Update wire protocol to version 7 and enhance presence management features

- Bumped the wire protocol version to 7, reflecting significant changes in the communication structure.
- Introduced a new presence message type for real-time occupancy updates, including node activity and individual presence states.
- Updated the API to include a directory endpoint for fetching short id→name mappings, improving client-side name resolution.
- Revised the map snapshot structure to be static, with people and current lessons now handled through the presence stream.
- Enhanced client-side handling of presence updates, including UI adjustments to display live occupancy and activity.
- Updated documentation to reflect the new protocol features and changes in presence management.
- Added tests to validate the new presence functionalities and ensure robust handling of real-time data.

docs/phases/19-presence-screen.md

@@ -12,33 +12,33 @@
 
 ## Задачи
 
-- [ ] Новое сообщение присутствия, ~2 раза в секунду, только по открытой школе: узлы со
+- [x] Новое сообщение присутствия, ~2 раза в секунду, только по открытой школе: узлы со
       счётчиками и люди с их узлом и состоянием
-- [ ] Снимок карты становится **статическим**: люди и текущий урок уезжают в присутствие,
+- [x] Снимок карты становится **статическим**: люди и текущий урок уезжают в присутствие,
       структура уходит один раз при открытии. Пересылка на смене слота убирается
-- [ ] `ProtocolCodec.cs`, `protocol.ts` и `docs/protocol.md` правятся тем же коммитом, версия
+- [x] `ProtocolCodec.cs`, `protocol.ts` и `docs/protocol.md` правятся тем же коммитом, версия
       бумпится до 7
-- [ ] Справочник «id → имя» по HTTP: клиент забирает один раз при открытии школы и перечитывает,
+- [x] Справочник «id → имя» по HTTP: клиент забирает один раз при открытии школы и перечитывает,
       увидев незнакомый id. Имена в кадр присутствия не кладутся
-- [ ] Дерево: число людей рядом с узлом, живое. Пустой узел остаётся без числа
+- [x] Дерево: число людей рядом с узлом, живое. Пустой узел остаётся без числа
-- [ ] Панель локации: кто здесь сейчас, списком с именами; урок в комнате берётся из присутствия,
+- [x] Панель локации: кто здесь сейчас, списком с именами; урок в комнате берётся из присутствия,
       а не из снимка
-- [ ] Карточка человека: где он сейчас — узел, «в пути» или «вне школы»
+- [x] Карточка человека: где он сейчас — узел, «в пути» или «вне школы»
-- [ ] Присутствие приходит по всей школе, выбранный узел фильтрует клиент
+- [x] Присутствие приходит по всей школе, выбранный узел фильтрует клиент
-- [ ] Кадр часов несёт разрешение на пропуск; клиент это разрешение **не вычисляет**
+- [x] Кадр часов несёт разрешение на пропуск; клиент это разрешение **не вычисляет**
-- [ ] Намерение «пропустить» — своё сообщение, как пауза и скорость. Сервер проверяет условия
+- [x] Намерение «пропустить» — своё сообщение, как пауза и скорость. Сервер проверяет условия
       заново: кадр из браузера не доверенный
-- [ ] Кнопка рядом с паузой и скоростями: появляется только когда сервер разрешил, подписана
+- [x] Кнопка рядом с паузой и скоростями: появляется только когда сервер разрешил, подписана
       датой, к которой перенесёт
-- [ ] Строки через `t(...)`, обе локали
+- [x] Строки через `t(...)`, обе локали
 
 ## Тесты, без которых фаза не закрыта
 
-- [ ] Байтовая раскладка присутствия сходится с обеих сторон
+- [x] Байтовая раскладка присутствия сходится с обеих сторон
-- [ ] Круговой прогон сообщения: сервер → клиент → те же значения
+- [x] Круговой прогон сообщения: сервер → клиент → те же значения
-- [ ] Снимок карты больше не содержит людей и урока
+- [x] Снимок карты больше не содержит людей и урока
-- [ ] Кадр часов с разрешением на пропуск читается обеими сторонами одинаково
+- [x] Кадр часов с разрешением на пропуск читается обеими сторонами одинаково
-- [ ] Пропуск, присланный в учебное время, сервер отбрасывает, а не исполняет
+- [x] Пропуск, присланный в учебное время, сервер отбрасывает, а не исполняет
 
 ## Критерий готовности
 

docs/phases/README.md

@@ -83,7 +83,7 @@
 | Фаза | Статус | Зачем |
 | --- | --- | --- |
 | [18. Присутствие и ходьба](18-presence-walking.md) | ✅ | `HSchool.Ai`, место человека, маршруты, приход и уход |
-| [19. Присутствие на экране](19-presence-screen.md) | ⬜ | Своё сообщение ~2 Гц, числа в дереве, статический снимок карты, пропуск пустого времени |
+| [19. Присутствие на экране](19-presence-screen.md) | ✅ | Своё сообщение ~2 Гц, числа в дереве, статический снимок карты, пропуск пустого времени |
 
 **Этап B — поведение.** Появляются нужды, действия и выбор между ними и обязанностью.
 

docs/protocol.md

@@ -1,13 +1,13 @@
-# Wire protocol v6
+# Wire protocol v7
 
 The client talks to the server two ways:
 
 - **HTTP/JSON** for the main menu and the in-school people browser — listing, creating and
   deleting schools, listing mods, loading a catalog for the create editor, reading a school's
-  roster (filtered list + one-person card), staffing, and the timetable. Those are request/response
+  roster (filtered list + one-person card), a short id→name directory, staffing, and the timetable. Those are request/response
   by nature, so they are plain REST.
-- **A binary WebSocket at `/ws/game`** for the school calendar (20 Hz) and the map snapshot
+- **A binary WebSocket at `/ws/game`** for the school calendar (20 Hz), a static map snapshot
-  sent when a school is opened and whenever the current lesson slot changes.
+  sent once when a school is opened, and a presence stream (~2 Hz) of who is where.
 
 This document covers both. One protocol message per WebSocket frame, no framing header beyond the
 message id. **All multi-byte numbers are little-endian.**
@@ -188,6 +188,25 @@ Applicants live in `saves/{id}.people.json` next to the roster and are **not** i
 They are not school staff until hired. A parent who is also looking for work keeps the same id
 in both places.
 
+### `GET /api/schools/{id}/directory`
+
+Short id→name directory for the presence stream. Reads the **published roster snapshot**; it
+does not post to the worker. Unknown `{id}` is `404` `unknown-school`. `?lang=ru|en` is accepted
+for symmetry with the other people endpoints — names are stored as written and not translated.
+
+The client fetches this once on OpenSchool and again when a presence frame carries an unknown
+id. Names do not ride the WebSocket.
+
+```json
+{
+  "people": [
+    { "id": "f0.c0", "fullName": "Иванова Мария Петровна" }
+  ]
+}
+```
+
+Applicants are not in this list.
+
 ### `GET /api/schools/{id}/people/{personId}`
 
 One person's card. Goes through the school's mailbox because need values live on entities and
@@ -415,11 +434,13 @@ frame is obvious at a glance.
 | `0x04` | C → S | CloseSchool |
 | `0x05` | C → S | SetRunning |
 | `0x06` | C → S | SetSpeed |
+| `0x07` | C → S | SkipEmpty |
 | `0x81` | S → C | Welcome |
 | `0x82` | S → C | Pong |
 | `0x83` | S → C | Clock |
 | `0x84` | S → C | SchoolGone |
 | `0x85` | S → C | MapSnapshot |
+| `0x86` | S → C | Presence |
 
 ## Client → server
 
@@ -443,8 +464,9 @@ The locale byte is the same language the catalog HTTP API takes as `?lang=`.
 
 ### `0x03` OpenSchool — 5 bytes
 
-Starts watching a school: a map snapshot in the Hello locale arrives once, then clock frames.
+Starts watching a school: a map snapshot in the Hello locale arrives once, then clock frames
-It does not start the calendar — every school runs on its own from the moment it is created.
+and presence frames. It does not start the calendar — every school runs on its own from the
+moment it is created.
 
 | Offset | Type | Field |
 | --- | --- | --- |
@@ -478,6 +500,15 @@ Speed indexes are `0 = ×½`, `1 = ×1`, `2 = ×2`, `3 = ×3`, `4 = ×4`; out-of
 ignored rather than fatal. The base rate is `gameMinutesPerRealSecond` (5), so ×1 is five game
 minutes per real second.
 
+### `0x07` SkipEmpty — 1 byte
+
+Jump empty nights, weekends and holidays. The server re-checks both conditions (campus empty
+**and** outside the day-frame work window) — a frame from the browser is untrusted. Ignored
+when the skip is not legal; the calendar does not move.
+
+Running, speed and skip are **separate messages on purpose**. A button that also resent a
+neighbouring field would clobber it with a stale client copy.
+
 ## Server → client
 
 ### `0x81` Welcome — 4 bytes
@@ -499,9 +530,11 @@ The first frame the client receives.
 | 1 | `i64` | client clock, echoed unchanged |
 | 9 | `u32` | server tick when the ping was handled |
 
-### `0x83` Clock — 15 bytes
+### `0x83` Clock — 24 bytes
 
 Sent every tick to every connection that has a school open, and only to those.
+`skipAllowed` is the server's verdict; the client must not recompute it.
+`skipTargetUnixMs` is 0 when skip is refused.
 
 | Offset | Type | Field |
 | --- | --- | --- |
@@ -510,6 +543,8 @@ Sent every tick to every connection that has a school open, and only to those.
 | 5 | `i64` | in-game date, milliseconds since the Unix epoch, read as UTC |
 | 13 | `u8` | `1` running, `0` paused |
 | 14 | `u8` | speed index |
+| 15 | `u8` | `1` skip allowed, `0` refused |
+| 16 | `i64` | skip target, milliseconds since the Unix epoch, UTC; `0` if refused |
 
 ### `0x84` SchoolGone — 5 bytes
 
@@ -523,10 +558,8 @@ client returns to the menu.
 
 ### `0x85` MapSnapshot — variable
 
-Sent when a school is opened, on reconnect OpenSchool, and again when the current lesson slot
+Sent when a school is opened, and on reconnect OpenSchool. Structure only — people and the
-changes (a bell, a weekend, a holiday — not every tick, not on tree clicks). Labels are in the
+current lesson ride the presence stream. Labels are in the Hello locale.
-Hello locale. Occupancy is computed from the timetable and the clock; the client must not
-derive it.
 
 Strings are `u16` byte length + UTF-8. Empty string is a zero length.
 
@@ -548,24 +581,56 @@ Each node:
 | `u16` | pupil slots — how many pupils can take a lesson here. Summed from things on the server. |
 | `u8` | item count, then that many records of: string name + `u8` count |
 | `u8` | position count, then that many strings |
-| `u8` | `1` if a lesson is in this room right now, then subject label + class label strings; `0` if free |
-| `u8` | character count, then that many name strings (teacher and pupils of the lesson) |
 
-Item `count` is how many of that thing stand in the room (`Парта ×16` is one record, not sixteen). The client must not recompute pupil slots from items. The location panel draws activity and characters from the last two fields.
+Item `count` is how many of that thing stand in the room (`Парта ×16` is one record, not sixteen). The client must not recompute pupil slots from items.
+
+### `0x86` Presence — variable
+
+Live occupancy of an open school, about twice a second, and also once on OpenSchool and after
+a successful empty-time skip. Covers the whole map; the client filters to the selected tree
+node. Off-campus people are omitted — a missing id means they are away. Walking people occupy
+their **current** node. Names are resolved over HTTP, not on this frame.
+
+Nodes listed are occupied **or** currently taught (count may be 0). Sorted by id. Labels are
+in the Hello locale, encoded per client.
+
+| Offset | Type | Field |
+| --- | --- | --- |
+| 0 | `u8` | `0x86` |
+| 1 | `i32` | school id |
+| 5 | `u16` | node count |
+| 7… | | nodes, then `u16` person count, then people |
+
+Each node:
+
+| Type | Field |
+| --- | --- |
+| string | instance id |
+| `u16` | headcount in this node |
+| `u8` | `1` if a lesson is in this room right now, then subject label + class label strings; `0` if free |
+
+Each person:
+
+| Type | Field |
+| --- | --- |
+| string | person id |
+| string | node id they occupy |
+| `u8` | `1` here, `2` walking |
 
 ## Guarantees and limits
 
 - **Inbound** frames larger than 8 KiB are refused with close status `1009 MessageTooBig`. That
   limit is about what the server reads; it does not bound what the server sends. A `MapSnapshot`
-  of a large school legitimately exceeds it, and the server sizes that frame from the message.
+  or `Presence` frame of a large school legitimately exceeds it, and the server sizes those frames
+  from the message.
 - A malformed frame closes the connection with `1007 InvalidPayloadData`.
 - Unknown message ids are ignored rather than fatal, so new ids can be added without breaking
   older clients within the same protocol version.
 - Clock delivery is lossy under back pressure: each connection buffers 32 clock frames and drops
   the oldest, because a stale clock is worthless once a newer one exists.
-- The map snapshot uses a separate reliable queue so ticks cannot crowd it out.
+- The map snapshot and presence use a separate reliable queue so ticks cannot crowd them out.
 
-## Not in v6 yet
+## Not in v7 yet
 
-Authentication, Sit orders, an event log, walking, and `OpenLocation` on the server — the tree is
+Authentication, Sit orders, an event log, walk animation, and `OpenLocation` on the server —
-filtered on the client from the snapshot.
+the tree and the location panel are filtered on the client from the snapshot plus presence.

src/HSchool.Client/src/i18n/strings.test.ts

@@ -26,6 +26,9 @@ describe('t', () => {
       .toBe('Not enough money: 8 000 of 10 000 is committed, 2 000 free, 12 000 needed.');
     expect(t('mapOccupancy', { name: 'Кабинет 204', activity: 'Математика · 5Б' }))
       .toBe('Кабинет 204 (Математика · 5Б)');
+    expect(t('mapHeadcount', { name: 'Коридор', count: 12 })).toBe('Коридор (12)');
+    expect(t('mapHeadcountActivity', { name: 'Класс 101', count: 18, activity: 'Математика · 5А' }))
+      .toBe('Класс 101 (18 · Математика · 5А)');
   });
 });
 

src/HSchool.Client/src/i18n/strings.ts

@@ -169,6 +169,12 @@ const ru = {
   staffErrorSubject: 'Такого предмета нет.',
 
   mapOccupancy: '{name} ({activity})',
+  mapHeadcount: '{name} ({count})',
+  mapHeadcountActivity: '{name} ({count} · {activity})',
+  skipTo: 'Пропустить до {date}',
+  presenceAt: '{name}',
+  presenceWalking: 'в пути ({name})',
+  presenceAway: 'вне школы',
   timetableTitle: 'Расписание',
   timetableClass: 'Класс',
   timetableEmpty: 'Нет уроков.',
@@ -360,6 +366,12 @@ const en: Messages = {
   staffErrorSubject: 'That subject is not in the catalog.',
 
   mapOccupancy: '{name} ({activity})',
+  mapHeadcount: '{name} ({count})',
+  mapHeadcountActivity: '{name} ({count} · {activity})',
+  skipTo: 'Skip to {date}',
+  presenceAt: '{name}',
+  presenceWalking: 'walking ({name})',
+  presenceAway: 'off campus',
   timetableTitle: 'Timetable',
   timetableClass: 'Class',
   timetableEmpty: 'No lessons.',

src/HSchool.Client/src/main.ts

@@ -32,6 +32,7 @@ function bootstrap(): void {
     onLeave: () => leaveSchool(),
     onSetRunning: (running) => connection.setRunning(running),
     onSetSpeed: (speedIndex) => connection.setSpeed(speedIndex),
+    onSkip: () => connection.skipEmpty(),
   });
 
   const connection = new GameConnection(gameSocketUrl(), {
@@ -49,6 +50,11 @@ function bootstrap(): void {
         game.applyMap(snapshot.schoolId, snapshot.nodes);
       }
     },
+    onPresence: (presence) => {
+      if (openSchool?.id === presence.schoolId) {
+        game.applyPresence(presence.schoolId, presence);
+      }
+    },
     onSchoolGone: (schoolId) => {
       // Deleted from another tab while we were inside it.
       if (openSchool?.id === schoolId) {

src/HSchool.Client/src/net/api.ts

@@ -292,6 +292,19 @@ export async function fetchPerson(schoolId: number, personId: string, lang: stri
   );
 }
 
+export interface DirectoryPerson {
+  readonly id: string;
+  readonly fullName: string;
+}
+
+export async function fetchDirectory(schoolId: number, lang: string): Promise<readonly DirectoryPerson[]> {
+  const params = new URLSearchParams({ lang });
+  const response = await request<{ people: readonly DirectoryPerson[] }>(
+    `/api/schools/${schoolId}/directory?${params.toString()}`,
+  );
+  return response.people;
+}
+
 export interface StaffingSubject {
   readonly defName: string;
   readonly label: string;

src/HSchool.Client/src/net/connection.ts

@@ -6,9 +6,11 @@ import {
   encodePing,
   encodeSetRunning,
   encodeSetSpeed,
+  encodeSkipEmpty,
   ProtocolError,
   type ClockMessage,
   type MapSnapshotMessage,
+  type PresenceMessage,
   type ServerMessage,
   type WelcomeMessage,
 } from './protocol.ts';
@@ -20,6 +22,7 @@ export interface ConnectionHandlers {
   onWelcome?(message: WelcomeMessage): void;
   onClock?(message: ClockMessage): void;
   onMapSnapshot?(message: MapSnapshotMessage): void;
+  onPresence?(message: PresenceMessage): void;
   /** The open school was deleted elsewhere; the UI has to leave it. */
   onSchoolGone?(schoolId: number): void;
   /** Round-trip time in milliseconds. */
@@ -118,6 +121,10 @@ export class GameConnection {
     this.send(encodeSetSpeed(speedIndex));
   }
 
+  skipEmpty(): void {
+    this.send(encodeSkipEmpty());
+  }
+
   close(): void {
     this.closedByUs = true;
     this.stopTimers();
@@ -162,6 +169,9 @@ export class GameConnection {
       case 'map-snapshot':
         this.handlers.onMapSnapshot?.(message);
         break;
+      case 'presence':
+        this.handlers.onPresence?.(message);
+        break;
       case 'school-gone':
         if (this.openSchoolId === message.schoolId) {
           this.openSchoolId = null;

src/HSchool.Client/src/net/protocol.test.ts

@@ -8,7 +8,9 @@ import {
   encodePing,
   encodeSetRunning,
   encodeSetSpeed,
+  encodeSkipEmpty,
   MessageType,
+  PresenceState,
   ProtocolError,
   PROTOCOL_VERSION,
 } from './protocol.ts';
@@ -66,6 +68,13 @@ describe('client encoders', () => {
     expect(view.getUint8(0)).toBe(MessageType.ClientSetSpeed);
     expect(view.getUint8(1)).toBe(4);
   });
+
+  it('writes a single-byte skip', () => {
+    const view = new DataView(encodeSkipEmpty());
+
+    expect(view.byteLength).toBe(1);
+    expect(view.getUint8(0)).toBe(MessageType.ClientSkipEmpty);
+  });
 });
 
 describe('decodeServerMessage', () => {
@@ -85,16 +94,19 @@ describe('decodeServerMessage', () => {
     });
   });
 
-  it('reads a clock frame as a UTC instant', () => {
+  it('reads a clock frame as a UTC instant, including skip permission', () => {
-    // 2012-04-03T06:00:00Z
+    // 2012-04-03T06:00:00Z → skip to 2012-04-04T06:00:00Z
     const gameTimeMs = Date.UTC(2012, 3, 3, 6, 0, 0);
-    const buffer = new ArrayBuffer(15);
+    const skipTargetMs = Date.UTC(2012, 3, 4, 6, 0, 0);
+    const buffer = new ArrayBuffer(24);
     const view = new DataView(buffer);
     view.setUint8(0, MessageType.ServerClock);
     view.setInt32(1, 7, true);
     view.setBigInt64(5, BigInt(gameTimeMs), true);
     view.setUint8(13, 1);
     view.setUint8(14, 2);
+    view.setUint8(15, 1);
+    view.setBigInt64(16, BigInt(skipTargetMs), true);
 
     expect(decodeServerMessage(buffer)).toEqual({
       type: 'clock',
@@ -102,6 +114,8 @@ describe('decodeServerMessage', () => {
       gameTime: new Date(gameTimeMs),
       running: true,
       speedIndex: 2,
+      skipAllowed: true,
+      skipTarget: new Date(skipTargetMs),
     });
   });
 
@@ -129,7 +143,7 @@ describe('decodeServerMessage', () => {
     const id = encoder.encode('yard');
     const parent = encoder.encode('');
     const name = encoder.encode('Двор');
-    const buffer = new ArrayBuffer(7 + 1 + 2 + id.length + 2 + parent.length + 2 + name.length + 2 + 1 + 1 + 1 + 1);
+    const buffer = new ArrayBuffer(7 + 1 + 2 + id.length + 2 + parent.length + 2 + name.length + 2 + 1 + 1);
     const view = new DataView(buffer);
     view.setUint8(0, MessageType.ServerMapSnapshot);
     view.setInt32(1, 7, true);
@@ -152,10 +166,6 @@ describe('decodeServerMessage', () => {
     view.setUint8(offset, 0);
     offset += 1;
     view.setUint8(offset, 0);
-    offset += 1;
-    view.setUint8(offset, 0);
-    offset += 1;
-    view.setUint8(offset, 0);
 
     expect(decodeServerMessage(buffer)).toEqual({
       type: 'map-snapshot',
@@ -169,9 +179,6 @@ describe('decodeServerMessage', () => {
           pupilSlots: 0,
           items: [],
           positions: [],
-          activitySubject: '',
-          activityClass: '',
-          characters: [],
         },
       ],
     });
@@ -184,7 +191,7 @@ describe('decodeServerMessage', () => {
     const name = encoder.encode('Класс 1A');
     const itemName = encoder.encode('Парта');
     const buffer = new ArrayBuffer(
-      7 + 1 + 2 + id.length + 2 + parent.length + 2 + name.length + 2 + 1 + 2 + itemName.length + 1 + 1 + 1 + 1,
+      7 + 1 + 2 + id.length + 2 + parent.length + 2 + name.length + 2 + 1 + 2 + itemName.length + 1 + 1,
     );
     const view = new DataView(buffer);
     view.setUint8(0, MessageType.ServerMapSnapshot);
@@ -216,10 +223,6 @@ describe('decodeServerMessage', () => {
     view.setUint8(offset, 16);
     offset += 1;
     view.setUint8(offset, 0);
-    offset += 1;
-    view.setUint8(offset, 0);
-    offset += 1;
-    view.setUint8(offset, 0);
 
     expect(decodeServerMessage(buffer)).toEqual({
       type: 'map-snapshot',
@@ -233,71 +236,41 @@ describe('decodeServerMessage', () => {
           pupilSlots: 16,
           items: [{ name: 'Парта', count: 16 }],
           positions: [],
-          activitySubject: '',
-          activityClass: '',
-          characters: [],
         },
       ],
     });
   });
 
-  it('reads occupancy after positions', () => {
+  it('reads a presence frame with node activity and people', () => {
     const encoder = new TextEncoder();
-    const id = encoder.encode('classroom-101');
+    const nodeId = encoder.encode('classroom-101');
-    const parent = encoder.encode('floor-1');
-    const name = encoder.encode('Класс 101');
-    const itemName = encoder.encode('Парта');
     const subject = encoder.encode('Математика');
     const schoolClass = encoder.encode('5А');
-    const teacher = encoder.encode('Иванова');
+    const personId = encoder.encode('f0.c0');
+    const personNode = encoder.encode('classroom-101');
     const buffer = new ArrayBuffer(
       7
-        + 1
+        + 2 + nodeId.length
-        + 2 + id.length
-        + 2 + parent.length
-        + 2 + name.length
         + 2
         + 1
-        + 2 + itemName.length
-        + 1
-        + 1
-        + 1
         + 2 + subject.length
         + 2 + schoolClass.length
-        + 1
+        + 2
-        + 2 + teacher.length,
+        + 2 + personId.length
+        + 2 + personNode.length
+        + 1,
     );
     const view = new DataView(buffer);
-    view.setUint8(0, MessageType.ServerMapSnapshot);
+    view.setUint8(0, MessageType.ServerPresence);
     view.setInt32(1, 3, true);
     view.setUint16(5, 1, true);
     let offset = 7;
-    view.setUint8(offset, 3);
+    view.setUint16(offset, nodeId.length, true);
-    offset += 1;
-    view.setUint16(offset, id.length, true);
     offset += 2;
-    new Uint8Array(buffer).set(id, offset);
+    new Uint8Array(buffer).set(nodeId, offset);
-    offset += id.length;
+    offset += nodeId.length;
-    view.setUint16(offset, parent.length, true);
+    view.setUint16(offset, 18, true);
     offset += 2;
-    new Uint8Array(buffer).set(parent, offset);
-    offset += parent.length;
-    view.setUint16(offset, name.length, true);
-    offset += 2;
-    new Uint8Array(buffer).set(name, offset);
-    offset += name.length;
-    view.setUint16(offset, 16, true);
-    offset += 2;
-    view.setUint8(offset, 1);
-    offset += 1;
-    view.setUint16(offset, itemName.length, true);
-    offset += 2;
-    new Uint8Array(buffer).set(itemName, offset);
-    offset += itemName.length;
-    view.setUint8(offset, 16);
-    offset += 1;
-    view.setUint8(offset, 0);
-    offset += 1;
     view.setUint8(offset, 1);
     offset += 1;
     view.setUint16(offset, subject.length, true);
@@ -308,29 +281,30 @@ describe('decodeServerMessage', () => {
     offset += 2;
     new Uint8Array(buffer).set(schoolClass, offset);
     offset += schoolClass.length;
-    view.setUint8(offset, 1);
+    view.setUint16(offset, 1, true);
-    offset += 1;
-    view.setUint16(offset, teacher.length, true);
     offset += 2;
-    new Uint8Array(buffer).set(teacher, offset);
+    view.setUint16(offset, personId.length, true);
+    offset += 2;
+    new Uint8Array(buffer).set(personId, offset);
+    offset += personId.length;
+    view.setUint16(offset, personNode.length, true);
+    offset += 2;
+    new Uint8Array(buffer).set(personNode, offset);
+    offset += personNode.length;
+    view.setUint8(offset, PresenceState.Here);
 
     expect(decodeServerMessage(buffer)).toEqual({
-      type: 'map-snapshot',
+      type: 'presence',
       schoolId: 3,
       nodes: [
         {
-          kind: 3,
           id: 'classroom-101',
-          parentId: 'floor-1',
+          count: 18,
-          name: 'Класс 101',
-          pupilSlots: 16,
-          items: [{ name: 'Парта', count: 16 }],
-          positions: [],
           activitySubject: 'Математика',
           activityClass: '5А',
-          characters: ['Иванова'],
         },
       ],
+      people: [{ id: 'f0.c0', nodeId: 'classroom-101', state: PresenceState.Here }],
     });
   });
 

src/HSchool.Client/src/net/protocol.ts

@@ -5,7 +5,7 @@
  * changed together and documented in `docs/protocol.md`. All numbers are little-endian.
  */
 
-export const PROTOCOL_VERSION = 6;
+export const PROTOCOL_VERSION = 7;
 
 export const MessageType = {
   ClientHello: 0x01,
@@ -14,11 +14,13 @@ export const MessageType = {
   ClientCloseSchool: 0x04,
   ClientSetRunning: 0x05,
   ClientSetSpeed: 0x06,
+  ClientSkipEmpty: 0x07,
   ServerWelcome: 0x81,
   ServerPong: 0x82,
   ServerClock: 0x83,
   ServerSchoolGone: 0x84,
   ServerMapSnapshot: 0x85,
+  ServerPresence: 0x86,
 } as const;
 
 /** Hello locale byte. Same mapping as `?lang=` on the catalog HTTP API. */
@@ -55,6 +57,10 @@ export interface ClockMessage {
   readonly gameTime: Date;
   readonly running: boolean;
   readonly speedIndex: number;
+  /** Server verdict; the client must not recompute this. */
+  readonly skipAllowed: boolean;
+  /** UTC instant the skip would land on; null when skip is refused. */
+  readonly skipTarget: Date | null;
 }
 
 export interface SchoolGoneMessage {
@@ -82,9 +88,6 @@ export interface MapSnapshotNode {
   readonly pupilSlots: number;
   readonly items: readonly MapSnapshotItem[];
   readonly positions: readonly string[];
-  readonly activitySubject: string;
-  readonly activityClass: string;
-  readonly characters: readonly string[];
 }
 
 export interface MapSnapshotMessage {
@@ -93,12 +96,38 @@ export interface MapSnapshotMessage {
   readonly nodes: readonly MapSnapshotNode[];
 }
 
+export const PresenceState = {
+  Here: 1,
+  Walking: 2,
+} as const;
+
+export interface PresenceNode {
+  readonly id: string;
+  readonly count: number;
+  readonly activitySubject: string;
+  readonly activityClass: string;
+}
+
+export interface PresencePerson {
+  readonly id: string;
+  readonly nodeId: string;
+  readonly state: number;
+}
+
+export interface PresenceMessage {
+  readonly type: 'presence';
+  readonly schoolId: number;
+  readonly nodes: readonly PresenceNode[];
+  readonly people: readonly PresencePerson[];
+}
+
 export type ServerMessage =
   | WelcomeMessage
   | PongMessage
   | ClockMessage
   | SchoolGoneMessage
-  | MapSnapshotMessage;
+  | MapSnapshotMessage
+  | PresenceMessage;
 
 /** Thrown when a frame is truncated or carries an unexpected message id. */
 export class ProtocolError extends Error {}
@@ -165,6 +194,12 @@ export function encodeSetSpeed(speedIndex: number): ArrayBuffer {
   return buffer;
 }
 
+export function encodeSkipEmpty(): ArrayBuffer {
+  const buffer = new ArrayBuffer(1);
+  new DataView(buffer).setUint8(0, MessageType.ClientSkipEmpty);
+  return buffer;
+}
+
 /** Decodes one server frame. Unknown message ids return `null` so new ids stay backwards compatible. */
 export function decodeServerMessage(data: ArrayBuffer): ServerMessage | null {
   if (data.byteLength === 0) {
@@ -184,6 +219,8 @@ export function decodeServerMessage(data: ArrayBuffer): ServerMessage | null {
       return decodeSchoolGone(view);
     case MessageType.ServerMapSnapshot:
       return decodeMapSnapshot(view);
+    case MessageType.ServerPresence:
+      return decodePresence(view);
     default:
       return null;
   }
@@ -211,7 +248,8 @@ function decodePong(view: DataView): PongMessage {
 }
 
 function decodeClock(view: DataView): ClockMessage {
-  ensure(view, 15);
+  ensure(view, 24);
+  const skipTargetMs = Number(view.getBigInt64(16, true));
 
   return {
     type: 'clock',
@@ -219,6 +257,8 @@ function decodeClock(view: DataView): ClockMessage {
     gameTime: new Date(Number(view.getBigInt64(5, true))),
     running: view.getUint8(13) !== 0,
     speedIndex: view.getUint8(14),
+    skipAllowed: view.getUint8(15) !== 0,
+    skipTarget: skipTargetMs === 0 ? null : new Date(skipTargetMs),
   };
 }
 
@@ -268,6 +308,34 @@ function decodeMapSnapshot(view: DataView): MapSnapshotMessage {
       offset = value.next;
     }
 
+    nodes.push({
+      kind,
+      id: id.text,
+      parentId: parentId.text,
+      name: name.text,
+      pupilSlots,
+      items,
+      positions,
+    });
+  }
+
+  return { type: 'map-snapshot', schoolId, nodes };
+}
+
+function decodePresence(view: DataView): PresenceMessage {
+  ensure(view, 7);
+
+  const schoolId = view.getInt32(1, true);
+  const nodeCount = view.getUint16(5, true);
+  let offset = 7;
+  const nodes: PresenceNode[] = [];
+
+  for (let i = 0; i < nodeCount; i++) {
+    const id = readString(view, offset);
+    offset = id.next;
+    ensure(view, offset + 2);
+    const count = view.getUint16(offset, true);
+    offset += 2;
     const hasActivity = readU8(view, offset);
     offset += 1;
     let activitySubject = '';
@@ -281,30 +349,24 @@ function decodeMapSnapshot(view: DataView): MapSnapshotMessage {
       activityClass = schoolClass.text;
     }
 
-    const characterCount = readU8(view, offset);
+    nodes.push({ id: id.text, count, activitySubject, activityClass });
-    offset += 1;
-    const characters: string[] = [];
-    for (let person = 0; person < characterCount; person++) {
-      const value = readString(view, offset);
-      characters.push(value.text);
-      offset = value.next;
-    }
-
-    nodes.push({
-      kind,
-      id: id.text,
-      parentId: parentId.text,
-      name: name.text,
-      pupilSlots,
-      items,
-      positions,
-      activitySubject,
-      activityClass,
-      characters,
-    });
   }
 
-  return { type: 'map-snapshot', schoolId, nodes };
+  ensure(view, offset + 2);
+  const personCount = view.getUint16(offset, true);
+  offset += 2;
+  const people: PresencePerson[] = [];
+  for (let i = 0; i < personCount; i++) {
+    const id = readString(view, offset);
+    offset = id.next;
+    const nodeId = readString(view, offset);
+    offset = nodeId.next;
+    const state = readU8(view, offset);
+    offset += 1;
+    people.push({ id: id.text, nodeId: nodeId.text, state });
+  }
+
+  return { type: 'presence', schoolId, nodes, people };
 }
 
 function readU8(view: DataView, offset: number): number {

src/HSchool.Client/src/ui/gameScreen.ts

@@ -1,23 +1,34 @@
-import { CLOCK_SPEEDS, type ClockMessage, type MapSnapshotItem, type MapSnapshotNode } from '../net/protocol.ts';
+import {
-import { formatGameDate, formatGameTimeOfDay, formatGameWeekday } from '../format/gameTime.ts';
+  CLOCK_SPEEDS,
+  PresenceState,
+  type ClockMessage,
+  type MapSnapshotItem,
+  type MapSnapshotNode,
+  type PresenceMessage,
+  type PresenceNode,
+} from '../net/protocol.ts';
+import { formatGameDate, formatGameDateTime, formatGameTimeOfDay, formatGameWeekday } from '../format/gameTime.ts';
+import { getLocale } from '../i18n/locale.ts';
 import { t } from '../i18n/strings.ts';
-import type { School } from '../net/api.ts';
+import { fetchDirectory, type School } from '../net/api.ts';
 import { clear, el } from './dom.ts';
 import { ManagementPanel } from './managementPanel.ts';
 import { PeoplePanel } from './peoplePanel.ts';
+import { formatPersonPlace } from './personCard.ts';
 
 interface GameScreenOptions {
   readonly onLeave: () => void;
   readonly onSetRunning: (running: boolean) => void;
   readonly onSetSpeed: (speedIndex: number) => void;
+  readonly onSkip: () => void;
 }
 
 const SPEED_LABELS = ['×½', '×1', '×2', '×3', '×4'];
 
 /**
- * The inside of a school: calendar controls plus the manager shell. The tree and location
+ * The inside of a school: calendar controls plus the manager shell. The tree comes from one map
- * lists come from one map snapshot on OpenSchool; clicking a node only filters that snapshot
+ * snapshot on OpenSchool; presence (~2 Hz) paints headcount and who is here. Clicking a node
- * on the client. The people panel loads its page over HTTP.
+ * only filters on the client. The people panel loads its page over HTTP.
  */
 export class GameScreen {
   private readonly root = el('section', { class: 'screen game' });
@@ -27,6 +38,7 @@ export class GameScreen {
   private readonly date = el('p', { class: 'clock__date' });
   private readonly weekday = el('p', { class: 'clock__weekday' });
   private readonly playPauseButton = el('button', { class: 'button button--icon', type: 'button', text: '▶' });
+  private readonly skipButton = el('button', { class: 'button button--small', type: 'button' });
   private readonly speedButtons: HTMLButtonElement[];
 
   private readonly mapTab = el('button', { class: 'panel__tab', type: 'button' });
@@ -62,11 +74,16 @@ export class GameScreen {
 
   private readonly treeButtons = new Map<string, HTMLButtonElement>();
   private nodes: readonly MapSnapshotNode[] = [];
+  private presence: PresenceMessage | null = null;
+  private directory = new Map<string, string>();
+  private directoryToken = 0;
   private selectedId: string | null = null;
   private schoolId: number | null = null;
   private running = false;
   private lastGameTime: Date | null = null;
   private lastSpeedIndex = 0;
+  private skipAllowed = false;
+  private skipTarget: Date | null = null;
   private inspected: 'location' | 'person' = 'location';
 
   constructor(options: GameScreenOptions) {
@@ -81,6 +98,8 @@ export class GameScreen {
 
     this.backButton.addEventListener('click', options.onLeave);
     this.playPauseButton.addEventListener('click', () => options.onSetRunning(!this.running));
+    this.skipButton.addEventListener('click', () => options.onSkip());
+    this.skipButton.hidden = true;
 
     this.root.append(
       el('header', { class: 'screen__header' }, this.backButton, this.schoolName),
@@ -93,7 +112,7 @@ export class GameScreen {
           this.time,
           el('div', { class: 'clockbar__labels' }, this.date, this.weekday),
         ),
-        el('div', { class: 'clock__controls' }, this.playPauseButton, ...this.speedButtons),
+        el('div', { class: 'clock__controls' }, this.playPauseButton, ...this.speedButtons, this.skipButton),
       ),
       el('div', { class: 'mode-tabs' }, this.overviewTab, this.manageTab),
       this.overview,
@@ -163,10 +182,14 @@ export class GameScreen {
     this.paintSelection();
 
     if (this.lastGameTime !== null) {
-      this.applyClock(this.lastGameTime, this.running, this.lastSpeedIndex);
+      this.applyClock(this.lastGameTime, this.running, this.lastSpeedIndex, this.skipAllowed, this.skipTarget);
     } else {
       this.playPauseButton.title = t('resume');
     }
+
+    this.paintSkip();
+    this.people.setLocate((id) => this.placeOf(id));
+    this.management.setLocate((id) => this.placeOf(id));
   }
 
   /** Called when the screen opens, before the first clock frame and snapshot arrive. */
@@ -174,18 +197,25 @@ export class GameScreen {
     this.schoolId = school.id;
     this.schoolName.textContent = school.name;
     this.nodes = [];
+    this.presence = null;
+    this.directory = new Map();
     this.selectedId = null;
+    this.skipAllowed = false;
+    this.skipTarget = null;
     this.rebuildTree();
-    this.applyClock(new Date(school.gameTime), school.running, school.speedIndex);
+    this.applyClock(new Date(school.gameTime), school.running, school.speedIndex, false, null);
     this.people.show(school.id);
+    this.people.setLocate((id) => this.placeOf(id));
+    this.management.setLocate((id) => this.placeOf(id));
     this.showTab('map');
     this.inspect('location');
     this.showMode('overview');
+    void this.loadDirectory();
   }
 
   /**
-   * The server sends the tree on OpenSchool and again when the current lesson slot changes.
+   * The server sends the tree once on OpenSchool. Occupancy is on the presence stream; this
-   * Occupancy is on the snapshot; this screen must not derive who is where from the clock.
+   * screen must not derive who is where from the clock.
    */
   applyMap(schoolId: number, nodes: readonly MapSnapshotNode[]): void {
     if (this.schoolId !== schoolId) {
@@ -200,8 +230,23 @@ export class GameScreen {
     this.paintSelection();
   }
 
+  applyPresence(schoolId: number, message: PresenceMessage): void {
+    if (this.schoolId !== schoolId) {
+      return;
+    }
+
+    this.presence = message;
+    this.paintTreeLabels();
+    this.paintSelection();
+    this.people.setLocate((id) => this.placeOf(id));
+    this.management.setLocate((id) => this.placeOf(id));
+    if (message.people.some((person) => !this.directory.has(person.id))) {
+      void this.loadDirectory();
+    }
+  }
+
   update(clock: ClockMessage): void {
-    this.applyClock(clock.gameTime, clock.running, clock.speedIndex);
+    this.applyClock(clock.gameTime, clock.running, clock.speedIndex, clock.skipAllowed, clock.skipTarget);
   }
 
   private rebuildTree(): void {
@@ -216,7 +261,7 @@ export class GameScreen {
       const button = el('button', {
         class: 'tree__button',
         type: 'button',
-        text: treeLabel(node),
+        text: treeLabel(node, this.liveNode(node.id)),
         onClick: () => this.select(node.id),
       });
       button.style.paddingLeft = `${8 + depth * 14}px`;
@@ -282,29 +327,38 @@ export class GameScreen {
     }
 
     const node = this.nodes.find((candidate) => candidate.id === this.selectedId);
+    const live = this.liveNode(this.selectedId);
     this.locationName.textContent = node?.name ?? '';
     paintList(this.itemsList, this.itemsEmpty, (node?.items ?? []).map(formatItem));
     const pupilSlots = node?.pupilSlots ?? 0;
     this.pupilSlotsLine.hidden = pupilSlots <= 0;
     this.pupilSlotsLine.textContent = pupilSlots > 0 ? t('pupilSlots', { count: pupilSlots }) : '';
     const activity = [];
-    if (node?.activitySubject) {
+    if (live?.activitySubject) {
-      activity.push(node.activitySubject);
+      activity.push(live.activitySubject);
     }
 
-    if (node?.activityClass) {
+    if (live?.activityClass) {
-      activity.push(node.activityClass);
+      activity.push(live.activityClass);
     }
 
     paintList(this.activitiesList, this.activitiesEmpty, activity);
-    paintList(this.charactersList, this.charactersEmpty, node?.characters ?? []);
+    paintList(this.charactersList, this.charactersEmpty, this.peopleAt(this.selectedId));
     paintList(this.positionsList, this.positionsEmpty, node?.positions ?? []);
   }
 
-  private applyClock(gameTime: Date, running: boolean, speedIndex: number): void {
+  private applyClock(
+    gameTime: Date,
+    running: boolean,
+    speedIndex: number,
+    skipAllowed: boolean,
+    skipTarget: Date | null,
+  ): void {
     this.running = running;
     this.lastGameTime = gameTime;
     this.lastSpeedIndex = speedIndex;
+    this.skipAllowed = skipAllowed;
+    this.skipTarget = skipTarget;
 
     this.time.textContent = formatGameTimeOfDay(gameTime);
     this.date.textContent = formatGameDate(gameTime);
@@ -316,6 +370,76 @@ export class GameScreen {
     this.speedButtons.forEach((button, index) => {
       button.classList.toggle('button--active', index === speedIndex);
     });
+    this.paintSkip();
+  }
+
+  private paintSkip(): void {
+    const allowed = this.skipAllowed && this.skipTarget !== null;
+    this.skipButton.hidden = !allowed;
+    this.skipButton.textContent = allowed && this.skipTarget !== null
+      ? t('skipTo', { date: formatGameDateTime(this.skipTarget) })
+      : '';
+  }
+
+  private paintTreeLabels(): void {
+    for (const [id, button] of this.treeButtons) {
+      const node = this.nodes.find((candidate) => candidate.id === id);
+      if (node !== undefined) {
+        button.textContent = treeLabel(node, this.liveNode(id));
+      }
+    }
+  }
+
+  private liveNode(id: string | null): PresenceNode | undefined {
+    if (id === null || this.presence === null) {
+      return undefined;
+    }
+
+    return this.presence.nodes.find((node) => node.id === id);
+  }
+
+  private peopleAt(id: string | null): string[] {
+    if (id === null || this.presence === null) {
+      return [];
+    }
+
+    const names = this.presence.people
+      .filter((person) => person.nodeId === id)
+      .map((person) => this.directory.get(person.id) ?? person.id);
+    names.sort((left, right) => left.localeCompare(right));
+    return names;
+  }
+
+  private placeOf(id: string): string {
+    const person = this.presence?.people.find((candidate) => candidate.id === id);
+    if (person === undefined) {
+      return formatPersonPlace('away');
+    }
+
+    const nodeName = this.nodes.find((node) => node.id === person.nodeId)?.name ?? person.nodeId;
+    return formatPersonPlace(person.state === PresenceState.Walking ? 'walking' : 'here', nodeName);
+  }
+
+  private async loadDirectory(): Promise<void> {
+    const schoolId = this.schoolId;
+    if (schoolId === null) {
+      return;
+    }
+
+    const token = ++this.directoryToken;
+    try {
+      const people = await fetchDirectory(schoolId, getLocale());
+      if (token !== this.directoryToken || this.schoolId !== schoolId) {
+        return;
+      }
+
+      this.directory = new Map(people.map((person) => [person.id, person.fullName]));
+      this.paintSelection();
+      this.people.setLocate((id) => this.placeOf(id));
+      this.management.setLocate((id) => this.placeOf(id));
+    } catch {
+      // Names stay as ids until the next presence frame retries.
+    }
   }
 }
 
@@ -323,8 +447,17 @@ function childrenOf(nodes: readonly MapSnapshotNode[], parentId: string): MapSna
   return nodes.filter((node) => node.parentId === parentId);
 }
 
-function treeLabel(node: MapSnapshotNode): string {
+function treeLabel(node: MapSnapshotNode, live: PresenceNode | undefined): string {
-  const activity = [node.activitySubject, node.activityClass].filter((part) => part.length > 0).join(' · ');
+  const count = live?.count ?? 0;
+  const activity = [live?.activitySubject ?? '', live?.activityClass ?? ''].filter((part) => part.length > 0).join(' · ');
+  if (count > 0 && activity.length > 0) {
+    return t('mapHeadcountActivity', { name: node.name, count, activity });
+  }
+
+  if (count > 0) {
+    return t('mapHeadcount', { name: node.name, count });
+  }
+
   return activity.length > 0 ? t('mapOccupancy', { name: node.name, activity }) : node.name;
 }
 

src/HSchool.Client/src/ui/managementPanel.ts

@@ -15,7 +15,7 @@ import {
 import { getLocale, intlTag } from '../i18n/locale.ts';
 import { t } from '../i18n/strings.ts';
 import { clear, el } from './dom.ts';
-import { renderPersonCard } from './personCard.ts';
+import { formatPersonPlace, renderPersonCard } from './personCard.ts';
 import { personTimetableQuery, TimetableGrid } from './timetableGrid.ts';
 
 const TEACHER = 'Teacher';
@@ -67,6 +67,8 @@ export class ManagementPanel {
   private loadToken = 0;
   private cardToken = 0;
   private busy = false;
+  private locate: ((id: string) => string) | null = null;
+  private painted: PersonCard | null = null;
 
   constructor() {
     this.error.hidden = true;
@@ -139,6 +141,11 @@ export class ManagementPanel {
     void this.reload();
   }
 
+  setLocate(locate: (id: string) => string): void {
+    this.locate = locate;
+    this.relocate();
+  }
+
   private async reload(): Promise<void> {
     const schoolId = this.schoolId;
     if (schoolId === null) {
@@ -401,16 +408,30 @@ export class ManagementPanel {
 
   private paintCard(card: PersonCard | null): void {
     clear(this.card);
+    this.painted = card;
     if (card === null) {
       this.card.append(el('p', { class: 'panel__empty', text: t('staffPickHint') }));
       return;
     }
 
-    renderPersonCard(this.card, card, (id) => void this.openRelative(id));
+    renderPersonCard(this.card, card, (id) => void this.openRelative(id), this.placeOf(card.id));
     this.mountPersonTimetable(card);
     this.appendActions(card.id);
   }
 
+  private relocate(): void {
+    const line = this.card.querySelector('.people__card-place');
+    if (!(line instanceof HTMLElement) || this.painted === null) {
+      return;
+    }
+
+    line.textContent = this.placeOf(this.painted.id);
+  }
+
+  private placeOf(id: string): string {
+    return this.locate?.(id) ?? formatPersonPlace('away');
+  }
+
   private mountPersonTimetable(card: PersonCard): void {
     const schoolId = this.schoolId;
     const query = personTimetableQuery(card);

src/HSchool.Client/src/ui/peoplePanel.ts

@@ -2,7 +2,7 @@ import { fetchPeople, fetchPerson, fetchTimetable, type PeoplePage, type PersonC
 import { getLocale } from '../i18n/locale.ts';
 import { t, type MessageKey } from '../i18n/strings.ts';
 import { clear, el } from './dom.ts';
-import { placement, renderPersonCard, roleLabels } from './personCard.ts';
+import { formatPersonPlace, placement, renderPersonCard, roleLabels } from './personCard.ts';
 import { personTimetableQuery, TimetableGrid } from './timetableGrid.ts';
 
 const COLUMNS: readonly { sort: PersonSort; label: MessageKey }[] = [
@@ -59,6 +59,8 @@ export class PeoplePanel {
   private selectedId: string | null = null;
   private token = 0;
   private cardToken = 0;
+  private locate: ((id: string) => string) | null = null;
+  private painted: PersonCard | null = null;
 
   constructor(private readonly options: PeoplePanelOptions) {
     this.ageMinInput.min = '0';
@@ -170,6 +172,11 @@ export class PeoplePanel {
     }
   }
 
+  setLocate(locate: (id: string) => string): void {
+    this.locate = locate;
+    this.relocate();
+  }
+
   private onFilterChange(): void {
     this.page = 1;
     void this.reload();
@@ -349,15 +356,29 @@ export class PeoplePanel {
 
   private paintCard(card: PersonCard | null): void {
     clear(this.card);
+    this.painted = card;
     if (card === null) {
       this.card.append(el('p', { class: 'panel__empty', text: t('peoplePickHint') }));
       return;
     }
 
-    renderPersonCard(this.card, card, (id) => void this.openCard(id));
+    renderPersonCard(this.card, card, (id) => void this.openCard(id), this.placeOf(card.id));
     this.mountPersonTimetable(card);
   }
 
+  private relocate(): void {
+    const line = this.card.querySelector('.people__card-place');
+    if (!(line instanceof HTMLElement) || this.painted === null) {
+      return;
+    }
+
+    line.textContent = this.placeOf(this.painted.id);
+  }
+
+  private placeOf(id: string): string {
+    return this.locate?.(id) ?? formatPersonPlace('away');
+  }
+
   private mountPersonTimetable(card: PersonCard): void {
     const schoolId = this.schoolId;
     const query = personTimetableQuery(card);

src/HSchool.Client/src/ui/personCard.ts

@@ -31,11 +31,15 @@ export function renderPersonCard(
   parent: HTMLElement,
   card: PersonCard,
   onRelative: (id: string) => void,
+  place?: string,
 ): void {
   parent.append(
     el('h3', { class: 'people__card-name', text: card.fullName }),
     el('p', { class: 'people__card-meta', text: cardMeta(card) }),
   );
+  if (place !== undefined && place.length > 0) {
+    parent.append(el('p', { class: 'people__card-place', text: place }));
+  }
   appendPairs(parent, t('peopleBody'), card.body);
   appendPairs(parent, t('peopleSkills'), card.skills);
   appendTags(parent, t('peopleTraits'), card.traits.map((row) => row.label));
@@ -61,6 +65,18 @@ function cardMeta(card: PersonCard): string {
   return bits.join(' · ');
 }
 
+export function formatPersonPlace(kind: 'here' | 'walking' | 'away', nodeName = ''): string {
+  if (kind === 'away') {
+    return t('presenceAway');
+  }
+
+  if (kind === 'walking') {
+    return t('presenceWalking', { name: nodeName });
+  }
+
+  return t('presenceAt', { name: nodeName });
+}
+
 function section(title: string): HTMLElement {
   return el('div', { class: 'people__section' }, el('h4', { class: 'people__section-title', text: title }));
 }

src/HSchool.Protocol/MessageType.cs

@@ -14,10 +14,12 @@ public enum MessageType : byte
     ClientCloseSchool = 0x04,
     ClientSetRunning = 0x05,
     ClientSetSpeed = 0x06,
+    ClientSkipEmpty = 0x07,
 
     ServerWelcome = 0x81,
     ServerPong = 0x82,
     ServerClock = 0x83,
     ServerSchoolGone = 0x84,
     ServerMapSnapshot = 0x85,
+    ServerPresence = 0x86,
 }

src/HSchool.Protocol/Messages.cs

@@ -31,12 +31,16 @@ public readonly record struct ServerPongMessage(long ClientTimeMs, uint ServerTi
 /// State of the open school's calendar, sent every tick.
 /// <paramref name="GameTimeUnixMs"/> is the in-game date as milliseconds since the Unix epoch,
 /// interpreted as UTC — the game calendar has no time zone.
+/// <paramref name="SkipAllowed"/> is the server's verdict; the client must not recompute it.
+/// <paramref name="SkipTargetUnixMs"/> is 0 when skip is refused.
 /// </summary>
 public readonly record struct ServerClockMessage(
     int SchoolId,
     long GameTimeUnixMs,
     bool Running,
-    byte SpeedIndex);
+    byte SpeedIndex,
+    bool SkipAllowed = false,
+    long SkipTargetUnixMs = 0);
 
 /// <summary>The open school no longer exists (deleted from another tab); the client returns to the menu.</summary>
 public readonly record struct ServerSchoolGoneMessage(int SchoolId);
@@ -45,9 +49,7 @@ public readonly record struct ServerSchoolGoneMessage(int SchoolId);
 /// Tree node in a map snapshot. Kind is <c>0</c> territory, <c>1</c> building, <c>2</c> floor, <c>3</c> room.
 /// <paramref name="ParentId"/> is empty for the yard.
 /// <paramref name="PupilSlots"/> is how many pupils can take a lesson here — summed from things
-/// on the server, not by the client.
+/// on the server, not by the client. Live occupancy lives on <see cref="ServerPresenceMessage"/>.
-/// <paramref name="ActivitySubject"/> and <paramref name="ActivityClass"/> are empty when the
-/// room is free. <paramref name="Characters"/> are the people the timetable puts there right now.
 /// </summary>
 public sealed record MapSnapshotNode(
     byte Kind,
@@ -56,19 +58,42 @@ public sealed record MapSnapshotNode(
     string Name,
     ushort PupilSlots,
     IReadOnlyList<MapSnapshotItem> Items,
-    IReadOnlyList<string> Positions,
+    IReadOnlyList<string> Positions);
-    string ActivitySubject = "",
-    string ActivityClass = "",
-    IReadOnlyList<string>? Characters = null)
-{
-    public IReadOnlyList<string> Present => Characters ?? [];
-}
 
 /// <summary>One stacked thing in a room. <paramref name="Count"/> is 1–255.</summary>
 public sealed record MapSnapshotItem(string Name, byte Count);
 
 /// <summary>
-/// One school's map, labelled in the Hello locale. Sent when that school is opened and again
+/// One school's map, labelled in the Hello locale. Sent once when that school is opened.
-/// when the current lesson slot changes. Occupancy is computed from the timetable and the clock.
+/// Structure only — people and the current lesson ride the presence stream.
 /// </summary>
 public sealed record ServerMapSnapshotMessage(int SchoolId, IReadOnlyList<MapSnapshotNode> Nodes);
+
+/// <summary>Jump empty nights, weekends and holidays. The server re-checks the conditions.</summary>
+public readonly record struct ClientSkipEmptyMessage;
+
+/// <summary>Where people are: 1 in a node, 2 walking through it. Off campus is omitted.</summary>
+public static class PresenceState
+{
+    public const byte Here = 1;
+    public const byte Walking = 2;
+}
+
+/// <summary>One occupied (or currently taught) map node in a presence frame.</summary>
+public sealed record PresenceNode(
+    string Id,
+    ushort Count,
+    string ActivitySubject = "",
+    string ActivityClass = "");
+
+/// <summary>One on-campus person. Names are resolved over HTTP, not on this frame.</summary>
+public sealed record PresencePerson(string Id, string NodeId, byte State);
+
+/// <summary>
+/// Live occupancy of an open school, about twice a second. Counts and people cover the whole
+/// map; the client filters to the selected tree node.
+/// </summary>
+public sealed record ServerPresenceMessage(
+    int SchoolId,
+    IReadOnlyList<PresenceNode> Nodes,
+    IReadOnlyList<PresencePerson> People);

src/HSchool.Protocol/ProtocolCodec.cs

@@ -10,10 +10,10 @@ namespace HSchool.Protocol;
 public static class ProtocolCodec
 {
     /// <summary>
-    /// Largest <em>fixed-size</em> frame this codec produces. Variable map snapshots use
+    /// Largest <em>fixed-size</em> frame this codec produces. Variable map snapshots and
-    /// <see cref="ProtocolConstants.MaxMessageSize"/> instead.
+    /// presence frames use <see cref="ProtocolConstants.MaxMessageSize"/> instead.
     /// </summary>
-    public const int MaxFrameSize = 16;
+    public const int MaxFrameSize = 24;
 
     public static int WriteHello(Span<byte> destination, in ClientHelloMessage message)
     {
@@ -63,6 +63,13 @@ public static class ProtocolCodec
         return writer.Position;
     }
 
+    public static int WriteSkipEmpty(Span<byte> destination)
+    {
+        var writer = new PacketWriter(destination);
+        writer.WriteMessageType(MessageType.ClientSkipEmpty);
+        return writer.Position;
+    }
+
     public static int WriteWelcome(Span<byte> destination, in ServerWelcomeMessage message)
     {
         var writer = new PacketWriter(destination);
@@ -90,6 +97,8 @@ public static class ProtocolCodec
         writer.WriteInt64(message.GameTimeUnixMs);
         writer.WriteByte(message.Running ? (byte)1 : (byte)0);
         writer.WriteByte(message.SpeedIndex);
+        writer.WriteByte(message.SkipAllowed ? (byte)1 : (byte)0);
+        writer.WriteInt64(message.SkipTargetUnixMs);
         return writer.Position;
     }
 
@@ -129,18 +138,6 @@ public static class ProtocolCodec
             {
                 size += StringSize(position);
             }
-
-            size += sizeof(byte);
-            if (HasActivity(node))
-            {
-                size += StringSize(node.ActivitySubject) + StringSize(node.ActivityClass);
-            }
-
-            size += sizeof(byte);
-            foreach (var person in node.Present)
-            {
-                size += StringSize(person);
-            }
         }
 
         return size;
@@ -160,9 +157,9 @@ public static class ProtocolCodec
 
         foreach (var node in message.Nodes)
         {
-            if (node.Items.Count > byte.MaxValue || node.Positions.Count > byte.MaxValue || node.Present.Count > byte.MaxValue)
+            if (node.Items.Count > byte.MaxValue || node.Positions.Count > byte.MaxValue)
             {
-                throw new ProtocolException($"Map node '{node.Id}' has too many items, positions or people for a u8 count.");
+                throw new ProtocolException($"Map node '{node.Id}' has too many items or positions for a u8 count.");
             }
 
             writer.WriteByte(node.Kind);
@@ -182,8 +179,53 @@ public static class ProtocolCodec
             {
                 writer.WriteString(position);
             }
+        }
 
-            if (HasActivity(node))
+        return writer.Position;
+    }
+
+    public static int PresenceSize(ServerPresenceMessage message)
+    {
+        var size = sizeof(byte) + sizeof(int) + sizeof(ushort);
+        foreach (var node in message.Nodes)
+        {
+            size += StringSize(node.Id) + sizeof(ushort) + sizeof(byte);
+            if (HasPresenceActivity(node))
+            {
+                size += StringSize(node.ActivitySubject) + StringSize(node.ActivityClass);
+            }
+        }
+
+        size += sizeof(ushort);
+        foreach (var person in message.People)
+        {
+            size += StringSize(person.Id) + StringSize(person.NodeId) + sizeof(byte);
+        }
+
+        return size;
+    }
+
+    public static int WritePresence(Span<byte> destination, ServerPresenceMessage message)
+    {
+        if (message.Nodes.Count > ushort.MaxValue)
+        {
+            throw new ProtocolException($"Presence has {message.Nodes.Count} nodes; u16 count cannot hold it.");
+        }
+
+        if (message.People.Count > ushort.MaxValue)
+        {
+            throw new ProtocolException($"Presence has {message.People.Count} people; u16 count cannot hold it.");
+        }
+
+        var writer = new PacketWriter(destination);
+        writer.WriteMessageType(MessageType.ServerPresence);
+        writer.WriteInt32(message.SchoolId);
+        writer.WriteUInt16((ushort)message.Nodes.Count);
+        foreach (var node in message.Nodes)
+        {
+            writer.WriteString(node.Id);
+            writer.WriteUInt16(node.Count);
+            if (HasPresenceActivity(node))
             {
                 writer.WriteByte(1);
                 writer.WriteString(node.ActivitySubject);
@@ -193,12 +235,14 @@ public static class ProtocolCodec
             {
                 writer.WriteByte(0);
             }
+        }
 
-            writer.WriteByte((byte)node.Present.Count);
+        writer.WriteUInt16((ushort)message.People.Count);
-            foreach (var person in node.Present)
+        foreach (var person in message.People)
-            {
+        {
-                writer.WriteString(person);
+            writer.WriteString(person.Id);
-            }
+            writer.WriteString(person.NodeId);
+            writer.WriteByte(person.State);
         }
 
         return writer.Position;
@@ -271,7 +315,9 @@ public static class ProtocolCodec
         var gameTime = reader.ReadInt64();
         var running = reader.ReadByte() != 0;
         var speedIndex = reader.ReadByte();
-        return new ServerClockMessage(schoolId, gameTime, running, speedIndex);
+        var skipAllowed = reader.ReadByte() != 0;
+        var skipTarget = reader.ReadInt64();
+        return new ServerClockMessage(schoolId, gameTime, running, speedIndex, skipAllowed, skipTarget);
     }
 
     public static ServerSchoolGoneMessage ReadSchoolGone(ReadOnlySpan<byte> source)
@@ -312,6 +358,23 @@ public static class ProtocolCodec
                 positions[position] = reader.ReadString();
             }
 
+            nodes[i] = new MapSnapshotNode(kind, id, parentId, name, pupilSlots, items, positions);
+        }
+
+        return new ServerMapSnapshotMessage(schoolId, nodes);
+    }
+
+    public static ServerPresenceMessage ReadPresence(ReadOnlySpan<byte> source)
+    {
+        var reader = new PacketReader(source);
+        Expect(ref reader, MessageType.ServerPresence);
+        var schoolId = reader.ReadInt32();
+        var nodeCount = reader.ReadUInt16();
+        var nodes = new PresenceNode[nodeCount];
+        for (var i = 0; i < nodeCount; i++)
+        {
+            var id = reader.ReadString();
+            var count = reader.ReadUInt16();
             var hasActivity = reader.ReadByte() != 0;
             var activitySubject = "";
             var activityClass = "";
@@ -321,30 +384,20 @@ public static class ProtocolCodec
                 activityClass = reader.ReadString();
             }
 
-            var characterCount = reader.ReadByte();
+            nodes[i] = new PresenceNode(id, count, activitySubject, activityClass);
-            var characters = new string[characterCount];
-            for (var person = 0; person < characterCount; person++)
-            {
-                characters[person] = reader.ReadString();
-            }
-
-            nodes[i] = new MapSnapshotNode(
-                kind,
-                id,
-                parentId,
-                name,
-                pupilSlots,
-                items,
-                positions,
-                activitySubject,
-                activityClass,
-                characters);
         }
 
-        return new ServerMapSnapshotMessage(schoolId, nodes);
+        var personCount = reader.ReadUInt16();
+        var people = new PresencePerson[personCount];
+        for (var i = 0; i < personCount; i++)
+        {
+            people[i] = new PresencePerson(reader.ReadString(), reader.ReadString(), reader.ReadByte());
+        }
+
+        return new ServerPresenceMessage(schoolId, nodes, people);
     }
 
-    private static bool HasActivity(MapSnapshotNode node) =>
+    private static bool HasPresenceActivity(PresenceNode node) =>
         node.ActivitySubject.Length > 0 || node.ActivityClass.Length > 0;
 
     /// <summary>Matches <see cref="PacketWriter.WriteString"/>: a <c>u16</c> length plus UTF-8.</summary>

src/HSchool.Protocol/ProtocolConstants.cs

@@ -4,7 +4,7 @@ namespace HSchool.Protocol;
 public static class ProtocolConstants
 {
     /// <summary>Bumped on every breaking change to the binary layout.</summary>
-    public const byte Version = 6;
+    public const byte Version = 7;
 
     /// <summary>Upper bound for a single WebSocket frame accepted by the server.</summary>
     public const int MaxMessageSize = 8 * 1024;

src/HSchool.Server/Api/PeopleModels.cs

@@ -73,6 +73,10 @@ internal sealed record PersonFamilyResponse(
 
 internal sealed record PersonRelResponse(string Id, string FullName, bool Female);
 
+internal sealed record DirectoryResponse(IReadOnlyList<DirectoryPersonResponse> People);
+
+internal sealed record DirectoryPersonResponse(string Id, string FullName);
+
 internal static class PeopleListMapper
 {
     public static PeopleListResponse From(

src/HSchool.Server/Api/SchoolEndpoints.cs

@@ -134,6 +134,29 @@ internal static class SchoolEndpoints
         })
         .WithName("GetSchoolPeople");
 
+        schools.MapGet("/{id:int}/directory", (int id, string? lang, GameLoopService loop) =>
+        {
+            var published = loop.FindPeople(id);
+            if (published is null)
+            {
+                return Problem(StatusCodes.Status404NotFound, "unknown-school", "That school does not exist.");
+            }
+
+            _ = ParseLocale(lang);
+            var roster = published.Roster;
+            if (roster is null)
+            {
+                return Results.Ok(new DirectoryResponse([]));
+            }
+
+            var people = roster.People
+                .OrderBy(person => person.Id, StringComparer.Ordinal)
+                .Select(person => new DirectoryPersonResponse(person.Id, person.Name.Full))
+                .ToArray();
+            return Results.Ok(new DirectoryResponse(people));
+        })
+        .WithName("GetSchoolDirectory");
+
         schools.MapGet("/{id:int}/people/{personId}", async (
             int id,
             string personId,

src/HSchool.Server/Game/GameCommand.cs

@@ -7,7 +7,7 @@ namespace HSchool.Server.Game;
 
 /// <summary>
 /// Work item handed from a request or connection thread to the supervisor. Create, delete and
-/// name suggestions stay here; open/close/running/speed are forwarded to the school's worker.
+/// name suggestions stay here; open/close/running/speed/skip are forwarded to the school's worker.
 /// </summary>
 internal abstract record GameCommand
 {
@@ -36,6 +36,8 @@ internal abstract record GameCommand
 
     internal sealed record SetSpeed(uint PlayerId, byte SpeedIndex) : GameCommand;
 
+    internal sealed record SkipEmpty(uint PlayerId) : GameCommand;
+
     /// <summary>Stops every worker, re-reads the save directory, starts workers from those files.</summary>
     internal sealed record ReloadSaves(TaskCompletionSource Result) : GameCommand;
 

src/HSchool.Server/Game/GameLoopService.cs

@@ -167,6 +167,10 @@ internal sealed class GameLoopService(
                 RouteOpenSchool(setSpeed.PlayerId, new WorkerCommand.SetSpeed(setSpeed.SpeedIndex));
                 break;
 
+            case GameCommand.SkipEmpty skipEmpty:
+                RouteOpenSchool(skipEmpty.PlayerId, new WorkerCommand.SkipEmpty());
+                break;
+
             case GameCommand.ReloadSaves reload:
                 await HandleReloadAsync(reload).ConfigureAwait(false);
                 break;

src/HSchool.Server/Game/MapOccupancy.cs

@@ -1,93 +0,0 @@
-using HSchool.Content;
-using HSchool.People;
-using HSchool.Protocol;
-using HSchool.Schedule;
-using HSchool.Simulation;
-
-namespace HSchool.Server.Game;
-
-/// <summary>
-/// Overlays the current lesson onto map-tree nodes. Occupancy is derived from the timetable and
-/// the clock; it is not stored on the map.
-/// </summary>
-internal static class MapOccupancy
-{
-    public static void Apply(
-        MapSnapshotNode[] nodes,
-        School school,
-        int weekDays,
-        string locale)
-    {
-        if (school.Timetable is null || school.Roster is null || school.Catalog is null)
-        {
-            return;
-        }
-
-        var occurring = TimetableClock.OccurringAt(
-            school.Timetable,
-            school.Catalog,
-            school.Clock.Time,
-            weekDays);
-        if (occurring.Count == 0)
-        {
-            return;
-        }
-
-        var catalog = school.Catalog;
-        var classes = school.Roster.Classes.ToDictionary(item => item.Id, StringComparer.Ordinal);
-        var people = school.Roster.People.ToDictionary(person => person.Id, StringComparer.Ordinal);
-        var byRoom = occurring.ToDictionary(lesson => lesson.RoomId, StringComparer.Ordinal);
-
-        for (var i = 0; i < nodes.Length; i++)
-        {
-            if (!byRoom.TryGetValue(nodes[i].Id, out var lesson))
-            {
-                continue;
-            }
-
-            classes.TryGetValue(lesson.ClassId, out var schoolClass);
-            var subjectLabel = catalog.Subjects.TryGetValue(lesson.Subject, out var subject)
-                ? catalog.Label(locale, subject)
-                : lesson.Subject;
-            var classLabel = schoolClass is null
-                ? lesson.ClassId
-                : $"{schoolClass.Year}{schoolClass.Letter}";
-
-            nodes[i] = nodes[i] with
-            {
-                ActivitySubject = subjectLabel,
-                ActivityClass = classLabel,
-                Characters = NamesOf(lesson, schoolClass, people),
-            };
-        }
-    }
-
-    private static string[] NamesOf(
-        LessonPlacement lesson,
-        SchoolClass? schoolClass,
-        IReadOnlyDictionary<string, Person> people)
-    {
-        var names = new List<string>();
-        if (people.TryGetValue(lesson.TeacherId, out var teacher))
-        {
-            names.Add(teacher.Name.Full);
-        }
-        else if (lesson.TeacherId.Length > 0)
-        {
-            names.Add(lesson.TeacherId);
-        }
-
-        if (schoolClass is not null)
-        {
-            foreach (var pupilId in schoolClass.PupilIds)
-            {
-                if (people.TryGetValue(pupilId, out var pupil))
-                {
-                    names.Add(pupil.Name.Full);
-                }
-            }
-        }
-
-        return names.Count > byte.MaxValue ? [.. names.Take(byte.MaxValue)] : [.. names];
-    }
-}

src/HSchool.Server/Game/PresenceFrame.cs

@@ -0,0 +1,98 @@
+using HSchool.Content;
+using HSchool.People;
+using HSchool.Protocol;
+using HSchool.Schedule;
+using HSchool.Simulation;
+
+namespace HSchool.Server.Game;
+
+/// <summary>
+/// Builds a presence frame from stored places plus the current lesson. Occupancy is state;
+/// the lesson labels are still derived from the timetable so an empty classroom during a period
+/// still shows what should be happening there.
+/// </summary>
+internal static class PresenceFrame
+{
+    public static ServerPresenceMessage Build(School school, int weekDays, string locale)
+    {
+        var people = new List<PresencePerson>();
+        var counts = new Dictionary<string, int>(StringComparer.Ordinal);
+        foreach (var row in school.CapturePresence())
+        {
+            if (row.NodeId is null)
+            {
+                continue;
+            }
+
+            var walking = row.Path.Count > 0 || row.RemainingMinutes > 0;
+            people.Add(new PresencePerson(
+                row.PersonId,
+                row.NodeId,
+                walking ? PresenceState.Walking : PresenceState.Here));
+            counts[row.NodeId] = counts.GetValueOrDefault(row.NodeId) + 1;
+        }
+
+        people.Sort((left, right) => StringComparer.Ordinal.Compare(left.Id, right.Id));
+
+        var activity = ActivityByRoom(school, weekDays, locale);
+        var nodeIds = counts.Keys
+            .Concat(activity.Keys)
+            .Distinct(StringComparer.Ordinal)
+            .OrderBy(id => id, StringComparer.Ordinal);
+
+        var nodes = new List<PresenceNode>();
+        foreach (var id in nodeIds)
+        {
+            var count = (ushort)Math.Min(counts.GetValueOrDefault(id), ushort.MaxValue);
+            var subject = "";
+            var classLabel = "";
+            if (activity.TryGetValue(id, out var labels))
+            {
+                subject = labels.Subject;
+                classLabel = labels.Class;
+            }
+
+            nodes.Add(new PresenceNode(id, count, subject, classLabel));
+        }
+
+        return new ServerPresenceMessage(school.Id, nodes, people);
+    }
+
+    private static Dictionary<string, (string Subject, string Class)> ActivityByRoom(
+        School school,
+        int weekDays,
+        string locale)
+    {
+        var labels = new Dictionary<string, (string Subject, string Class)>(StringComparer.Ordinal);
+        if (school.Timetable is null || school.Roster is null || school.Catalog is null)
+        {
+            return labels;
+        }
+
+        var occurring = TimetableClock.OccurringAt(
+            school.Timetable,
+            school.Catalog,
+            school.Clock.Time,
+            weekDays);
+        if (occurring.Count == 0)
+        {
+            return labels;
+        }
+
+        var catalog = school.Catalog;
+        var classes = school.Roster.Classes.ToDictionary(item => item.Id, StringComparer.Ordinal);
+        foreach (var lesson in occurring)
+        {
+            classes.TryGetValue(lesson.ClassId, out var schoolClass);
+            var subjectLabel = catalog.Subjects.TryGetValue(lesson.Subject, out var subject)
+                ? catalog.Label(locale, subject)
+                : lesson.Subject;
+            var classLabel = schoolClass is null
+                ? lesson.ClassId
+                : $"{schoolClass.Year}{schoolClass.Letter}";
+            labels[lesson.RoomId] = (subjectLabel, classLabel);
+        }
+
+        return labels;
+    }
+}

src/HSchool.Server/Game/SchoolWorker.cs

@@ -48,7 +48,7 @@ internal sealed class SchoolWorker
     private DefCatalog? _catalogSnapshot;
     private Timetable? _timetableSnapshot;
     private MapLayout? _mapSnapshot;
-    private OccupancyKey _occupancyKey;
+    private int _presenceAge;
     private School? _school;
     private Task? _run;
     private bool _persistOnStop = true;
@@ -308,7 +308,7 @@ internal sealed class SchoolWorker
                 {
                     PublishSnapshot();
                     BroadcastClock();
-                    MaybeBroadcastOccupancy(school);
+                    MaybeBroadcastPresence(school);
                 }
 
                 FlushSettings();
@@ -381,6 +381,7 @@ internal sealed class SchoolWorker
                         open.Client.OpenSchoolId = _id;
                         SendMapSnapshot(open.Client, school);
                         BroadcastClockTo(open.Client, school);
+                        SendPresence(open.Client, school);
                         break;
 
                     case WorkerCommand.Close close:
@@ -402,6 +403,10 @@ internal sealed class SchoolWorker
                         dirty = true;
                         break;
 
+                    case WorkerCommand.SkipEmpty:
+                        ApplySkip(school);
+                        break;
+
                     case WorkerCommand.GetPerson getPerson:
                         var card = PersonCardReader.Read(school, getPerson.PersonId, getPerson.Locale);
                         getPerson.Result.TrySetResult(
@@ -613,7 +618,6 @@ internal sealed class SchoolWorker
                     PersistTimetable(school);
                 }
 
-                RememberOccupancy(school);
                 return;
             }
         }
@@ -770,11 +774,7 @@ internal sealed class SchoolWorker
         PublishSnapshot();
         if (broadcast)
         {
-            MaybeBroadcastOccupancy(school, force: true);
+            BroadcastPresence();
-        }
-        else
-        {
-            RememberOccupancy(school);
         }
     }
 
@@ -799,35 +799,41 @@ internal sealed class SchoolWorker
         }
     }
 
-    private void RememberOccupancy(School school)
+    private void MaybeBroadcastPresence(School school)
     {
-        if (school.Catalog is not null)
+        _presenceAge++;
+        var interval = Math.Max(1, _options.TickRate / 2);
+        if (_presenceAge < interval)
         {
-            _occupancyKey = TimetableClock.Key(school.Catalog, school.Clock.Time, _options.SchoolWeekDays);
+            return;
         }
+
+        _presenceAge = 0;
+        BroadcastPresence();
     }
 
-    private void MaybeBroadcastOccupancy(School school, bool force = false)
+    private void ApplySkip(School school)
     {
-        if (school.Catalog is null)
+        var result = school.TrySkipEmpty();
+        if (!result.Succeeded)
         {
             return;
         }
 
-        var key = TimetableClock.Key(school.Catalog, school.Clock.Time, _options.SchoolWeekDays);
+        if (result.PeopleChanged)
-        if (!force && key == _occupancyKey)
         {
-            return;
+            PersistPeople();
-        }
+            if (school.TimetableDirty)
-
-        _occupancyKey = key;
-        foreach (var client in _clients.All)
-        {
-            if (client.IsReady && client.OpenSchoolId == _id)
             {
-                SendMapSnapshot(client, school);
+                RebuildTimetable(school);
             }
         }
+
+        PublishSnapshot();
+        Persist();
+        BroadcastClock();
+        BroadcastPresence();
+        _presenceAge = 0;
     }
 
     private bool InstallPeople(School school, DefCatalog catalog, MapLayout map)
@@ -987,8 +993,6 @@ internal sealed class SchoolWorker
                 node.Positions);
         }
 
-        MapOccupancy.Apply(nodes, school, _options.SchoolWeekDays, locale);
-
         // Sized from the message, not from the inbound frame limit: a map the player enlarged in
         // the create editor outgrows 8 KiB somewhere past sixty furnished rooms.
         var message = new ServerMapSnapshotMessage(school.Id, nodes);
@@ -997,15 +1001,44 @@ internal sealed class SchoolWorker
         client.TrySendReliable(frame.AsMemory(0, length));
     }
 
-    private static void BroadcastClockTo(GameClient client, School school)
+    private void BroadcastClockTo(GameClient client, School school)
     {
+        var skip = school.PeekSkipEmpty();
         var frame = new byte[ProtocolCodec.MaxFrameSize];
         var length = ProtocolCodec.WriteClock(frame, new ServerClockMessage(
             school.Id,
             new DateTimeOffset(school.Clock.Time).ToUnixTimeMilliseconds(),
             school.Clock.IsRunning,
-            (byte)school.Clock.SpeedIndex));
+            (byte)school.Clock.SpeedIndex,
+            skip.Allowed,
+            skip.Time is { } target ? new DateTimeOffset(target).ToUnixTimeMilliseconds() : 0));
 
         client.TrySend(frame.AsMemory(0, length));
     }
+
+    private void BroadcastPresence()
+    {
+        var school = _school;
+        if (school is null)
+        {
+            return;
+        }
+
+        foreach (var client in _clients.All)
+        {
+            if (client.IsReady && client.OpenSchoolId == _id)
+            {
+                SendPresence(client, school);
+            }
+        }
+    }
+
+    private void SendPresence(GameClient client, School school)
+    {
+        var locale = ProtocolConstants.CatalogLocale(client.Locale);
+        var message = PresenceFrame.Build(school, _options.SchoolWeekDays, locale);
+        var frame = new byte[ProtocolCodec.PresenceSize(message)];
+        var length = ProtocolCodec.WritePresence(frame, message);
+        client.TrySendReliable(frame.AsMemory(0, length));
+    }
 }

src/HSchool.Server/Game/WorkerCommand.cs

@@ -18,6 +18,8 @@ internal abstract record WorkerCommand
 
     internal sealed record SetSpeed(byte SpeedIndex) : WorkerCommand;
 
+    internal sealed record SkipEmpty : WorkerCommand;
+
     internal sealed record GetPerson(
         string PersonId,
         string Locale,

src/HSchool.Server/Net/GameSocketHandler.cs

@@ -153,6 +153,10 @@ internal sealed class GameSocketHandler(
                     commands.Enqueue(new GameCommand.SetSpeed(client.PlayerId, setSpeed.SpeedIndex));
                     break;
 
+                case MessageType.ClientSkipEmpty:
+                    commands.Enqueue(new GameCommand.SkipEmpty(client.PlayerId));
+                    break;
+
                 default:
                     logger.LogDebug(
                         "Ignoring unexpected frame 0x{MessageType:X2} from client {PlayerId}.",

src/HSchool.Simulation/School.cs

@@ -138,6 +138,18 @@ public sealed class School : IDisposable
 
     public bool IsCampusEmpty() => PresenceSystem.IsEmpty(this);
 
+    public SkipEmptyPeek PeekSkipEmpty()
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        if (Catalog is null || !IsCampusEmpty() || SchoolDay.InWorkWindow(Catalog, Clock.Time, SchoolWeekDays))
+        {
+            return SkipEmptyPeek.Refused;
+        }
+
+        var next = SchoolDay.NextWorkMorning(Catalog, Clock.Time, SchoolWeekDays, MaxSkipDays);
+        return next is null ? SkipEmptyPeek.Refused : new SkipEmptyPeek(true, next.Value);
+    }
+
     public SkipEmptyResult TrySkipEmpty()
     {
         ObjectDisposedException.ThrowIf(_disposed, this);
@@ -295,6 +307,11 @@ public enum SkipEmptyError
     NoMorning,
 }
 
+public readonly record struct SkipEmptyPeek(bool Allowed, DateTime? Time)
+{
+    public static SkipEmptyPeek Refused { get; } = new(false, null);
+}
+
 public readonly record struct SkipEmptyResult(SkipEmptyError Error, DateTime? Time, bool PeopleChanged)
 {
     public bool Succeeded => Error == SkipEmptyError.None;

tests/HSchool.AppHost.Tests/GameSocketTests.cs

@@ -111,8 +111,6 @@ public class GameSocketTests(AppHostFixture fixture)
         Assert.Equal(16, classroom.PupilSlots);
         Assert.Contains(classroom.Items, item => item.Name == "Парта" && item.Count == 16);
         Assert.DoesNotContain(classroom.Items, item => item.Name == "Стул");
-        Assert.Equal("", classroom.ActivitySubject);
-        Assert.Empty(classroom.Present);
     }
 
     [Fact]
@@ -161,13 +159,21 @@ public class GameSocketTests(AppHostFixture fixture)
     }
 
     [Fact]
-    public async Task OpeningASchoolDuringAMathLesson_PutsOccupancyOnTheRoom()
+    public async Task OpeningASchoolDuringAMathLesson_PutsOccupancyOnPresenceNotTheSnapshot()
     {
         using var client = fixture.App.CreateHttpClient("server");
         await SchoolApiTests.ResetAsync(client);
         var start = new DateTime(2012, 4, 3, 10, 20, 0, DateTimeKind.Utc);
         var school = await SchoolApiTests.CreateAsync(client, "Кто где сейчас", start);
 
+        using var socket = await OpenSchoolAsync(school.Id);
+        var snapshot = ProtocolCodec.ReadMapSnapshot(await ReceiveUntilAsync(socket, MessageType.ServerMapSnapshot));
+        Assert.Contains(snapshot.Nodes, node => node.Id == "classroom-101");
+
+        await SendAsync(socket, buffer =>
+            ProtocolCodec.WriteSetRunning(buffer, new ClientSetRunningMessage(Running: false)));
+        await ReceiveClockWhereAsync(socket, clock => !clock.Running);
+
         var staffing = await client.GetFromJsonAsync<StaffingSnapshot>(
             $"/api/schools/{school.Id}/staffing",
             TestContext.Current.CancellationToken);
@@ -184,14 +190,49 @@ public class GameSocketTests(AppHostFixture fixture)
             TestContext.Current.CancellationToken);
         assign.EnsureSuccessStatusCode();
 
-        using var socket = await OpenSchoolAsync(school.Id);
+        var presence = await ReceivePresenceWhereAsync(
-        var snapshot = ProtocolCodec.ReadMapSnapshot(await ReceiveUntilAsync(socket, MessageType.ServerMapSnapshot));
+            socket,
-        var occupied = Assert.Single(snapshot.Nodes, node => node.ActivitySubject.Length > 0);
+            frame => frame.Nodes.Any(node => node.ActivitySubject.Length > 0));
+        var occupied = Assert.Single(presence.Nodes, node => node.ActivitySubject.Length > 0);
 
         Assert.Equal("Математика", occupied.ActivitySubject);
         Assert.NotEmpty(occupied.ActivityClass);
-        Assert.Contains(applicant.FullName, occupied.Present);
+
-        Assert.True(occupied.Present.Count > 1);
+        var directory = await client.GetFromJsonAsync<DirectorySnapshot>(
+            $"/api/schools/{school.Id}/directory",
+            TestContext.Current.CancellationToken);
+        Assert.NotNull(directory);
+        Assert.Contains(directory.People, person => person.Id == applicant.Id && person.FullName == applicant.FullName);
+
+        await SendAsync(socket, buffer =>
+            ProtocolCodec.WriteSetRunning(buffer, new ClientSetRunningMessage(Running: true)));
+        presence = await ReceivePresenceWhereAsync(
+            socket,
+            frame => frame.People.Any(person => person.Id == applicant.Id));
+        Assert.Contains(presence.People, person => person.Id == applicant.Id);
+    }
+
+    [Fact]
+    public async Task SkipEmpty_DuringWorkHours_IsIgnored()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await SchoolApiTests.ResetAsync(client);
+        var start = new DateTime(2012, 4, 3, 10, 20, 0, DateTimeKind.Utc);
+        var school = await SchoolApiTests.CreateAsync(client, "Пропуск в учебное время", start);
+
+        using var socket = await OpenSchoolAsync(school.Id);
+        await SendAsync(socket, buffer =>
+            ProtocolCodec.WriteSetRunning(buffer, new ClientSetRunningMessage(Running: false)));
+        var paused = await ReceiveClockWhereAsync(socket, clock => !clock.Running);
+
+        Assert.False(paused.SkipAllowed);
+        Assert.Equal(0, paused.SkipTargetUnixMs);
+
+        await SendAsync(socket, buffer => ProtocolCodec.WriteSkipEmpty(buffer));
+        var later = await ReceiveClockAfterAsync(socket, TimeSpan.FromSeconds(1));
+
+        Assert.Equal(paused.GameTimeUnixMs, later.GameTimeUnixMs);
+        Assert.False(later.SkipAllowed);
     }
 
     [Fact]
@@ -465,6 +506,22 @@ public class GameSocketTests(AppHostFixture fixture)
         throw new InvalidOperationException("No clock frame matched within 40 frames.");
     }
 
+    private static async Task<ServerPresenceMessage> ReceivePresenceWhereAsync(
+        WebSocket socket,
+        Func<ServerPresenceMessage, bool> predicate)
+    {
+        for (var attempt = 0; attempt < 40; attempt++)
+        {
+            var presence = ProtocolCodec.ReadPresence(await ReceiveUntilAsync(socket, MessageType.ServerPresence));
+            if (predicate(presence))
+            {
+                return presence;
+            }
+        }
+
+        throw new InvalidOperationException("No presence frame matched within 40 frames.");
+    }
+
     /// <summary>Keeps reading clock frames for <paramref name="duration"/> and returns the last one.</summary>
     private static async Task<ServerClockMessage> ReceiveClockAfterAsync(WebSocket socket, TimeSpan duration)
     {
@@ -523,4 +580,8 @@ public class GameSocketTests(AppHostFixture fixture)
     private sealed record StaffingSnapshot(IReadOnlyList<ApplicantSnapshot> Applicants);
 
     private sealed record ApplicantSnapshot(string Id, string FullName);
+
+    private sealed record DirectorySnapshot(IReadOnlyList<DirectoryPersonSnapshot> People);
+
+    private sealed record DirectoryPersonSnapshot(string Id, string FullName);
 }

tests/HSchool.AppHost.Tests/PeopleApiTests.cs

@@ -81,6 +81,32 @@ public class PeopleApiTests(AppHostFixture fixture)
         Assert.Empty(staff.People);
     }
 
+    [Fact]
+    public async Task Directory_ListsRosterIdsAndNames()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await SchoolApiTests.ResetAsync(client);
+        var school = await SchoolApiTests.CreateAsync(client, "Справочник", Start);
+
+        var directory = await client.GetFromJsonAsync<DirectoryResponse>(
+            $"/api/schools/{school.Id}/directory",
+            TestContext.Current.CancellationToken);
+        Assert.NotNull(directory);
+        Assert.NotEmpty(directory.People);
+        Assert.All(directory.People, person =>
+        {
+            Assert.False(string.IsNullOrWhiteSpace(person.Id));
+            Assert.False(string.IsNullOrWhiteSpace(person.FullName));
+        });
+
+        var page = await GetPeopleAsync(client, school.Id, "pageSize=10");
+        Assert.Contains(directory.People, person => person.Id == page.People[0].Id && person.FullName == page.People[0].FullName);
+
+        using var missing = await client.GetAsync("/api/schools/999999/directory", TestContext.Current.CancellationToken);
+        Assert.Equal(HttpStatusCode.NotFound, missing.StatusCode);
+        Assert.Equal("unknown-school", await ProblemCodeAsync(missing));
+    }
+
     [Fact]
     public async Task List_UnknownSchool_IsNotFound()
     {
@@ -204,4 +230,8 @@ public class PeopleApiTests(AppHostFixture fixture)
         IReadOnlyList<PersonRelResponse> Partners);
 
     private sealed record PersonRelResponse(string Id, string FullName, bool Female);
+
+    private sealed record DirectoryResponse(IReadOnlyList<DirectoryPersonResponse> People);
+
+    private sealed record DirectoryPersonResponse(string Id, string FullName);
 }

tests/HSchool.Protocol.Tests/ProtocolCodecTests.cs

@@ -85,6 +85,17 @@ public class ProtocolCodecTests
         Assert.Equal(message, ProtocolCodec.ReadSetSpeed(buffer[..length]));
     }
 
+    [Fact]
+    public void SkipEmpty_IsASingleByte()
+    {
+        Span<byte> buffer = stackalloc byte[ProtocolCodec.MaxFrameSize];
+
+        var length = ProtocolCodec.WriteSkipEmpty(buffer);
+
+        Assert.Equal(1, length);
+        Assert.Equal(MessageType.ClientSkipEmpty, ProtocolCodec.PeekMessageType(buffer[..length]));
+    }
+
     [Fact]
     public void Welcome_RoundTripsAndIsFourBytes()
     {
@@ -110,17 +121,44 @@ public class ProtocolCodecTests
     }
 
     [Fact]
-    public void Clock_RoundTripsAndIsFifteenBytes()
+    public void Clock_RoundTripsAndIsTwentyFourBytes()
     {
-        var message = new ServerClockMessage(7, 1_333_432_800_000, Running: true, SpeedIndex: 2);
+        var message = new ServerClockMessage(
+            7,
+            1_333_432_800_000,
+            Running: true,
+            SpeedIndex: 2,
+            SkipAllowed: true,
+            SkipTargetUnixMs: 1_333_516_800_000);
         Span<byte> buffer = stackalloc byte[ProtocolCodec.MaxFrameSize];
 
         var length = ProtocolCodec.WriteClock(buffer, message);
 
-        Assert.Equal(15, length);
+        Assert.Equal(24, length);
+        Assert.Equal((byte)MessageType.ServerClock, buffer[0]);
+        Assert.Equal(7, BitConverter.ToInt32(buffer[1..5]));
+        Assert.Equal(1_333_432_800_000, BitConverter.ToInt64(buffer[5..13]));
+        Assert.Equal(1, buffer[13]);
+        Assert.Equal(2, buffer[14]);
+        Assert.Equal(1, buffer[15]);
+        Assert.Equal(1_333_516_800_000, BitConverter.ToInt64(buffer[16..24]));
         Assert.Equal(message, ProtocolCodec.ReadClock(buffer[..length]));
     }
 
+    [Fact]
+    public void Clock_WithoutSkip_WritesZeroTarget()
+    {
+        var message = new ServerClockMessage(1, 0, Running: false, SpeedIndex: 1);
+        Span<byte> buffer = stackalloc byte[ProtocolCodec.MaxFrameSize];
+
+        var length = ProtocolCodec.WriteClock(buffer, message);
+        var read = ProtocolCodec.ReadClock(buffer[..length]);
+
+        Assert.Equal(24, length);
+        Assert.False(read.SkipAllowed);
+        Assert.Equal(0, read.SkipTargetUnixMs);
+    }
+
     [Fact]
     public void SchoolGone_RoundTripsAndIsFiveBytes()
     {
@@ -164,34 +202,45 @@ public class ProtocolCodecTests
         Assert.Equal(0, read.Nodes[0].PupilSlots);
         Assert.Equal([new MapSnapshotItem("Стул", 2)], read.Nodes[1].Items);
         Assert.Equal(["Директор"], read.Nodes[1].Positions);
-        Assert.Equal("", read.Nodes[0].ActivitySubject);
-        Assert.Empty(read.Nodes[0].Present);
     }
 
     [Fact]
-    public void MapSnapshot_RoundTripsOccupancyAfterPositions()
+    public void Presence_RoundTripsAndWritesHeaderOffsets()
     {
-        var message = new ServerMapSnapshotMessage(3, [
+        var message = new ServerPresenceMessage(
-            new MapSnapshotNode(
+            7,
-                3,
+            [
-                "classroom-101",
+                new PresenceNode("classroom-101", 18, "Математика", "5А"),
-                "floor-1",
+                new PresenceNode("corridor-1", 4),
-                "Класс 101",
+            ],
-                16,
+            [
-                [new MapSnapshotItem("Парта", 16)],
+                new PresencePerson("f0.c0", "classroom-101", PresenceState.Here),
-                [],
+                new PresencePerson("f3.p1", "corridor-1", PresenceState.Walking),
-                "Математика",
+            ]);
-                "5А",
+        var buffer = new byte[ProtocolCodec.PresenceSize(message)];
-                ["Иванова Ольга Михайловна", "Соколов Иван Петрович"]),
-        ]);
-        var buffer = new byte[ProtocolCodec.MapSnapshotSize(message)];
 
-        var length = ProtocolCodec.WriteMapSnapshot(buffer, message);
+        var length = ProtocolCodec.WritePresence(buffer, message);
-        var read = ProtocolCodec.ReadMapSnapshot(buffer.AsSpan(0, length));
 
+        Assert.Equal((byte)MessageType.ServerPresence, buffer[0]);
+        Assert.Equal(7, BitConverter.ToInt32(buffer.AsSpan(1, 4)));
+        Assert.Equal((ushort)2, BitConverter.ToUInt16(buffer.AsSpan(5, 2)));
+        Assert.Equal(length, ProtocolCodec.PresenceSize(message));
+
+        var read = ProtocolCodec.ReadPresence(buffer.AsSpan(0, length));
+        Assert.Equal(message.SchoolId, read.SchoolId);
+        Assert.Equal(2, read.Nodes.Count);
+        Assert.Equal("classroom-101", read.Nodes[0].Id);
+        Assert.Equal(18, read.Nodes[0].Count);
         Assert.Equal("Математика", read.Nodes[0].ActivitySubject);
         Assert.Equal("5А", read.Nodes[0].ActivityClass);
-        Assert.Equal(["Иванова Ольга Михайловна", "Соколов Иван Петрович"], read.Nodes[0].Present);
+        Assert.Equal("corridor-1", read.Nodes[1].Id);
+        Assert.Equal(4, read.Nodes[1].Count);
+        Assert.Equal("", read.Nodes[1].ActivitySubject);
+        Assert.Equal(2, read.People.Count);
+        Assert.Equal("f0.c0", read.People[0].Id);
+        Assert.Equal("classroom-101", read.People[0].NodeId);
+        Assert.Equal(PresenceState.Here, read.People[0].State);
+        Assert.Equal(PresenceState.Walking, read.People[1].State);
     }
 
     [Fact]
@@ -287,7 +336,9 @@ public class ProtocolCodecTests
     {
         // Handlers size clock/welcome/pong buffers from this constant; map snapshots use MaxMessageSize.
         Span<byte> buffer = stackalloc byte[ProtocolCodec.MaxFrameSize];
-        var clock = ProtocolCodec.WriteClock(buffer, new ServerClockMessage(1, long.MaxValue, true, 4));
+        var clock = ProtocolCodec.WriteClock(
+            buffer,
+            new ServerClockMessage(1, long.MaxValue, true, 4, SkipAllowed: true, SkipTargetUnixMs: long.MaxValue));
 
         Assert.True(clock <= ProtocolCodec.MaxFrameSize);
     }