Merge remote-tracking branch 'gitea/develop' into feat/481-version-coherence

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -463,6 +463,7 @@ Vite SPA. Code is organized by feature under `apps/client/src/features/*` (mirro
 - The editor is Tiptap; shared node/mark extensions live in `packages/editor-ext` and are imported by **both the client and the server** (collaboration, schema, `canonicalizeFootnotes`) — editor schema changes often need to be made in `editor-ext`, not just the client. Server-side markdown import/export no longer lives in `editor-ext`: it goes through the canonical converter (#345, see below). The ProseMirror↔Markdown converter and its Docmost schema mirror now live in a SINGLE package, `@docmost/prosemirror-markdown` (#293), consumed by `mcp`, `git-sync`, `apps/server` (#345), and `apps/client` (#347) — do NOT reintroduce a per-package copy. The client uses the package's `browser` entry (`@docmost/prosemirror-markdown/browser`): markdown paste (`markdown-clipboard.ts`), copy-as-markdown, and AI-chat rendering now all go through the canonical converter, so the hand-written `marked`/`turndown` markdown layer that used to live in `editor-ext` was deleted (#347). The browser entry runs the HTML→DOM stage on the native `DOMParser`, so jsdom stays out of the client bundle. `editor-ext` is the upstream source of the Tiptap schema; the package's `docmost-schema.ts` mirrors it and a serializer-contract test (`packages/prosemirror-markdown/test/serializer-contract.test.ts`) guards the boundary (every schema node must have a converter case), so a drift surfaces as a failing test rather than silent divergence. For the converter's property-testing and counterexample→fixture process (P1–P4 invariants, the `PROPERTY_SEED`/`PROPERTY_NUM_RUNS` knobs, and the nightly fuzz workflow), see `packages/prosemirror-markdown/README.md`.
 - API access goes through `apps/client/src/lib/api-client.ts` (axios). The `@` alias maps to `apps/client/src`.
 - Runtime config is injected at build time by `vite.config.ts` via `define` (`APP_URL`, `COLLAB_URL`, `APP_VERSION`, …) — these come from the root `.env`, not from `import.meta.env`.
+- The build also emits `client/dist/version.json` (`{"version": …}`) from a small `vite.config.ts` plugin using the **same** `appVersion` that feeds `define.APP_VERSION`, so the file and the baked-in bundle version are identical by construction. The server reads it at startup (`ws.gateway.ts` via `readClientBuildVersion`/`resolveClientDistPath`) and announces it to each socket on connect (`app-version` event) so a tab left open across a redeploy can guard-reload before hitting a stale chunk (version-coherence). No runtime env / Dockerfile change — the file already ships in `client/dist`; missing/empty file ⇒ feature inert.
 
 ## Conventions
 

CHANGELOG.md

@@ -142,6 +142,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   snapshots switched from a fixed interval to a trailing idle-flush with a
   max-wait ceiling, and a boundary snapshot is pinned whenever the editing source
   changes (e.g. a person's edits followed by the AI agent). (#370)
+- **Open tabs pick up a new deploy on their own.** After the server is
+  redeployed while a tab is left open for hours, the tab now learns the new
+  build version over the existing WebSocket (announced per-connect, so a natural
+  reconnect delivers it) and shows a "A new version is available" banner with an
+  Update button. To avoid dropping a half-written comment or form, the tab is
+  not reloaded when you merely switch away from it; instead it auto-reloads at
+  the next safe point — the next in-app navigation (or immediately if you click
+  Update) — before it can hit a stale lazy-loaded chunk. At most one automatic
+  reload happens per 5-minute window, shared with the existing chunk-load
+  recovery, so a permanent version skew degrades to the banner rather than a
+  reload loop while a second deploy in the same tab still recovers. When the
+  build carries no version info the feature stays inert. (#481)
 
 - **Place several images side by side in a row.** A new "Inline (side by
   side)" alignment mode in the image bubble menu renders consecutive inline

apps/client/public/locales/en-US/translation.json

@@ -1,4 +1,5 @@
 {
+  "A new version is available": "A new version is available",
   "Account": "Account",
   "Active": "Active",
   "Add": "Add",

apps/client/public/locales/ru-RU/translation.json

@@ -1,4 +1,5 @@
 {
+  "A new version is available": "Доступна новая версия",
   "Account": "Аккаунт",
   "Active": "Активный",
   "Add": "Добавить",

apps/client/src/components/chunk-load-error-boundary.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from "vitest";
-import { isChunkLoadError, shouldAutoReload } from "./chunk-load-error-boundary";
+import { isChunkLoadError } from "./chunk-load-error-boundary";
 
 // The detector decides whether a caught render error is a stale-deploy chunk-404
 // (→ auto-reload to fetch the new manifest) vs a genuine app error (→ generic
@@ -35,31 +35,3 @@ describe("isChunkLoadError", () => {
     expect(isChunkLoadError(err)).toBe(false);
   });
 });
-
-// The window gate replaces the old one-shot flag: it must permit recovery across
-// several deploys in one tab (each > window apart) while still stopping an infinite
-// reload loop when a lazy chunk is permanently broken (a second failure < window).
-describe("shouldAutoReload", () => {
-  const WINDOW = 5 * 60 * 1000;
-  const NOW = 1_000_000_000_000;
-
-  it("allows a reload when we have never auto-reloaded", () => {
-    expect(shouldAutoReload(NOW, null, WINDOW)).toBe(true);
-  });
-
-  it("allows a reload when the last one was 6 minutes ago (outside the window)", () => {
-    expect(shouldAutoReload(NOW, NOW - 6 * 60 * 1000, WINDOW)).toBe(true);
-  });
-
-  it("blocks a reload when the last one was 1 minute ago (inside the window)", () => {
-    expect(shouldAutoReload(NOW, NOW - 1 * 60 * 1000, WINDOW)).toBe(false);
-  });
-
-  it("blocks a reload exactly at the window boundary (not strictly older)", () => {
-    expect(shouldAutoReload(NOW, NOW - WINDOW, WINDOW)).toBe(false);
-  });
-
-  it("allows a reload when the stored timestamp is unparseable (NaN)", () => {
-    expect(shouldAutoReload(NOW, NaN, WINDOW)).toBe(true);
-  });
-});

apps/client/src/components/chunk-load-error-boundary.tsx

@@ -1,26 +1,11 @@
 import { ReactNode } from "react";
 import { ErrorBoundary } from "react-error-boundary";
 import { Button, Center, Stack, Text } from "@mantine/core";
-
+import {
-// sessionStorage key holding the epoch-ms timestamp of the last automatic reload.
+  hasAutoReloaded,
-const RELOAD_AT_KEY = "chunk-reload-at";
+  markAutoReloaded,
-// Allow at most one automatic reload per this window. A stale-deploy 404 is cured
+  recordReloadBreadcrumb,
-// by a single reload, so anything inside the window is treated as a reload loop
+} from "@/lib/reload-guard";
-// (permanently-broken chunk) and falls through to the manual UI. A window (rather
-// than a one-shot flag) lets a SECOND deploy in the same tab's lifetime recover too.
-const RELOAD_WINDOW_MS = 5 * 60 * 1000;
-
-// Pure window decision, unit-tested in isolation: auto-reload only if we have never
-// auto-reloaded (lastReloadAt null/NaN) or the last one was strictly older than the
-// window. Anything inside the window is suppressed to break an infinite reload loop.
-export function shouldAutoReload(
-  now: number,
-  lastReloadAt: number | null,
-  windowMs: number,
-): boolean {
-  if (lastReloadAt === null || Number.isNaN(lastReloadAt)) return true;
-  return now - lastReloadAt > windowMs;
-}
 
 // Heuristic detection of a failed dynamic import. Since the code-splitting work,
 // every route (plus Aside / AiChatWindow) is React.lazy: when a new deploy
@@ -39,24 +24,26 @@ export function isChunkLoadError(error: unknown): boolean {
   );
 }
 
-function handleError(error: unknown) {
+// Exported for tests: the reactive chunk-load reload decision, so the shared
+// window budget (invariant: ≤1 auto-reload per window across this path AND the
+// proactive version-coherence path) can be exercised against the real guard.
+export function handleError(error: unknown) {
   if (!isChunkLoadError(error)) return;
   // A stale-chunk 404 is cured by a full reload that re-fetches index.html and
-  // the new chunk manifest. Auto-reload at most once per RELOAD_WINDOW_MS: this
+  // the new chunk manifest. Auto-reload at most once per window via the SHARED
-  // recovers across multiple deploys in a single tab's lifetime, yet a
+  // window-based reload guard (see @/lib/reload-guard — the same budget the
-  // permanently-broken lazy chunk (which would loop) is stopped after the first
+  // proactive version-coherence path consumes, so a mismatch that arrives on
-  // reload and falls through to the manual recovery UI below.
+  // both paths reloads at most once per window across BOTH). This recovers
-  try {
+  // across multiple deploys in a single tab's lifetime, yet a permanently-broken
-    const raw = sessionStorage.getItem(RELOAD_AT_KEY);
+  // lazy chunk (which would loop) is stopped after the first reload and falls
-    const lastReloadAt = raw === null ? null : Number.parseInt(raw, 10);
+  // through to the manual recovery UI below. If the shared budget is already
-    const now = Date.now();
+  // spent this window, or the stamp write fails (storage unavailable), we return
-    if (!shouldAutoReload(now, lastReloadAt, RELOAD_WINDOW_MS)) return;
+  // without reloading rather than risk a loop.
-    sessionStorage.setItem(RELOAD_AT_KEY, String(now));
+  if (hasAutoReloaded()) return;
-  } catch {
+  if (!markAutoReloaded()) return;
-    // sessionStorage unavailable (private mode / disabled): skip the automatic
+  // Trace before the reload clears the console (same diagnostic breadcrumb the
-    // reload rather than risk an unguarded loop; the fallback UI still recovers.
+  // proactive version-coherence path writes, tagged with this path).
-    return;
+  recordReloadBreadcrumb({ path: "chunk-boundary" });
-  }
   window.location.reload();
 }
 

apps/client/src/features/user/guarded-reload.test.tsx

@@ -0,0 +1,195 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { render, act, cleanup } from "@testing-library/react";
+import { MemoryRouter, useNavigate } from "react-router-dom";
+
+// Mocks for the dirty shell's side-effecting collaborators.
+vi.mock("@mantine/notifications", () => ({
+  notifications: { show: vi.fn() },
+}));
+vi.mock("@/i18n.ts", () => ({ default: { t: (k: string) => k } }));
+vi.mock("@/lib/reload-guard", () => ({
+  hasAutoReloaded: vi.fn(() => false),
+  markAutoReloaded: vi.fn(() => true),
+  recordReloadBreadcrumb: vi.fn(),
+  takeReloadBreadcrumb: vi.fn(() => null),
+}));
+
+import { notifications } from "@mantine/notifications";
+import { hasAutoReloaded, markAutoReloaded } from "@/lib/reload-guard";
+import {
+  triggerGuardedReload,
+  useVersionReloadOnNavigation,
+  __resetGuardedReloadForTests,
+} from "./guarded-reload";
+
+const show = notifications.show as unknown as ReturnType<typeof vi.fn>;
+const mockHasAutoReloaded = hasAutoReloaded as unknown as ReturnType<
+  typeof vi.fn
+>;
+const mockMarkAutoReloaded = markAutoReloaded as unknown as ReturnType<
+  typeof vi.fn
+>;
+
+let reload: ReturnType<typeof vi.fn>;
+let visibility: DocumentVisibilityState;
+
+// Test harness mounted inside a router: it installs the navigation hook and
+// exposes `navigate` so a test can drive an in-app router navigation.
+let doNavigate: (to: string) => void;
+function Harness() {
+  useVersionReloadOnNavigation();
+  const navigate = useNavigate();
+  doNavigate = navigate;
+  return null;
+}
+
+function mountHarness() {
+  render(
+    <MemoryRouter initialEntries={["/start"]}>
+      <Harness />
+    </MemoryRouter>,
+  );
+}
+
+function navigateTo(path: string) {
+  act(() => {
+    doNavigate(path);
+  });
+}
+
+beforeEach(() => {
+  __resetGuardedReloadForTests();
+  vi.clearAllMocks();
+  mockHasAutoReloaded.mockReturnValue(false);
+  mockMarkAutoReloaded.mockReturnValue(true);
+
+  vi.stubGlobal("APP_VERSION", "test-A");
+
+  reload = vi.fn();
+  Object.defineProperty(window, "location", {
+    configurable: true,
+    value: { reload },
+  });
+
+  visibility = "visible";
+  Object.defineProperty(document, "visibilityState", {
+    configurable: true,
+    get: () => visibility,
+  });
+});
+
+afterEach(() => {
+  cleanup();
+  vi.unstubAllGlobals();
+});
+
+describe("triggerGuardedReload (variant C)", () => {
+  it("noop when versions match: no banner, no reload", () => {
+    triggerGuardedReload("test-A");
+    expect(show).not.toHaveBeenCalled();
+    expect(reload).not.toHaveBeenCalled();
+  });
+
+  it("noop when the server version is empty (fail-safe)", () => {
+    triggerGuardedReload("");
+    triggerGuardedReload(undefined);
+    expect(show).not.toHaveBeenCalled();
+    expect(reload).not.toHaveBeenCalled();
+  });
+
+  it("real mismatch shows the banner but does NOT reload immediately", () => {
+    mountHarness();
+    triggerGuardedReload("test-B");
+    expect(show).toHaveBeenCalledTimes(1);
+    expect(show.mock.calls[0][0]).toMatchObject({
+      id: "app-version-reload",
+      autoClose: false,
+      withCloseButton: true,
+    });
+    expect(reload).not.toHaveBeenCalled();
+  });
+
+  it("reloads EXACTLY ONCE on the first in-app navigation after a mismatch", () => {
+    mountHarness();
+    triggerGuardedReload("test-B");
+    expect(reload).not.toHaveBeenCalled();
+
+    navigateTo("/next");
+    expect(reload).toHaveBeenCalledTimes(1);
+
+    // A second navigation must NOT reload again (one-shot was consumed).
+    navigateTo("/again");
+    expect(reload).toHaveBeenCalledTimes(1);
+  });
+
+  it("does NOT reload on a 2nd mismatch after the first was armed/consumed (one-shot)", () => {
+    mountHarness();
+    triggerGuardedReload("test-B");
+    navigateTo("/next");
+    expect(reload).toHaveBeenCalledTimes(1);
+
+    // Another app-version mismatch arrives (reconnect): must not re-arm.
+    triggerGuardedReload("test-C");
+    navigateTo("/again");
+    expect(reload).toHaveBeenCalledTimes(1);
+  });
+
+  it("does NOT reload merely from the tab going to the background", () => {
+    mountHarness();
+    triggerGuardedReload("test-B");
+    expect(reload).not.toHaveBeenCalled();
+
+    visibility = "hidden";
+    act(() => {
+      document.dispatchEvent(new Event("visibilitychange"));
+    });
+    expect(reload).not.toHaveBeenCalled();
+  });
+
+  it("a hidden-at-receipt tab is also NOT reloaded immediately (variant C uniform); reloads on next navigation", () => {
+    visibility = "hidden";
+    mountHarness();
+    triggerGuardedReload("test-B");
+    expect(reload).not.toHaveBeenCalled();
+    expect(show).toHaveBeenCalledTimes(1);
+
+    navigateTo("/next");
+    expect(reload).toHaveBeenCalledTimes(1);
+  });
+
+  it("the banner's Update button reloads immediately", () => {
+    triggerGuardedReload("test-B");
+    const message = show.mock.calls[0][0].message as {
+      props: { onClick: () => void };
+    };
+    message.props.onClick();
+    expect(reload).toHaveBeenCalledTimes(1);
+  });
+
+  it("banner-only (auto-reload already spent): banner, never auto-reload on navigation", () => {
+    mockHasAutoReloaded.mockReturnValue(true);
+    mountHarness();
+    triggerGuardedReload("test-B");
+    expect(show).toHaveBeenCalledTimes(1);
+
+    navigateTo("/next");
+    expect(reload).not.toHaveBeenCalled();
+  });
+
+  it("does NOT reload when the flag write fails; falls back to the banner", () => {
+    mockMarkAutoReloaded.mockReturnValue(false);
+    mountHarness();
+    triggerGuardedReload("test-B");
+    navigateTo("/next");
+    expect(reload).not.toHaveBeenCalled();
+    // performAutoReload falls back to showing the banner (initial + fallback).
+    expect(show).toHaveBeenCalled();
+  });
+
+  it("is idempotent within a tab-load: repeated emits do not stack banners", () => {
+    triggerGuardedReload("test-B");
+    triggerGuardedReload("test-B");
+    triggerGuardedReload("test-C");
+    expect(show).toHaveBeenCalledTimes(1);
+  });
+});

apps/client/src/features/user/guarded-reload.tsx

@@ -0,0 +1,188 @@
+import { useEffect, useRef } from "react";
+import { useLocation } from "react-router-dom";
+import { Button } from "@mantine/core";
+import { notifications } from "@mantine/notifications";
+import i18n from "@/i18n.ts";
+import {
+  hasAutoReloaded,
+  markAutoReloaded,
+  recordReloadBreadcrumb,
+  takeReloadBreadcrumb,
+} from "@/lib/reload-guard";
+import { decideVersionAction } from "@/features/user/version-coherence";
+
+// Dirty shell around the pure `decideVersionAction`: it reads globals
+// (APP_VERSION), touches sessionStorage via the shared reload-guard, drives the
+// Mantine notification, and arms the router-navigation reload hook. Kept
+// separate from the pure module so the decision stays unit-testable without a
+// DOM.
+
+// One fixed id so repeated app-version signals (e.g. every reconnect) update a
+// single banner instead of stacking a new one each time.
+const BANNER_ID = "app-version-reload";
+
+// Module-level idempotency for the current tab-load: once a mismatch has been
+// handled we don't re-arm the navigation reload or re-show the banner on
+// subsequent app-version emits.
+let handled = false;
+
+// Variant C: on a real mismatch we do NOT reload the tab when it merely goes to
+// the background (that would silently drop a half-written comment/form). Instead
+// we arm a one-shot reload for the NEXT in-app router navigation — a point where
+// the user is already leaving the current page, so an in-app navigation would
+// discard that unsaved component-state anyway and the reload adds no extra loss.
+let pendingNavReload = false;
+
+// Remembered from the last detected mismatch for the pre-reload breadcrumb and
+// the (already-visible) banner.
+let lastServerVersion = "";
+let lastClientVersion = "";
+
+// Read the build version baked into THIS bundle. The `typeof` guard avoids a
+// ReferenceError where the `APP_VERSION` global is absent (e.g. under vitest,
+// where Vite's `define` did not run) — an unknown client version makes the
+// pure decision no-op (fail-safe).
+function readClientVersion(): string {
+  return (typeof APP_VERSION !== "undefined" ? APP_VERSION : "").trim();
+}
+
+// Perform the actual reload — but only after the shared one-shot flag is
+// persisted. If the write fails (storage unavailable) we must NOT reload
+// (mirrors the reactive chunk-load boundary's `catch → return`), and fall back
+// to the manual banner so the user can still recover.
+function performAutoReload(): void {
+  if (!markAutoReloaded()) {
+    showReloadBanner();
+    return;
+  }
+  // Trace right before the reload (which clears the console): a persistent
+  // breadcrumb + a log line so the auto-reload is observable in a field report.
+  recordReloadBreadcrumb({
+    path: "proactive",
+    serverVersion: lastServerVersion,
+    clientVersion: lastClientVersion,
+  });
+  console.warn(
+    `[version-coherence] auto-reloading: client=${lastClientVersion} -> server=${lastServerVersion}`,
+  );
+  window.location.reload();
+}
+
+function showReloadBanner(): void {
+  notifications.show({
+    id: BANNER_ID,
+    title: i18n.t("A new version is available"),
+    message: (
+      <Button size="xs" mt="xs" onClick={() => performAutoReload()}>
+        {i18n.t("Update")}
+      </Button>
+    ),
+    autoClose: false,
+    withCloseButton: true,
+  });
+}
+
+/**
+ * Handle a server `app-version` announcement: compare it to this bundle's
+ * version and, on a real mismatch, show the banner and arm a guarded reload for
+ * the next in-app navigation (variant C).
+ *
+ * - real mismatch (window budget available) → banner + arm navigation reload.
+ *   The banner's "Update" button reloads immediately (same shared window guard).
+ *   The tab is NOT reloaded on visibility change.
+ * - auto-reload already used this window / storage error → banner only (no arm),
+ *   so there is at most one automatic reload per RELOAD_WINDOW_MS window (loop
+ *   safety).
+ * - in sync / unknown version → noop (fail-safe).
+ */
+export function triggerGuardedReload(
+  rawServerVersion: string | undefined | null,
+): void {
+  const serverVersion = (rawServerVersion ?? "").trim();
+  const clientVersion = readClientVersion();
+
+  // A storage read error surfaces as autoReloadUsed=true → fail toward NOT
+  // reloading (banner only).
+  const autoReloadUsed = hasAutoReloaded();
+
+  const action = decideVersionAction({
+    serverVersion,
+    clientVersion,
+    autoReloadUsed,
+  });
+  if (action === "noop") return;
+
+  // Idempotent per tab-load: don't re-arm or re-stack the banner across repeated
+  // emits (reconnects) once we've already acted.
+  if (handled) return;
+  handled = true;
+
+  lastServerVersion = serverVersion;
+  lastClientVersion = clientVersion;
+
+  if (action === "banner") {
+    // Entered banner-only (permanent skew, node oscillation, or the window's
+    // auto-reload budget already spent). Log for diagnosability; show the banner.
+    console.warn(
+      `[version-coherence] server=${serverVersion} client=${clientVersion}: ` +
+        "auto-reload budget already spent this window — showing manual banner",
+    );
+    showReloadBanner();
+    return;
+  }
+
+  // action === "reload" (variant C): show the banner and defer the auto-reload
+  // to the next in-app navigation instead of reloading now / on visibility.
+  showReloadBanner();
+  pendingNavReload = true;
+}
+
+/**
+ * Consume the armed one-shot navigation reload, if any. Called by
+ * `useVersionReloadOnNavigation` on each in-app router navigation.
+ */
+export function consumeNavigationReload(): void {
+  if (!pendingNavReload) return;
+  pendingNavReload = false;
+  performAutoReload();
+}
+
+/**
+ * Hook (mounted inside the Router) that fires the armed one-shot reload on the
+ * NEXT in-app router navigation after a version mismatch. Skips the initial
+ * render so it only reacts to real navigations, not the first location.
+ */
+export function useVersionReloadOnNavigation(): void {
+  const location = useLocation();
+  const firstRender = useRef(true);
+  useEffect(() => {
+    if (firstRender.current) {
+      firstRender.current = false;
+      return;
+    }
+    consumeNavigationReload();
+  }, [location.key]);
+}
+
+/**
+ * Surface (log once) the breadcrumb left by an auto-reload in the previous page
+ * load — the reload cleared the console, so this makes a "tab reloaded itself"
+ * report diagnosable. Call once on app startup.
+ */
+export function surfacePreviousReloadBreadcrumb(): void {
+  const crumb = takeReloadBreadcrumb();
+  if (!crumb) return;
+  console.info(
+    `[version-coherence] previous auto-reload: path=${crumb.path} ` +
+      `client=${crumb.clientVersion ?? ""} -> server=${crumb.serverVersion ?? ""} ` +
+      `at=${new Date(crumb.at).toISOString()}`,
+  );
+}
+
+// Test-only: reset module-level latches between cases.
+export function __resetGuardedReloadForTests(): void {
+  handled = false;
+  pendingNavReload = false;
+  lastServerVersion = "";
+  lastClientVersion = "";
+}

apps/client/src/features/user/reload-budget.integration.test.tsx

@@ -0,0 +1,171 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { render, act, cleanup } from "@testing-library/react";
+import { MemoryRouter, useNavigate } from "react-router-dom";
+
+// Integration test for the SHARED, window-based auto-reload budget (invariant a):
+// the reactive chunk-load boundary and the proactive version-coherence path both
+// route through the REAL @/lib/reload-guard, so at most one automatic reload
+// happens per RELOAD_WINDOW_MS across BOTH paths combined. Only the two paths'
+// side-effecting collaborators are mocked — the reload guard is intentionally
+// REAL so this exercises the actual shared sessionStorage budget.
+vi.mock("@mantine/notifications", () => ({
+  notifications: { show: vi.fn() },
+}));
+vi.mock("@/i18n.ts", () => ({ default: { t: (k: string) => k } }));
+
+import { handleError } from "@/components/chunk-load-error-boundary";
+import {
+  triggerGuardedReload,
+  useVersionReloadOnNavigation,
+  __resetGuardedReloadForTests,
+} from "./guarded-reload";
+import { RELOAD_WINDOW_MS } from "@/lib/reload-guard";
+
+const CHUNK_ERROR = { name: "ChunkLoadError", message: "boom" };
+const T0 = 1_000_000_000_000;
+
+let reload: ReturnType<typeof vi.fn>;
+let nowMock: ReturnType<typeof vi.spyOn>;
+
+// Harness mounted inside a router: installs the navigation hook and exposes
+// `navigate` so a test can drive an in-app router navigation (the point where the
+// proactive path fires its armed reload).
+let doNavigate: (to: string) => void;
+function Harness() {
+  useVersionReloadOnNavigation();
+  doNavigate = useNavigate();
+  return null;
+}
+function mountHarness() {
+  render(
+    <MemoryRouter initialEntries={["/start"]}>
+      <Harness />
+    </MemoryRouter>,
+  );
+}
+function navigateTo(path: string) {
+  act(() => {
+    doNavigate(path);
+  });
+}
+function setNow(t: number) {
+  nowMock.mockReturnValue(t);
+}
+
+beforeEach(() => {
+  sessionStorage.clear();
+  __resetGuardedReloadForTests();
+  vi.clearAllMocks();
+  nowMock = vi.spyOn(Date, "now").mockReturnValue(T0);
+  vi.stubGlobal("APP_VERSION", "test-A");
+  reload = vi.fn();
+  Object.defineProperty(window, "location", {
+    configurable: true,
+    value: { reload },
+  });
+});
+
+afterEach(() => {
+  cleanup();
+  vi.unstubAllGlobals();
+  vi.restoreAllMocks();
+  sessionStorage.clear();
+});
+
+describe("shared window-based reload budget (invariant a)", () => {
+  it("a chunk-load reload spends the budget: a version-coherence mismatch within the window shows the banner but does NOT reload", () => {
+    // Path 1 (reactive): a stale-chunk 404 auto-reloads once and stamps the window.
+    handleError(CHUNK_ERROR);
+    expect(reload).toHaveBeenCalledTimes(1);
+    reload.mockClear();
+
+    // Path 2 (proactive), 1 min later — still inside the window. The shared budget
+    // is spent, so the version mismatch degrades to the banner and never reloads.
+    setNow(T0 + 60_000);
+    mountHarness();
+    triggerGuardedReload("test-B");
+    navigateTo("/next");
+    expect(reload).not.toHaveBeenCalled();
+  });
+
+  it("a version-coherence reload spends the SAME budget: a chunk-load error within the window does NOT reload", () => {
+    // Path 2 (proactive) first: real mismatch → arm → fire on navigation.
+    mountHarness();
+    triggerGuardedReload("test-B");
+    navigateTo("/next");
+    expect(reload).toHaveBeenCalledTimes(1);
+    reload.mockClear();
+
+    // Path 1 (reactive), 2 min later — inside the window. Budget already spent by
+    // the proactive path, so the stale-chunk error must NOT trigger a second reload.
+    setNow(T0 + 2 * 60_000);
+    handleError(CHUNK_ERROR);
+    expect(reload).not.toHaveBeenCalled();
+  });
+
+  it("recovers after the window: a reload strictly older than the window is allowed again (second deploy)", () => {
+    // First auto-reload (reactive) stamps the window.
+    handleError(CHUNK_ERROR);
+    expect(reload).toHaveBeenCalledTimes(1);
+    reload.mockClear();
+
+    // A second deploy arrives after the window has fully elapsed → the proactive
+    // path is allowed to reload again (window, not a permanent one-shot).
+    __resetGuardedReloadForTests();
+    setNow(T0 + RELOAD_WINDOW_MS + 1);
+    mountHarness();
+    triggerGuardedReload("test-B");
+    navigateTo("/next");
+    expect(reload).toHaveBeenCalledTimes(1);
+  });
+
+  it("reactive path fails closed when storage READS but cannot WRITE (quota / Safari private): no unguarded reload", () => {
+    // getItem→null makes hasAutoReloaded() report the budget as available, so
+    // handleError passes the first guard and reaches `if (!markAutoReloaded())
+    // return;`. setItem throws → the stamp cannot stick, so markAutoReloaded()
+    // returns false and that guard MUST bail — otherwise the reactive path would
+    // reload on every stale-chunk error with no persisted budget (an unguarded
+    // loop). This is the asymmetric gap: the proactive path's equivalent is
+    // covered by guarded-reload.test.tsx "does NOT reload when the flag write
+    // fails".
+    vi.stubGlobal("sessionStorage", {
+      getItem: () => null,
+      setItem: () => {
+        throw new Error("quota exceeded");
+      },
+      removeItem: () => {},
+      clear: () => {},
+    });
+    try {
+      handleError(CHUNK_ERROR);
+      expect(reload).not.toHaveBeenCalled();
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+
+  it("sessionStorage unavailable: neither path performs an unguarded reload", () => {
+    // The real guard fails toward NOT reloading when storage throws.
+    vi.stubGlobal("sessionStorage", {
+      getItem: () => {
+        throw new Error("storage disabled");
+      },
+      setItem: () => {
+        throw new Error("storage disabled");
+      },
+      removeItem: () => {},
+      clear: () => {},
+    });
+    try {
+      handleError(CHUNK_ERROR);
+      expect(reload).not.toHaveBeenCalled();
+
+      mountHarness();
+      triggerGuardedReload("test-B");
+      navigateTo("/next");
+      expect(reload).not.toHaveBeenCalled();
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+});

apps/client/src/features/user/user-provider.tsx

@@ -13,6 +13,12 @@ import { useCollabToken } from "@/features/auth/queries/auth-query.tsx";
 import { Error404 } from "@/components/ui/error-404.tsx";
 import { queryClient } from "@/main.tsx";
 import { makeConnectHandler } from "@/features/user/connect-resync.ts";
+import {
+  triggerGuardedReload,
+  useVersionReloadOnNavigation,
+  surfacePreviousReloadBreadcrumb,
+} from "@/features/user/guarded-reload.tsx";
+import type { AppVersionSocketPayload } from "@/features/user/version-coherence.ts";
 
 export function UserProvider({ children }: React.PropsWithChildren) {
   const [, setCurrentUser] = useAtom(currentUserAtom);
@@ -22,6 +28,16 @@ export function UserProvider({ children }: React.PropsWithChildren) {
   // fetch collab token on load
   const { data: collab } = useCollabToken();
 
+  // version-coherence: fire the armed one-shot reload on the next in-app
+  // navigation (variant C — a safe point, not on tab backgrounding).
+  useVersionReloadOnNavigation();
+
+  // Surface any breadcrumb left by an auto-reload in the previous page load
+  // (the reload cleared the console) so a field report stays diagnosable.
+  useEffect(() => {
+    surfacePreviousReloadBreadcrumb();
+  }, []);
+
   useEffect(() => {
     if (isLoading || isError) {
       return;
@@ -47,6 +63,16 @@ export function UserProvider({ children }: React.PropsWithChildren) {
       handleConnect();
     });
 
+    // Register the version-coherence listener SYNCHRONOUSLY, before the socket
+    // connects: the server emits `app-version` immediately in handleConnection,
+    // so a listener attached after connect would miss it on a fast localhost
+    // connect. On a version mismatch the client shows a banner and defers the
+    // auto-reload to the next in-app navigation (variant C — avoids reloading a
+    // backgrounded tab that may hold unsaved input) before it hits a stale chunk.
+    newSocket.on("app-version", (payload?: AppVersionSocketPayload) => {
+      triggerGuardedReload(payload?.version);
+    });
+
     return () => {
       console.log("ws disconnected");
       newSocket.disconnect();

apps/client/src/features/user/version-coherence.test.ts

@@ -0,0 +1,64 @@
+import { describe, it, expect } from "vitest";
+import { decideVersionAction } from "./version-coherence";
+
+describe("decideVersionAction", () => {
+  it("noop when the server version is empty (fail-safe)", () => {
+    expect(
+      decideVersionAction({
+        serverVersion: "",
+        clientVersion: "v1",
+        autoReloadUsed: false,
+      }),
+    ).toBe("noop");
+  });
+
+  it("noop when the client version is empty (fail-safe)", () => {
+    expect(
+      decideVersionAction({
+        serverVersion: "v1",
+        clientVersion: "",
+        autoReloadUsed: false,
+      }),
+    ).toBe("noop");
+  });
+
+  it("noop when versions are equal (in sync)", () => {
+    expect(
+      decideVersionAction({
+        serverVersion: "v1",
+        clientVersion: "v1",
+        autoReloadUsed: false,
+      }),
+    ).toBe("noop");
+  });
+
+  it("reload on a real mismatch the first time this session", () => {
+    expect(
+      decideVersionAction({
+        serverVersion: "test-B",
+        clientVersion: "test-A",
+        autoReloadUsed: false,
+      }),
+    ).toBe("reload");
+  });
+
+  it("banner on a mismatch once the session auto-reload is spent", () => {
+    expect(
+      decideVersionAction({
+        serverVersion: "test-B",
+        clientVersion: "test-A",
+        autoReloadUsed: true,
+      }),
+    ).toBe("banner");
+  });
+
+  it("equal versions stay noop even if auto-reload was already used", () => {
+    expect(
+      decideVersionAction({
+        serverVersion: "v1",
+        clientVersion: "v1",
+        autoReloadUsed: true,
+      }),
+    ).toBe("noop");
+  });
+});

apps/client/src/features/user/version-coherence.ts

@@ -0,0 +1,32 @@
+// Payload of the per-connect `app-version` socket.io event announced by the
+// server (ws.gateway.ts) after a successful auth. A dedicated event — NOT a
+// member of the room-scoped `WebSocketEvent` union (which is discriminated by
+// `operation`), so it never touches use-query-subscription.
+export type AppVersionSocketPayload = { version: string };
+
+/**
+ * Pure decision for the version-coherence guard.
+ *
+ * All inputs are injected (no globals, no side effects) so it is unit-testable
+ * without a DOM or the build-time `APP_VERSION` global (undefined under vitest).
+ *
+ * - `autoReloadUsed` = an automatic reload has already happened within the
+ *   current ~5-min window, so we must not auto-reload again (loop safety,
+ *   shared window budget with the reactive chunk-load boundary).
+ *
+ * Returns:
+ * - "noop"   — do nothing (unknown version on either side, or already in sync).
+ * - "banner" — show the manual "update available" banner only (no auto-reload).
+ * - "reload" — real first-time mismatch: eligible for a guarded auto-reload.
+ */
+export function decideVersionAction(args: {
+  serverVersion: string;
+  clientVersion: string;
+  autoReloadUsed: boolean;
+}): "reload" | "banner" | "noop" {
+  const { serverVersion, clientVersion, autoReloadUsed } = args;
+  if (!serverVersion || !clientVersion) return "noop"; // fail-safe: unknown version → never act
+  if (serverVersion === clientVersion) return "noop"; // in sync
+  if (autoReloadUsed) return "banner"; // one auto-reload per RELOAD_WINDOW_MS window already spent
+  return "reload"; // real mismatch, window budget available
+}

apps/client/src/lib/reload-guard.test.ts

@@ -0,0 +1,145 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import {
+  hasAutoReloaded,
+  markAutoReloaded,
+  shouldAutoReload,
+  recordReloadBreadcrumb,
+  takeReloadBreadcrumb,
+  RELOAD_WINDOW_MS,
+} from "./reload-guard";
+
+// The shared budget is a single sessionStorage timestamp keyed here; both the
+// reactive chunk-load boundary and the proactive version-coherence path read and
+// stamp it, so at most one auto-reload happens per RELOAD_WINDOW_MS across BOTH.
+const RELOAD_AT_KEY = "chunk-reload-at";
+const NOW = 1_000_000_000_000;
+
+describe("reload-guard", () => {
+  beforeEach(() => {
+    sessionStorage.clear();
+    vi.restoreAllMocks();
+  });
+
+  afterEach(() => {
+    sessionStorage.clear();
+    vi.restoreAllMocks();
+  });
+
+  it("hasAutoReloaded is false before any reload, true within the window after mark", () => {
+    expect(hasAutoReloaded(NOW)).toBe(false);
+    expect(markAutoReloaded(NOW)).toBe(true);
+    // Same key both paths share; stores the reload timestamp, not a flag.
+    expect(sessionStorage.getItem(RELOAD_AT_KEY)).toBe(String(NOW));
+    // Inside the window → budget spent → true (fall through to manual UI).
+    expect(hasAutoReloaded(NOW)).toBe(true);
+    expect(hasAutoReloaded(NOW + RELOAD_WINDOW_MS)).toBe(true);
+  });
+
+  it("hasAutoReloaded is false again once the window has elapsed (a later deploy recovers)", () => {
+    markAutoReloaded(NOW);
+    // Strictly older than the window → a new deploy's mismatch may reload again.
+    expect(hasAutoReloaded(NOW + RELOAD_WINDOW_MS + 1)).toBe(false);
+  });
+
+  it("hasAutoReloaded returns true when reading storage throws (fail toward not reloading)", () => {
+    vi.stubGlobal("sessionStorage", {
+      getItem: () => {
+        throw new Error("storage disabled");
+      },
+      setItem: () => {
+        throw new Error("storage disabled");
+      },
+    });
+    try {
+      expect(hasAutoReloaded()).toBe(true);
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+
+  it("hasAutoReloaded treats an unparseable stored timestamp as never-reloaded", () => {
+    sessionStorage.setItem(RELOAD_AT_KEY, "not-a-number");
+    expect(hasAutoReloaded(NOW)).toBe(false);
+  });
+
+  it("markAutoReloaded returns false when writing storage throws", () => {
+    vi.stubGlobal("sessionStorage", {
+      getItem: () => null,
+      setItem: () => {
+        throw new Error("storage disabled");
+      },
+    });
+    try {
+      expect(markAutoReloaded()).toBe(false);
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+
+  it("records and then takes a breadcrumb once (cleared on read)", () => {
+    recordReloadBreadcrumb({
+      path: "proactive",
+      serverVersion: "test-B",
+      clientVersion: "test-A",
+    });
+    const crumb = takeReloadBreadcrumb();
+    expect(crumb).toMatchObject({
+      path: "proactive",
+      serverVersion: "test-B",
+      clientVersion: "test-A",
+    });
+    expect(typeof crumb?.at).toBe("number");
+    // Cleared on read → a second take returns null.
+    expect(takeReloadBreadcrumb()).toBeNull();
+  });
+
+  it("takeReloadBreadcrumb returns null when nothing was recorded", () => {
+    expect(takeReloadBreadcrumb()).toBeNull();
+  });
+
+  it("recordReloadBreadcrumb swallows a storage-write error (diagnostics only)", () => {
+    vi.stubGlobal("sessionStorage", {
+      getItem: () => null,
+      setItem: () => {
+        throw new Error("storage disabled");
+      },
+      removeItem: () => {},
+    });
+    try {
+      expect(() =>
+        recordReloadBreadcrumb({ path: "chunk-boundary" }),
+      ).not.toThrow();
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+});
+
+// The pure window gate replaces the old one-shot flag: it must permit recovery
+// across several deploys in one tab (each > window apart) while still stopping an
+// infinite reload loop when a lazy chunk is permanently broken (a second failure
+// < window). Moved here from the chunk-load boundary now that it is the shared
+// guard both paths route through.
+describe("shouldAutoReload", () => {
+  const WINDOW = RELOAD_WINDOW_MS;
+
+  it("allows a reload when we have never auto-reloaded", () => {
+    expect(shouldAutoReload(NOW, null, WINDOW)).toBe(true);
+  });
+
+  it("allows a reload when the last one was 6 minutes ago (outside the window)", () => {
+    expect(shouldAutoReload(NOW, NOW - 6 * 60 * 1000, WINDOW)).toBe(true);
+  });
+
+  it("blocks a reload when the last one was 1 minute ago (inside the window)", () => {
+    expect(shouldAutoReload(NOW, NOW - 1 * 60 * 1000, WINDOW)).toBe(false);
+  });
+
+  it("blocks a reload exactly at the window boundary (not strictly older)", () => {
+    expect(shouldAutoReload(NOW, NOW - WINDOW, WINDOW)).toBe(false);
+  });
+
+  it("allows a reload when the stored timestamp is unparseable (NaN)", () => {
+    expect(shouldAutoReload(NOW, NaN, WINDOW)).toBe(true);
+  });
+});

apps/client/src/lib/reload-guard.ts

@@ -0,0 +1,121 @@
+// Shared, window-based auto-reload budget.
+//
+// Both auto-reload paths — the reactive chunk-load-error-boundary (recovers
+// AFTER a stale lazy chunk 404s) and the proactive version-coherence feature
+// (reloads BEFORE the tab hits a stale chunk) — go through these functions so
+// they share ONE window-scoped reload budget: at most a single automatic
+// reload per RELOAD_WINDOW_MS across BOTH paths. A window (rather than a
+// permanent one-shot flag) lets a SECOND deploy in the same tab's lifetime
+// recover too, while a permanent skew, node oscillation, or a genuinely-missing
+// chunk still degrades to a manual banner/UI after the first reload instead of
+// looping. When sessionStorage is unavailable every mismatch degrades to the
+// manual UI — no unguarded reload.
+
+// sessionStorage key holding the epoch-ms timestamp of the last automatic reload
+// (shared by both paths).
+const RELOAD_AT_KEY = "chunk-reload-at";
+
+// Allow at most one automatic reload per this window. A stale-deploy 404 is cured
+// by a single reload, so anything inside the window is treated as a reload loop
+// (permanently-broken chunk / permanent skew) and falls through to the manual UI.
+export const RELOAD_WINDOW_MS = 5 * 60 * 1000;
+
+/**
+ * Pure window decision, unit-tested in isolation: auto-reload only if we have
+ * never auto-reloaded (lastReloadAt null/NaN) or the last one was strictly older
+ * than the window. Anything inside the window is suppressed to break an infinite
+ * reload loop.
+ */
+export function shouldAutoReload(
+  now: number,
+  lastReloadAt: number | null,
+  windowMs: number,
+): boolean {
+  if (lastReloadAt === null || Number.isNaN(lastReloadAt)) return true;
+  return now - lastReloadAt > windowMs;
+}
+
+/**
+ * Has an automatic reload already happened within the current window (so the
+ * shared budget is spent right now)? Both paths check this before reloading; a
+ * `true` return means fall through to the manual banner/UI instead of reloading.
+ *
+ * A storage read error (private mode / disabled) is reported as `true` so the
+ * caller fails toward NOT reloading — an unguarded loop is worse than a stale
+ * tab the user can reload manually. Note a window (not a permanent flag): once
+ * the window elapses a later deploy's mismatch is allowed to reload again.
+ */
+export function hasAutoReloaded(now: number = Date.now()): boolean {
+  try {
+    const raw = sessionStorage.getItem(RELOAD_AT_KEY);
+    const lastReloadAt = raw === null ? null : Number.parseInt(raw, 10);
+    return !shouldAutoReload(now, lastReloadAt, RELOAD_WINDOW_MS);
+  } catch {
+    return true;
+  }
+}
+
+/**
+ * Stamp the shared window as consumed now — record that an automatic reload is
+ * being performed within the current RELOAD_WINDOW_MS window.
+ *
+ * Returns whether the write succeeded. A `false` return (storage unavailable)
+ * means the caller MUST NOT reload — otherwise the stamp would never stick and
+ * the reload could loop.
+ */
+export function markAutoReloaded(now: number = Date.now()): boolean {
+  try {
+    sessionStorage.setItem(RELOAD_AT_KEY, String(now));
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+// Diagnostic breadcrumb for an automatic reload. Written right before
+// window.location.reload() (which clears the console) and read back on the next
+// page load, so a "the tab reloaded itself / it's looping" field report is
+// diagnosable: which path fired (proactive version-coherence vs the reactive
+// chunk-load boundary) and which version pair triggered it. sessionStorage
+// survives a same-tab reload, unlike the console.
+const RELOAD_BREADCRUMB_KEY = "reload-breadcrumb";
+
+export type ReloadBreadcrumb = {
+  path: "proactive" | "chunk-boundary";
+  serverVersion?: string;
+  clientVersion?: string;
+  at: number;
+};
+
+/**
+ * Persist a best-effort breadcrumb just before an automatic reload. Failures
+ * (storage unavailable) are swallowed — this is diagnostics only and must never
+ * block or alter the reload decision.
+ */
+export function recordReloadBreadcrumb(
+  entry: Omit<ReloadBreadcrumb, "at">,
+): void {
+  try {
+    sessionStorage.setItem(
+      RELOAD_BREADCRUMB_KEY,
+      JSON.stringify({ ...entry, at: Date.now() }),
+    );
+  } catch {
+    // best-effort diagnostics only
+  }
+}
+
+/**
+ * Read and clear the breadcrumb left by an auto-reload in the previous page
+ * load. Cleared on read so it surfaces exactly once per reload.
+ */
+export function takeReloadBreadcrumb(): ReloadBreadcrumb | null {
+  try {
+    const raw = sessionStorage.getItem(RELOAD_BREADCRUMB_KEY);
+    if (!raw) return null;
+    sessionStorage.removeItem(RELOAD_BREADCRUMB_KEY);
+    return JSON.parse(raw) as ReloadBreadcrumb;
+  } catch {
+    return null;
+  }
+}

apps/client/vite.config.ts

@@ -1,7 +1,8 @@
-import { defineConfig, loadEnv } from "vite";
+import { defineConfig, loadEnv, type Plugin } from "vite";
 import react from "@vitejs/plugin-react";
 import { compression } from "vite-plugin-compression2";
 import * as path from "path";
+import * as fs from "node:fs";
 import { execSync } from "node:child_process";
 
 const envPath = path.resolve(process.cwd(), "..", "..");
@@ -24,7 +25,32 @@ function resolveAppVersion(cwd: string): string {
   }
 }
 
+// Emit <outDir>/version.json = { "version": appVersion } so the server can read
+// the exact same build id the bundle was compiled with. The value is the SAME
+// `appVersion` fed into `define.APP_VERSION`, so version.json and the baked-in
+// global are identical by construction — the single source of truth (no
+// runtime-env second copy that could drift and cause a false version mismatch).
+function versionJsonPlugin(version: string): Plugin {
+  let outDir = "dist";
+  return {
+    name: "emit-version-json",
+    apply: "build",
+    configResolved(config) {
+      outDir = config.build.outDir;
+    },
+    writeBundle() {
+      const root = path.resolve(process.cwd(), outDir);
+      fs.mkdirSync(root, { recursive: true });
+      fs.writeFileSync(
+        path.join(root, "version.json"),
+        JSON.stringify({ version }),
+      );
+    },
+  };
+}
+
 export default defineConfig(({ mode }) => {
+  const appVersion = resolveAppVersion(envPath);
   const {
     APP_URL,
     FILE_UPLOAD_SIZE_LIMIT,
@@ -52,10 +78,11 @@ export default defineConfig(({ mode }) => {
         POSTHOG_HOST,
         POSTHOG_KEY,
       },
-      APP_VERSION: JSON.stringify(resolveAppVersion(envPath)),
+      APP_VERSION: JSON.stringify(appVersion),
     },
     plugins: [
       react(),
+      versionJsonPlugin(appVersion),
       // Emit .br and .gz next to every built asset so the server can serve the
       // precompressed copy (see @fastify/static preCompressed in static.module.ts).
       compression({

apps/server/src/common/helpers/client-version.spec.ts

@@ -0,0 +1,52 @@
+import { join } from 'path';
+import * as fs from 'node:fs';
+import * as os from 'node:os';
+import { readClientBuildVersion } from './client-version';
+
+describe('readClientBuildVersion', () => {
+  let dir: string;
+
+  beforeEach(() => {
+    dir = fs.mkdtempSync(join(os.tmpdir(), 'client-version-'));
+  });
+
+  afterEach(() => {
+    fs.rmSync(dir, { recursive: true, force: true });
+  });
+
+  const writeVersionJson = (content: string) =>
+    fs.writeFileSync(join(dir, 'version.json'), content);
+
+  it('returns the version from a valid version.json', () => {
+    writeVersionJson(JSON.stringify({ version: 'test-A' }));
+    expect(readClientBuildVersion(dir)).toBe('test-A');
+  });
+
+  it('trims surrounding whitespace in the version', () => {
+    writeVersionJson(JSON.stringify({ version: '  v1.2.3  ' }));
+    expect(readClientBuildVersion(dir)).toBe('v1.2.3');
+  });
+
+  it('returns "" when version.json is missing', () => {
+    expect(readClientBuildVersion(dir)).toBe('');
+  });
+
+  it('returns "" on malformed JSON', () => {
+    writeVersionJson('{ not json');
+    expect(readClientBuildVersion(dir)).toBe('');
+  });
+
+  it('returns "" when the version field is absent', () => {
+    writeVersionJson(JSON.stringify({ notVersion: 'x' }));
+    expect(readClientBuildVersion(dir)).toBe('');
+  });
+
+  it('returns "" when the version field is not a string', () => {
+    writeVersionJson(JSON.stringify({ version: 123 }));
+    expect(readClientBuildVersion(dir)).toBe('');
+  });
+
+  it('returns "" when the path does not exist at all', () => {
+    expect(readClientBuildVersion(join(dir, 'nope'))).toBe('');
+  });
+});

apps/server/src/common/helpers/client-version.ts

@@ -0,0 +1,36 @@
+import { join } from 'path';
+import * as fs from 'node:fs';
+
+/**
+ * Resolve the absolute path to the built client bundle directory
+ * (`apps/client/dist`) shipped into the runtime image.
+ *
+ * The `../` depth is anchored on THIS module's compiled location
+ * (`dist/common/helpers`). `integrations/static` sits at the same depth under
+ * the compiled root, so both callers (StaticModule and readClientBuildVersion)
+ * MUST share this single helper rather than duplicating the depth — a copy in a
+ * module at a different depth would silently resolve to the wrong directory.
+ */
+export function resolveClientDistPath(): string {
+  return join(__dirname, '..', '..', '..', '..', 'client/dist');
+}
+
+/**
+ * Read the build version the client bundle was compiled with, from
+ * `<clientDistPath>/version.json` (written by the Vite build — the single
+ * source of truth shared by the baked-in `APP_VERSION` global and this file).
+ *
+ * Fail-safe: any error (missing file, unreadable, bad JSON, non-string
+ * version) yields `''`. The caller treats an empty version as "unknown" and
+ * the whole version-coherence feature stays silently inert — existing deploys
+ * without the file keep working unchanged.
+ */
+export function readClientBuildVersion(clientDistPath: string): string {
+  try {
+    const raw = fs.readFileSync(join(clientDistPath, 'version.json'), 'utf8');
+    const version = (JSON.parse(raw) as { version?: unknown }).version;
+    return typeof version === 'string' ? version.trim() : '';
+  } catch {
+    return '';
+  }
+}

apps/server/src/common/helpers/index.ts

@@ -3,3 +3,4 @@ export * from './nanoid.utils';
 export * from './file.helper';
 export * from './constants';
 export * from './security-headers';
+export * from './client-version';

apps/server/src/integrations/static/static.module.ts

@@ -4,6 +4,7 @@ import { join } from 'path';
 import * as fs from 'node:fs';
 import fastifyStatic from '@fastify/static';
 import { EnvironmentService } from '../environment/environment.service';
+import { resolveClientDistPath } from '../../common/helpers/client-version';
 
 /**
  * Resolve the response headers for a statically served client asset.
@@ -56,14 +57,7 @@ export class StaticModule implements OnModuleInit {
     const httpAdapter = this.httpAdapterHost.httpAdapter;
     const app = httpAdapter.getInstance();
 
-    const clientDistPath = join(
+    const clientDistPath = resolveClientDistPath();
-      __dirname,
-      '..',
-      '..',
-      '..',
-      '..',
-      'client/dist',
-    );
 
     const indexFilePath = join(clientDistPath, 'index.html');
 

apps/server/src/ws/ws.gateway.ts

@@ -9,10 +9,14 @@ import {
 import { Server, Socket } from 'socket.io';
 import { TokenService } from '../core/auth/services/token.service';
 import { JwtPayload, JwtType } from '../core/auth/dto/jwt-payload';
-import { OnModuleDestroy } from '@nestjs/common';
+import { Logger, OnModuleDestroy, OnModuleInit } from '@nestjs/common';
 import { SpaceMemberRepo } from '@docmost/db/repos/space/space-member.repo';
 import { WsService } from './ws.service';
 import { getSpaceRoomName, getUserRoomName } from './ws.utils';
+import {
+  readClientBuildVersion,
+  resolveClientDistPath,
+} from '../common/helpers/client-version';
 import * as cookie from 'cookie';
 
 @WebSocketGateway({
@@ -20,17 +24,40 @@ import * as cookie from 'cookie';
   transports: ['websocket'],
 })
 export class WsGateway
-  implements OnGatewayConnection, OnGatewayInit, OnModuleDestroy
+  implements
+    OnGatewayConnection,
+    OnGatewayInit,
+    OnModuleInit,
+    OnModuleDestroy
 {
   @WebSocketServer()
   server: Server;
 
+  private readonly logger = new Logger(WsGateway.name);
+
+  // The build version of the client bundle shipped in this image, read once at
+  // startup from client/dist/version.json (single source of truth, same value
+  // baked into the client's APP_VERSION). Empty string => version.json missing
+  // or empty => the proactive version-coherence reload feature stays inert.
+  private appVersion = '';
+
   constructor(
     private tokenService: TokenService,
     private spaceMemberRepo: SpaceMemberRepo,
     private wsService: WsService,
   ) {}
 
+  onModuleInit(): void {
+    this.appVersion = readClientBuildVersion(resolveClientDistPath());
+    if (this.appVersion) {
+      this.logger.log(`app-version reload: ACTIVE (v=${this.appVersion})`);
+    } else {
+      this.logger.log(
+        'app-version reload: DISABLED (version.json missing/empty)',
+      );
+    }
+  }
+
   afterInit(server: Server): void {
     this.wsService.setServer(server);
   }
@@ -55,6 +82,14 @@ export class WsGateway
       const spaceRooms = userSpaceIds.map((id) => getSpaceRoomName(id));
 
       client.join([userRoom, workspaceRoom, ...spaceRooms]);
+
+      // Announce this container's client build version to the freshly
+      // authenticated socket. On a redeploy the client reconnects to the new
+      // container and receives the new version here, letting it guard-reload
+      // before it hits a stale lazy chunk. Per-connect only (no broadcast):
+      // natural reconnect covers both single-container and cluster without a
+      // thundering-herd fleet reload.
+      client.emit('app-version', { version: this.appVersion });
     } catch (err) {
       client.emit('Unauthorized');
       client.disconnect();