Hona · May 25, 2026 · May 20, 2026 · May 20, 2026 · May 20, 2026 · May 20, 2026
diff --git a/bun.lock b/bun.lock
diff --git a/package.json b/package.json
@@ -140,6 +140,7 @@
     "@silvia-odwyer/photon-node@0.3.4": "patches/@silvia-odwyer%2Fphoton-node@0.3.4.patch",
     "@standard-community/standard-openapi@0.2.9": "patches/@standard-community%2Fstandard-openapi@0.2.9.patch",
     "solid-js@1.9.10": "patches/solid-js@1.9.10.patch",
+    "virtua@0.49.1": "patches/virtua@0.49.1.patch",
     "@ai-sdk/xai@3.0.82": "patches/@ai-sdk%2Fxai@3.0.82.patch"
   }
 }
diff --git a/packages/app/e2e/regression/session-timeline-collapse-state.spec.ts b/packages/app/e2e/regression/session-timeline-collapse-state.spec.ts
@@ -0,0 +1,353 @@
+import { expect, test, type Locator, type Page, type Route } from "@playwright/test"
+
+const directory = "C:/OpenCode/TimelineStateRegression"
+const projectID = "proj_timeline_state_regression"
+const sessionID = "ses_timeline_state_regression"
+const userMessageID = "msg_user_regression"
+const assistantMessageID = "msg_assistant_regression"
+const editPartID = "prt_0001_edit"
+const textPartID = "prt_9999_text"
+const title = "Timeline collapse state regression"
+const model = { providerID: "opencode", modelID: "claude-opus-4-6", variant: "max" }
+
+type EventPayload = {
+  directory: string
+  payload: Record<string, unknown>
+}
+
+declare global {
+  interface Window {
+    __timelineDiffProbe: {
+      reset: () => void
+      shadowRoots: () => number
+    }
+  }
+}
+
+const userMessage = {
+  info: {
+    id: userMessageID,
+    sessionID,
+    role: "user",
+    time: { created: 1700000000000 },
+    summary: { diffs: [] },
+    agent: "build",
+    model,
+  },
+  parts: [
+    {
+      id: "prt_user_text",
+      sessionID,
+      messageID: userMessageID,
+      type: "text",
+      text: "Please edit the file.",
+    },
+  ],
+}
+
+const editPart = {
+  id: editPartID,
+  sessionID,
+  messageID: assistantMessageID,
+  type: "tool",
+  callID: "call_edit_regression",
+  tool: "edit",
+  state: {
+    status: "completed",
+    input: { filePath: "src/regression.ts" },
+    output: "Edited src/regression.ts",
+    title: "src/regression.ts",
+    metadata: {
+      filediff: {
+        file: "src/regression.ts",
+        additions: 1,
+        deletions: 1,
+        before: "export const value = 'before'\n",
+        after: "export const value = 'after'\n",
+      },
+      diff: "diff --git a/src/regression.ts b/src/regression.ts\n-export const value = 'before'\n+export const value = 'after'\n",
+    },
+    time: { start: 1700000001000, end: 1700000002000 },
+  },
+}
+
+const streamedTextPart = {
+  id: textPartID,
+  sessionID,
+  messageID: assistantMessageID,
+  type: "text",
+  text: "Streaming added a later assistant text part.",
+}
+
+const assistantMessage = {
+  info: {
+    id: assistantMessageID,
+    sessionID,
+    role: "assistant",
+    time: { created: 1700000001000 },
+    parentID: userMessageID,
+    modelID: model.modelID,
+    providerID: model.providerID,
+    mode: "build",
+    agent: "build",
+    path: { cwd: directory, root: directory },
+    cost: 0.01,
+    tokens: { input: 100, output: 200, reasoning: 0, cache: { read: 0, write: 0 } },
+    variant: "max",
+  },
+  parts: [editPart],
+}
+
+test.describe("regression: session timeline local row state", () => {
+  test("keeps a manually collapsed tool collapsed when later assistant content streams", async ({ page }) => {
+    const events: EventPayload[] = []
+    await mockServer(page, events)
+    await configurePage(page)
+
+    await page.goto(`/${base64Encode(directory)}/session/${sessionID}`)
+    await expect(page.getByRole("heading", { name: title })).toBeVisible()
+
+    const wrapper = page.locator(`[data-timeline-part-id="${editPartID}"]`).first()
+    await expect(wrapper).toBeVisible()
+    await expectExpanded(wrapper, true)
+
+    await wrapper.evaluate((element) => {
+      ;(element as HTMLElement).dataset.regressionMarker = "before-stream"
+    })
+    await wrapper.locator('[data-slot="collapsible-trigger"]').first().click()
+    await expectExpanded(wrapper, false)
+
+    events.push({
+      directory,
+      payload: {
+        type: "message.part.updated",
+        properties: { part: streamedTextPart },
+      },
+    })
+
+    await expect(page.locator(`[data-timeline-part-id="${textPartID}"]`).first()).toBeVisible({ timeout: 10_000 })
+
+    expect(await readToolState(page)).toEqual({
+      expanded: false,
+      row: "AssistantPart",
+      streamedTextVisible: true,
+    })
+  })
+
+  test("does not remount an edit diff when sibling parts or diff counts update", async ({ page }) => {
+    const events: EventPayload[] = []
+    await installDiffProbe(page)
+    await mockServer(page, events)
+    await configurePage(page)
+
+    await page.goto(`/${base64Encode(directory)}/session/${sessionID}`)
+    await expect(page.getByRole("heading", { name: title })).toBeVisible()
+
+    const wrapper = page.locator(`[data-timeline-part-id="${editPartID}"]`).first()
+    await expect(wrapper).toBeVisible()
+    await expect(wrapper.locator('[data-component="file"][data-mode="diff"]').first()).toBeVisible()
+    await markDiffProbe(page)
+
+    events.push({
+      directory,
+      payload: {
+        type: "message.part.updated",
+        properties: { part: streamedTextPart },
+      },
+    })
+
+    await expect(page.locator(`[data-timeline-part-id="${textPartID}"]`).first()).toBeVisible({ timeout: 10_000 })
+    expect(await readDiffProbe(page)).toEqual({ fileMarker: "before", shadowRoots: 0, toolMarker: "before" })
+
+    await markDiffProbe(page)
+    events.push({
+      directory,
+      payload: {
+        type: "message.part.updated",
+        properties: { part: editPartWithAdditions(2) },
+      },
+    })
+
+    await expect(wrapper.locator('[data-slot="diff-changes-additions"]').filter({ hasText: "+2" }).first()).toBeVisible({ timeout: 10_000 })
+    expect(await readDiffProbe(page)).toEqual({ fileMarker: "before", shadowRoots: 0, toolMarker: "before" })
+  })
+})
+
+async function configurePage(page: Page) {
+  await page.addInitScript(() => {
+    localStorage.setItem(
+      "settings.v3",
+      JSON.stringify({
+        general: {
+          editToolPartsExpanded: true,
+          shellToolPartsExpanded: true,
+          showReasoningSummaries: true,
+          showSessionProgressBar: true,
+        },
+      }),
+    )
+  })
+}
+
+async function expectExpanded(locator: Locator, expected: boolean) {
+  await expect.poll(() => locator.evaluate(readExpanded)).toBe(expected)
+}
+
+async function readToolState(page: Page) {
+  return page.locator(`[data-timeline-part-id="${editPartID}"]`).first().evaluate((element, textPartID) => ({
+    expanded: (() => {
+      const trigger = element.querySelector('[data-slot="collapsible-trigger"]')
+      const aria = trigger?.getAttribute("aria-expanded")
+      if (aria === "true") return true
+      if (aria === "false") return false
+
+      const root = element.querySelector('[data-component="collapsible"]')
+      if (root?.hasAttribute("data-expanded")) return true
+      if (root?.hasAttribute("data-closed")) return false
+
+      const content = element.querySelector<HTMLElement>('[data-slot="collapsible-content"]')
+      return !!content && content.getBoundingClientRect().height > 0
+    })(),
+    row: element.closest("[data-timeline-row]")?.getAttribute("data-timeline-row"),
+    streamedTextVisible: !!document.querySelector(`[data-timeline-part-id="${textPartID}"]`),
+  }), textPartID)
+}
+
+async function installDiffProbe(page: Page) {
+  await page.addInitScript(() => {
+    let shadowRootCount = 0
+    const attachShadow = Element.prototype.attachShadow
+    Element.prototype.attachShadow = function (init) {
+      shadowRootCount += 1
+      return attachShadow.call(this, init)
+    }
+    window.__timelineDiffProbe = {
+      reset: () => {
+        shadowRootCount = 0
+      },
+      shadowRoots: () => shadowRootCount,
+    }
+  })
+}
+
+async function markDiffProbe(page: Page) {
+  await page.locator(`[data-timeline-part-id="${editPartID}"]`).first().evaluate((element) => {
+    const tool = element as HTMLElement
+    const file = tool.querySelector<HTMLElement>('[data-component="file"][data-mode="diff"]')
+    if (!file) throw new Error("missing edit diff file")
+
+    tool.dataset.timelineProbe = "before"
+    file.dataset.timelineProbe = "before"
+    window.__timelineDiffProbe.reset()
+  })
+}
+
+async function readDiffProbe(page: Page) {
+  return page.locator(`[data-timeline-part-id="${editPartID}"]`).first().evaluate((element) => {
+    const tool = element as HTMLElement
+    const file = tool.querySelector<HTMLElement>('[data-component="file"][data-mode="diff"]')
+    return {
+      fileMarker: file?.dataset.timelineProbe,
+      shadowRoots: window.__timelineDiffProbe.shadowRoots(),
+      toolMarker: tool.dataset.timelineProbe,
+    }
+  })
+}
+
+function editPartWithAdditions(additions: number) {
+  return {
+    ...editPart,
+    state: {
+      ...editPart.state,
+      metadata: {
+        ...editPart.state.metadata,
+        filediff: {
+          ...editPart.state.metadata.filediff,
+          additions,
+        },
+      },
+    },
+  }
+}
+
+function readExpanded(element: Element) {
+  const trigger = element.querySelector('[data-slot="collapsible-trigger"]')
+  const aria = trigger?.getAttribute("aria-expanded")
+  if (aria === "true") return true
+  if (aria === "false") return false
+
+  const root = element.querySelector('[data-component="collapsible"]')
+  if (root?.hasAttribute("data-expanded")) return true
+  if (root?.hasAttribute("data-closed")) return false
+
+  const content = element.querySelector<HTMLElement>('[data-slot="collapsible-content"]')
+  return !!content && content.getBoundingClientRect().height > 0
+}
+
+async function mockServer(page: Page, events: EventPayload[]) {
+  await page.route("**/*", async (route) => {
+    const url = new URL(route.request().url())
+    const targetPort = process.env.PLAYWRIGHT_SERVER_PORT ?? "4096"
+    if (url.port !== targetPort) return route.fallback()
+
+    const path = url.pathname
+    if (path === "/global/event") return sse(route, events.splice(0))
+    if (path === "/global/config" || path === "/config" || path === "/provider/auth" || path === "/mcp" || path === "/session/status") return json(route, {})
+    if (["/skill", "/command", "/lsp", "/formatter", "/permission", "/question", "/vcs/status", "/vcs/diff"].includes(path)) return json(route, [])
+    if (path === "/provider") return json(route, provider())
+    if (path === "/path") return json(route, { state: directory, config: directory, worktree: directory, directory, home: "C:/OpenCode" })
+    if (path === "/project") return json(route, [project()])
+    if (path === "/project/current") return json(route, project())
+    if (path === "/agent") return json(route, [{ name: "build", mode: "primary" }])
+    if (path === "/vcs") return json(route, { branch: "main", default_branch: "main" })
+    if (path === "/session") return json(route, [session()])
+    if (path === `/session/${sessionID}`) return json(route, session())
+    if (/^\/session\/[^/]+\/(children|todo|diff)$/.test(path)) return json(route, [])
+    if (path === `/session/${sessionID}/message`) return json(route, [userMessage, assistantMessage])
+    return json(route, {})
+  })
+}
+
+function project() {
+  return { id: projectID, worktree: directory, vcs: "git", name: "timeline-state-regression", time: { created: 1700000000000, updated: 1700000000000 }, sandboxes: [] }
+}
+
+function session() {
+  return { id: sessionID, slug: "timeline-state-regression", projectID, directory, title, version: "dev", time: { created: 1700000000000, updated: 1700000000000 } }
+}
+
+function provider() {
+  return {
+    all: [
+      {
+        id: "opencode",
+        name: "OpenCode",
+        models: { "claude-opus-4-6": { id: "claude-opus-4-6", name: "Claude Opus 4.6", limit: { context: 200_000 } } },
+      },
+    ],
+    connected: ["opencode"],
+    default: { providerID: "opencode", modelID: "claude-opus-4-6" },
+  }
+}
+
+function json(route: Route, body: unknown, headers?: Record<string, string>) {
+  return route.fulfill({
+    status: 200,
+    contentType: "application/json",
+    headers: { "access-control-allow-origin": "*", "access-control-expose-headers": "x-next-cursor", ...headers },
+    body: JSON.stringify(body ?? null),
+  })
+}
+
+function sse(route: Route, events: EventPayload[]) {
+  return route.fulfill({
+    status: 200,
+    contentType: "text/event-stream",
+    headers: { "access-control-allow-origin": "*" },
+    body: events.map((event) => `data: ${JSON.stringify(event)}\n\n`).join(""),
+  })
+}
+
+function base64Encode(value: string) {
+  return Buffer.from(value, "utf8").toString("base64").replace(/\+/g, "-").replace(/\//g, "_").replace(/=/g, "")
+}