const samples: FirstNavigationSample[] = []
+      let started: number | undefined
+      let running = true
+      const visible = (selector: string) =>
+        [...document.querySelectorAll<HTMLElement>(selector)].some((element) => {
+          const rect = element.getBoundingClientRect()
+          const style = getComputedStyle(element)
+          return rect.width > 0 && rect.height > 0 && style.visibility !== "hidden" && style.display !== "none"
+        })
+      const sample = () => {
+        if (!running || started === undefined) return
+        requestAnimationFrame(() => {
+          setTimeout(() => {
+            if (!running || started === undefined) return
+            samples.push({
+              observedAtMs: performance.now() - started,
+              source: visible(sourceSelector),
+              destination: `${location.pathname}${location.search}` === destinationPath && visible(destinationSelector),
+              content: visible(contentSelector),
+              pathname: `${location.pathname}${location.search}`,
+              center: document.elementFromPoint(innerWidth / 2, innerHeight / 2)?.textContent?.slice(0, 80),
+            })
+            sample()
+          }, 0)
+        })
+      }
+      document.addEventListener(
+        "click",
+        (event) => {
+          const link = event.target instanceof Element ? event.target.closest("a") : undefined
+          if (link?.getAttribute("href") !== href) return
+          started = performance.now()
+          sample()
+        },
+        { capture: true, once: true },
+      )
+      ;(window as Window & { __firstNavigationProbe?: FirstNavigationProbe }).__firstNavigationProbe = {
+        samples,
+        stop: () => {
+          running = false
+        },
+      }
+    },
+    {
+      href: input.href,
+      destinationPath: input.destinationPath,
+      sourceSelector: input.sourceSelector,
+      destinationSelector: input.destinationSelector,
+      contentSelector: input.contentSelector,
+    },
+  )
+  await input.navigate()
+  await page.waitForFunction(() => {
+    const samples = (window as Window & { __firstNavigationProbe?: FirstNavigationProbe }).__firstNavigationProbe?.samples
+    if (!samples) return false
+    return samples.length >= 3 && samples.slice(-3).every((sample) => sample.destination && !sample.source)
+  })
+  const samples = await page.evaluate(() => {
+    const probe = (window as Window & { __firstNavigationProbe?: FirstNavigationProbe }).__firstNavigationProbe!
+    probe.stop()
+    return probe.samples
+  })
+  return { summary: summarizeFirstNavigation(samples), samples }
+}

packages/app/e2e/performance/timeline/home-tab-navigation-benchmark.spec.ts

@@ -0,0 +1,114 @@
+import { benchmark, expect } from "../benchmark"
+import { expectSessionTitle } from "../../utils/waits"
+import { measureNavigationMilestones } from "./navigation-milestones"
+import { fixture } from "./session-timeline-stress.fixture"
+import {
+  installStressSessionTabs,
+  installTimelineSettings,
+  mockStressTimeline,
+  stressSessionHref,
+} from "./timeline-test-helpers"
+import { waitForStableTimeline } from "./session-tab-switch-probe"
+
+const homeRow = '[data-component="home-session-row"]'
+const homeShell = '[data-component="home-session-search"]'
+
+benchmark.describe("performance: home and tab navigation", () => {
+  benchmark("opens a home session and paints its titlebar tab", async ({ page, report }) => {
+    await setup(page, [])
+    await page.goto("/")
+    const row = page.locator(homeRow).filter({ hasText: fixture.expected.targetTitle }).first()
+    await expect(row).toBeVisible()
+    const href = stressSessionHref(fixture.targetID)
+    const result = await measureNavigationMilestones(page, {
+      triggerSelector: homeRow,
+      milestones: {
+        content: { selector: messageSelector(fixture.expected.targetMessageIDs.at(-1)!) },
+        tab: { selector: `[data-slot="titlebar-tabs"] a[href="${href}"]` },
+      },
+      navigate: async () => {
+        await row.click()
+        await expectSessionTitle(page, fixture.expected.targetTitle)
+      },
+    })
+    report(result)
+    await expect(page.locator(`[data-slot="titlebar-tabs"] a[href="${href}"]`)).toContainText(
+      fixture.expected.targetTitle,
+    )
+  })
+
+  benchmark("stages the review body after cold session content", async ({ page, report }) => {
+    await setup(page, [])
+    await page.goto("/")
+    const row = page.locator(homeRow).filter({ hasText: fixture.expected.targetTitle }).first()
+    await expect(row).toBeVisible()
+    const result = await page.evaluate(
+      ({ rowSelector, title, contentSelector }) =>
+        new Promise<{ contentBeforeReview: boolean; samples: number }>((resolve) => {
+          let samples = 0
+          const sample = () => {
+            samples++
+            const content = !!document.querySelector(contentSelector)
+            const review = !!document.querySelector('[data-component="session-review"]')
+            if (content && !review) {
+              resolve({ contentBeforeReview: true, samples })
+              return
+            }
+            if (content && review) {
+              resolve({ contentBeforeReview: false, samples })
+              return
+            }
+            requestAnimationFrame(sample)
+          }
+          const target = [...document.querySelectorAll<HTMLElement>(rowSelector)].find((item) =>
+            item.textContent?.includes(title),
+          )
+          if (!target) throw new Error(`Home session row not found: ${title}`)
+          target.click()
+          requestAnimationFrame(sample)
+        }),
+      {
+        rowSelector: homeRow,
+        title: fixture.expected.targetTitle,
+        contentSelector: messageSelector(fixture.expected.targetMessageIDs.at(-1)!),
+      },
+    )
+    report(result)
+    expect(result.contentBeforeReview).toBe(true)
+    await expect(page.locator('[data-component="session-review"]')).toBeVisible()
+  })
+
+  benchmark("closes the only session tab and paints home", async ({ page, report }) => {
+    await setup(page, [fixture.sourceID])
+    const href = stressSessionHref(fixture.sourceID)
+    await page.goto(href)
+    await expectSessionTitle(page, fixture.expected.sourceTitle)
+    await waitForStableTimeline(page, fixture.expected.sourceMessageIDs.at(-1)!)
+    const tab = page.locator(`[data-slot="titlebar-tabs"] a[href="${href}"]`).first()
+    const close = tab.locator("..").locator('[data-component="icon-button-v2"]')
+    await expect(close).toBeVisible()
+    const result = await measureNavigationMilestones(page, {
+      triggerSelector: '[data-slot="titlebar-tabs"] [data-component="icon-button-v2"]',
+      milestones: {
+        home: { selector: homeShell },
+        row: { selector: homeRow },
+        tabRemoved: { selector: `[data-slot="titlebar-tabs"] a[href="${href}"]`, visible: false },
+      },
+      navigate: async () => {
+        await close.click()
+        await expect(page).toHaveURL("/")
+      },
+    })
+    report(result)
+  })
+})
+
+async function setup(page: Parameters<typeof mockStressTimeline>[0], sessionIDs: string[]) {
+  await mockStressTimeline(page)
+  await installTimelineSettings(page)
+  await installStressSessionTabs(page, { sessionIDs })
+}
+
+function messageSelector(id: string) {
+  return `[data-message-id="${id}"]`
+}