# 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), 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), a static map snapshot
  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.**

Three files must stay in sync — change them in the same commit:

| Where | File |
| --- | --- |
| Server codec | [`src/HSchool.Protocol/ProtocolCodec.cs`](../src/HSchool.Protocol/ProtocolCodec.cs) |
| Client codec | [`src/HSchool.Client/src/net/protocol.ts`](../src/HSchool.Client/src/net/protocol.ts) |
| This document | `docs/protocol.md` |

Any change to a layout below bumps `ProtocolConstants.Version` / `PROTOCOL_VERSION`. The server
closes connections whose hello carries a different version with `1002 ProtocolError`.

## HTTP API

Game dates are ISO-8601 UTC instants. The in-game calendar has no time zone — UTC is only used so
the wire format is unambiguous, and the client formats it back in UTC.

### `GET /api/schools`

Everything the main menu needs in one request. `schoolWeekDays` is 5–7 working days counted
from Monday (five is Mon–Fri; six adds Saturday). It is a school rule, not a catalog def.
`seed` is the roster generator seed: it is not the school id. Share it to recreate the same
people; it does not change on a living school.

```json
{
  "maxSchools": 6,
  "defaultStartDate": "2012-03-31T06:00:00Z",
  "gameMinutesPerRealSecond": 5,
  "schoolWeekDays": 5,
  "schools": [
    { "id": 1, "name": "Гимназия №14", "gameTime": "2012-03-31T07:35:00Z", "running": false, "speedIndex": 1, "modIds": ["core"], "seed": 1847291 }
  ]
}
```

### `GET /api/schools/random-name`

`{ "name": "Лицей «Северная»" }` — a suggestion that is not already taken.

Optional `?lang=en` draws from the English word list (`Northern Academy`); any other value, or
none, stays Russian. The client sends the active UI language. Names the player types are not
translated — they are saved as written.

### `GET /api/mods?lang=ru|en`

Folders under the server's `mods/` directory. `core` is always first and `required: true`; other
packs can be switched off in the create dialog. `lang` is the same value Hello carries — not
`Accept-Language`. Anything other than `en` is Russian.

Each pack carries a human label, a version string and the ids it `requires`. The label is the pack
id looked up in that pack's own `localizations/<lang>.jsonc`. A folder without `pack.jsonc` is
still a pack: the id stands in for the name, `version` is empty, `requires` is empty.

```json
{ "mods": [{ "id": "core", "required": true, "label": "Базовая игра", "version": "1.0", "requires": [] }] }
```

The repo also ships `example` next to `core` — a sample pack, not required. It appears in this
list with `required: false` and `requires: ["core"]`. Vanilla create omits it.

### `GET /api/catalog?lang=ru|en&mods=addon1,addon2`

Placeable (non-abstract) types plus labels in `lang`, and the last-wins `maps/default.jsonc` for
`core` plus the listed extras. The server always prepends `core` and then reorders extras so
`requires` load first, same as create. `mods` is a comma-separated list of extra pack ids; omit
it for vanilla. Unknown extras return `400` `unknown-mod`. A selected pack whose dependency was
not listed returns `400` `missing-mod`; a cycle returns `400` `mod-cycle`.

Room defs that are homerooms carry `homeroom`, `seatThing` and `defaultSeats` instead of a
slot table. A map classroom stores `seats` — how many of that thing occupy the room. Capacity is
still `ThingDef.pupilSlots × seats`. Named slots remain on rooms whose furnishing actually
varies (cafeteria, medical office, principal's office, library). The create editor shows a
single seats field on a homeroom and the old slot rows on everything else.

Things carry `pupilSlots` — how many pupils that thing hosts. The snapshot's per-node pupil-slot
total is computed on the server.

`nameSets` is the list of placeable name packs (`defName` + label + `nativeLanguages`). Each
`nativeLanguages` entry is a skill (`defName` + label). The create dialog picks a name set and a
native language; the language list comes from that set (vanilla Slavic: Russian, Belarusian,
Ukrainian). It is independent of the UI language. Everyone in the school is generated with that
native. Other languages of the same set often appear at a low skill — a Russian speaker who
understands Belarusian. Those rolls live on the `NameSetDef` (`relatedLanguageChance` and
neighbours), not on this catalog payload.

`subjects` is the list of placeable subjects (`defName`, label, `gradeMin`/`gradeMax`,
`hoursPerWeek`, `skills` with shares, and optional `room`). `room` is the RoomDef the lesson
needs — PE uses a gym, informatics a computer lab; omit it and the class homeroom is used.

`dayFrame` is the one concrete bell schedule (`firstLesson` as `HH:mm`, lesson count and
lengths, which break is the long one). `holidays` are month-day ranges that repeat every
academic year; a range whose start is after its end wraps across 1 January.

The assignment form in a later phase reads subjects; the timetable grid reads the day frame.
The create editor does not.

`lang` is the same value Hello carries — not `Accept-Language`. Anything other than `en` is
Russian.

### `POST /api/schools`

Body:

```json
{
  "name": "Гимназия №14",
  "startDate": "2012-03-31T06:00:00Z",
  "modIds": [],
  "map": null,
  "nameSetId": "Slavic",
  "nativeLanguage": null,
  "seed": null
}
```

`modIds` are extras; the server always prepends `core`, then **reorders** the selection so each
pack's `requires` load first (stable topological sort over the player's order). The resolved
order is returned as `modIds` on the created school and written to the save, so a restart loads
the same catalog. Omit `map` (or send `null`) to use that pack set's default layout. A supplied map is validated as a connected yard-and-rooms graph.
`nameSetId` is a `NameSetDef`; omit it to use the first placeable set in the catalog (vanilla:
`Slavic`). Unknown ids return `400` `unknown-name-set`.
`nativeLanguage` is a skill from that set's `nativeLanguages`. Omit it (or send `null`) to pick
one from the school seed. An id that is not in the set returns `400` `unknown-native-language`.
`seed` is an optional integer. Send it to reproduce a known school; omit it (or send `null`) and
the server rolls one. Existing saves keep the seed already stored in the people file.

| Status | Meaning |
| --- | --- |
| `201` | Created; body is the school. |
| `400` `invalid-name` | Blank, or longer than 40 characters. |
| `400` `invalid-start-date` | Outside 1900–2999. |
| `400` `invalid-map` | Missing yard, no rooms, unknown def, or a disconnected graph. |
| `400` `unknown-mod` | An extra pack id is missing under `mods/`. |
| `400` `missing-mod` | A selected pack `requires` an id that was not selected. `missing` is that id. |
| `400` `mod-cycle` | Selected packs require each other in a cycle. |
| `400` `invalid-catalog` | The selected packs could not be loaded. |
| `400` `unknown-name-set` | `nameSetId` is not a placeable `NameSetDef` in those packs. |
| `400` `unknown-native-language` | `nativeLanguage` is not in that name set's `nativeLanguages`. |
| `409` `school-limit-reached` | `maxSchools` schools already exist. |

Failures are RFC 7807 problem details with an extra `code` field — that is what the UI switches on.

### `DELETE /api/schools/{id}`

`204` when deleted, `404` when the id is unknown. Anyone watching that school over a WebSocket
gets a `SchoolGone` frame.

### `GET /api/schools/{id}/people`

The in-school people list. Reads the **published roster snapshot** and that school's last clock;
it does not post to the worker. Unknown `{id}` is `404` `unknown-school`. Bad query parameters
are `400` `invalid-query`. `lang` is `ru` or `en`, same as the catalog — anything other than
`en` is Russian.

| Query | Meaning |
| --- | --- |
| `role` | `student`, `staff` or `parent`. A staff parent matches `parent`. |
| `year` | Class parallel (`5` for fifth year). |
| `letter` | Class letter as stored on the roster (`А`, not a room number). |
| `position` | Staff `PositionDef` name (`Teacher`). |
| `sex` | `male` or `female`. |
| `ageMin` / `ageMax` | Inclusive age in full years at the school's current game time. |
| `sort` | `surname` (default), `age`, `year`, `position`. |
| `dir` | `asc` (default) or `desc`. |
| `page` | 1-based. Default `1`. `0` is invalid. A page past the end is empty and still reports `total`. |
| `pageSize` | Default `50`, max `100`. |
| `lang` | Label language for positions and filter options. |

```json
{
  "total": 512,
  "page": 1,
  "pageSize": 50,
  "people": [
    {
      "id": "f0.c0",
      "fullName": "Иванова Мария Петровна",
      "surname": "Иванова",
      "given": "Мария",
      "patronymic": "Петровна",
      "female": true,
      "age": 12,
      "roles": ["student"],
      "classYear": 5,
      "classLetter": "А",
      "position": null,
      "positionLabel": null
    }
  ],
  "filters": {
    "years": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
    "letters": ["А"],
    "positions": [{ "defName": "Teacher", "label": "Учитель" }]
  }
}
```

The list row is identity only — skills, traits and needs stay on the card. Age is computed from
`birthDate` and the published game time, not from the World.

Applicants live in `saves/{id}.people.json` next to the roster and are **not** in this list.
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
tick with the clock. Unknown school is `404` `unknown-school`; unknown person is `404`
`unknown-person`. `?lang=ru|en` labels body, skills, traits, needs and the position.

Family links are other members of the same family: parents and siblings for a child, children
and partners for a parent. The client opens another card by id; this response does not nest
cards. `classId` is the homeroom class for a pupil and `null` otherwise — the personal timetable
grid fetches `GET .../timetable?classId=` with it.

`activity` is the ActionDef name currently in progress, or `null` when idle. `activityLabel`
is that def in the request locale. HTTP JSON is additive — no protocol version bump.

`skills` lists only keys the person has, not every `SkillDef` in the catalog. A first-year has
no Chemistry; a related tongue from the name set may sit beside the native at a low value.

```json
{
  "id": "f0.c0",
  "fullName": "Иванова Мария Петровна",
  "female": true,
  "age": 12,
  "birthDate": "2000-03-14T00:00:00Z",
  "roles": ["student"],
  "classYear": 5,
  "classLetter": "А",
  "classId": "class-classroom-105",
  "body": [{ "id": "Height", "label": "Рост", "value": "164" }],
  "skills": [{ "id": "Math", "label": "Математика", "value": "62" }],
  "traits": [{ "defName": "Diligent", "label": "Усидчивый" }],
  "needs": [{ "id": "Sleep", "label": "Сон", "value": 1 }],
  "activity": null,
  "activityLabel": null,
  "family": {
    "parents": [{ "id": "f0.p1", "fullName": "Иванова Ольга Михайловна", "female": true }],
    "children": [],
    "siblings": [{ "id": "f0.c1", "fullName": "Иванов Кирилл Петрович", "female": false }],
    "partners": []
  }
}
```

### `GET /api/schools/{id}/staffing`

Money, uncovered subjects, the applicant pool and current staff. Reads the **published**
roster, applicant snapshot and catalog — it does not post to the worker. Unknown `{id}` is
`404` `unknown-school`. `?lang=ru|en` labels subjects and positions.

`allocated` is `Simulation:MonthlyPayrollCap`. A staff member is paid
`hourlyWageAsk × weeklyHours × weeksPerMonth`, never less than one full rate
(`baseWeeklyHours`), and `payroll` is the sum over staff. The cap is checked when hiring or
assigning, not at month end; money itself does not move.

`weeklyHours` is not stored: it is the curriculum. For every subject assigned to a person,
`hoursPerWeek` of that subject across the classes that study it, divided between everyone
teaching it. So a second teacher of a subject halves what the first one carries — and costs.

A subject appears in `uncovered` when nobody teaches it **or** when the people who do cannot
between them carry its hours (`maxWeeklyHours` each). Both mean the same thing to a player:
those lessons will not happen. `teachersShort` is how many more people that subject still
needs — primary school on a vanilla map is three, and hiring the second teacher leaves it at
one.

```json
{
  "allocated": 100000,
  "payroll": 5000,
  "remaining": 95000,
  "uncovered": [
    {
      "defName": "Mathematics",
      "label": "Математика",
      "gradeMin": 5,
      "gradeMax": 11,
      "hoursPerWeek": 5,
      "teachersShort": 1
    }
  ],
  "applicants": [
    {
      "id": "a0.p0",
      "fullName": "Соколов Иван Петрович",
      "female": false,
      "age": 34,
      "isParent": false,
      "hourlyWageAsk": 50,
      "monthlyBase": 4000,
      "skills": [{ "id": "Mathematics", "label": "Математика", "value": "72" }]
    }
  ],
  "staff": [
    {
      "id": "f3.p1",
      "fullName": "Иванова Ольга Михайловна",
      "female": true,
      "age": 41,
      "isParent": true,
      "position": "Teacher",
      "positionLabel": "Учитель",
      "hourlyWageAsk": 50,
      "weeklyHours": 35,
      "monthlyPay": 7000,
      "subjects": [{ "defName": "Mathematics", "label": "Математика" }]
    }
  ],
  "positions": [{ "defName": "Teacher", "label": "Учитель" }],
  "subjects": [
    {
      "defName": "Mathematics",
      "label": "Математика",
      "gradeMin": 5,
      "gradeMax": 11,
      "hoursPerWeek": 5
    }
  ]
}
```

Applicants here are the same people as in `saves/{id}.people.json`. A parent keeps the same
id on the roster; hiring them sets `isStaff` on that person and does not create a second
entity. Generated candidates (`aN.p0`) join the roster only when hired. `skills` on an
applicant are the three strongest, for the management list; the card lists every skill they
have, not the three strongest. `positions` and `subjects` are the school's catalog, so the hire and assign pickers
do not need a second request.

`GET /api/schools/{id}/people/{personId}` also opens a card for someone who is only in the
applicant pool (needs are the frozen snapshot — they are not in the World yet). Unknown
ids that are in neither place stay `404` `unknown-person`.

### `POST /api/schools/{id}/staff/hire`

Body: `{ "personId": "a0.p0", "position": "Teacher" }`. Goes through the school's mailbox.
On success returns the same payload as `GET .../staffing`, so it takes the same `?lang=ru|en`.
`Teacher` needs no room opening; other positions fill the first free `RoomDef.positions` slot
of that kind.

| Status | `code` | When |
| --- | --- | --- |
| `404` | `unknown-school` | No school with that id. |
| `404` | `unknown-applicant` | `personId` is not in the pool. |
| `409` | `already-hired` | That person is already staff. |
| `400` | `unknown-position` | Not a concrete `PositionDef`. |
| `409` | `no-opening` | Every opening of that position is filled. |
| `409` | `payroll-exceeded` | Hire would take `payroll` past `allocated`. |

`payroll-exceeded` includes `allocated`, `payroll` (current), `remaining` and `attempted`
(what payroll would become). Same RFC 7807 `code` field as the other errors.

### `POST /api/schools/{id}/staff/{personId}/subjects`

Body: `{ "subject": "Mathematics" }`. Teachers only. Same success payload as GET staffing,
and the same `?lang=ru|en`.

| Status | `code` | When |
| --- | --- | --- |
| `400` | `not-staff` | Person is not staff. |
| `400` | `not-teacher` | Position is not `Teacher`. |
| `400` | `unknown-subject` | Not a concrete `SubjectDef`. |
| `409` | `already-assigned` | Already on this person. |
| `409` | `payroll-exceeded` | Extra subject would exceed the cap. |

### `DELETE /api/schools/{id}/staff/{personId}/subjects/{subject}`

Removes one assignment. Payroll drops when the subject was not the only one. Same success
payload and `?lang=ru|en` as the other two. Unknown assignment is `404` `unknown-assignment`.

### `GET /api/schools/{id}/timetable`

The published lesson table and uncovered hours. Optional `?classId=` or `?personId=` filter
the lessons. `?lang=ru|en` labels subjects and rooms. Reads the snapshot — it does not post to the
worker. Unknown `{id}` is `404` `unknown-school`. `classes` and `rooms` are the full school lists
so a picker does not need a second request.

`day` is 0 = Monday. `period` is the 1-based lesson number from the day frame.

```json
{
  "weekDays": 5,
  "lessonCount": 7,
  "lessons": [
    {
      "classId": "c5A",
      "classYear": 5,
      "classLetter": "A",
      "subject": "Mathematics",
      "subjectLabel": "Математика",
      "teacherId": "f3.p1",
      "teacherName": "Иванова Ольга Михайловна",
      "roomId": "classroom-204",
      "roomLabel": "Класс 204",
      "day": 1,
      "period": 3,
      "locked": false
    }
  ],
  "uncovered": [
    {
      "classId": "c5A",
      "classYear": 5,
      "classLetter": "A",
      "subject": "Informatics",
      "subjectLabel": "Информатика",
      "hours": 1
    }
  ],
  "classes": [{ "id": "c5A", "year": 5, "letter": "A" }],
  "rooms": [{ "id": "classroom-204", "label": "Класс 204" }]
}
```

### `POST /api/schools/{id}/timetable/pin`

Body: `{ "classId", "subject", "roomId", "day", "period" }`. Pins a locked lesson there and
rebuilds the rest around it. Same success payload as GET timetable.

| Status | `code` | When |
| --- | --- | --- |
| `400` | `unknown-class` / `unknown-subject` / `unknown-room` | Not in this school. |
| `409` | `no-teacher` | Nobody is assigned that subject. |
| `409` | `pin-rejected` | The slot or room violates the four constraints. |

### `DELETE /api/schools/{id}/timetable/pin`

Query: `classId`, `subject`, `day`, `period`. Drops that lock and rebuilds. Unknown lock is
`404` `unknown-lesson`.

## Dev endpoints

These exist only when `HSchool:AllowSaveReload` is true (headless AppHost tests). They are never
mapped in production by default. Same switch as `POST /api/dev/reload-schools`.

### `GET /api/dev/schools/{id}/dump`

Roster, live presence, live needs and the timetable as one JSON. The roster and lesson table come
from the published snapshots; nodes and needs go through that school's mailbox — HTTP does not
read the `World`. Unknown `{id}` is `404` `unknown-school`.

```json
{
  "id": 1,
  "name": "Гимназия №14",
  "gameTime": "2012-04-03T10:20:00Z",
  "running": true,
  "people": [
    {
      "id": "f3.p1",
      "fullName": "Иванова Ольга Михайловна",
      "nodeId": "classroom-101",
      "needs": { "Hunger": 0.92, "Toilet": 1, "Social": 0.8, "Sleep": 1 }
    }
  ],
  "now": [
    {
      "classId": "c5A",
      "subject": "Mathematics",
      "teacherId": "f3.p1",
      "roomId": "classroom-101",
      "day": 1,
      "period": 3
    }
  ],
  "lessons": [
    {
      "classId": "c5A",
      "subject": "Mathematics",
      "teacherId": "f3.p1",
      "roomId": "classroom-101",
      "day": 1,
      "period": 3
    }
  ]
}
```

`nodeId` is null when the person is off campus. `now` is the lessons occurring at `gameTime`
(empty on a break, night, weekend or holiday). `lessons` is the published table.

## WebSocket message ids

Client-to-server ids live in `0x00–0x7F`, server-to-client ids in `0x80–0xFF`, so a misrouted
frame is obvious at a glance.

| Id | Direction | Message |
| --- | --- | --- |
| `0x01` | C → S | Hello |
| `0x02` | C → S | Ping |
| `0x03` | C → S | OpenSchool |
| `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

### `0x01` Hello — 3 bytes

Must be the first frame; the server drops the connection if it does not arrive within 5 seconds.
The locale byte is the same language the catalog HTTP API takes as `?lang=`.

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x01` |
| 1 | `u8` | protocol version |
| 2 | `u8` | locale: `0` Russian, `1` English; any other value is treated as Russian |

### `0x02` Ping — 9 bytes

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x02` |
| 1 | `i64` | client clock in milliseconds |

### `0x03` OpenSchool — 5 bytes

Starts watching a school: a map snapshot in the Hello locale arrives once, then clock frames
and presence frames. It does not start the calendar — every school runs on its own from the
moment it is created.

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x03` |
| 1 | `i32` | school id |

### `0x04` CloseSchool — 1 byte

Back to the menu: the clock frames stop. The school keeps running — only `SetRunning` pauses it,
and that pause survives leaving and reconnecting.

### `0x05` SetRunning — 2 bytes

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x05` |
| 1 | `u8` | `1` running, `0` paused |

### `0x06` SetSpeed — 2 bytes

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x06` |
| 1 | `u8` | speed index |

Running and speed are **separate messages on purpose**. A single "set clock" message forces each
button to resend the other field from the client's own copy of the state, which is always at least
one tick stale — pressing play and then a speed button would pause the school again.

Speed indexes are `0 = ×½`, `1 = ×1`, `2 = ×2`, `3 = ×3`, `4 = ×4`; out-of-range values are
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

The first frame the client receives.

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x81` |
| 1 | `u8` | protocol version |
| 2 | `u8` | tick rate in Hz |
| 3 | `u8` | maximum number of schools |

### `0x82` Pong — 13 bytes

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x82` |
| 1 | `i64` | client clock, echoed unchanged |
| 9 | `u32` | server tick when the ping was handled |

### `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 |
| --- | --- | --- |
| 0 | `u8` | `0x83` |
| 1 | `i32` | school id |
| 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

The open school no longer exists — deleted from the menu in another tab, or never existed. The
client returns to the menu.

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x84` |
| 1 | `i32` | school id |

### `0x85` MapSnapshot — variable

Sent when a school is opened, and on reconnect OpenSchool. Structure only — people and the
current lesson ride the presence stream. Labels are in the Hello locale.

Strings are `u16` byte length + UTF-8. Empty string is a zero length.

| Offset | Type | Field |
| --- | --- | --- |
| 0 | `u8` | `0x85` |
| 1 | `i32` | school id |
| 5 | `u16` | node count |
| 7… | | nodes |

Each node:

| Type | Field |
| --- | --- |
| `u8` | kind: `0` territory, `1` building, `2` floor, `3` room |
| string | instance id |
| string | parent id (empty for the yard) |
| string | display name |
| `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 |

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`
  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 and presence use a separate reliable queue so ticks cannot crowd them out.

## Not in v7 yet

Authentication, Sit orders, an event log, walk animation, and `OpenLocation` on the server —
the tree and the location panel are filtered on the client from the snapshot plus presence.