diff --git a/apps/api/package.json b/apps/api/package.json
index 8ccf511..9731811 100644
--- a/apps/api/package.json
+++ b/apps/api/package.json
@@ -23,10 +23,12 @@
     "@batch-cooking/shared": "workspace:*",
     "@prisma/client": "^5.22.0",
     "argon2": "0.31.2",
+    "cookie": "^2.0.1",
     "dotenv": "^16.4.5",
     "express": "^4.21.1",
     "jsonwebtoken": "^9.0.3",
     "prisma": "^5.22.0",
+    "socket.io": "^4.8.3",
     "zod": "^3.23.8"
   },
   "devDependencies": {
@@ -38,6 +40,7 @@
     "chai": "^5.1.2",
     "cross-env": "^10.1.0",
     "mocha": "^10.8.2",
+    "socket.io-client": "^4.8.3",
     "supertest": "^7.0.0",
     "tsx": "^4.19.2",
     "typescript": "^5.7.2"
diff --git a/apps/api/src/lib/monitoring-broadcast.service.ts b/apps/api/src/lib/monitoring-broadcast.service.ts
new file mode 100644
index 0000000..79aec89
--- /dev/null
+++ b/apps/api/src/lib/monitoring-broadcast.service.ts
@@ -0,0 +1,95 @@
+import type { MonitoringView } from "@batch-cooking/shared";
+import type { Server as SocketIoServer } from "socket.io";
+import { requireAdminSocket } from "../middlewares/require-admin-socket.js";
+import { getMonitoring } from "../modules/admin/admin-monitoring.service.js";
+import { logger } from "./logger.service.js";
+
+/** How often the server re-probes every dependency, in ms — see `MonitoringBroadcastService`. */
+const PROBE_INTERVAL_MS = 60_000;
+
+/** Every authenticated admin socket joins this one room — a single probe loop serves every open tab, instead of each polling independently. */
+const MONITORING_ROOM = "monitoring";
+
+/** Event name every `monitoring:update` push carries — the sole message this service ever emits. */
+const UPDATE_EVENT = "monitoring:update";
+
+/**
+ * Pushes the admin monitoring status board to every connected admin over
+ * WebSocket, replacing the old `GET /admin/api/monitoring` polling
+ * endpoint entirely (removed — see `admin.routes.ts`'s doc comment): one
+ * server-side probe loop, shared by every viewer, instead of each browser
+ * tab re-probing Postgres/the API/the intent-service/the LLM worker on its
+ * own timer.
+ *
+ * Owns the *whole* `socket.io` server passed to it (`io.use`, top-level
+ * `"connection"` handler) — fine while this is the server's only
+ * real-time feature; a second one added later should likely get its own
+ * namespace rather than share this room's connection handler.
+ */
+export class MonitoringBroadcastService {
+  private readonly _io: SocketIoServer;
+  /**
+   * Most recent probe result — replayed to a newly-joined admin
+   * immediately (see the `"connection"` handler below), so a freshly
+   * opened tab isn't left blank for up to a minute waiting for the next
+   * scheduled tick. `null` until the very first probe (kicked off by
+   * {@link start}) completes.
+   */
+  private _lastSnapshot: MonitoringView | null = null;
+  /** Handle for the running probe loop, or `null` before {@link start}/after {@link stop}. */
+  private _intervalHandle: NodeJS.Timeout | null = null;
+
+  public constructor(io: SocketIoServer) {
+    this._io = io;
+    this._io.use(requireAdminSocket);
+    this._io.on("connection", (socket) => {
+      void socket.join(MONITORING_ROOM);
+      if (this._lastSnapshot) {
+        socket.emit(UPDATE_EVENT, this._lastSnapshot);
+      }
+    });
+  }
+
+  /**
+   * Starts the probe loop: one immediate probe (so the very first admin
+   * to connect after a server restart doesn't wait a full minute), then
+   * every {@link PROBE_INTERVAL_MS}. Call once, at server boot
+   * (`server.ts`) — meant to run for the lifetime of the process, same
+   * posture as the tech-step worker's own cron (`server.ts` never calls
+   * {@link stop} today; the process exiting takes the interval with it).
+   */
+  public start(): void {
+    void this._tick();
+    this._intervalHandle = setInterval(() => void this._tick(), PROBE_INTERVAL_MS);
+  }
+
+  /**
+   * Stops the probe loop. Nothing in production calls this today — it
+   * exists so a graceful-shutdown hook could use it later, and so tests
+   * can tear an instance down cleanly instead of leaking a live
+   * `setInterval` past their own lifetime (which would otherwise hold the
+   * whole Mocha process open).
+   */
+  public stop(): void {
+    if (this._intervalHandle) {
+      clearInterval(this._intervalHandle);
+      this._intervalHandle = null;
+    }
+  }
+
+  /** Probes every dependency, caches the result, and broadcasts it to {@link MONITORING_ROOM}. */
+  private async _tick(): Promise<void> {
+    try {
+      this._lastSnapshot = await getMonitoring();
+      this._io.to(MONITORING_ROOM).emit(UPDATE_EVENT, this._lastSnapshot);
+    } catch (err) {
+      // getMonitoring() itself never rejects — every individual probe is
+      // already bounded/caught (see its own doc comment) — so this is
+      // purely defensive, per the repo's await-in-try/catch rule; not
+      // expected to actually fire.
+      logger.error("Monitoring probe tick failed unexpectedly", {
+        error: err instanceof Error ? err.message : String(err),
+      });
+    }
+  }
+}
diff --git a/apps/api/src/middlewares/require-admin-socket.ts b/apps/api/src/middlewares/require-admin-socket.ts
new file mode 100644
index 0000000..fff0a16
--- /dev/null
+++ b/apps/api/src/middlewares/require-admin-socket.ts
@@ -0,0 +1,43 @@
+import { parseCookie } from "cookie";
+import type { Socket } from "socket.io";
+import { env } from "../config/env.js";
+import { resolveAdminFromToken } from "./require-admin.js";
+
+/**
+ * `socket.io` handshake middleware guarding the admin WebSocket surface —
+ * the connection-level equivalent of {@link requireAdmin} (`require-
+ * admin.ts`). A `socket.io` handshake is a plain HTTP request that never
+ * runs through Express's own middleware stack (`cookie-parser` included),
+ * so the raw `Cookie` header has to be parsed by hand here with the
+ * `cookie` package (the same one `cookie-parser` itself wraps).
+ *
+ * Registered via `io.use(requireAdminSocket)` — `socket.io` calls every
+ * `io.use` middleware once per connection attempt, before `"connection"`
+ * fires, exactly like Express's per-request middleware chain. Calling
+ * `next()` with no argument admits the connection; calling it with an
+ * `Error` rejects it, which the client sees as a `connect_error` event
+ * (`socket.io-client` never even fires `"connect"` for it).
+ *
+ * On success, stashes the resolved admin on `socket.data.adminUser` —
+ * `socket.io`'s per-connection storage bag, the WebSocket equivalent of
+ * `res.locals` — for any handler that ends up needing it later.
+ */
+export async function requireAdminSocket(
+  socket: Socket,
+  next: (err?: Error) => void,
+): Promise<void> {
+  try {
+    const cookieHeader = socket.handshake.headers.cookie;
+    const token = cookieHeader ? parseCookie(cookieHeader)[env.ADMIN_COOKIE_NAME] : undefined;
+    if (typeof token !== "string") {
+      throw new Error("Not authenticated");
+    }
+
+    socket.data.adminUser = await resolveAdminFromToken(token);
+    next();
+  } catch {
+    // Covers everything resolveAdminFromToken can throw, plus a missing
+    // cookie — same "never distinguish the reason" posture as requireAdmin.
+    next(new Error("Not authenticated"));
+  }
+}
diff --git a/apps/api/src/middlewares/require-admin.ts b/apps/api/src/middlewares/require-admin.ts
index e20f24f..be56be0 100644
--- a/apps/api/src/middlewares/require-admin.ts
+++ b/apps/api/src/middlewares/require-admin.ts
@@ -19,26 +19,50 @@ export interface AdminLocals {
 }
 
 /**
- * Express middleware guarding every `/admin/*` route — the operations UI
- * (`apps/web`'s `/admin/*` routes) authenticating as an `AdminUser`. Reads the admin
- * session cookie (`ADMIN_COOKIE_NAME`, deliberately **not** the same cookie
- * as end-user sessions), verifies the JWT against `ADMIN_JWT_SECRET`
- * (a different secret than `JWT_SECRET`), and re-checks `tokenVersion`
- * against the database so a stateless JWT can still be invalidated
- * server-side.
+ * Verifies an admin session JWT and resolves the `AdminUser` it belongs
+ * to — the transport-agnostic core both {@link requireAdmin} (HTTP) and
+ * `requireAdminSocket` (`require-admin-socket.ts`, the WebSocket handshake
+ * equivalent) build on; they only differ in *where* they read the raw
+ * cookie value from (`req.cookies`, already parsed by `cookie-parser`, vs
+ * a `socket.io` handshake's raw `Cookie` header, which isn't). Kept here
+ * rather than in `lib/admin-jwt.ts`, since it also does the DB
+ * `tokenVersion` re-check that file deliberately doesn't know about.
+ *
+ * @throws {Error} for any failure — malformed/expired JWT, unknown admin,
+ *   stale `tokenVersion`, or no `ADMIN_JWT_SECRET` configured (from
+ *   {@link verifyAdminToken}). Always the same generic message; callers
+ *   map it to their own transport's "unauthenticated" shape.
+ */
+export async function resolveAdminFromToken(token: string): Promise<AdminUserView> {
+  const payload = verifyAdminToken(token);
+  const admin = await prisma.adminUser.findUnique({ where: { id: payload.adminUserId } });
+
+  if (!admin || admin.tokenVersion !== payload.tokenVersion) {
+    throw new Error("Not authenticated");
+  }
+
+  return toSafeAdmin(admin);
+}
+
+/**
+ * Express middleware guarding every `/admin/api/*` route — the operations
+ * UI (`apps/web`'s `/admin/*` pages) authenticating as an `AdminUser`.
+ * Reads the admin session cookie (`ADMIN_COOKIE_NAME`, deliberately
+ * **not** the same cookie as end-user sessions) and resolves it via
+ * {@link resolveAdminFromToken}.
  *
  * A completely separate mechanism from {@link requireAuth}, not layered on
  * it: an end-user session token and an admin session token are never
  * interchangeable in either direction.
  *
  * Fails closed: an unset `ADMIN_JWT_SECRET` (the default for any instance
- * that doesn't run the admin app) makes {@link verifyAdminToken} throw, so
- * every request is rejected rather than the surface left open — same
- * posture as `requireInternalWorker`.
+ * that doesn't run the admin app) makes {@link resolveAdminFromToken}
+ * throw, so every request is rejected rather than the surface left open —
+ * same posture as `requireInternalWorker`.
  *
  * @throws {HttpError} `401 NOT_AUTHENTICATED` for any failure — missing
- *   cookie, malformed/expired JWT, unknown admin, stale tokenVersion, or
- *   no secret configured. Never distinguishes the reason.
+ *   cookie or anything {@link resolveAdminFromToken} rejects on. Never
+ *   distinguishes the reason.
  */
 export async function requireAdmin(
   req: Request,
@@ -51,20 +75,13 @@ export async function requireAdmin(
       throw new HttpError(401, ErrorCode.NOT_AUTHENTICATED, "Not authenticated");
     }
 
-    const payload = verifyAdminToken(token);
-    const admin = await prisma.adminUser.findUnique({ where: { id: payload.adminUserId } });
-
-    if (!admin || admin.tokenVersion !== payload.tokenVersion) {
-      throw new HttpError(401, ErrorCode.NOT_AUTHENTICATED, "Not authenticated");
-    }
-
-    res.locals.adminUser = toSafeAdmin(admin);
+    res.locals.adminUser = await resolveAdminFromToken(token);
     next();
   } catch (err) {
     if (err instanceof HttpError) {
       next(err);
     } else {
-      // Covers jwt.verify failures and the unset-secret throw from verifyAdminToken.
+      // Covers everything resolveAdminFromToken can throw.
       next(new HttpError(401, ErrorCode.NOT_AUTHENTICATED, "Not authenticated"));
     }
   }
diff --git a/apps/api/src/modules/admin/admin-monitoring.routes.ts b/apps/api/src/modules/admin/admin-monitoring.routes.ts
deleted file mode 100644
index bc07113..0000000
--- a/apps/api/src/modules/admin/admin-monitoring.routes.ts
+++ /dev/null
@@ -1,20 +0,0 @@
-import { wrapAsyncHandler } from "@batch-cooking/express-tools";
-import { Router } from "express";
-import { requireAdmin } from "../../middlewares/require-admin.js";
-import { getMonitoring } from "./admin-monitoring.service.js";
-
-/** Router mounted at `/admin/api/monitoring` (via `admin.routes.ts`) — behind {@link requireAdmin}. */
-export const adminMonitoringRouter = Router();
-
-/**
- * Actively probes Postgres, the API, `tech-step-intent-service` and the LLM
- * worker's heartbeat, returning a {@link MonitoringView} status board (see
- * {@link getMonitoring}). No params; the admin UI polls it on an interval.
- */
-adminMonitoringRouter.get(
-  "/",
-  requireAdmin,
-  wrapAsyncHandler(async (_req, res) => {
-    res.status(200).json(await getMonitoring());
-  }),
-);
diff --git a/apps/api/src/modules/admin/admin-monitoring.service.ts b/apps/api/src/modules/admin/admin-monitoring.service.ts
index db0ffd8..2cac19f 100644
--- a/apps/api/src/modules/admin/admin-monitoring.service.ts
+++ b/apps/api/src/modules/admin/admin-monitoring.service.ts
@@ -155,7 +155,13 @@ async function probeWorker(): Promise<ServiceHealthView> {
  * Postgres, the API itself, `tech-step-intent-service` (`/health`), and the
  * LLM worker (via its stored heartbeat). Each probe is independent and
  * bounded ({@link PROBE_TIMEOUT_MS}); one being `down` never fails the
- * others or the endpoint.
+ * others or this call as a whole.
+ *
+ * No HTTP route calls this directly (there was one, `GET
+ * /admin/api/monitoring` — removed) — `MonitoringBroadcastService`
+ * (`lib/monitoring-broadcast.service.ts`) is the only caller now, on a
+ * server-side timer, broadcasting the result over WebSocket instead of
+ * each admin's browser polling this on its own.
  */
 export async function getMonitoring(): Promise<MonitoringView> {
   try {
diff --git a/apps/api/src/modules/admin/admin.routes.ts b/apps/api/src/modules/admin/admin.routes.ts
index 7994653..11073d6 100644
--- a/apps/api/src/modules/admin/admin.routes.ts
+++ b/apps/api/src/modules/admin/admin.routes.ts
@@ -2,7 +2,6 @@ import { Router } from "express";
 import { adminAuthRouter } from "./admin-auth.routes.js";
 import { adminCatalogRouter } from "./admin-catalog.routes.js";
 import { adminMetricsRouter } from "./admin-metrics.routes.js";
-import { adminMonitoringRouter } from "./admin-monitoring.routes.js";
 import { adminTechStepsRouter } from "./admin-tech-steps.routes.js";
 
 /**
@@ -11,14 +10,17 @@ import { adminTechStepsRouter } from "./admin-tech-steps.routes.js";
  * comment for why: it would collide with apps/web's `/admin/*` page
  * routes). Every sub-router here backs one of those pages —
  * `/admin/api/auth` is public (login), everything added later
- * (`/admin/api/metrics`, `/admin/api/monitoring`, `/admin/api/tech-steps/*`,
- * `/admin/api/catalog/*`) sits behind `requireAdmin`
- * (`middlewares/require-admin.ts`).
+ * (`/admin/api/metrics`, `/admin/api/tech-steps/*`, `/admin/api/catalog/*`)
+ * sits behind `requireAdmin` (`middlewares/require-admin.ts`).
+ *
+ * Monitoring has **no** REST route here on purpose — it's pushed over
+ * WebSocket instead (`lib/monitoring-broadcast.service.ts`, wired in
+ * `server.ts`), not requested per-page-load. See that service's doc
+ * comment for the full mechanism.
  */
 export const adminRouter = Router();
 
 adminRouter.use("/auth", adminAuthRouter);
 adminRouter.use("/metrics", adminMetricsRouter);
-adminRouter.use("/monitoring", adminMonitoringRouter);
 adminRouter.use("/tech-steps", adminTechStepsRouter);
 adminRouter.use("/catalog", adminCatalogRouter);
diff --git a/apps/api/src/server.ts b/apps/api/src/server.ts
index 4f124c1..c197cf9 100644
--- a/apps/api/src/server.ts
+++ b/apps/api/src/server.ts
@@ -1,6 +1,8 @@
+import { Server as SocketIoServer } from "socket.io";
 import { createServer } from "./app.js";
 import { env } from "./config/env.js";
 import { logger } from "./lib/logger.service.js";
+import { MonitoringBroadcastService } from "./lib/monitoring-broadcast.service.js";
 import { techStepClassifier } from "./lib/recipe-matching/tech-step-matcher.js";
 import { registerAllRecipeSources } from "./sources/index.js";
 
@@ -50,6 +52,17 @@ await warmUpTechStepClassifier();
 
 const server = createServer();
 
+// Attaches to the same underlying `http.Server` `server.listen()` below
+// will start — `socket.io` binds to the HTTP server itself, not to
+// Express or a port, hence `ExpressServer.httpServer` (packages/express-
+// tools) rather than going through `server.instance` (the Express app).
+// Own CORS config: the WebSocket handshake is a separate HTTP upgrade
+// request that never runs through `setupCore`'s `cors()` middleware.
+const io = new SocketIoServer(server.httpServer, {
+  cors: { origin: env.CORS_ORIGIN, credentials: true },
+});
+new MonitoringBroadcastService(io).start();
+
 server.listen(env.PORT, () => {
   logger.info("API listening", { port: env.PORT, nodeEnv: env.NODE_ENV });
 });
diff --git a/apps/api/test/admin-monitoring-socket.test.ts b/apps/api/test/admin-monitoring-socket.test.ts
new file mode 100644
index 0000000..70e7b44
--- /dev/null
+++ b/apps/api/test/admin-monitoring-socket.test.ts
@@ -0,0 +1,159 @@
+import type { AddressInfo } from "node:net";
+import type { MonitoringView } from "@batch-cooking/shared";
+import { faker } from "@faker-js/faker";
+import { expect } from "chai";
+import { Server as SocketIoServer } from "socket.io";
+import { type Socket as ClientSocket, io as ioClient } from "socket.io-client";
+import { createServer } from "../src/app.js";
+import { env } from "../src/config/env.js";
+import { prisma } from "../src/db/prisma.js";
+import { signAdminToken } from "../src/lib/admin-jwt.js";
+import { MonitoringBroadcastService } from "../src/lib/monitoring-broadcast.service.js";
+import { hashAdminPassword } from "../src/modules/admin/admin-auth.service.js";
+import { resetDatabase } from "../test-support/reset-db.js";
+
+const VALID_STATUSES = ["up", "degraded", "down", "unknown"];
+const adminSecretConfigured = env.ADMIN_JWT_SECRET !== undefined;
+
+async function seedAdmin(): Promise<{ adminUserId: number; tokenVersion: number }> {
+  const admin = await prisma.adminUser.create({
+    data: {
+      email: faker.internet.email().toLowerCase(),
+      name: faker.person.fullName(),
+      passwordHash: await hashAdminPassword(faker.internet.password({ length: 16 })),
+    },
+  });
+  return { adminUserId: admin.id, tokenVersion: admin.tokenVersion };
+}
+
+/**
+ * Waits for `event` on `socket`, rejecting after `timeoutMs` (default
+ * tuned for the auth-rejection tests, which never touch a real probe and
+ * so resolve almost immediately — the probe-touching tests below pass a
+ * larger value explicitly) — every real WebSocket round-trip in this file
+ * goes through this instead of a bare `socket.once`, so a broken push
+ * fails the test with a clear message instead of hanging until Mocha's
+ * own default test timeout.
+ */
+function waitForEvent<T>(socket: ClientSocket, event: string, timeoutMs = 1500): Promise<T> {
+  return new Promise((resolve, reject) => {
+    const timer = setTimeout(
+      () => reject(new Error(`Timed out waiting for "${event}"`)),
+      timeoutMs,
+    );
+    socket.once(event, (payload: T) => {
+      clearTimeout(timer);
+      resolve(payload);
+    });
+  });
+}
+
+describe("Admin monitoring — WebSocket push", () => {
+  let baseUrl: string;
+  let broadcast: MonitoringBroadcastService;
+  const clientSockets: ClientSocket[] = [];
+
+  // A real listening server, not just createApp()'s bare Express instance
+  // (supertest's usual approach elsewhere in this suite) — socket.io needs
+  // an actual http.Server to attach to, and a real client (socket.io-
+  // client) needs a real port to connect to. Port 0 lets the OS pick a
+  // free one, so this suite never collides with anything else listening.
+  before(async () => {
+    const httpServer = createServer().httpServer;
+    const io = new SocketIoServer(httpServer, { cors: { origin: "*" } });
+    broadcast = new MonitoringBroadcastService(io);
+    await new Promise<void>((resolve) => httpServer.listen(0, resolve));
+    const { port } = httpServer.address() as AddressInfo;
+    baseUrl = `http://localhost:${port}`;
+    broadcast.start();
+  });
+
+  after(async () => {
+    broadcast.stop();
+    await prisma.$disconnect();
+  });
+
+  beforeEach(async () => {
+    await resetDatabase();
+  });
+
+  afterEach(() => {
+    for (const socket of clientSockets.splice(0)) {
+      socket.disconnect();
+    }
+  });
+
+  /** Connects a client with the given cookie header (or none), tracked for automatic teardown in `afterEach`. */
+  function connect(cookie?: string): ClientSocket {
+    const socket = ioClient(baseUrl, {
+      extraHeaders: cookie ? { Cookie: cookie } : undefined,
+      // This suite creates several short-lived connections in a row —
+      // socket.io-client's default reconnection would otherwise keep
+      // retrying a deliberately-rejected connection in the background
+      // after its own test has already moved on.
+      reconnection: false,
+      forceNew: true,
+    });
+    clientSockets.push(socket);
+    return socket;
+  }
+
+  it("rejects a connection with no admin cookie at all", async () => {
+    const socket = connect();
+    const err = await waitForEvent<Error>(socket, "connect_error");
+    expect(err.message).to.equal("Not authenticated");
+  });
+
+  it("rejects a connection carrying an end-user session cookie, not an admin one", async () => {
+    const socket = connect("session=whatever-not-an-admin-token");
+    const err = await waitForEvent<Error>(socket, "connect_error");
+    expect(err.message).to.equal("Not authenticated");
+  });
+
+  it("accepts a valid admin session and pushes a monitoring:update covering all four targets", async function () {
+    if (!adminSecretConfigured) {
+      // biome-ignore lint/suspicious/noExplicitAny: mocha's `this.skip()` isn't typed here.
+      (this as any).skip();
+      return;
+    }
+    // Longer than Mocha's 2000ms default: the very first probe tick can
+    // take close to PROBE_TIMEOUT_MS (2s) if e.g. the intent-service isn't
+    // reachable from this test environment (a probe timing out is a valid,
+    // expected outcome here — this test doesn't assert *which* status
+    // comes back, only that the shape is right).
+    this.timeout(8000);
+    const { adminUserId, tokenVersion } = await seedAdmin();
+    const token = signAdminToken({ adminUserId, tokenVersion });
+
+    const socket = connect(`${env.ADMIN_COOKIE_NAME}=${token}`);
+    const snapshot = await waitForEvent<MonitoringView>(socket, "monitoring:update", 6000);
+
+    expect(typeof snapshot.generatedAt).to.equal("string");
+    const keys = snapshot.services.map((service) => service.key);
+    expect(keys).to.have.members(["postgres", "api", "intent-service", "tech-step-llm-worker"]);
+    for (const service of snapshot.services) {
+      expect(VALID_STATUSES).to.include(service.status);
+    }
+  });
+
+  it("broadcasts the same update to every connected admin, not one probe per socket", async function () {
+    if (!adminSecretConfigured) {
+      // biome-ignore lint/suspicious/noExplicitAny: see above.
+      (this as any).skip();
+      return;
+    }
+    this.timeout(8000); // see the previous test's comment
+    const { adminUserId, tokenVersion } = await seedAdmin();
+    const token = signAdminToken({ adminUserId, tokenVersion });
+    const cookie = `${env.ADMIN_COOKIE_NAME}=${token}`;
+
+    const first = connect(cookie);
+    const second = connect(cookie);
+    const [firstSnapshot, secondSnapshot] = await Promise.all([
+      waitForEvent<MonitoringView>(first, "monitoring:update", 6000),
+      waitForEvent<MonitoringView>(second, "monitoring:update", 6000),
+    ]);
+
+    expect(firstSnapshot.generatedAt).to.equal(secondSnapshot.generatedAt);
+  });
+});
diff --git a/apps/api/test/admin-monitoring.test.ts b/apps/api/test/admin-monitoring.test.ts
deleted file mode 100644
index 80d3767..0000000
--- a/apps/api/test/admin-monitoring.test.ts
+++ /dev/null
@@ -1,160 +0,0 @@
-import { faker } from "@faker-js/faker";
-import { expect } from "chai";
-import request from "supertest";
-import { createApp } from "../src/app.js";
-import { env } from "../src/config/env.js";
-import { prisma } from "../src/db/prisma.js";
-import { hashAdminPassword } from "../src/modules/admin/admin-auth.service.js";
-import { resetDatabase } from "../test-support/reset-db.js";
-
-const SECRET_HEADER = "X-Internal-Worker-Secret";
-const VALID_STATUSES = ["up", "degraded", "down", "unknown"];
-
-async function seedAdmin(): Promise<{ email: string; password: string }> {
-  const email = faker.internet.email().toLowerCase();
-  const password = faker.internet.password({ length: 16 });
-  await prisma.adminUser.create({
-    data: { email, name: faker.person.fullName(), passwordHash: await hashAdminPassword(password) },
-  });
-  return { email, password };
-}
-
-const adminSecretConfigured = env.ADMIN_JWT_SECRET !== undefined;
-const workerSecretConfigured = env.INTERNAL_WORKER_SECRET !== undefined;
-
-describe("Admin monitoring", () => {
-  const app = createApp();
-
-  beforeEach(async () => {
-    await resetDatabase();
-  });
-
-  after(async () => {
-    await prisma.$disconnect();
-  });
-
-  describe("POST /internal/tech-steps/heartbeat", () => {
-    it("rejects a request with no worker secret with 401", async () => {
-      const res = await request(app).post("/internal/tech-steps/heartbeat").send({ event: "boot" });
-      expect(res.status).to.equal(401);
-    });
-
-    it("rejects a malformed body with 400", async function () {
-      if (!workerSecretConfigured) {
-        // biome-ignore lint/suspicious/noExplicitAny: mocha's `this.skip()` isn't typed here.
-        (this as any).skip();
-        return;
-      }
-      const res = await request(app)
-        .post("/internal/tech-steps/heartbeat")
-        .set(SECRET_HEADER, env.INTERNAL_WORKER_SECRET as string)
-        .send({ event: "not-a-real-event" });
-      expect(res.status).to.equal(400);
-    });
-
-    it("upserts the worker heartbeat, recording lastRunAt/lastResult for a job ping", async function () {
-      if (!workerSecretConfigured) {
-        // biome-ignore lint/suspicious/noExplicitAny: see above.
-        (this as any).skip();
-        return;
-      }
-      const res = await request(app)
-        .post("/internal/tech-steps/heartbeat")
-        .set(SECRET_HEADER, env.INTERNAL_WORKER_SECRET as string)
-        .send({
-          event: "job",
-          job: "audit-low-confidence",
-          ok: true,
-          counts: { suggestions: 3 },
-        });
-      expect(res.status).to.equal(200);
-      expect(res.body).to.deep.equal({ ok: true });
-
-      const stored = await prisma.workerHeartbeat.findUniqueOrThrow({
-        where: { workerKey: "tech-step-llm-worker" },
-      });
-      expect(stored.lastRunAt).to.not.equal(null);
-      expect(stored.lastResult).to.deep.equal({
-        job: "audit-low-confidence",
-        ok: true,
-        counts: { suggestions: 3 },
-      });
-    });
-
-    it("leaves lastRunAt null for a boot/tick ping", async function () {
-      if (!workerSecretConfigured) {
-        // biome-ignore lint/suspicious/noExplicitAny: see above.
-        (this as any).skip();
-        return;
-      }
-      await request(app)
-        .post("/internal/tech-steps/heartbeat")
-        .set(SECRET_HEADER, env.INTERNAL_WORKER_SECRET as string)
-        .send({ event: "boot" });
-
-      const stored = await prisma.workerHeartbeat.findUniqueOrThrow({
-        where: { workerKey: "tech-step-llm-worker" },
-      });
-      expect(stored.lastSeenAt).to.be.instanceOf(Date);
-      expect(stored.lastRunAt).to.equal(null);
-    });
-  });
-
-  describe("GET /admin/api/monitoring", () => {
-    it("rejects a request with no admin session with 401", async () => {
-      const res = await request(app).get("/admin/api/monitoring");
-      expect(res.status).to.equal(401);
-    });
-
-    it("returns a status board covering all four targets, never crashing on an unreachable probe", async function () {
-      if (!adminSecretConfigured) {
-        // biome-ignore lint/suspicious/noExplicitAny: see above.
-        (this as any).skip();
-        return;
-      }
-      const { email, password } = await seedAdmin();
-      const agent = request.agent(app);
-      await agent.post("/admin/api/auth/login").send({ email, password });
-
-      const res = await agent.get("/admin/api/monitoring");
-      expect(res.status).to.equal(200);
-
-      const keys = res.body.services.map((s: { key: string }) => s.key);
-      expect(keys).to.have.members(["postgres", "api", "intent-service", "tech-step-llm-worker"]);
-      for (const service of res.body.services) {
-        expect(VALID_STATUSES).to.include(service.status);
-      }
-
-      const byKey = Object.fromEntries(res.body.services.map((s: { key: string }) => [s.key, s]));
-      // The DB is up during the test run, and the API is answering us.
-      expect(byKey.postgres.status).to.equal("up");
-      expect(byKey.api.status).to.equal("up");
-      // No heartbeat has ever been recorded (resetDatabase truncated it).
-      expect(byKey["tech-step-llm-worker"].status).to.equal("unknown");
-    });
-
-    it("reports the worker as up once it has sent a recent heartbeat", async function () {
-      if (!adminSecretConfigured || !workerSecretConfigured) {
-        // biome-ignore lint/suspicious/noExplicitAny: see above.
-        (this as any).skip();
-        return;
-      }
-      await request(app)
-        .post("/internal/tech-steps/heartbeat")
-        .set(SECRET_HEADER, env.INTERNAL_WORKER_SECRET as string)
-        .send({ event: "job", job: "transform-corrections", ok: true, counts: { suggestions: 0 } });
-
-      const { email, password } = await seedAdmin();
-      const agent = request.agent(app);
-      await agent.post("/admin/api/auth/login").send({ email, password });
-
-      const res = await agent.get("/admin/api/monitoring");
-      const worker = res.body.services.find(
-        (s: { key: string }) => s.key === "tech-step-llm-worker",
-      );
-      expect(worker.status).to.equal("up");
-      expect(worker.lastResult.job).to.equal("transform-corrections");
-      expect(worker.lastRunAt).to.be.a("string");
-    });
-  });
-});
diff --git a/apps/api/test/internal/tech-step-worker.routes.test.ts b/apps/api/test/internal/tech-step-worker.routes.test.ts
index b969270..1977cbf 100644
--- a/apps/api/test/internal/tech-step-worker.routes.test.ts
+++ b/apps/api/test/internal/tech-step-worker.routes.test.ts
@@ -302,5 +302,58 @@ describe("Internal tech-step worker routes", () => {
         expect(res.body.code).to.equal(ErrorCode.TECH_STEP_NOT_FOUND);
       });
     });
+
+    // Moved here from the now-deleted admin-monitoring.test.ts when that
+    // file's own REST route (GET /admin/api/monitoring) was replaced by a
+    // WebSocket push (see admin-monitoring-socket.test.ts) — this route
+    // (POST /internal/tech-steps/heartbeat) is unrelated to that change
+    // and belongs with the rest of this router's own tests. No separate
+    // "rejects with no secret" case here: `requireInternalWorker` above
+    // already proves that generically for this whole router.
+    describe("POST /internal/tech-steps/heartbeat", () => {
+      it("rejects a malformed body with 400", async () => {
+        const res = await withSecret(
+          request(app).post("/internal/tech-steps/heartbeat").send({ event: "not-a-real-event" }),
+        );
+        expect(res.status).to.equal(400);
+      });
+
+      it("upserts the worker heartbeat, recording lastRunAt/lastResult for a job ping", async () => {
+        const res = await withSecret(
+          request(app)
+            .post("/internal/tech-steps/heartbeat")
+            .send({
+              event: "job",
+              job: "audit-low-confidence",
+              ok: true,
+              counts: { suggestions: 3 },
+            }),
+        );
+        expect(res.status).to.equal(200);
+        expect(res.body).to.deep.equal({ ok: true });
+
+        const stored = await prisma.workerHeartbeat.findUniqueOrThrow({
+          where: { workerKey: "tech-step-llm-worker" },
+        });
+        expect(stored.lastRunAt).to.not.equal(null);
+        expect(stored.lastResult).to.deep.equal({
+          job: "audit-low-confidence",
+          ok: true,
+          counts: { suggestions: 3 },
+        });
+      });
+
+      it("leaves lastRunAt null for a boot/tick ping", async () => {
+        await withSecret(
+          request(app).post("/internal/tech-steps/heartbeat").send({ event: "boot" }),
+        );
+
+        const stored = await prisma.workerHeartbeat.findUniqueOrThrow({
+          where: { workerKey: "tech-step-llm-worker" },
+        });
+        expect(stored.lastSeenAt).to.be.instanceOf(Date);
+        expect(stored.lastRunAt).to.equal(null);
+      });
+    });
   });
 });
diff --git a/apps/web/cypress/component/MonitoringPage.cy.tsx b/apps/web/cypress/component/MonitoringPage.cy.tsx
new file mode 100644
index 0000000..24a3213
--- /dev/null
+++ b/apps/web/cypress/component/MonitoringPage.cy.tsx
@@ -0,0 +1,140 @@
+import type { MonitoringView } from "@batch-cooking/shared";
+import "../../src/i18n/i18n";
+import type {
+  MonitoringConnectionState,
+  MonitoringSocketClientLike,
+} from "../../src/api/monitoring-socket";
+import { MonitoringPage } from "../../src/pages/admin/monitoring/MonitoringPage";
+
+// MonitoringPage takes its WebSocket client as a prop specifically so it
+// can be driven like this — no real socket.io server involved. See that
+// prop's own doc comment in MonitoringPage.tsx for why.
+class FakeMonitoringSocketClient implements MonitoringSocketClientLike {
+  public connectCallCount = 0;
+  public disconnectCallCount = 0;
+  private readonly _updateListeners = new Set<(data: MonitoringView) => void>();
+  private readonly _stateListeners = new Set<(state: MonitoringConnectionState) => void>();
+
+  public connect(): void {
+    this.connectCallCount += 1;
+  }
+
+  public disconnect(): void {
+    this.disconnectCallCount += 1;
+  }
+
+  public onUpdate(listener: (data: MonitoringView) => void): () => void {
+    this._updateListeners.add(listener);
+    return () => this._updateListeners.delete(listener);
+  }
+
+  public onConnectionStateChange(listener: (state: MonitoringConnectionState) => void): () => void {
+    this._stateListeners.add(listener);
+    return () => this._stateListeners.delete(listener);
+  }
+
+  /** Test-only: simulates the server pushing a snapshot. */
+  public emitUpdate(data: MonitoringView): void {
+    for (const listener of this._updateListeners) listener(data);
+  }
+
+  /** Test-only: simulates a connection-state change. */
+  public emitState(state: MonitoringConnectionState): void {
+    for (const listener of this._stateListeners) listener(state);
+  }
+}
+
+function monitoringFixture(): MonitoringView {
+  return {
+    generatedAt: "2026-09-05T09:15:00.000Z",
+    services: [
+      {
+        key: "postgres",
+        status: "up",
+        latencyMs: 3.2,
+        detail: null,
+        checkedAt: "2026-09-05T09:15:00.000Z",
+      },
+      {
+        key: "api",
+        status: "up",
+        latencyMs: 0,
+        detail: "uptime 3 h · RSS 120 Mo",
+        checkedAt: "2026-09-05T09:15:00.000Z",
+      },
+      {
+        key: "intent-service",
+        status: "down",
+        latencyMs: null,
+        detail: "fetch failed",
+        checkedAt: "2026-09-05T09:15:00.000Z",
+      },
+      {
+        key: "tech-step-llm-worker",
+        status: "degraded",
+        latencyMs: null,
+        detail: "dernier battement il y a 9 j",
+        checkedAt: "2026-09-05T09:15:00.000Z",
+        lastRunAt: "2026-08-19T03:00:00.000Z",
+        lastResult: { job: "audit-low-confidence", ok: true, counts: { suggestions: 2 } },
+      },
+    ],
+  };
+}
+
+describe("MonitoringPage", () => {
+  it("shows a loading placeholder before the first update arrives, and connects on mount", () => {
+    const client = new FakeMonitoringSocketClient();
+    cy.mount(<MonitoringPage socketClient={client} />);
+
+    cy.contains("Chargement").should("be.visible");
+    cy.get(".monitoring-grid").should("not.exist");
+    // `.should(...)` (not a bare `cy.then` + chai `expect`) so Cypress
+    // retries: `connect()` is called from a `useEffect`, which commits
+    // asynchronously after `cy.mount` itself has already resolved.
+    cy.wrap(client).its("connectCallCount").should("equal", 1);
+  });
+
+  it("renders one card per service once a snapshot arrives", () => {
+    const client = new FakeMonitoringSocketClient();
+    cy.mount(<MonitoringPage socketClient={client} />);
+    cy.then(() => {
+      client.emitState("connected");
+      client.emitUpdate(monitoringFixture());
+    });
+
+    cy.get(".monitoring-card").should("have.length", 4);
+    cy.contains(".monitoring-card", "Base de données").should("have.class", "monitoring-card--up");
+    cy.contains(".monitoring-card", "Service NLP (spaCy)").should(
+      "have.class",
+      "monitoring-card--down",
+    );
+    cy.get(".monitoring-connection-badge").should("not.exist");
+  });
+
+  it("shows a reconnecting badge without hiding the last known board", () => {
+    const client = new FakeMonitoringSocketClient();
+    cy.mount(<MonitoringPage socketClient={client} />);
+    cy.then(() => {
+      client.emitState("connected");
+      client.emitUpdate(monitoringFixture());
+    });
+    cy.get(".monitoring-card").should("have.length", 4);
+
+    cy.then(() => client.emitState("reconnecting"));
+
+    cy.get(".monitoring-connection-badge--reconnecting").should("be.visible");
+    // The board itself is still the one from before the drop — never
+    // replaced by a loading state just because the connection blipped.
+    cy.get(".monitoring-card").should("have.length", 4);
+  });
+
+  it("shows an error placeholder when the connection fails before any data ever arrived", () => {
+    const client = new FakeMonitoringSocketClient();
+    cy.mount(<MonitoringPage socketClient={client} />);
+    cy.then(() => client.emitState("error"));
+
+    cy.contains("Impossible de charger").should("be.visible");
+    cy.get(".monitoring-grid").should("not.exist");
+  });
+});
diff --git a/apps/web/cypress/e2e/admin-monitoring.cy.ts b/apps/web/cypress/e2e/admin-monitoring.cy.ts
deleted file mode 100644
index b5faa28..0000000
--- a/apps/web/cypress/e2e/admin-monitoring.cy.ts
+++ /dev/null
@@ -1,101 +0,0 @@
-// Mocks the admin API via cy.intercept — no live backend.
-
-const adminBody = {
-  id: 1,
-  email: "ops@example.com",
-  name: "Ops",
-  createdAt: "2026-08-01T00:00:00.000Z",
-  lastLoginAt: "2026-08-28T09:00:00.000Z",
-};
-
-function monitoringFixture() {
-  return {
-    generatedAt: "2026-08-28T09:15:00.000Z",
-    services: [
-      {
-        key: "postgres",
-        status: "up",
-        latencyMs: 3.2,
-        detail: null,
-        checkedAt: "2026-08-28T09:15:00.000Z",
-      },
-      {
-        key: "api",
-        status: "up",
-        latencyMs: 0,
-        detail: "uptime 3 h 12 min · RSS 120 Mo",
-        checkedAt: "2026-08-28T09:15:00.000Z",
-      },
-      {
-        key: "intent-service",
-        status: "down",
-        latencyMs: null,
-        detail: "fetch failed",
-        checkedAt: "2026-08-28T09:15:00.000Z",
-      },
-      {
-        key: "tech-step-llm-worker",
-        status: "degraded",
-        latencyMs: null,
-        detail: "dernier battement il y a 9 j",
-        checkedAt: "2026-08-28T09:15:00.000Z",
-        lastRunAt: "2026-08-19T03:00:00.000Z",
-        lastResult: { job: "audit-low-confidence", ok: true, counts: { suggestions: 2 } },
-      },
-    ],
-  };
-}
-
-describe("Admin monitoring", () => {
-  beforeEach(() => {
-    cy.viewport(1400, 900);
-    cy.intercept("GET", "**/admin/api/auth/me", { statusCode: 200, body: adminBody });
-  });
-
-  // Plain URL/method matcher is enough here: the API's `/admin/api/monitoring`
-  // can no longer collide with the page route `/admin/monitoring` (see
-  // `mountRouter("/admin/api", ...)`'s comment in the API's `app.ts` for the
-  // incident that made that distinction necessary in the first place). This
-  // used to need a `resourceType`-based workaround for that collision, which
-  // also surfaced an unrelated Cypress bug: on this machine's Chrome build, a
-  // *declarative* `resourceType` route matcher silently never caught a
-  // request whose own `req.resourceType` genuinely was that type — worth
-  // remembering if a `resourceType` matcher elsewhere in this suite ever
-  // starts failing the same way.
-  function interceptMonitoringApi(response: { statusCode: number; body: unknown }) {
-    return cy.intercept("GET", "**/admin/api/monitoring", response);
-  }
-
-  it("renders one card per service with its status and details", () => {
-    interceptMonitoringApi({ statusCode: 200, body: monitoringFixture() }).as("getMonitoring");
-    cy.visit("/admin/monitoring");
-    cy.wait("@getMonitoring");
-
-    cy.get(".monitoring-card").should("have.length", 4);
-
-    cy.contains(".monitoring-card", "Base de données")
-      .should("have.class", "monitoring-card--up")
-      .and("contain.text", "3.2 ms");
-    cy.contains(".monitoring-card", "Service NLP (spaCy)")
-      .should("have.class", "monitoring-card--down")
-      .and("contain.text", "Hors service");
-    cy.contains(".monitoring-card", "Worker LLM")
-      .should("have.class", "monitoring-card--degraded")
-      .and("contain.text", "audit-low-confidence");
-  });
-
-  it("shows an error state when the request fails", () => {
-    // Aliased and waited on (unlike the other tests' plain intercepts) so
-    // this genuinely proves the 500 came from the mock — without a live API
-    // server, an unmatched request fails at the network level too, which
-    // `MonitoringPage`'s `.catch()` can't tell apart from a real 500 (see
-    // the comment above `interceptMonitoringApi`, this is exactly the class
-    // of bug that let this test pass for the wrong reason before).
-    interceptMonitoringApi({ statusCode: 500, body: { code: 5000, message: "x" } }).as(
-      "getMonitoringError",
-    );
-    cy.visit("/admin/monitoring");
-    cy.wait("@getMonitoringError");
-    cy.contains("Impossible de charger").should("be.visible");
-  });
-});
diff --git a/apps/web/package.json b/apps/web/package.json
index 57dd08d..19ede70 100644
--- a/apps/web/package.json
+++ b/apps/web/package.json
@@ -23,6 +23,7 @@
     "react-i18next": "^17.0.11",
     "react-router-dom": "^7.18.2",
     "recharts": "^2.15.0",
+    "socket.io-client": "^4.8.3",
     "zod": "^3.25.76"
   },
   "devDependencies": {
diff --git a/apps/web/src/api/admin-client.ts b/apps/web/src/api/admin-client.ts
index 4a11b2c..f6dcf30 100644
--- a/apps/web/src/api/admin-client.ts
+++ b/apps/web/src/api/admin-client.ts
@@ -7,7 +7,6 @@ import {
   ErrorCode,
   type MarkPlaceholdersReviewedInput,
   type MetricsView,
-  type MonitoringView,
   type PruneOrphansResultView,
   type RetrainRequestInput,
   type RetrainResultView,
@@ -123,11 +122,6 @@ export class AdminApiClient {
     return this._request(`/metrics?days=${days}`);
   }
 
-  /** Live health of Postgres, the API, the intent-service and the LLM worker — polled by the monitoring board. */
-  public getMonitoring(): Promise<MonitoringView> {
-    return this._request("/monitoring");
-  }
-
   /** Training suggestions, grouped by technique, filtered by the given (all-optional) criteria. */
   public getSuggestions(filters: {
     status?: string;
diff --git a/apps/web/src/api/monitoring-socket.ts b/apps/web/src/api/monitoring-socket.ts
new file mode 100644
index 0000000..aef2c2d
--- /dev/null
+++ b/apps/web/src/api/monitoring-socket.ts
@@ -0,0 +1,105 @@
+import type { MonitoringView } from "@batch-cooking/shared";
+import { io, type Socket } from "socket.io-client";
+
+/** Event name the server pushes on — must match `UPDATE_EVENT` in `monitoring-broadcast.service.ts` (apps/api). */
+const UPDATE_EVENT = "monitoring:update";
+
+/**
+ * Connection state {@link MonitoringPage} renders a badge for whenever it
+ * isn't `"connected"` — `"connecting"` covers both the very first attempt
+ * and any later drop that happens *before* a first successful connect
+ * (rare, but distinct from `"reconnecting"`, which implies the board
+ * already has real data on screen worth not blanking out).
+ */
+export type MonitoringConnectionState = "connecting" | "connected" | "reconnecting" | "error";
+
+/**
+ * The shape {@link MonitoringPage} actually depends on — deliberately
+ * small, and satisfied by both {@link MonitoringSocketClient} (the real
+ * thing) and a fake `socket.io`-free test double, so a Cypress component
+ * test can drive the page's connection/update states without a real
+ * server. See `MonitoringPage.cy.tsx`.
+ */
+export interface MonitoringSocketClientLike {
+  connect(): void;
+  disconnect(): void;
+  /** Registers a listener for each pushed snapshot; returns an unsubscribe function. */
+  onUpdate(listener: (data: MonitoringView) => void): () => void;
+  /** Registers a listener for connection-state changes; returns an unsubscribe function. */
+  onConnectionStateChange(listener: (state: MonitoringConnectionState) => void): () => void;
+}
+
+/**
+ * Thin wrapper around a single `socket.io-client` connection to the admin
+ * monitoring room — the WebSocket counterpart of `AdminApiClient`
+ * (`admin-client.ts`), used only by `MonitoringPage`. Connects to the bare
+ * API origin (`VITE_API_URL`, same as `AdminApiClient`), **not** the
+ * `/admin/api` REST prefix: `socket.io` binds directly to the underlying
+ * `http.Server` (see `ExpressServer.httpServer`, `packages/express-tools`),
+ * independently of Express route mounting, at its own well-known
+ * `/socket.io/` handshake path.
+ *
+ * `withCredentials: true` is what makes the `admin_session` httpOnly
+ * cookie ride along on the handshake — the server-side auth
+ * (`requireAdminSocket`, `apps/api/src/middlewares/require-admin-socket.ts`)
+ * reads it from there exactly like `requireAdmin` reads it from a normal
+ * request's cookies.
+ */
+export class MonitoringSocketClient implements MonitoringSocketClientLike {
+  private _socket: Socket | null = null;
+  /** Once a connection has succeeded at least once, a later drop is a "reconnecting" (keep the board), not an "error" (nothing to show yet). */
+  private _hasConnectedOnce = false;
+  private readonly _updateListeners = new Set<(data: MonitoringView) => void>();
+  private readonly _stateListeners = new Set<(state: MonitoringConnectionState) => void>();
+
+  /** Opens the connection. Idempotent — calling it while already connected/connecting does nothing. */
+  public connect(): void {
+    if (this._socket) {
+      return;
+    }
+
+    const baseUrl: string = import.meta.env.VITE_API_URL ?? "";
+    this._socket = io(baseUrl, { withCredentials: true });
+
+    this._socket.on("connect", () => {
+      this._hasConnectedOnce = true;
+      this._emitState("connected");
+    });
+    this._socket.on(UPDATE_EVENT, (data: MonitoringView) => {
+      for (const listener of this._updateListeners) {
+        listener(data);
+      }
+    });
+    this._socket.on("disconnect", () => {
+      this._emitState(this._hasConnectedOnce ? "reconnecting" : "connecting");
+    });
+    this._socket.on("connect_error", () => {
+      this._emitState(this._hasConnectedOnce ? "reconnecting" : "error");
+    });
+
+    this._emitState("connecting");
+  }
+
+  /** Closes the connection. Registered listeners' subscriptions are left intact — callers still own their own unsubscribe functions from {@link onUpdate}/{@link onConnectionStateChange}; this just stops the transport, ready for a later {@link connect} to reuse the same subscriptions. */
+  public disconnect(): void {
+    this._socket?.disconnect();
+    this._socket = null;
+    this._hasConnectedOnce = false;
+  }
+
+  public onUpdate(listener: (data: MonitoringView) => void): () => void {
+    this._updateListeners.add(listener);
+    return () => this._updateListeners.delete(listener);
+  }
+
+  public onConnectionStateChange(listener: (state: MonitoringConnectionState) => void): () => void {
+    this._stateListeners.add(listener);
+    return () => this._stateListeners.delete(listener);
+  }
+
+  private _emitState(state: MonitoringConnectionState): void {
+    for (const listener of this._stateListeners) {
+      listener(state);
+    }
+  }
+}
diff --git a/apps/web/src/locales/fr/translation.json b/apps/web/src/locales/fr/translation.json
index 3f525ed..4f18e31 100644
--- a/apps/web/src/locales/fr/translation.json
+++ b/apps/web/src/locales/fr/translation.json
@@ -1220,6 +1220,11 @@
       "lastRun": "Dernier job",
       "never": "jamais",
       "jobFailed": "échec",
+      "connectionState": {
+        "connecting": "Connexion en cours…",
+        "reconnecting": "Connexion perdue, reconnexion en cours…",
+        "error": "Connexion impossible"
+      },
       "status": {
         "up": "OK",
         "degraded": "Dégradé",
diff --git a/apps/web/src/pages/admin/monitoring/MonitoringPage.tsx b/apps/web/src/pages/admin/monitoring/MonitoringPage.tsx
index cf80284..1e391ee 100644
--- a/apps/web/src/pages/admin/monitoring/MonitoringPage.tsx
+++ b/apps/web/src/pages/admin/monitoring/MonitoringPage.tsx
@@ -1,66 +1,89 @@
 import type { MonitoringView, ServiceHealthView } from "@batch-cooking/shared";
 import { useEffect, useState } from "react";
 import { useTranslation } from "react-i18next";
-import { adminApiClient } from "../../../api/admin-client";
+import {
+  type MonitoringConnectionState,
+  MonitoringSocketClient,
+  type MonitoringSocketClientLike,
+} from "../../../api/monitoring-socket";
 import "../admin-page.scss";
 import "./monitoring-page.scss";
-import { clockTime, POLL_INTERVAL_MS, statusModifier } from "./monitoring";
+import { clockTime, statusModifier } from "./monitoring";
 
-type MonitoringState =
-  | { status: "loading" }
-  | { status: "loaded"; data: MonitoringView }
-  | { status: "error" };
+interface MonitoringPageProps {
+  /**
+   * Overrides the real WebSocket client — for Cypress component tests
+   * (`MonitoringPage.cy.tsx`), which drive connection/update events
+   * synthetically through a fake implementing {@link MonitoringSocketClientLike}
+   * instead of a real `socket.io` server. Defaults to a real
+   * {@link MonitoringSocketClient}; production never passes this prop.
+   */
+  socketClient?: MonitoringSocketClientLike;
+}
 
 /**
- * Microservice health board. Fetches `GET /admin/api/monitoring` on mount and
- * re-polls every {@link POLL_INTERVAL_MS} ms. One card per probed target
- * (Postgres, API, intent-service, LLM worker), coloured by status.
+ * Microservice health board. No REST endpoint backs this any more — the
+ * server probes once a minute and pushes `monitoring:update` over
+ * WebSocket to every connected admin (`MonitoringBroadcastService`,
+ * apps/api), instead of each open tab polling independently. One card per
+ * probed target (Postgres, API, intent-service, LLM worker), coloured by
+ * status.
+ *
+ * `data` and `connectionState` are deliberately separate: a connection
+ * drop after the board has already loaded once shows a small badge
+ * (`socket.io-client`'s own automatic reconnection handles the retry) —
+ * it never blanks the last known board back to a loading state. Only the
+ * very first connect, before any data has ever arrived, shows the
+ * full-page loading/error placeholder.
  */
-export function MonitoringPage() {
+export function MonitoringPage({ socketClient }: MonitoringPageProps) {
   const { t } = useTranslation();
-  const [state, setState] = useState<MonitoringState>({ status: "loading" });
+  const [data, setData] = useState<MonitoringView | null>(null);
+  const [connectionState, setConnectionState] = useState<MonitoringConnectionState>("connecting");
+  // Lazy useState initializer, not a plain `new MonitoringSocketClient()`
+  // above it or a bare module-level singleton: this must run exactly once
+  // per component instance (a fresh client per mount), and must not be
+  // recreated on every re-render.
+  const [client] = useState<MonitoringSocketClientLike>(
+    () => socketClient ?? new MonitoringSocketClient(),
+  );
 
   useEffect(() => {
-    let cancelled = false;
-
-    function load() {
-      adminApiClient
-        .getMonitoring()
-        .then((data) => {
-          if (!cancelled) setState({ status: "loaded", data });
-        })
-        .catch(() => {
-          if (!cancelled)
-            setState((prev) => (prev.status === "loaded" ? prev : { status: "error" }));
-        });
-    }
-
-    load();
-    const timer = setInterval(load, POLL_INTERVAL_MS);
+    const unsubscribeUpdate = client.onUpdate(setData);
+    const unsubscribeState = client.onConnectionStateChange(setConnectionState);
+    client.connect();
     return () => {
-      cancelled = true;
-      clearInterval(timer);
+      unsubscribeUpdate();
+      unsubscribeState();
+      client.disconnect();
     };
-  }, []);
+  }, [client]);
 
   return (
     <div className="admin-page">
       <h1 className="admin-page__title">{t("admin.monitoring.title")}</h1>
       <p className="admin-page__lead">{t("admin.monitoring.lead")}</p>
 
-      {state.status === "loading" && (
+      {data === null && connectionState !== "error" && (
         <p className="admin-page__placeholder">{t("admin.common.loading")}</p>
       )}
-      {state.status === "error" && (
+      {data === null && connectionState === "error" && (
         <p className="admin-page__placeholder">{t("admin.common.loadError")}</p>
       )}
-      {state.status === "loaded" && (
+      {data !== null && (
         <>
+          {connectionState !== "connected" && (
+            <p
+              className={`monitoring-connection-badge monitoring-connection-badge--${connectionState}`}
+            >
+              {t(`admin.monitoring.connectionState.${connectionState}`)}
+            </p>
+          )}
           <p className="monitoring-checked">
-            {t("admin.monitoring.lastChecked", { time: clockTime(state.data.generatedAt) })}
+            {t("admin.monitoring.lastChecked", { time: clockTime(data.generatedAt) })}
           </p>
           <div className="monitoring-grid">
-            {state.data.services.map((service) => (
+            {data.services.map((service) => (
               <ServiceCard key={service.key} service={service} />
             ))}
           </div>
diff --git a/apps/web/src/pages/admin/monitoring/monitoring-page.scss b/apps/web/src/pages/admin/monitoring/monitoring-page.scss
index d9fe572..7473621 100644
--- a/apps/web/src/pages/admin/monitoring/monitoring-page.scss
+++ b/apps/web/src/pages/admin/monitoring/monitoring-page.scss
@@ -9,6 +9,30 @@
   color: var(--color-text-muted);
 }
 
+// Shown above the board only while the WebSocket connection isn't
+// currently up — the board itself always stays on screen underneath
+// (see MonitoringPage.tsx's own comment on why `data` and
+// `connectionState` are kept separate), this is just a heads-up that
+// what's showing may be stale.
+.monitoring-connection-badge {
+  display: inline-block;
+  margin: 0 0 var(--space-md);
+  padding: var(--space-xs) var(--space-sm);
+  border-radius: var(--radius-md);
+  font-size: var(--font-size-sm);
+  font-weight: 700;
+
+  &--reconnecting {
+    color: var(--color-warning);
+    background: color-mix(in srgb, var(--color-warning) 12%, transparent);
+  }
+
+  &--error {
+    color: var(--color-error);
+    background: color-mix(in srgb, var(--color-error) 12%, transparent);
+  }
+}
+
 .monitoring-grid {
   display: grid;
   grid-template-columns: repeat(auto-fill, minmax(18rem, 1fr));
diff --git a/apps/web/src/pages/admin/monitoring/monitoring.ts b/apps/web/src/pages/admin/monitoring/monitoring.ts
index 95344db..9fb32ca 100644
--- a/apps/web/src/pages/admin/monitoring/monitoring.ts
+++ b/apps/web/src/pages/admin/monitoring/monitoring.ts
@@ -10,9 +10,6 @@ export function statusModifier(status: ServiceStatus): string {
   return status;
 }
 
-/** How often the board re-polls `GET /admin/api/monitoring`, in ms. */
-export const POLL_INTERVAL_MS = 15_000;
-
 /** `"2026-08-28T09:00:00.000Z"` → `"09:00:00"` (local time) for the "last checked" line. */
 export function clockTime(iso: string): string {
   return new Date(iso).toLocaleTimeString("fr-FR");
diff --git a/packages/express-tools/src/express-server.ts b/packages/express-tools/src/express-server.ts
index ce46149..8acf62d 100644
--- a/packages/express-tools/src/express-server.ts
+++ b/packages/express-tools/src/express-server.ts
@@ -1,3 +1,4 @@
+import http from "node:http";
 import path from "node:path";
 import cookieParser from "cookie-parser";
 import cors from "cors";
@@ -38,11 +39,22 @@ export interface ExpressServerCoreOptions {
 export class ExpressServer {
   /** The underlying Express application. */
   private readonly _app: Express;
+  /**
+   * The raw Node HTTP server wrapping {@link _app} — created up front
+   * (not lazily inside {@link listen}) so callers can attach something
+   * that needs the actual `http.Server` *before* it starts accepting
+   * connections, e.g. a `socket.io` server, which binds to the HTTP
+   * server itself rather than to Express or a port. Express's own
+   * `.listen()` creates one of these internally too, but never hands it
+   * back — that's the whole reason this class creates it explicitly.
+   */
+  private readonly _httpServer: http.Server;
   /** Tracks `"METHOD path"` keys already registered via {@link addRoute}, to warn instead of silently double-registering a route. */
   private readonly _registeredRoutes = new Set<string>();
 
   public constructor() {
     this._app = express();
+    this._httpServer = http.createServer(this._app);
   }
 
   /** The underlying Express application — needed by test tooling (e.g. supertest) that expects a raw `Express` instance. */
@@ -50,6 +62,11 @@ export class ExpressServer {
     return this._app;
   }
 
+  /** The underlying `http.Server` — for anything that needs to attach directly to it (e.g. a `socket.io` server) rather than go through Express. Safe to read before {@link listen} is called; it just won't be accepting connections yet. */
+  public get httpServer(): http.Server {
+    return this._httpServer;
+  }
+
   /**
    * Registers the standard middleware stack every service in this
    * monorepo needs: CORS (with credentials, for the session cookie),
@@ -117,6 +134,6 @@ export class ExpressServer {
 
   /** Starts listening on the given port. `onListening` is called once the server is up (e.g. to log the URL). */
   public listen(port: number, onListening?: () => void): void {
-    this._app.listen(port, onListening);
+    this._httpServer.listen(port, onListening);
   }
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index a23699f..fb8e91c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -35,6 +35,9 @@ importers:
       argon2:
         specifier: 0.31.2
         version: 0.31.2
+      cookie:
+        specifier: ^2.0.1
+        version: 2.0.1
       dotenv:
         specifier: ^16.4.5
         version: 16.6.1
@@ -47,6 +50,9 @@ importers:
       prisma:
         specifier: ^5.22.0
         version: 5.22.0
+      socket.io:
+        specifier: ^4.8.3
+        version: 4.8.3
       zod:
         specifier: ^3.23.8
         version: 3.25.76
@@ -75,6 +81,9 @@ importers:
       mocha:
         specifier: ^10.8.2
         version: 10.8.2
+      socket.io-client:
+        specifier: ^4.8.3
+        version: 4.8.3
       supertest:
         specifier: ^7.0.0
         version: 7.2.2
@@ -114,6 +123,9 @@ importers:
       recharts:
         specifier: ^2.15.0
         version: 2.15.4(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      socket.io-client:
+        specifier: ^4.8.3
+        version: 4.8.3
       zod:
         specifier: ^3.25.76
         version: 3.25.76
@@ -1114,6 +1126,9 @@ packages:
     cpu: [x64]
     os: [win32]
 
+  '@socket.io/component-emitter@3.1.2':
+    resolution: {integrity: sha512-9BCxFwvbGg/RsZK9tjXd8s4UcwR0MWeFQ1XEKIQVVvAGJyINdrqKMcTRyLoK8Rse1GjzLV9cwjWV1olXRWEXVA==, tarball: https://registry.npmjs.org/@socket.io/component-emitter/-/component-emitter-3.1.2.tgz}
+
   '@standard-schema/spec@1.1.0':
     resolution: {integrity: sha512-l2aFy5jALhniG5HgqrD6jXLi/rUWrKvqN/qJx6yoJsgKhblVd+iqqU4RCXavm/jPityDo5TCvKMnpjKnOriy0w==, tarball: https://registry.npmjs.org/@standard-schema/spec/-/spec-1.1.0.tgz}
 
@@ -1251,6 +1266,9 @@ packages:
   '@types/uuid@10.0.0':
     resolution: {integrity: sha512-7gqG38EyHgyP1S+7+xomFtL+ZNHcKv6DwNaCZmJmo1vgMugyF3TCnXVg4t1uk89mLNwnLtnY3TpOpCOyp1/xHQ==, tarball: https://registry.npmjs.org/@types/uuid/-/uuid-10.0.0.tgz}
 
+  '@types/ws@8.18.1':
+    resolution: {integrity: sha512-ThVF6DCVhA8kUGy+aazFQ4kXQ7E1Ty7A3ypFOe0IcJV8O/M511G99AW24irKrW56Wt44yG9+ij8FaqoBGkuBXg==, tarball: https://registry.npmjs.org/@types/ws/-/ws-8.18.1.tgz}
+
   '@types/yauzl@2.10.3':
     resolution: {integrity: sha512-oJoftv0LSuaDZE3Le4DbKX+KS9G36NzOeSap90UIK0yMA/NhKJhqlSGtNDORNRaIbQfzjXDrQa0ytJ6mNRGz/Q==, tarball: https://registry.npmjs.org/@types/yauzl/-/yauzl-2.10.3.tgz}
 
@@ -1453,6 +1471,10 @@ packages:
   base64-js@1.5.1:
     resolution: {integrity: sha512-AKpaYlHn8t4SVbOHCy+b5+KKgvR4vrsD8vbvrbiQJps7fKDTkjkDry6ji0rUJjC0kzbNePLwzxq8iypo41qeWA==, tarball: https://registry.npmjs.org/base64-js/-/base64-js-1.5.1.tgz}
 
+  base64id@2.0.0:
+    resolution: {integrity: sha512-lGe34o6EHj9y3Kts9R4ZYs/Gr+6N7MCaMlIFA3F1R2O5/m7K06AxfSeO5530PEERE6/WyEg3lsuyw4GHlPZHog==, tarball: https://registry.npmjs.org/base64id/-/base64id-2.0.0.tgz}
+    engines: {node: ^4.5.0 || >= 5.9}
+
   baseline-browser-mapping@2.11.14:
     resolution: {integrity: sha512-JyJ954WzuIR8/FFzX0o5krdSTrBAkcCSRfWSleRsIHSWV+cZe2FI1PKggVkFke1hBldRs+LRxUczzE9iPmgZww==, tarball: https://registry.npmjs.org/baseline-browser-mapping/-/baseline-browser-mapping-2.11.14.tgz}
     engines: {node: '>=6.0.0'}
@@ -1718,6 +1740,10 @@ packages:
     resolution: {integrity: sha512-ei8Aos7ja0weRpFzJnEA9UHJ/7XQmqglbRwnf2ATjcB9Wq874VKH9kfjjirM6UhU2/E5fFYadylyhFldcqSidQ==, tarball: https://registry.npmjs.org/cookie/-/cookie-1.1.1.tgz}
     engines: {node: '>=18'}
 
+  cookie@2.0.1:
+    resolution: {integrity: sha512-yuToqVvRrj6pfDXREyQAAv8SkAEk/8GS3jQRTiUMm66TVtBYmqQeoEjL2Lmq8Rpo6271vH76InTChTitEAm65w==, tarball: https://registry.npmjs.org/cookie/-/cookie-2.0.1.tgz}
+    engines: {node: '>=22'}
+
   cookiejar@2.1.4:
     resolution: {integrity: sha512-LDx6oHrK+PhzLKJU9j5S7/Y3jM/mUHvD/DeI1WQmJn652iPC5Y4TBzC9l+5OMOXlyTTA+SmVUPm0HQUwpD5Jqw==, tarball: https://registry.npmjs.org/cookiejar/-/cookiejar-2.1.4.tgz}
 
@@ -2012,6 +2038,17 @@ packages:
   end-of-stream@1.4.5:
     resolution: {integrity: sha512-ooEGc6HP26xXq/N+GCGOT0JKCLDGrq2bQUZrQ7gyrJiZANJ/8YDTxTpQBXGMn+WbIQXNVpyWymm7KYVICQnyOg==, tarball: https://registry.npmjs.org/end-of-stream/-/end-of-stream-1.4.5.tgz}
 
+  engine.io-client@6.6.6:
+    resolution: {integrity: sha512-iY6QdftLQ9pyiPoX082bpf/u1UewnOaJrtJIF9T0++QB34lZrj0uP+Q/bj8AlUsAxqhnkTV2BS8SBZSxOmoV5Q==, tarball: https://registry.npmjs.org/engine.io-client/-/engine.io-client-6.6.6.tgz}
+
+  engine.io-parser@5.2.3:
+    resolution: {integrity: sha512-HqD3yTBfnBxIrbnM1DoD6Pcq8NECnh8d4As1Qgh0z5Gg3jRRIqijury0CL3ghu/edArpUYiYqQiDUQBIs4np3Q==, tarball: https://registry.npmjs.org/engine.io-parser/-/engine.io-parser-5.2.3.tgz}
+    engines: {node: '>=10.0.0'}
+
+  engine.io@6.6.10:
+    resolution: {integrity: sha512-9/lX2bdlizlCXMHRMOIm03VBQHQYC7VvydcxtTAUJRxNW1QzM/2PMFSmr6h/lCiMHcyCP6abK+t9Q+j4vekk8Q==, tarball: https://registry.npmjs.org/engine.io/-/engine.io-6.6.10.tgz}
+    engines: {node: '>=10.2.0'}
+
   enhanced-resolve@5.24.5:
     resolution: {integrity: sha512-L1l8TNvomm6UVW5B253AGxQagSQr+vGwhMlrrfRS2qmhx46AMpMVJKQYLvWYbysTMY8VoicOvzHzoHMbyzB+4A==, tarball: https://registry.npmjs.org/enhanced-resolve/-/enhanced-resolve-5.24.5.tgz}
     engines: {node: '>=10.13.0'}
@@ -3465,6 +3502,21 @@ packages:
     resolution: {integrity: sha512-qMCMfhY040cVHT43K9BFygqYbUPFZKHOg7K73mtTWJRb8pyP3fzf4Ixd5SzdEJQ6MRUg/WBnOLxghZtKKurENQ==, tarball: https://registry.npmjs.org/slice-ansi/-/slice-ansi-4.0.0.tgz}
     engines: {node: '>=10'}
 
+  socket.io-adapter@2.5.8:
+    resolution: {integrity: sha512-6Oy52pbg+kvdCVvjcN+FnY7BvxZ7cIHNScbvztT/It5d0vbwoJoVZmF2gjJmnV0/4WlXRfG15zc45ySk9Ah8bw==, tarball: https://registry.npmjs.org/socket.io-adapter/-/socket.io-adapter-2.5.8.tgz}
+
+  socket.io-client@4.8.3:
+    resolution: {integrity: sha512-uP0bpjWrjQmUt5DTHq9RuoCBdFJF10cdX9X+a368j/Ft0wmaVgxlrjvK3kjvgCODOMMOz9lcaRzxmso0bTWZ/g==, tarball: https://registry.npmjs.org/socket.io-client/-/socket.io-client-4.8.3.tgz}
+    engines: {node: '>=10.0.0'}
+
+  socket.io-parser@4.2.7:
+    resolution: {integrity: sha512-IH/iSeO9T6gz1KkFleGDWkG9N3dl4jXVYUtMhIqH10Md0ttMer8nUNWiP1DKuNrybD2xBrixLJdCC9J6ECoYkg==, tarball: https://registry.npmjs.org/socket.io-parser/-/socket.io-parser-4.2.7.tgz}
+    engines: {node: '>=10.0.0'}
+
+  socket.io@4.8.3:
+    resolution: {integrity: sha512-2Dd78bqzzjE6KPkD5fHZmDAKRNe3J15q+YHDrIsy9WEkqttc7GY+kT9OBLSMaPbQaEd0x1BjcmtMtXkfpc+T5A==, tarball: https://registry.npmjs.org/socket.io/-/socket.io-4.8.3.tgz}
+    engines: {node: '>=10.2.0'}
+
   source-map-js@1.2.1:
     resolution: {integrity: sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==, tarball: https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.1.tgz}
     engines: {node: '>=0.10.0'}
@@ -3865,10 +3917,26 @@ packages:
   wrappy@1.0.2:
     resolution: {integrity: sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ==, tarball: https://registry.npmjs.org/wrappy/-/wrappy-1.0.2.tgz}
 
+  ws@8.21.3:
+    resolution: {integrity: sha512-201TZ/kPWxoPr/OKWjquZR1SWKXcvxdH+e1xrx89b3YbmzLMFCLfnaG1HFIgWzJOEWZ7MvpK++odZufgYR50Rw==, tarball: https://registry.npmjs.org/ws/-/ws-8.21.3.tgz}
+    engines: {node: '>=10.0.0'}
+    peerDependencies:
+      bufferutil: ^4.0.1
+      utf-8-validate: '>=5.0.2'
+    peerDependenciesMeta:
+      bufferutil:
+        optional: true
+      utf-8-validate:
+        optional: true
+
   xmlbuilder@15.1.1:
     resolution: {integrity: sha512-yMqGBqtXyeN1e3TGYvgNgDVZ3j84W4cwkOXQswghol6APgZWaff9lnbvN7MHYJOiXsvGPXtjTYJEiC9J2wv9Eg==, tarball: https://registry.npmjs.org/xmlbuilder/-/xmlbuilder-15.1.1.tgz}
     engines: {node: '>=8.0'}
 
+  xmlhttprequest-ssl@2.1.2:
+    resolution: {integrity: sha512-TEU+nJVUUnA4CYJFLvK5X9AOeH4KvDvhIfm0vV1GaQRtchnG0hgK5p8hw/xjv8cunWYCsiPCSDzObPyhEwq3KQ==, tarball: https://registry.npmjs.org/xmlhttprequest-ssl/-/xmlhttprequest-ssl-2.1.2.tgz}
+    engines: {node: '>=0.4.0'}
+
   y18n@5.0.8:
     resolution: {integrity: sha512-0pfFzegeDWJHJIAmTLRP2DwHjdF5s7jo9tuztdQxAhINCdvS+3nGINqPd00AphqJR/0LhANUS6/+7SCb98YOfA==, tarball: https://registry.npmjs.org/y18n/-/y18n-5.0.8.tgz}
     engines: {node: '>=10'}
@@ -4711,6 +4779,8 @@ snapshots:
   '@rollup/rollup-win32-x64-msvc@4.62.4':
     optional: true
 
+  '@socket.io/component-emitter@3.1.2': {}
+
   '@standard-schema/spec@1.1.0': {}
 
   '@teppeis/multimaps@3.0.0': {}
@@ -4864,6 +4934,10 @@ snapshots:
 
   '@types/uuid@10.0.0': {}
 
+  '@types/ws@8.18.1':
+    dependencies:
+      '@types/node': 22.20.1
+
   '@types/yauzl@2.10.3':
     dependencies:
       '@types/node': 22.20.1
@@ -5080,6 +5154,8 @@ snapshots:
 
   base64-js@1.5.1: {}
 
+  base64id@2.0.0: {}
+
   baseline-browser-mapping@2.11.14: {}
 
   bcrypt-pbkdf@1.0.2:
@@ -5328,6 +5404,8 @@ snapshots:
 
   cookie@1.1.1: {}
 
+  cookie@2.0.1: {}
+
   cookiejar@2.1.4: {}
 
   core-util-is@1.0.2: {}
@@ -5672,6 +5750,36 @@ snapshots:
     dependencies:
       once: 1.4.0
 
+  engine.io-client@6.6.6:
+    dependencies:
+      '@socket.io/component-emitter': 3.1.2
+      debug: 4.4.3(supports-color@8.1.1)
+      engine.io-parser: 5.2.3
+      ws: 8.21.3
+      xmlhttprequest-ssl: 2.1.2
+    transitivePeerDependencies:
+      - bufferutil
+      - supports-color
+      - utf-8-validate
+
+  engine.io-parser@5.2.3: {}
+
+  engine.io@6.6.10:
+    dependencies:
+      '@types/cors': 2.8.19
+      '@types/node': 22.20.1
+      '@types/ws': 8.18.1
+      accepts: 1.3.8
+      cookie: 0.7.2
+      cors: 2.8.6
+      debug: 4.4.3(supports-color@8.1.1)
+      engine.io-parser: 5.2.3
+      ws: 8.21.3
+    transitivePeerDependencies:
+      - bufferutil
+      - supports-color
+      - utf-8-validate
+
   enhanced-resolve@5.24.5:
     dependencies:
       graceful-fs: 4.2.11
@@ -7287,6 +7395,47 @@ snapshots:
       astral-regex: 2.0.0
       is-fullwidth-code-point: 3.0.0
 
+  socket.io-adapter@2.5.8:
+    dependencies:
+      debug: 4.4.3(supports-color@8.1.1)
+      ws: 8.21.3
+    transitivePeerDependencies:
+      - bufferutil
+      - supports-color
+      - utf-8-validate
+
+  socket.io-client@4.8.3:
+    dependencies:
+      '@socket.io/component-emitter': 3.1.2
+      debug: 4.4.3(supports-color@8.1.1)
+      engine.io-client: 6.6.6
+      socket.io-parser: 4.2.7
+    transitivePeerDependencies:
+      - bufferutil
+      - supports-color
+      - utf-8-validate
+
+  socket.io-parser@4.2.7:
+    dependencies:
+      '@socket.io/component-emitter': 3.1.2
+      debug: 4.4.3(supports-color@8.1.1)
+    transitivePeerDependencies:
+      - supports-color
+
+  socket.io@4.8.3:
+    dependencies:
+      accepts: 1.3.8
+      base64id: 2.0.0
+      cors: 2.8.6
+      debug: 4.4.3(supports-color@8.1.1)
+      engine.io: 6.6.10
+      socket.io-adapter: 2.5.8
+      socket.io-parser: 4.2.7
+    transitivePeerDependencies:
+      - bufferutil
+      - supports-color
+      - utf-8-validate
+
   source-map-js@1.2.1: {}
 
   source-map-support@0.5.21:
@@ -7696,8 +7845,12 @@ snapshots:
 
   wrappy@1.0.2: {}
 
+  ws@8.21.3: {}
+
   xmlbuilder@15.1.1: {}
 
+  xmlhttprequest-ssl@2.1.2: {}
+
   y18n@5.0.8: {}
 
   yallist@3.1.1: {}
diff --git a/specs/backend-architecture.md b/specs/backend-architecture.md
index ffba337..a4e1e3f 100644
--- a/specs/backend-architecture.md
+++ b/specs/backend-architecture.md
@@ -395,13 +395,31 @@ est un `String` libre (`"user.signup"`, `"recipe.imported"`, `"recipe.created"`,
 ligne, **sans migration**. `AnalyticsEvent.actorId` n'a **pas** de FK (un
 évènement est un fait historique qui survit au compte qu'il décrit).
 
-**Monitoring** (`admin-monitoring.service.ts`, `GET /admin/api/monitoring`,
-`requireAdmin`) — sonde active, chaque cible bornée à ~2 s, latence mesurée :
-Postgres (`SELECT 1`), l'API elle-même (uptime/RSS), `tech-step-intent-service`
+**Monitoring** (`admin-monitoring.service.ts`'s `getMonitoring()`) — sonde
+active, chaque cible bornée à ~2 s, latence mesurée : Postgres
+(`SELECT 1`), l'API elle-même (uptime/RSS), `tech-step-intent-service`
 (`GET /health`, sans secret), et le **worker LLM** via sa ligne
-`WorkerHeartbeat`. `MonitoringView { services: ServiceHealthView[] }`, statut
-`up | degraded | down | unknown` ; une sonde `down` ne fait jamais échouer les
-autres ni l'endpoint. Le front (`MonitoringPage`) re-poll toutes les 15 s.
+`WorkerHeartbeat`. `MonitoringView { services: ServiceHealthView[] }`,
+statut `up | degraded | down | unknown` ; une sonde `down` ne fait jamais
+échouer les autres ni cet appel dans son ensemble.
+
+**Pas de route REST** — poussé en WebSocket. `MonitoringBroadcastService`
+(`lib/monitoring-broadcast.service.ts`) sonde une fois au démarrage puis
+toutes les 60 s (un seul `setInterval` pour tout le process, pas par
+onglet admin ouvert) et diffuse le résultat (`monitoring:update`) à la
+room `socket.io` `"monitoring"`. Auth au handshake via
+`requireAdminSocket` (`middlewares/require-admin-socket.ts`) — même
+vérification que `requireAdmin` (cookie `ADMIN_COOKIE_NAME` +
+`verifyAdminToken` + re-check `tokenVersion`, factorisée dans
+`resolveAdminFromToken`), lue depuis l'en-tête `Cookie` brut du handshake
+(parsé à la main avec le package `cookie` — un handshake `socket.io` ne
+passe pas par `cookie-parser`). Le dernier résultat est mis en cache et
+rejoué immédiatement à tout admin qui rejoint la room, pour qu'un onglet
+fraîchement ouvert n'attende pas la prochaine minute. Le `socket.io`
+`Server` s'attache directement au `http.Server` sous-jacent
+(`ExpressServer.httpServer`, `packages/express-tools`), pas à Express —
+câblé dans `server.ts`, pas `app.ts` (les tests supertest n'ont pas besoin
+d'un serveur WebSocket).
 
 Le worker (`services/tech-step-llm-worker`) n'a **aucune** surface HTTP
 entrante — il devient observable via `POST /internal/tech-steps/heartbeat`