diff --git a/apps/web/tests/connection-recovery.e2e.ts b/apps/web/tests/connection-recovery.e2e.ts
new file mode 100644
index 0000000000..6f1568df50
--- /dev/null
+++ b/apps/web/tests/connection-recovery.e2e.ts
@@ -0,0 +1,89 @@
+/** Real WebSocket loss without replacing Client plugins or navigating the page. */
+import { fileURLToPath } from 'node:url'
+import { readFile } from 'node:fs/promises'
+import { chromium, type WebSocketRoute } from 'playwright'
+import { expect, it, onTestFailed, onTestFinished } from 'vitest'
+import { launchWebScaffold, seedSession, watchConsole } from './scaffold.ts'
+import { newEnglishPage, saveFailureShot, writeComposerDraft } from './support.ts'
+
+it.each([false, true])('retains the mounted application across WebSocket recovery with an active Session: %s', async (activeSession) => {
+  const scaffold = await launchWebScaffold({
+    extraOverlayPath: fileURLToPath(new URL('./pin-browse-picker.overlay.yml', import.meta.url)),
+  })
+  onTestFinished(() => scaffold.close())
+  const title = 'Connection recovery session'
+  const draft = 'Unsent draft retained across connection recovery'
+  if (activeSession) {
+    const workspace = await scaffold.ctx.workspaceRegistry.create(scaffold.workspaceCwd)
+    const seed = fileURLToPath(new URL('../../../snapshots/web/seeded-history/session.v3.jsonl', import.meta.url))
+    const sessionId = await seedSession(scaffold, await readFile(seed, 'utf8'), 'connection-recovery-session')
+    await workspace.attachSession(sessionId)
+    await scaffold.ctx.sessionController.rename({ sessionId, title })
+  }
+  const browser = await chromium.launch()
+  onTestFinished(() => browser.close())
+  const page = await newEnglishPage(browser)
+  const console = watchConsole(page)
+  onTestFailed(() => saveFailureShot(page, 'web-e2e-connection-recovery'))
+  const sockets: { client: WebSocketRoute; server: WebSocketRoute }[] = []
+  let readyFrames = 0
+  let sessionBaselines = 0
+  await page.routeWebSocket('**/api/remote.mux', (client) => {
+    const server = client.connectToServer()
+    sockets.push({ client, server })
+    const endpoints = new Map<string, string>()
+    client.onMessage((message) => {
+      if (typeof message === 'string') {
+        const frame = JSON.parse(message) as { type?: string; streamId: string; endpoint: string }
+        if (frame.type === 'open') endpoints.set(frame.streamId, frame.endpoint)
+      }
+      server.send(message)
+    })
+    server.onMessage((message) => {
+      if (typeof message === 'string') {
+        const frame = JSON.parse(message) as { type?: string; streamId: string; value?: { type?: string } }
+        if (frame.type === 'item' && frame.value?.type === 'ready') readyFrames++
+        if (frame.type === 'item' && endpoints.get(frame.streamId) === 'session/follow'
+          && frame.value?.type === 'snapshot') sessionBaselines++
+      }
+      client.send(message)
+    })
+  })
+  await page.goto(scaffold.authenticatedUrl, { waitUntil: 'load' })
+  const composer = page.locator('[data-composer-input][contenteditable="true"]')
+  if (activeSession) {
+    await page.getByRole('treeitem').filter({ has: page.getByText(title, { exact: true }) }).click({ timeout: 20_000 })
+    await writeComposerDraft(page, composer, draft)
+    await expect.poll(() => sessionBaselines).toBeGreaterThan(0)
+  } else {
+    await page.getByText('Into the Unknown', { exact: true }).waitFor({ timeout: 20_000 })
+  }
+  await expect.poll(() => readyFrames).toBeGreaterThan(0)
+  const root = await page.locator('[data-slot="root"]').elementHandle()
+  expect(root).not.toBeNull()
+  let navigations = 0
+  page.on('framenavigated', () => { navigations++ })
+
+  for (let attempt = 0; attempt < 3; attempt++) {
+    const previousReady = readyFrames
+    const previousBaseline = sessionBaselines
+    const active = sockets.at(-1)!
+    await Promise.all([
+      active.client.close({ code: 1012, reason: 'test connection loss' }),
+      active.server.close({ code: 1012, reason: 'test connection loss' }),
+    ])
+    await expect.poll(() => readyFrames, { timeout: 20_000 }).toBeGreaterThan(previousReady)
+    if (activeSession) {
+      await expect.poll(() => sessionBaselines, { timeout: 20_000 }).toBeGreaterThan(previousBaseline)
+    }
+    await page.evaluate(() => new Promise<void>((resolve) => {
+      requestAnimationFrame(() => { requestAnimationFrame(() => { resolve() }) })
+    }))
+    expect(await root!.evaluate(element => element.isConnected)).toBe(true)
+    expect(console.pageErrors).toEqual([])
+    if (activeSession) expect(await composer.textContent()).toBe(draft)
+  }
+
+  expect(navigations).toBe(0)
+  if (!activeSession) expect(await page.getByText('Into the Unknown', { exact: true }).isVisible()).toBe(true)
+})
diff --git a/apps/web/tests/server-restart.e2e.ts b/apps/web/tests/server-restart.e2e.ts
new file mode 100644
index 0000000000..c3d5565e40
--- /dev/null
+++ b/apps/web/tests/server-restart.e2e.ts
@@ -0,0 +1,199 @@
+/** Persisted Session recovery across two real dsh server processes on the same port. */
+import { spawn, type ChildProcess } from 'node:child_process'
+import { randomUUID } from 'node:crypto'
+import { createServer } from 'node:http'
+import { mkdir, mkdtemp, rm, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+import { chromium } from 'playwright'
+import { expect, it, onTestFailed, onTestFinished } from 'vitest'
+import { REPO_ROOT, newEnglishPage, saveFailureShot, writeComposerDraft } from './support.ts'
+
+class RestartableServer {
+  private child: ChildProcess | undefined
+  private closed: Promise<void> | undefined
+  private output = ''
+
+  constructor(private readonly world: string, private readonly modelUrl: string) {}
+
+  async start(port: number): Promise<string> {
+    if (this.child !== undefined) throw new Error('Server is already running')
+    this.output = ''
+    const ready = Promise.withResolvers<string>()
+    const child = spawn(process.execPath, [
+      join(REPO_ROOT, 'apps/cli/lib/bin.js'), '--profile', 'web',
+      '--patch', fileURLToPath(new URL('./pin-browse-picker.overlay.yml', import.meta.url)),
+      '--no-open', '--port', String(port),
+    ], {
+      cwd: this.world,
+      env: {
+        ...process.env, NODE_OPTIONS: '',
+        DSH_HOME: join(this.world, 'home'), DSH_AGENTS_HOME: join(this.world, 'agents'),
+        DSH_TELEMETRY_DISABLED: '1', DEEPSEEK_API_KEY: 'keyless-server-restart-fixture',
+        DEEPSEEK_BASE_URL: this.modelUrl,
+      },
+      stdio: ['ignore', 'pipe', 'pipe'],
+    })
+    this.child = child
+    const receive = (data: Buffer): void => {
+      this.output += data.toString()
+      const url = /dsh web: (http:\/\/[^\s]+)/u.exec(this.output)?.[1]
+      if (url !== undefined) ready.resolve(url)
+    }
+    child.stdout?.on('data', receive)
+    child.stderr?.on('data', receive)
+    child.once('error', (error) => { ready.reject(error) })
+    this.closed = new Promise((resolve) => {
+      child.once('close', (code, signal) => {
+        ready.reject(new Error('Server exited before readiness: ' + JSON.stringify({ code, signal }) + '\n' + this.logs()))
+        resolve()
+      })
+    })
+    const timer = setTimeout(() => { ready.reject(new Error('Server readiness timed out\n' + this.logs())) }, 30_000)
+    try { return await ready.promise }
+    finally { clearTimeout(timer) }
+  }
+
+  async stop(): Promise<void> {
+    const child = this.child
+    if (child === undefined) return
+    let forced = false
+    const timer = setTimeout(() => { forced = true; child.kill('SIGKILL') }, 15_000)
+    try {
+      if (child.exitCode === null && child.signalCode === null) child.kill('SIGTERM')
+      await this.closed
+    } finally {
+      clearTimeout(timer)
+      this.child = undefined
+    }
+    if (forced) throw new Error('Server did not stop after SIGTERM\n' + this.logs())
+  }
+
+  logs(): string { return this.output.replace(/([?&]token=)[A-Za-z0-9_-]+/gu, '$1<redacted>') }
+}
+
+it('keeps an opened Session and draft when the server restarts on the same port', async () => {
+  const world = await mkdtemp(join(tmpdir(), 'dsh-server-restart-'))
+  onTestFinished(() => rm(world, { recursive: true, force: true }))
+  const model = createServer((request, response) => {
+    request.resume()
+    request.once('end', () => {
+      response.writeHead(200, { 'content-type': 'text/event-stream' })
+      const events = [
+        { type: 'message_start', message: { id: 'restart-fixture', model: 'mock-model', usage: { input_tokens: 3, output_tokens: 0 } } },
+        { type: 'content_block_start', index: 0, content_block: { type: 'text', text: 'Persisted server restart fixture.' } },
+        { type: 'content_block_stop', index: 0 },
+        { type: 'message_delta', delta: { stop_reason: 'end_turn' }, usage: { output_tokens: 1 } },
+        { type: 'message_stop' },
+      ]
+      response.end(events.map(event => 'data: ' + JSON.stringify(event) + '\n\n').join(''))
+    })
+  })
+  onTestFinished(() => new Promise<void>((resolve, reject) => {
+    model.close((error) => { if (error) reject(error); else resolve() })
+    model.closeAllConnections()
+  }))
+  await new Promise<void>((resolve, reject) => {
+    model.once('error', reject)
+    model.listen(0, '127.0.0.1', resolve)
+  })
+  const modelAddress = model.address()
+  if (modelAddress === null || typeof modelAddress === 'string') throw new Error('Model fixture did not listen')
+  const server = new RestartableServer(world, `http://127.0.0.1:${String(modelAddress.port)}`)
+  onTestFinished(() => server.stop())
+  const workspacePath = join(world, 'workspace')
+  await mkdir(workspacePath)
+
+  const url = await server.start(0)
+  const port = Number(new URL(url).port)
+  const authenticated = await fetch(url, { redirect: 'manual' })
+  const cookie = authenticated.headers.get('set-cookie')?.split(';', 1)[0]
+  if (cookie === undefined) throw new Error('Server did not issue an authentication cookie')
+  const rpc = async <T>(endpoint: string, args: object): Promise<T> => {
+    const response = await fetch(new URL('/api/' + endpoint, url), {
+      method: 'POST', headers: { 'content-type': 'application/json', cookie },
+      body: JSON.stringify({ type: 'client-request', rpcId: randomUUID(), method: endpoint, payload: { args } }),
+    })
+    const result = await response.json() as { result: { ok: boolean; value: T; error?: { message: string } } }
+    if (!result.result.ok) throw new Error(`${endpoint}: ${String(result.result.error?.message)}`)
+    return result.result.value
+  }
+  await rpc('workspace/create', { request: { path: workspacePath } })
+  const scenarioId = randomUUID()
+
+  const browser = await chromium.launch({ headless: true })
+  onTestFinished(() => browser.close())
+  const page = await newEnglishPage(browser)
+  const errors: string[] = []
+  const graphs: { rev: string; entries: { id: string; rev: string }[] }[] = []
+  let readyFrames = 0
+  let sessionBaselines = 0
+  let navigations = 0
+  page.on('pageerror', (error) => { errors.push(String(error)) })
+  page.on('websocket', (socket) => {
+    const endpoints = new Map<string, string>()
+    socket.on('framesent', ({ payload }) => {
+      if (typeof payload !== 'string') return
+      const frame = JSON.parse(payload) as { type?: string; streamId: string; endpoint: string }
+      if (frame.type === 'open') endpoints.set(frame.streamId, frame.endpoint)
+    })
+    socket.on('framereceived', ({ payload }) => {
+      if (typeof payload !== 'string') return
+      const message = JSON.parse(payload) as { type?: string; streamId: string; value?: { type?: string } }
+      if (message.type === 'item' && message.value?.type === 'ready') readyFrames++
+      if (message.type === 'item' && endpoints.get(message.streamId) === 'session/follow'
+        && message.value?.type === 'snapshot') sessionBaselines++
+    })
+  })
+  const network = await page.context().newCDPSession(page)
+  await network.send('Network.enable')
+  network.on('Network.eventSourceMessageReceived', (event) => {
+    const message = JSON.parse(event.data) as { type?: string; graph: typeof graphs[number] }
+    if (message.type === 'graph') graphs.push(message.graph)
+  })
+  onTestFailed(async () => {
+    await saveFailureShot(page, 'web-server-restart-' + scenarioId)
+    await writeFile(join(REPO_ROOT, '.artifacts', 'server-restart-' + scenarioId + '.json'), JSON.stringify({ errors, graphs, server: server.logs() }, null, 2))
+  })
+  await page.goto(url, { waitUntil: 'load' })
+  await page.locator('[data-slot="root"]').waitFor({ state: 'attached', timeout: 20_000 })
+  const notice = page.getByRole('button', { name: 'Continue', exact: true })
+  await notice.click({ timeout: 15_000 })
+  const composer = page.locator('[data-composer-input][contenteditable="true"]')
+  await writeComposerDraft(page, composer, 'Create a completed turn for the server restart test.')
+  await composer.press('Enter')
+  const response = page.getByRole('paragraph').filter({ hasText: /^Persisted server restart fixture\.$/u })
+  await response.last().waitFor({ timeout: 20_000 })
+  const draft = 'Unsent draft across a server restart'
+  await writeComposerDraft(page, composer, draft)
+  await expect.poll(() => graphs.length).toBeGreaterThan(0)
+  await expect.poll(() => sessionBaselines).toBeGreaterThan(0)
+  const originalRoot = await page.locator('[data-slot="root"]').elementHandle()
+  expect(originalRoot).not.toBeNull()
+  const beforeReady = readyFrames
+  const beforeBaseline = sessionBaselines
+  const beforeGraphs = graphs.length
+  page.on('framenavigated', () => { navigations++ })
+
+  await server.stop()
+  const restarted = await server.start(port)
+  expect(new URL(restarted).origin).toBe(new URL(url).origin)
+  await expect.poll(() => readyFrames, { timeout: 30_000 }).toBeGreaterThan(beforeReady)
+  await expect.poll(() => sessionBaselines, { timeout: 30_000 }).toBeGreaterThan(beforeBaseline)
+  await expect.poll(() => graphs.length, { timeout: 30_000 }).toBeGreaterThan(beforeGraphs)
+  await page.evaluate(() => new Promise<void>((resolve) => {
+    requestAnimationFrame(() => { requestAnimationFrame(() => { resolve() }) })
+  }))
+
+  expect(errors).toEqual([])
+  expect(graphs.at(-1)).toEqual(graphs[beforeGraphs - 1])
+  expect(await originalRoot!.evaluate(element => element.isConnected)).toBe(true)
+  expect(await composer.textContent()).toBe(draft)
+  expect(await response.isVisible()).toBe(true)
+
+  await composer.press('Enter')
+  await expect.poll(() => response.count(), { timeout: 20_000 }).toBe(2)
+  expect(errors).toEqual([])
+  expect(navigations).toBe(0)
+})
diff --git a/apps/web/tsconfig.json b/apps/web/tsconfig.json
index 9af71ce894..0608096055 100644
--- a/apps/web/tsconfig.json
+++ b/apps/web/tsconfig.json
@@ -22,6 +22,8 @@
   // this client-registered project must not also hold them (one program
   // cannot see both sides of the cordis Context merges).
   "exclude": [
+    "tests/connection-recovery.e2e.ts",
+    "tests/server-restart.e2e.ts",
     "tests/default-product-isolation.e2e.ts",
     "tests/diff-context.e2e.ts",
     "tests/scaffold.ts",
diff --git a/packages/client/ui-renderer/tests/reconnect.client.spec.tsx b/packages/client/ui-renderer/tests/reconnect.client.spec.tsx
new file mode 100644
index 0000000000..55293c494c
--- /dev/null
+++ b/packages/client/ui-renderer/tests/reconnect.client.spec.tsx
@@ -0,0 +1,27 @@
+// @vitest-environment jsdom
+import { act } from '@testing-library/react'
+import { describe, expect, it, onTestFinished, vi } from 'vitest'
+import { RemoteMock } from '@deepseek-ai/dsh-remote-mock'
+import { TestClient, remoteDefaultResponses, webApp } from '@deepseek-ai/dsh-client-test-runtime/src/assembly/index.ts'
+import type {} from '@deepseek-ai/dsh-client-ui-session/client'
+
+describe('assembled renderer connection recovery', () => {
+  it('keeps the mounted root across a transport reconnect', async () => {
+    const mock = RemoteMock.create().load(remoteDefaultResponses)
+    const client = await TestClient.start({ roster: webApp }, mock, { mount: true })
+    onTestFinished(() => client.dispose())
+    const root = client.container!.querySelector('[data-slot="root"]')
+    const generation = client.connection.generation.getSnapshot()!.id
+    expect(root).not.toBeNull()
+
+    await act(async () => {
+      client.connection.reconnect()
+      await vi.waitFor(() => {
+        expect(client.connection.generation.getSnapshot()?.id).toBeGreaterThan(generation)
+        expect(client.connection.state.getSnapshot()).toBe('connected')
+      })
+    })
+
+    expect(client.container!.querySelector('[data-slot="root"]')).toBe(root)
+  }, 60_000)
+})
diff --git a/tsconfig.host.json b/tsconfig.host.json
index 140e9f5894..8452b2ac30 100644
--- a/tsconfig.host.json
+++ b/tsconfig.host.json
@@ -10,6 +10,8 @@
   "files": [],
   "include": [
     "apps/web/product-isolation.ts",
+    "apps/web/tests/connection-recovery.e2e.ts",
+    "apps/web/tests/server-restart.e2e.ts",
     "apps/web/tests/default-product-isolation.e2e.ts",
     "apps/web/tests/diff-context.e2e.ts",
     "apps/web/tests/scaffold.ts",