diff --git a/frontend/scripts/test-ws-outbox.mjs b/frontend/scripts/test-ws-outbox.mjs
index 516396e..96c28d8 100644
--- a/frontend/scripts/test-ws-outbox.mjs
+++ b/frontend/scripts/test-ws-outbox.mjs
@@ -5,7 +5,7 @@ import { transform } from "esbuild";
 const source = await readFile(new URL("../src/shared/api/ws.ts", import.meta.url), "utf8");
 const { code } = await transform(source, { loader: "ts", format: "esm" });
 const moduleUrl = `data:text/javascript;base64,${Buffer.from(code).toString("base64")}`;
-const { callChannel, stationChannel } = await import(moduleUrl);
+const { callChannel, randomUuid, stationChannel } = await import(moduleUrl);
 const mergeSource = await readFile(new URL("../src/features/kio-card/merge.ts", import.meta.url), "utf8");
 const { code: mergeCode } = await transform(mergeSource, { loader: "ts", format: "esm" });
 const { applyPatch, applyState, edit, empty } = await import(
@@ -119,4 +119,19 @@ socket.receive({ type: "station.state", snapshot: { card_id: "card-1", reply_tex
 socket = reconnect(socket);
 assert.deepEqual(socket.sent, [], "matching persisted station snapshot clears the reply");
 
+// Стенд по http://<IP> — не защищённый контекст: randomUUID у браузера нет.
+const nativeRandomUuid = Object.getOwnPropertyDescriptor(globalThis.crypto, "randomUUID");
+Object.defineProperty(globalThis.crypto, "randomUUID", { value: undefined, configurable: true });
+try {
+  const ids = Array.from({ length: 200 }, () => randomUuid());
+  for (const id of ids) {
+    assert.match(id, /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/, "UUID v4 without randomUUID");
+  }
+  assert.equal(new Set(ids).size, ids.length, "UUIDs without randomUUID do not repeat");
+} finally {
+  if (nativeRandomUuid) Object.defineProperty(globalThis.crypto, "randomUUID", nativeRandomUuid);
+  else delete globalThis.crypto.randomUUID;
+}
+assert.match(randomUuid(), /^[0-9a-f-]{36}$/, "native randomUUID is used when present");
+
 console.log("WebSocket durable outbox replay/ack tests passed");
diff --git a/frontend/src/features/debrief/FindingReview.tsx b/frontend/src/features/debrief/FindingReview.tsx
index ef47f23..580d6af 100644
--- a/frontend/src/features/debrief/FindingReview.tsx
+++ b/frontend/src/features/debrief/FindingReview.tsx
@@ -5,6 +5,7 @@
 
 import { useRef, useState } from "react";
 
+import { randomUuid } from "@/shared/api/ws";
 import type { ErrorCode, FindingDecision, SessionReport } from "@/shared/types/generated";
 
 const DDS_CODES: ErrorCode[] = ["D1", "D2", "D3", "D4", "D5", "D6"];
@@ -77,7 +78,7 @@ export function FindingReview({ report, onChange }: {
       setError("Для отметки нужны факт и норма.");
       return;
     }
-    pendingId.current ??= crypto.randomUUID();
+    pendingId.current ??= randomUuid();
     const clientId = pendingId.current;
     void run(async () => {
       const updated = await send(base, {
diff --git a/frontend/src/pages/instructor/Instructor.tsx b/frontend/src/pages/instructor/Instructor.tsx
index 2cc8806..a2a97ec 100644
--- a/frontend/src/pages/instructor/Instructor.tsx
+++ b/frontend/src/pages/instructor/Instructor.tsx
@@ -25,6 +25,7 @@ import {
 } from "@/shared/api/http";
 import type { Signal } from "@/shared/api/http";
 import { sessionIdFromUrl } from "@/shared/api/session";
+import { randomUuid } from "@/shared/api/ws";
 import type { Level, SessionMode, SessionReport } from "@/shared/types/generated";
 
 const MODES: { value: SessionMode; label: string; hint: string }[] = [
@@ -214,7 +215,7 @@ export function Instructor() {
   function startLesson() {
     if (startPendingId || toStart.current || startDisabledReason) return;
     if (trainees.data?.length && (!traineeId || (traineeId === "__demo__" && !DEMO_MODE))) return;
-    const id = crypto.randomUUID();
+    const id = randomUuid();
     // Номер занятия живёт в адресе: монитор и АРМ курсанта открываются ссылкой.
     window.history.replaceState(null, "", `/instructor?session=${id}`);
     toStart.current = id;
diff --git a/frontend/src/shared/api/ws.ts b/frontend/src/shared/api/ws.ts
index 6012c6e..9179e8b 100644
--- a/frontend/src/shared/api/ws.ts
+++ b/frontend/src/shared/api/ws.ts
@@ -34,6 +34,18 @@ const BUFFER_MAX_ITEMS = 100;
 
 interface Buffered<Out> { key: string; commandId: string; event: Out; at: number }
 
+/** UUID v4 для номера занятия и команд. `crypto.randomUUID` браузер отдаёт только
+ *  в защищённом контексте (HTTPS, localhost): стенд по `http://<IP>` в классе
+ *  его не видит, и запуск занятия молча падал. `getRandomValues` есть везде. */
+export function randomUuid(): string {
+  if (typeof crypto.randomUUID === "function") return crypto.randomUUID();
+  const bytes = crypto.getRandomValues(new Uint8Array(16));
+  bytes[6] = (bytes[6] & 0x0f) | 0x40;
+  bytes[8] = (bytes[8] & 0x3f) | 0x80;
+  const hex = Array.from(bytes, (byte) => byte.toString(16).padStart(2, "0")).join("");
+  return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
+}
+
 export class Channel<In extends { type: string }, Out extends { type: string }> {
   private socket: WebSocket | null = null;
   private attempt = 0;
@@ -127,7 +139,7 @@ export class Channel<In extends { type: string }, Out extends { type: string }>
       existing.at = Date.now();
       pending = existing;
     } else {
-      pending = { key, commandId: crypto.randomUUID(), event, at: Date.now() };
+      pending = { key, commandId: randomUuid(), event, at: Date.now() };
       this.buffered.push(pending);
       if (this.buffered.length > BUFFER_MAX_ITEMS) this.buffered.shift();
     }
@@ -196,7 +208,7 @@ export const stationChannel = (
     if (event.type === "card.reply") return `card.reply:${event.card_id}`;
     // Non-replacement station actions are each their own replayable command.
     // The server deduplicates by this ID inside its persisted session snapshot.
-    return `command:${crypto.randomUUID()}`;
+    return `command:${randomUuid()}`;
   },
   isAcknowledged: (incoming, pending) => incoming.type === "station.state"
     && pending.type === "card.reply"