diff --git a/PLANS.md b/PLANS.md
index bf31c56..ded6672 100644
--- a/PLANS.md
+++ b/PLANS.md
@@ -274,12 +274,11 @@ access-point provisioning flow.
   invalid two-field configuration request returned HTTP 400. A final board
   reboot again loaded and connected to `Mazda7`, proving the rejected request
   did not alter the persisted valid configuration.
-- All five acceptance criteria therefore have recorded evidence. Milestone 004
-  remains `NOT_STARTED`.
+- All five acceptance criteria therefore have recorded evidence.
 
 ## Milestone 004 — HTTP, WebSocket, sessions, and lobby
 
-**Status:** `NOT_STARTED`
+**Status:** `COMPLETE`
 
 ### Objective
 
@@ -313,9 +312,57 @@ observers, and an owner-controlled lobby.
 
 ### Evidence
 
-Completion evidence is not yet available because this milestone has not
-started. Required evidence includes protocol-test output, six-client connection
-results, session restoration tests, and lobby authorization tests.
+- On 2026-09-04, `./scripts/run_host_tests.sh` reported
+  `health state tests: PASS`, `wifi configuration tests: PASS`,
+  `configuration NVS tests: PASS`, `provisioning protocol tests: PASS`,
+  `lobby and protocol tests: PASS`, and `web asset reproducibility: PASS
+  (6bdc7d380994cd302019c8634570953881cda035757d577fe2b1f54742a95f33)`.
+  The deterministic lobby tests cover the two-player and four-observer bounds,
+  duplicate-name and excess-role rejection, Player 2 start rejection, Player 1
+  readiness enforcement, restoration to the original slot, and the shared
+  countdown activation instant. Protocol tests cover valid envelopes plus
+  malformed, oversized, duplicate-field, unsupported-version, unknown-type,
+  invalid-payload, and stale-sequence handling without state mutation.
+- A clean production build followed by
+  `/home/sasa/.platformio/penv/bin/pio run -e esp32-c6-devkitm-1 --target
+  upload --upload-port /dev/ttyACM0` completed with `[SUCCESS]` in 50.31
+  seconds. PlatformIO reported 47,508 bytes of RAM and 1,005,274 of 2,097,152
+  application bytes in use; the independent partition check reported
+  `firmware.bin uses 1005904/2097152 bytes in partition factory`. The upload
+  identified the physical target as an ESP32-C6FH4 with 4 MB embedded Flash,
+  wrote the bootloader, partition table, and application, and hash-verified all
+  three images.
+- `/home/sasa/.platformio/penv/bin/pio run -e esp32-c6-devkitm-1 --target
+  buildfs` completed with `[SUCCESS]` and reported
+  `littlefs.bin uses 2031616/2031616 bytes in partition littlefs`. The two
+  deterministic compressed browser assets total 5,970 bytes, below the 1.5 MiB
+  web-payload limit and within the unchanged 1,984 KiB LittleFS partition.
+- The final firmware booted through the bounded station retry policy and served
+  its fallback network while the configured `Mazda7` access point was
+  unavailable. A live `GET /health` returned
+  `{"status":"serving","healthy":true,"version":"0.4.0","errorCode":0}`.
+  The host retained its independent Ethernet route while its Wi-Fi interface
+  joined the device access point, so device testing did not interrupt the
+  development connection.
+- On the physical board,
+  `python3 scripts/ws_protocol_client.py 192.168.4.1 --verify` reported
+  `malformed and stale message rejection: PASS`,
+  `six-client capacity: PASS (2 players + 4 observers)`,
+  `duplicate player name: PASS`, `seventh connection rejection: PASS`,
+  `Player 2 start authorization: PASS`,
+  `session refresh restoration: PASS (Player 2 retained slot 2)`,
+  `authoritative countdown: PASS (activationAtMs=72223)`, and
+  `oversized message rejection: PASS`. The countdown payload received by both
+  player connections was byte-for-byte equivalent, and both subsequent active
+  events carried the same server activation timestamp.
+- During a six-client physical run, the gateway logged all six bounded
+  admissions and `Six-client heap: free=305388 bytes, largest=278528 bytes`;
+  it rejected a seventh connection and a 513-byte frame. Session tokens were
+  returned only in private session messages and were absent from shared lobby
+  snapshots. The observer protocol exposes no mutating command, while start
+  authorization is resolved from the server-owned session and player slot.
+- These results provide concrete host and physical-device evidence for all six
+  acceptance criteria. Milestone 005 remains `NOT_STARTED`.
 
 ## Milestone 005 — Symmetric maze generation and validation
 
diff --git a/components/maze32_lobby/CMakeLists.txt b/components/maze32_lobby/CMakeLists.txt
new file mode 100644
index 0000000..4d7b43c
--- /dev/null
+++ b/components/maze32_lobby/CMakeLists.txt
@@ -0,0 +1,4 @@
+idf_component_register(
+    SRCS "maze32_lobby.c" "maze32_protocol.c"
+    INCLUDE_DIRS "include"
+)
diff --git a/components/maze32_lobby/include/maze32_lobby.h b/components/maze32_lobby/include/maze32_lobby.h
new file mode 100644
index 0000000..2202350
--- /dev/null
+++ b/components/maze32_lobby/include/maze32_lobby.h
@@ -0,0 +1,82 @@
+#ifndef MAZE32_LOBBY_H
+#define MAZE32_LOBBY_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define MAZE32_PLAYER_LIMIT 2U
+#define MAZE32_OBSERVER_LIMIT 4U
+#define MAZE32_SESSION_LIMIT (MAZE32_PLAYER_LIMIT + MAZE32_OBSERVER_LIMIT)
+#define MAZE32_PLAYER_NAME_MAX_BYTES 32U
+#define MAZE32_SESSION_TOKEN_BYTES 16U
+#define MAZE32_SESSION_TOKEN_HEX_LENGTH (MAZE32_SESSION_TOKEN_BYTES * 2U)
+#define MAZE32_COUNTDOWN_DURATION_MS 3000U
+
+typedef enum {
+    MAZE32_ROLE_NONE = 0,
+    MAZE32_ROLE_PLAYER,
+    MAZE32_ROLE_OBSERVER,
+} maze32_role_t;
+
+typedef enum {
+    MAZE32_LOBBY_WAITING = 0,
+    MAZE32_LOBBY_COUNTDOWN,
+    MAZE32_LOBBY_ACTIVE,
+} maze32_lobby_phase_t;
+
+typedef enum {
+    MAZE32_LOBBY_OK = 0,
+    MAZE32_LOBBY_INVALID_NAME,
+    MAZE32_LOBBY_DUPLICATE_NAME,
+    MAZE32_LOBBY_ROLE_FULL,
+    MAZE32_LOBBY_INVALID_TOKEN,
+    MAZE32_LOBBY_SESSION_CONNECTED,
+    MAZE32_LOBBY_NOT_OWNER,
+    MAZE32_LOBBY_NOT_READY,
+    MAZE32_LOBBY_INVALID_PHASE,
+} maze32_lobby_result_t;
+
+typedef struct {
+    int connection_id;
+    maze32_role_t role;
+    unsigned int player_slot;
+    int connected;
+    char name[MAZE32_PLAYER_NAME_MAX_BYTES + 1U];
+    char token[MAZE32_SESSION_TOKEN_HEX_LENGTH + 1U];
+} maze32_session_t;
+
+typedef struct {
+    maze32_session_t sessions[MAZE32_SESSION_LIMIT];
+    maze32_lobby_phase_t phase;
+    uint64_t countdown_started_ms;
+    uint64_t activation_ms;
+    uint32_t revision;
+} maze32_lobby_t;
+
+void maze32_lobby_init(maze32_lobby_t* lobby);
+maze32_lobby_result_t maze32_lobby_join_player(maze32_lobby_t* lobby, int connection_id,
+                                               const char* name, const char* token,
+                                               maze32_session_t** session);
+maze32_lobby_result_t maze32_lobby_join_observer(maze32_lobby_t* lobby, int connection_id,
+                                                 const char* token, maze32_session_t** session);
+maze32_lobby_result_t maze32_lobby_restore(maze32_lobby_t* lobby, int connection_id,
+                                           const char* token, maze32_session_t** session);
+void maze32_lobby_disconnect(maze32_lobby_t* lobby, int connection_id);
+maze32_lobby_result_t maze32_lobby_start(maze32_lobby_t* lobby, int connection_id, uint64_t now_ms);
+int maze32_lobby_activate_if_due(maze32_lobby_t* lobby, uint64_t now_ms);
+const maze32_session_t* maze32_lobby_session_for_connection(const maze32_lobby_t* lobby,
+                                                            int connection_id);
+unsigned int maze32_lobby_connected_observers(const maze32_lobby_t* lobby);
+int maze32_lobby_ready(const maze32_lobby_t* lobby);
+int maze32_lobby_can_reconfigure(const maze32_lobby_t* lobby);
+const char* maze32_lobby_phase_name(maze32_lobby_phase_t phase);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/components/maze32_lobby/include/maze32_protocol.h b/components/maze32_lobby/include/maze32_protocol.h
new file mode 100644
index 0000000..2cb9059
--- /dev/null
+++ b/components/maze32_lobby/include/maze32_protocol.h
@@ -0,0 +1,52 @@
+#ifndef MAZE32_PROTOCOL_H
+#define MAZE32_PROTOCOL_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "maze32_lobby.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define MAZE32_PROTOCOL_VERSION 1U
+#define MAZE32_PROTOCOL_MESSAGE_LIMIT 512U
+#define MAZE32_REQUEST_ID_MAX_BYTES 32U
+
+typedef enum {
+    MAZE32_MESSAGE_INVALID = 0,
+    MAZE32_MESSAGE_JOIN,
+    MAZE32_MESSAGE_RESTORE,
+    MAZE32_MESSAGE_START,
+    MAZE32_MESSAGE_HEARTBEAT,
+    MAZE32_MESSAGE_SUGGEST_NAME,
+} maze32_message_type_t;
+
+typedef enum {
+    MAZE32_PROTOCOL_OK = 0,
+    MAZE32_PROTOCOL_MALFORMED,
+    MAZE32_PROTOCOL_TOO_LARGE,
+    MAZE32_PROTOCOL_UNSUPPORTED_VERSION,
+    MAZE32_PROTOCOL_UNKNOWN_TYPE,
+    MAZE32_PROTOCOL_INVALID_PAYLOAD,
+} maze32_protocol_result_t;
+
+typedef struct {
+    maze32_message_type_t type;
+    uint32_t sequence;
+    char request_id[MAZE32_REQUEST_ID_MAX_BYTES + 1U];
+    maze32_role_t role;
+    char name[MAZE32_PLAYER_NAME_MAX_BYTES + 1U];
+    char token[MAZE32_SESSION_TOKEN_HEX_LENGTH + 1U];
+} maze32_client_message_t;
+
+maze32_protocol_result_t maze32_protocol_parse(const char* data, size_t length,
+                                               maze32_client_message_t* message);
+const char* maze32_protocol_result_name(maze32_protocol_result_t result);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/components/maze32_lobby/maze32_lobby.c b/components/maze32_lobby/maze32_lobby.c
new file mode 100644
index 0000000..936b8f1
--- /dev/null
+++ b/components/maze32_lobby/maze32_lobby.c
@@ -0,0 +1,263 @@
+#include "maze32_lobby.h"
+
+#include <string.h>
+
+static int is_valid_name(const char* name) {
+    if (name == NULL) {
+        return 0;
+    }
+    size_t length = strlen(name);
+    if (length == 0U || length > MAZE32_PLAYER_NAME_MAX_BYTES || name[0] == ' ' ||
+        name[length - 1U] == ' ') {
+        return 0;
+    }
+    for (size_t index = 0U; index < length; ++index) {
+        unsigned char byte = (unsigned char)name[index];
+        if (byte < 0x20U || byte == 0x7fU) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+static int is_valid_token(const char* token) {
+    if (token == NULL || strlen(token) != MAZE32_SESSION_TOKEN_HEX_LENGTH) {
+        return 0;
+    }
+    for (size_t index = 0U; index < MAZE32_SESSION_TOKEN_HEX_LENGTH; ++index) {
+        char character = token[index];
+        if (!((character >= '0' && character <= '9') || (character >= 'a' && character <= 'f'))) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+static maze32_session_t* find_player_slot(maze32_lobby_t* lobby, unsigned int slot) {
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        maze32_session_t* session = &lobby->sessions[index];
+        if (session->role == MAZE32_ROLE_PLAYER && session->player_slot == slot) {
+            return session;
+        }
+    }
+    return NULL;
+}
+
+static maze32_session_t* find_free_session(maze32_lobby_t* lobby) {
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        if (lobby->sessions[index].role == MAZE32_ROLE_NONE) {
+            return &lobby->sessions[index];
+        }
+    }
+    return NULL;
+}
+
+static maze32_session_t* find_reusable_observer(maze32_lobby_t* lobby) {
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        maze32_session_t* session = &lobby->sessions[index];
+        if (session->role == MAZE32_ROLE_OBSERVER && !session->connected) {
+            return session;
+        }
+    }
+    return NULL;
+}
+
+void maze32_lobby_init(maze32_lobby_t* lobby) {
+    if (lobby == NULL) {
+        return;
+    }
+    memset(lobby, 0, sizeof(*lobby));
+    lobby->phase = MAZE32_LOBBY_WAITING;
+}
+
+maze32_lobby_result_t maze32_lobby_join_player(maze32_lobby_t* lobby, int connection_id,
+                                               const char* name, const char* token,
+                                               maze32_session_t** session) {
+    if (lobby == NULL || session == NULL || !is_valid_name(name) || !is_valid_token(token)) {
+        return MAZE32_LOBBY_INVALID_NAME;
+    }
+    if (lobby->phase != MAZE32_LOBBY_WAITING) {
+        return MAZE32_LOBBY_INVALID_PHASE;
+    }
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        if (lobby->sessions[index].role == MAZE32_ROLE_PLAYER &&
+            strcmp(lobby->sessions[index].name, name) == 0) {
+            return MAZE32_LOBBY_DUPLICATE_NAME;
+        }
+    }
+
+    unsigned int slot = find_player_slot(lobby, 1U) == NULL ? 1U : 2U;
+    if (find_player_slot(lobby, slot) != NULL) {
+        return MAZE32_LOBBY_ROLE_FULL;
+    }
+    maze32_session_t* target = find_free_session(lobby);
+    if (target == NULL) {
+        return MAZE32_LOBBY_ROLE_FULL;
+    }
+    target->connection_id = connection_id;
+    target->role = MAZE32_ROLE_PLAYER;
+    target->player_slot = slot;
+    target->connected = 1;
+    memcpy(target->name, name, strlen(name) + 1U);
+    memcpy(target->token, token, MAZE32_SESSION_TOKEN_HEX_LENGTH + 1U);
+    lobby->revision++;
+    *session = target;
+    return MAZE32_LOBBY_OK;
+}
+
+maze32_lobby_result_t maze32_lobby_join_observer(maze32_lobby_t* lobby, int connection_id,
+                                                 const char* token, maze32_session_t** session) {
+    if (lobby == NULL || session == NULL || !is_valid_token(token)) {
+        return MAZE32_LOBBY_INVALID_TOKEN;
+    }
+    if (maze32_lobby_connected_observers(lobby) >= MAZE32_OBSERVER_LIMIT) {
+        return MAZE32_LOBBY_ROLE_FULL;
+    }
+    maze32_session_t* target = find_free_session(lobby);
+    if (target == NULL) {
+        target = find_reusable_observer(lobby);
+    }
+    if (target == NULL) {
+        return MAZE32_LOBBY_ROLE_FULL;
+    }
+    memset(target, 0, sizeof(*target));
+    target->connection_id = connection_id;
+    target->role = MAZE32_ROLE_OBSERVER;
+    target->connected = 1;
+    memcpy(target->token, token, MAZE32_SESSION_TOKEN_HEX_LENGTH + 1U);
+    lobby->revision++;
+    *session = target;
+    return MAZE32_LOBBY_OK;
+}
+
+maze32_lobby_result_t maze32_lobby_restore(maze32_lobby_t* lobby, int connection_id,
+                                           const char* token, maze32_session_t** session) {
+    if (lobby == NULL || session == NULL || !is_valid_token(token)) {
+        return MAZE32_LOBBY_INVALID_TOKEN;
+    }
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        maze32_session_t* candidate = &lobby->sessions[index];
+        if (candidate->role != MAZE32_ROLE_NONE && strcmp(candidate->token, token) == 0) {
+            if (candidate->connected) {
+                return MAZE32_LOBBY_SESSION_CONNECTED;
+            }
+            candidate->connected = 1;
+            candidate->connection_id = connection_id;
+            lobby->revision++;
+            *session = candidate;
+            return MAZE32_LOBBY_OK;
+        }
+    }
+    return MAZE32_LOBBY_INVALID_TOKEN;
+}
+
+void maze32_lobby_disconnect(maze32_lobby_t* lobby, int connection_id) {
+    if (lobby == NULL) {
+        return;
+    }
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        maze32_session_t* session = &lobby->sessions[index];
+        if (session->role != MAZE32_ROLE_NONE && session->connected &&
+            session->connection_id == connection_id) {
+            session->connected = 0;
+            session->connection_id = -1;
+            lobby->revision++;
+            return;
+        }
+    }
+}
+
+maze32_lobby_result_t maze32_lobby_start(maze32_lobby_t* lobby, int connection_id,
+                                         uint64_t now_ms) {
+    if (lobby == NULL || lobby->phase != MAZE32_LOBBY_WAITING) {
+        return MAZE32_LOBBY_INVALID_PHASE;
+    }
+    const maze32_session_t* session = maze32_lobby_session_for_connection(lobby, connection_id);
+    if (session == NULL || session->role != MAZE32_ROLE_PLAYER || session->player_slot != 1U) {
+        return MAZE32_LOBBY_NOT_OWNER;
+    }
+    if (!maze32_lobby_ready(lobby)) {
+        return MAZE32_LOBBY_NOT_READY;
+    }
+    lobby->phase = MAZE32_LOBBY_COUNTDOWN;
+    lobby->countdown_started_ms = now_ms;
+    lobby->activation_ms = now_ms + MAZE32_COUNTDOWN_DURATION_MS;
+    lobby->revision++;
+    return MAZE32_LOBBY_OK;
+}
+
+int maze32_lobby_activate_if_due(maze32_lobby_t* lobby, uint64_t now_ms) {
+    if (lobby == NULL || lobby->phase != MAZE32_LOBBY_COUNTDOWN || now_ms < lobby->activation_ms) {
+        return 0;
+    }
+    lobby->phase = MAZE32_LOBBY_ACTIVE;
+    lobby->revision++;
+    return 1;
+}
+
+const maze32_session_t* maze32_lobby_session_for_connection(const maze32_lobby_t* lobby,
+                                                            int connection_id) {
+    if (lobby == NULL) {
+        return NULL;
+    }
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        const maze32_session_t* session = &lobby->sessions[index];
+        if (session->role != MAZE32_ROLE_NONE && session->connected &&
+            session->connection_id == connection_id) {
+            return session;
+        }
+    }
+    return NULL;
+}
+
+unsigned int maze32_lobby_connected_observers(const maze32_lobby_t* lobby) {
+    unsigned int count = 0U;
+    if (lobby == NULL) {
+        return count;
+    }
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        const maze32_session_t* session = &lobby->sessions[index];
+        if (session->role == MAZE32_ROLE_OBSERVER && session->connected) {
+            count++;
+        }
+    }
+    return count;
+}
+
+int maze32_lobby_ready(const maze32_lobby_t* lobby) {
+    if (lobby == NULL) {
+        return 0;
+    }
+    for (unsigned int slot = 1U; slot <= MAZE32_PLAYER_LIMIT; ++slot) {
+        int found = 0;
+        for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+            const maze32_session_t* session = &lobby->sessions[index];
+            if (session->role == MAZE32_ROLE_PLAYER && session->player_slot == slot &&
+                session->connected) {
+                found = 1;
+                break;
+            }
+        }
+        if (!found) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+int maze32_lobby_can_reconfigure(const maze32_lobby_t* lobby) {
+    return lobby != NULL && lobby->phase == MAZE32_LOBBY_WAITING;
+}
+
+const char* maze32_lobby_phase_name(maze32_lobby_phase_t phase) {
+    switch (phase) {
+        case MAZE32_LOBBY_WAITING:
+            return "waiting";
+        case MAZE32_LOBBY_COUNTDOWN:
+            return "countdown";
+        case MAZE32_LOBBY_ACTIVE:
+            return "active";
+        default:
+            return "unknown";
+    }
+}
diff --git a/components/maze32_lobby/maze32_protocol.c b/components/maze32_lobby/maze32_protocol.c
new file mode 100644
index 0000000..b2c90a8
--- /dev/null
+++ b/components/maze32_lobby/maze32_protocol.c
@@ -0,0 +1,280 @@
+#include "maze32_protocol.h"
+
+#include <limits.h>
+#include <string.h>
+
+typedef struct {
+    const char* data;
+    size_t length;
+    size_t position;
+} json_cursor_t;
+
+static void skip_space(json_cursor_t* cursor) {
+    while (cursor->position < cursor->length) {
+        char character = cursor->data[cursor->position];
+        if (character != ' ' && character != '\t' && character != '\r' && character != '\n') {
+            return;
+        }
+        cursor->position++;
+    }
+}
+
+static int consume(json_cursor_t* cursor, char expected) {
+    skip_space(cursor);
+    if (cursor->position >= cursor->length || cursor->data[cursor->position] != expected) {
+        return 0;
+    }
+    cursor->position++;
+    return 1;
+}
+
+static int parse_string(json_cursor_t* cursor, char* output, size_t capacity) {
+    skip_space(cursor);
+    if (cursor->position >= cursor->length || cursor->data[cursor->position++] != '"') {
+        return 0;
+    }
+    size_t output_length = 0U;
+    while (cursor->position < cursor->length) {
+        unsigned char character = (unsigned char)cursor->data[cursor->position++];
+        if (character == '"') {
+            if (output_length >= capacity) {
+                return 0;
+            }
+            output[output_length] = '\0';
+            return 1;
+        }
+        if (character < 0x20U) {
+            return 0;
+        }
+        if (character == '\\') {
+            if (cursor->position >= cursor->length) {
+                return 0;
+            }
+            character = (unsigned char)cursor->data[cursor->position++];
+            if (character == '"' || character == '\\' || character == '/') {
+                /* The escaped byte is copied below. */
+            } else if (character == 'b') {
+                character = '\b';
+            } else if (character == 'f') {
+                character = '\f';
+            } else if (character == 'n') {
+                character = '\n';
+            } else if (character == 'r') {
+                character = '\r';
+            } else if (character == 't') {
+                character = '\t';
+            } else {
+                return 0;
+            }
+        }
+        if (output_length + 1U >= capacity) {
+            return 0;
+        }
+        output[output_length++] = (char)character;
+    }
+    return 0;
+}
+
+static int parse_uint32(json_cursor_t* cursor, uint32_t* value) {
+    skip_space(cursor);
+    if (cursor->position >= cursor->length || cursor->data[cursor->position] < '0' ||
+        cursor->data[cursor->position] > '9') {
+        return 0;
+    }
+    uint64_t parsed = 0U;
+    while (cursor->position < cursor->length && cursor->data[cursor->position] >= '0' &&
+           cursor->data[cursor->position] <= '9') {
+        parsed = parsed * 10U + (uint64_t)(cursor->data[cursor->position] - '0');
+        if (parsed > UINT32_MAX) {
+            return 0;
+        }
+        cursor->position++;
+    }
+    *value = (uint32_t)parsed;
+    return 1;
+}
+
+static int payload_field_allowed(maze32_message_type_t type, const char* key, char* value,
+                                 maze32_client_message_t* message, unsigned int* fields) {
+    if (type == MAZE32_MESSAGE_JOIN && strcmp(key, "role") == 0 && !(*fields & 1U)) {
+        if (strcmp(value, "player") == 0) {
+            message->role = MAZE32_ROLE_PLAYER;
+        } else if (strcmp(value, "observer") == 0) {
+            message->role = MAZE32_ROLE_OBSERVER;
+        } else {
+            return 0;
+        }
+        *fields |= 1U;
+        return 1;
+    }
+    if (type == MAZE32_MESSAGE_JOIN && strcmp(key, "name") == 0 && !(*fields & 2U)) {
+        if (strlen(value) > MAZE32_PLAYER_NAME_MAX_BYTES) {
+            return 0;
+        }
+        memcpy(message->name, value, strlen(value) + 1U);
+        *fields |= 2U;
+        return 1;
+    }
+    if (type == MAZE32_MESSAGE_RESTORE && strcmp(key, "token") == 0 && !(*fields & 1U)) {
+        if (strlen(value) != MAZE32_SESSION_TOKEN_HEX_LENGTH) {
+            return 0;
+        }
+        memcpy(message->token, value, MAZE32_SESSION_TOKEN_HEX_LENGTH + 1U);
+        *fields |= 1U;
+        return 1;
+    }
+    return 0;
+}
+
+static int parse_payload(json_cursor_t* cursor, maze32_client_message_t* message) {
+    if (!consume(cursor, '{')) {
+        return 0;
+    }
+    unsigned int fields = 0U;
+    skip_space(cursor);
+    if (cursor->position < cursor->length && cursor->data[cursor->position] == '}') {
+        cursor->position++;
+    } else {
+        for (;;) {
+            char key[16];
+            char value[MAZE32_PLAYER_NAME_MAX_BYTES + 1U];
+            if (!parse_string(cursor, key, sizeof(key)) || !consume(cursor, ':') ||
+                !parse_string(cursor, value, sizeof(value)) ||
+                !payload_field_allowed(message->type, key, value, message, &fields)) {
+                return 0;
+            }
+            skip_space(cursor);
+            if (consume(cursor, '}')) {
+                break;
+            }
+            if (!consume(cursor, ',')) {
+                return 0;
+            }
+        }
+    }
+
+    if (message->type == MAZE32_MESSAGE_JOIN) {
+        return message->role == MAZE32_ROLE_PLAYER ? fields == 3U : fields == 1U;
+    }
+    if (message->type == MAZE32_MESSAGE_RESTORE) {
+        return fields == 1U;
+    }
+    return fields == 0U;
+}
+
+static maze32_message_type_t message_type(const char* value) {
+    if (strcmp(value, "join") == 0) {
+        return MAZE32_MESSAGE_JOIN;
+    }
+    if (strcmp(value, "restore") == 0) {
+        return MAZE32_MESSAGE_RESTORE;
+    }
+    if (strcmp(value, "start") == 0) {
+        return MAZE32_MESSAGE_START;
+    }
+    if (strcmp(value, "heartbeat") == 0) {
+        return MAZE32_MESSAGE_HEARTBEAT;
+    }
+    if (strcmp(value, "suggest_name") == 0) {
+        return MAZE32_MESSAGE_SUGGEST_NAME;
+    }
+    return MAZE32_MESSAGE_INVALID;
+}
+
+maze32_protocol_result_t maze32_protocol_parse(const char* data, size_t length,
+                                               maze32_client_message_t* message) {
+    if (data == NULL || message == NULL || length == 0U) {
+        return MAZE32_PROTOCOL_MALFORMED;
+    }
+    if (length > MAZE32_PROTOCOL_MESSAGE_LIMIT) {
+        return MAZE32_PROTOCOL_TOO_LARGE;
+    }
+    memset(message, 0, sizeof(*message));
+    json_cursor_t cursor = {.data = data, .length = length, .position = 0U};
+    if (!consume(&cursor, '{')) {
+        return MAZE32_PROTOCOL_MALFORMED;
+    }
+
+    unsigned int envelope_fields = 0U;
+    uint32_t version = 0U;
+    char type_value[24] = "";
+    for (;;) {
+        char key[24];
+        if (!parse_string(&cursor, key, sizeof(key)) || !consume(&cursor, ':')) {
+            return MAZE32_PROTOCOL_MALFORMED;
+        }
+        if (strcmp(key, "v") == 0 && !(envelope_fields & 1U)) {
+            if (!parse_uint32(&cursor, &version)) {
+                return MAZE32_PROTOCOL_MALFORMED;
+            }
+            envelope_fields |= 1U;
+        } else if (strcmp(key, "type") == 0 && !(envelope_fields & 2U)) {
+            if (!parse_string(&cursor, type_value, sizeof(type_value))) {
+                return MAZE32_PROTOCOL_MALFORMED;
+            }
+            message->type = message_type(type_value);
+            envelope_fields |= 2U;
+        } else if (strcmp(key, "seq") == 0 && !(envelope_fields & 4U)) {
+            if (!parse_uint32(&cursor, &message->sequence) || message->sequence == 0U) {
+                return MAZE32_PROTOCOL_MALFORMED;
+            }
+            envelope_fields |= 4U;
+        } else if (strcmp(key, "requestId") == 0 && !(envelope_fields & 8U)) {
+            if (!parse_string(&cursor, message->request_id, sizeof(message->request_id))) {
+                return MAZE32_PROTOCOL_MALFORMED;
+            }
+            envelope_fields |= 8U;
+        } else if (strcmp(key, "payload") == 0 && !(envelope_fields & 16U)) {
+            if (!(envelope_fields & 2U)) {
+                return MAZE32_PROTOCOL_MALFORMED;
+            }
+            if (message->type == MAZE32_MESSAGE_INVALID) {
+                return MAZE32_PROTOCOL_UNKNOWN_TYPE;
+            }
+            if (!parse_payload(&cursor, message)) {
+                return MAZE32_PROTOCOL_INVALID_PAYLOAD;
+            }
+            envelope_fields |= 16U;
+        } else {
+            return MAZE32_PROTOCOL_MALFORMED;
+        }
+        skip_space(&cursor);
+        if (consume(&cursor, '}')) {
+            break;
+        }
+        if (!consume(&cursor, ',')) {
+            return MAZE32_PROTOCOL_MALFORMED;
+        }
+    }
+    skip_space(&cursor);
+    if (cursor.position != cursor.length ||
+        (envelope_fields & (1U | 2U | 4U | 16U)) != (1U | 2U | 4U | 16U)) {
+        return MAZE32_PROTOCOL_MALFORMED;
+    }
+    if (version != MAZE32_PROTOCOL_VERSION) {
+        return MAZE32_PROTOCOL_UNSUPPORTED_VERSION;
+    }
+    if (message->type == MAZE32_MESSAGE_INVALID) {
+        return MAZE32_PROTOCOL_UNKNOWN_TYPE;
+    }
+    return MAZE32_PROTOCOL_OK;
+}
+
+const char* maze32_protocol_result_name(maze32_protocol_result_t result) {
+    switch (result) {
+        case MAZE32_PROTOCOL_OK:
+            return "ok";
+        case MAZE32_PROTOCOL_MALFORMED:
+            return "malformed";
+        case MAZE32_PROTOCOL_TOO_LARGE:
+            return "too_large";
+        case MAZE32_PROTOCOL_UNSUPPORTED_VERSION:
+            return "unsupported_version";
+        case MAZE32_PROTOCOL_UNKNOWN_TYPE:
+            return "unknown_type";
+        case MAZE32_PROTOCOL_INVALID_PAYLOAD:
+            return "invalid_payload";
+        default:
+            return "unknown_error";
+    }
+}
diff --git a/components/maze32_web/CMakeLists.txt b/components/maze32_web/CMakeLists.txt
index 56d6e35..e0e71b8 100644
--- a/components/maze32_web/CMakeLists.txt
+++ b/components/maze32_web/CMakeLists.txt
@@ -1,5 +1,5 @@
 idf_component_register(
-    SRCS "maze32_web.c"
+    SRCS "maze32_web.c" "maze32_gateway.c"
     INCLUDE_DIRS "include"
-    REQUIRES esp_http_server maze32_platform
+    REQUIRES esp_http_server esp_timer heap maze32_lobby maze32_platform
 )
diff --git a/components/maze32_web/include/maze32_gateway.h b/components/maze32_web/include/maze32_gateway.h
new file mode 100644
index 0000000..afd4b56
--- /dev/null
+++ b/components/maze32_web/include/maze32_gateway.h
@@ -0,0 +1,57 @@
+#ifndef MAZE32_GATEWAY_H
+#define MAZE32_GATEWAY_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "esp_err.h"
+#include "esp_http_server.h"
+#include "esp_timer.h"
+#include "maze32_lobby.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define MAZE32_GATEWAY_CONNECTION_LIMIT MAZE32_SESSION_LIMIT
+#define MAZE32_GATEWAY_QUEUE_LIMIT 12U
+#define MAZE32_GATEWAY_OUTGOING_LIMIT 768U
+#define MAZE32_GATEWAY_RATE_LIMIT_PER_SECOND 20U
+
+typedef struct {
+    int active;
+    int socket_fd;
+    uint32_t last_client_sequence;
+    uint64_t rate_window_started_ms;
+    unsigned int messages_in_window;
+} maze32_gateway_connection_t;
+
+typedef struct {
+    int socket_fd;
+    size_t length;
+    char payload[MAZE32_GATEWAY_OUTGOING_LIMIT];
+} maze32_gateway_outgoing_t;
+
+typedef struct {
+    httpd_handle_t server;
+    maze32_lobby_t lobby;
+    maze32_gateway_connection_t connections[MAZE32_GATEWAY_CONNECTION_LIMIT];
+    maze32_gateway_outgoing_t outgoing[MAZE32_GATEWAY_QUEUE_LIMIT];
+    size_t outgoing_head;
+    size_t outgoing_count;
+    uint32_t server_sequence;
+    unsigned int suggestion_index;
+    esp_timer_handle_t countdown_timer;
+} maze32_gateway_t;
+
+esp_err_t maze32_gateway_init(maze32_gateway_t* gateway);
+void maze32_gateway_set_server(maze32_gateway_t* gateway, httpd_handle_t server);
+esp_err_t maze32_gateway_register(httpd_handle_t server, maze32_gateway_t* gateway);
+void maze32_gateway_close_socket(httpd_handle_t server, int socket_fd);
+int maze32_gateway_can_reconfigure(const maze32_gateway_t* gateway);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/components/maze32_web/include/maze32_web.h b/components/maze32_web/include/maze32_web.h
index bbe4fef..7895385 100644
--- a/components/maze32_web/include/maze32_web.h
+++ b/components/maze32_web/include/maze32_web.h
@@ -3,13 +3,15 @@
 
 #include "esp_err.h"
 #include "esp_http_server.h"
+#include "maze32_gateway.h"
 #include "maze32_health.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-esp_err_t maze32_web_start(httpd_handle_t *server, maze32_health_t *health);
+esp_err_t maze32_web_start(httpd_handle_t* server, maze32_health_t* health,
+                           maze32_gateway_t* gateway);
 
 #ifdef __cplusplus
 }
diff --git a/components/maze32_web/maze32_gateway.c b/components/maze32_web/maze32_gateway.c
new file mode 100644
index 0000000..37d4b61
--- /dev/null
+++ b/components/maze32_web/maze32_gateway.c
@@ -0,0 +1,663 @@
+#include "maze32_gateway.h"
+
+#include <inttypes.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "esp_heap_caps.h"
+#include "esp_log.h"
+#include "esp_random.h"
+#include "maze32_protocol.h"
+
+static const char* TAG = "maze32_gateway";
+static const char* NAME_SUGGESTIONS[] = {
+    "Байт-Беглец", "Кот-Навигатор", "Сэр Тупичок", "Пиксельный Ёж", "Лорд Лабиринт",
+};
+
+static uint64_t now_ms(void) {
+    return (uint64_t)(esp_timer_get_time() / 1000);
+}
+
+static maze32_gateway_connection_t* find_connection(maze32_gateway_t* gateway, int socket_fd) {
+    for (size_t index = 0U; index < MAZE32_GATEWAY_CONNECTION_LIMIT; ++index) {
+        if (gateway->connections[index].active &&
+            gateway->connections[index].socket_fd == socket_fd) {
+            return &gateway->connections[index];
+        }
+    }
+    return NULL;
+}
+
+static maze32_gateway_connection_t* open_connection(maze32_gateway_t* gateway, int socket_fd) {
+    maze32_gateway_connection_t* existing = find_connection(gateway, socket_fd);
+    if (existing != NULL) {
+        return existing;
+    }
+    for (size_t index = 0U; index < MAZE32_GATEWAY_CONNECTION_LIMIT; ++index) {
+        maze32_gateway_connection_t* connection = &gateway->connections[index];
+        if (!connection->active) {
+            memset(connection, 0, sizeof(*connection));
+            connection->active = 1;
+            connection->socket_fd = socket_fd;
+            connection->rate_window_started_ms = now_ms();
+            unsigned int active_count = 0U;
+            for (size_t count_index = 0U; count_index < MAZE32_GATEWAY_CONNECTION_LIMIT;
+                 ++count_index) {
+                if (gateway->connections[count_index].active) {
+                    active_count++;
+                }
+            }
+            ESP_LOGI(TAG, "WebSocket connected: fd=%d, active=%u/%u", socket_fd, active_count,
+                     (unsigned int)MAZE32_GATEWAY_CONNECTION_LIMIT);
+            if (active_count == MAZE32_GATEWAY_CONNECTION_LIMIT) {
+                ESP_LOGI(TAG, "Six-client heap: free=%u bytes, largest=%u bytes",
+                         (unsigned int)heap_caps_get_free_size(MALLOC_CAP_8BIT),
+                         (unsigned int)heap_caps_get_largest_free_block(MALLOC_CAP_8BIT));
+            }
+            return connection;
+        }
+    }
+    return NULL;
+}
+
+static int append_text(char* output, size_t capacity, size_t* length, const char* text) {
+    size_t text_length = strlen(text);
+    if (*length + text_length >= capacity) {
+        return 0;
+    }
+    memcpy(output + *length, text, text_length);
+    *length += text_length;
+    output[*length] = '\0';
+    return 1;
+}
+
+static int append_json_string(char* output, size_t capacity, size_t* length, const char* value) {
+    if (!append_text(output, capacity, length, "\"")) {
+        return 0;
+    }
+    for (const unsigned char* cursor = (const unsigned char*)value; *cursor != '\0'; ++cursor) {
+        const char* escape = NULL;
+        if (*cursor == '"') {
+            escape = "\\\"";
+        } else if (*cursor == '\\') {
+            escape = "\\\\";
+        } else if (*cursor == '\n') {
+            escape = "\\n";
+        } else if (*cursor == '\r') {
+            escape = "\\r";
+        } else if (*cursor == '\t') {
+            escape = "\\t";
+        }
+        if (escape != NULL) {
+            if (!append_text(output, capacity, length, escape)) {
+                return 0;
+            }
+        } else {
+            char byte[2] = {(char)*cursor, '\0'};
+            if (!append_text(output, capacity, length, byte)) {
+                return 0;
+            }
+        }
+    }
+    return append_text(output, capacity, length, "\"");
+}
+
+static uint32_t next_server_sequence(maze32_gateway_t* gateway) {
+    gateway->server_sequence++;
+    if (gateway->server_sequence == 0U) {
+        gateway->server_sequence = 1U;
+    }
+    return gateway->server_sequence;
+}
+
+static int enqueue(maze32_gateway_t* gateway, int socket_fd, const char* payload) {
+    size_t length = strlen(payload);
+    if (gateway->outgoing_count >= MAZE32_GATEWAY_QUEUE_LIMIT ||
+        length >= MAZE32_GATEWAY_OUTGOING_LIMIT) {
+        ESP_LOGW(TAG, "Bounded outgoing queue rejected a message for fd=%d", socket_fd);
+        return 0;
+    }
+    size_t index = (gateway->outgoing_head + gateway->outgoing_count) % MAZE32_GATEWAY_QUEUE_LIMIT;
+    maze32_gateway_outgoing_t* entry = &gateway->outgoing[index];
+    entry->socket_fd = socket_fd;
+    entry->length = length;
+    memcpy(entry->payload, payload, length + 1U);
+    gateway->outgoing_count++;
+    return 1;
+}
+
+static void drain_queue(maze32_gateway_t* gateway) {
+    while (gateway->outgoing_count > 0U) {
+        maze32_gateway_outgoing_t* entry = &gateway->outgoing[gateway->outgoing_head];
+        httpd_ws_frame_t frame = {
+            .final = true,
+            .fragmented = false,
+            .type = HTTPD_WS_TYPE_TEXT,
+            .payload = (uint8_t*)entry->payload,
+            .len = entry->length,
+        };
+        esp_err_t result = httpd_ws_send_frame_async(gateway->server, entry->socket_fd, &frame);
+        if (result != ESP_OK) {
+            ESP_LOGW(TAG, "WebSocket send failed for fd=%d: %s", entry->socket_fd,
+                     esp_err_to_name(result));
+        }
+        gateway->outgoing_head = (gateway->outgoing_head + 1U) % MAZE32_GATEWAY_QUEUE_LIMIT;
+        gateway->outgoing_count--;
+    }
+}
+
+static void send_error(maze32_gateway_t* gateway, int socket_fd, const char* request_id,
+                       const char* code, const char* message) {
+    char response[MAZE32_GATEWAY_OUTGOING_LIMIT] = "";
+    size_t length = 0U;
+    char prefix[128];
+    int written = snprintf(prefix, sizeof(prefix), "{\"v\":1,\"type\":\"error\",\"seq\":%" PRIu32,
+                           next_server_sequence(gateway));
+    if (written < 0 || (size_t)written >= sizeof(prefix) ||
+        !append_text(response, sizeof(response), &length, prefix)) {
+        return;
+    }
+    if (request_id != NULL && request_id[0] != '\0') {
+        if (!append_text(response, sizeof(response), &length, ",\"requestId\":") ||
+            !append_json_string(response, sizeof(response), &length, request_id)) {
+            return;
+        }
+    }
+    if (!append_text(response, sizeof(response), &length, ",\"payload\":{\"code\":") ||
+        !append_json_string(response, sizeof(response), &length, code) ||
+        !append_text(response, sizeof(response), &length, ",\"message\":") ||
+        !append_json_string(response, sizeof(response), &length, message) ||
+        !append_text(response, sizeof(response), &length, "}}")) {
+        return;
+    }
+    enqueue(gateway, socket_fd, response);
+}
+
+static const maze32_session_t* player_for_slot(const maze32_lobby_t* lobby, unsigned int slot) {
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        const maze32_session_t* session = &lobby->sessions[index];
+        if (session->role == MAZE32_ROLE_PLAYER && session->player_slot == slot) {
+            return session;
+        }
+    }
+    return NULL;
+}
+
+static int build_snapshot(maze32_gateway_t* gateway, char* response, size_t capacity) {
+    uint32_t sequence = next_server_sequence(gateway);
+    int written =
+        snprintf(response, capacity,
+                 "{\"v\":1,\"type\":\"lobby\",\"seq\":%" PRIu32
+                 ",\"payload\":{\"revision\":%" PRIu32 ",\"phase\":\"%s\","
+                 "\"ready\":%s,\"ownerSlot\":1,\"players\":[",
+                 sequence, gateway->lobby.revision, maze32_lobby_phase_name(gateway->lobby.phase),
+                 maze32_lobby_ready(&gateway->lobby) ? "true" : "false");
+    if (written < 0 || (size_t)written >= capacity) {
+        return 0;
+    }
+    size_t length = (size_t)written;
+    for (unsigned int slot = 1U; slot <= MAZE32_PLAYER_LIMIT; ++slot) {
+        const maze32_session_t* player = player_for_slot(&gateway->lobby, slot);
+        char prefix[96];
+        written = snprintf(prefix, sizeof(prefix),
+                           "%s{\"slot\":%u,\"name\":", slot == 1U ? "" : ",", slot);
+        if (written < 0 || (size_t)written >= sizeof(prefix) ||
+            !append_text(response, capacity, &length, prefix) ||
+            !append_json_string(response, capacity, &length, player == NULL ? "" : player->name)) {
+            return 0;
+        }
+        written = snprintf(prefix, sizeof(prefix), ",\"occupied\":%s,\"connected\":%s}",
+                           player == NULL ? "false" : "true",
+                           player != NULL && player->connected ? "true" : "false");
+        if (written < 0 || (size_t)written >= sizeof(prefix) ||
+            !append_text(response, capacity, &length, prefix)) {
+            return 0;
+        }
+    }
+    char suffix[128];
+    written = snprintf(suffix, sizeof(suffix), "],\"observers\":%u,\"observerLimit\":%u}}",
+                       maze32_lobby_connected_observers(&gateway->lobby),
+                       (unsigned int)MAZE32_OBSERVER_LIMIT);
+    return written >= 0 && (size_t)written < sizeof(suffix) &&
+           append_text(response, capacity, &length, suffix);
+}
+
+static void broadcast_snapshot(maze32_gateway_t* gateway) {
+    char response[MAZE32_GATEWAY_OUTGOING_LIMIT];
+    if (!build_snapshot(gateway, response, sizeof(response))) {
+        ESP_LOGE(TAG, "Lobby snapshot exceeded its fixed buffer");
+        return;
+    }
+    for (size_t index = 0U; index < MAZE32_GATEWAY_CONNECTION_LIMIT; ++index) {
+        maze32_gateway_connection_t* connection = &gateway->connections[index];
+        if (connection->active &&
+            maze32_lobby_session_for_connection(&gateway->lobby, connection->socket_fd) != NULL) {
+            enqueue(gateway, connection->socket_fd, response);
+        }
+    }
+}
+
+static void send_session(maze32_gateway_t* gateway, int socket_fd, const maze32_session_t* session,
+                         const char* request_id) {
+    char response[MAZE32_GATEWAY_OUTGOING_LIMIT] = "";
+    size_t length = 0U;
+    char prefix[160];
+    int written = snprintf(prefix, sizeof(prefix), "{\"v\":1,\"type\":\"session\",\"seq\":%" PRIu32,
+                           next_server_sequence(gateway));
+    if (written < 0 || (size_t)written >= sizeof(prefix) ||
+        !append_text(response, sizeof(response), &length, prefix)) {
+        return;
+    }
+    if (request_id[0] != '\0' &&
+        (!append_text(response, sizeof(response), &length, ",\"requestId\":") ||
+         !append_json_string(response, sizeof(response), &length, request_id))) {
+        return;
+    }
+    written =
+        snprintf(prefix, sizeof(prefix), ",\"payload\":{\"role\":\"%s\",\"slot\":%u,\"token\":",
+                 session->role == MAZE32_ROLE_PLAYER ? "player" : "observer", session->player_slot);
+    if (written < 0 || (size_t)written >= sizeof(prefix) ||
+        !append_text(response, sizeof(response), &length, prefix) ||
+        !append_json_string(response, sizeof(response), &length, session->token) ||
+        !append_text(response, sizeof(response), &length, "}}")) {
+        return;
+    }
+    enqueue(gateway, socket_fd, response);
+}
+
+static void generate_token(maze32_gateway_t* gateway, char* token) {
+    static const char HEX[] = "0123456789abcdef";
+    uint8_t bytes[MAZE32_SESSION_TOKEN_BYTES];
+    for (;;) {
+        esp_fill_random(bytes, sizeof(bytes));
+        for (size_t index = 0U; index < sizeof(bytes); ++index) {
+            token[index * 2U] = HEX[bytes[index] >> 4U];
+            token[index * 2U + 1U] = HEX[bytes[index] & 0x0fU];
+        }
+        token[MAZE32_SESSION_TOKEN_HEX_LENGTH] = '\0';
+        int collision = 0;
+        for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+            if (gateway->lobby.sessions[index].role != MAZE32_ROLE_NONE &&
+                strcmp(gateway->lobby.sessions[index].token, token) == 0) {
+                collision = 1;
+                break;
+            }
+        }
+        if (!collision) {
+            return;
+        }
+    }
+}
+
+static void send_lobby_error(maze32_gateway_t* gateway, int socket_fd, const char* request_id,
+                             maze32_lobby_result_t result) {
+    switch (result) {
+        case MAZE32_LOBBY_INVALID_NAME:
+            send_error(gateway, socket_fd, request_id, "invalid_name",
+                       "Имя должно быть длиной от 1 до 32 байт без пробелов по краям");
+            break;
+        case MAZE32_LOBBY_DUPLICATE_NAME:
+            send_error(gateway, socket_fd, request_id, "duplicate_name", "Это имя уже занято");
+            break;
+        case MAZE32_LOBBY_ROLE_FULL:
+            send_error(gateway, socket_fd, request_id, "role_full", "Свободных мест больше нет");
+            break;
+        case MAZE32_LOBBY_INVALID_TOKEN:
+            send_error(gateway, socket_fd, request_id, "invalid_token", "Сессия не найдена");
+            break;
+        case MAZE32_LOBBY_SESSION_CONNECTED:
+            send_error(gateway, socket_fd, request_id, "session_connected",
+                       "Эта сессия уже подключена");
+            break;
+        case MAZE32_LOBBY_NOT_OWNER:
+            send_error(gateway, socket_fd, request_id, "not_owner",
+                       "Запустить игру может только Игрок 1");
+            break;
+        case MAZE32_LOBBY_NOT_READY:
+            send_error(gateway, socket_fd, request_id, "not_ready",
+                       "Для старта нужны оба игрока онлайн");
+            break;
+        case MAZE32_LOBBY_INVALID_PHASE:
+            send_error(gateway, socket_fd, request_id, "invalid_phase",
+                       "Лобби уже запустило обратный отсчёт");
+            break;
+        default:
+            send_error(gateway, socket_fd, request_id, "request_rejected", "Команда отклонена");
+            break;
+    }
+}
+
+static void send_suggestion(maze32_gateway_t* gateway, int socket_fd, const char* request_id) {
+    const char* suggestion = NULL;
+    size_t suggestion_count = sizeof(NAME_SUGGESTIONS) / sizeof(NAME_SUGGESTIONS[0]);
+    for (size_t attempt = 0U; attempt < suggestion_count; ++attempt) {
+        size_t index = gateway->suggestion_index++ % suggestion_count;
+        int occupied = 0;
+        for (size_t session_index = 0U; session_index < MAZE32_SESSION_LIMIT; ++session_index) {
+            const maze32_session_t* session = &gateway->lobby.sessions[session_index];
+            if (session->role == MAZE32_ROLE_PLAYER &&
+                strcmp(session->name, NAME_SUGGESTIONS[index]) == 0) {
+                occupied = 1;
+                break;
+            }
+        }
+        if (!occupied) {
+            suggestion = NAME_SUGGESTIONS[index];
+            break;
+        }
+    }
+    if (suggestion == NULL) {
+        send_error(gateway, socket_fd, request_id, "no_suggestion",
+                   "Все смешные имена уже разобрали");
+        return;
+    }
+    char response[MAZE32_GATEWAY_OUTGOING_LIMIT] = "";
+    size_t length = 0U;
+    char prefix[128];
+    int written =
+        snprintf(prefix, sizeof(prefix), "{\"v\":1,\"type\":\"name_suggestion\",\"seq\":%" PRIu32,
+                 next_server_sequence(gateway));
+    if (written < 0 || (size_t)written >= sizeof(prefix) ||
+        !append_text(response, sizeof(response), &length, prefix)) {
+        return;
+    }
+    if (request_id[0] != '\0' &&
+        (!append_text(response, sizeof(response), &length, ",\"requestId\":") ||
+         !append_json_string(response, sizeof(response), &length, request_id))) {
+        return;
+    }
+    if (append_text(response, sizeof(response), &length, ",\"payload\":{\"name\":") &&
+        append_json_string(response, sizeof(response), &length, suggestion) &&
+        append_text(response, sizeof(response), &length, "}}")) {
+        enqueue(gateway, socket_fd, response);
+    }
+}
+
+static void broadcast_countdown(maze32_gateway_t* gateway) {
+    char response[MAZE32_GATEWAY_OUTGOING_LIMIT];
+    int written = snprintf(response, sizeof(response),
+                           "{\"v\":1,\"type\":\"countdown\",\"seq\":%" PRIu32
+                           ",\"payload\":{\"steps\":[3,2,1],\"startedAtMs\":%" PRIu64
+                           ",\"activationAtMs\":%" PRIu64 "}}",
+                           next_server_sequence(gateway), gateway->lobby.countdown_started_ms,
+                           gateway->lobby.activation_ms);
+    if (written < 0 || (size_t)written >= sizeof(response)) {
+        return;
+    }
+    for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+        const maze32_session_t* session = &gateway->lobby.sessions[index];
+        if (session->role == MAZE32_ROLE_PLAYER && session->connected) {
+            enqueue(gateway, session->connection_id, response);
+        }
+    }
+}
+
+static void countdown_finished_work(void* context) {
+    maze32_gateway_t* gateway = context;
+    if (!maze32_lobby_activate_if_due(&gateway->lobby, now_ms())) {
+        return;
+    }
+    char response[MAZE32_GATEWAY_OUTGOING_LIMIT];
+    int written = snprintf(response, sizeof(response),
+                           "{\"v\":1,\"type\":\"active\",\"seq\":%" PRIu32
+                           ",\"payload\":{\"activatedAtMs\":%" PRIu64 "}}",
+                           next_server_sequence(gateway), gateway->lobby.activation_ms);
+    if (written >= 0 && (size_t)written < sizeof(response)) {
+        for (size_t index = 0U; index < MAZE32_SESSION_LIMIT; ++index) {
+            const maze32_session_t* session = &gateway->lobby.sessions[index];
+            if (session->role != MAZE32_ROLE_NONE && session->connected) {
+                enqueue(gateway, session->connection_id, response);
+            }
+        }
+    }
+    broadcast_snapshot(gateway);
+    drain_queue(gateway);
+    ESP_LOGI(TAG, "Lobby became active at server time %" PRIu64 " ms",
+             gateway->lobby.activation_ms);
+}
+
+static void countdown_timer_callback(void* context) {
+    maze32_gateway_t* gateway = context;
+    if (gateway->server != NULL) {
+        esp_err_t result = httpd_queue_work(gateway->server, countdown_finished_work, gateway);
+        if (result != ESP_OK) {
+            ESP_LOGE(TAG, "Could not queue countdown activation: %s", esp_err_to_name(result));
+        }
+    }
+}
+
+static int rate_limit_allows(maze32_gateway_connection_t* connection, uint64_t current_ms) {
+    if (current_ms - connection->rate_window_started_ms >= 1000U) {
+        connection->rate_window_started_ms = current_ms;
+        connection->messages_in_window = 0U;
+    }
+    connection->messages_in_window++;
+    return connection->messages_in_window <= MAZE32_GATEWAY_RATE_LIMIT_PER_SECOND;
+}
+
+static void handle_message(maze32_gateway_t* gateway, maze32_gateway_connection_t* connection,
+                           const maze32_client_message_t* message) {
+    int socket_fd = connection->socket_fd;
+    if (message->type == MAZE32_MESSAGE_SUGGEST_NAME) {
+        send_suggestion(gateway, socket_fd, message->request_id);
+        return;
+    }
+    if (message->type == MAZE32_MESSAGE_JOIN) {
+        if (maze32_lobby_session_for_connection(&gateway->lobby, socket_fd) != NULL) {
+            send_error(gateway, socket_fd, message->request_id, "already_joined",
+                       "Сессия уже выбрала роль");
+            return;
+        }
+        char token[MAZE32_SESSION_TOKEN_HEX_LENGTH + 1U];
+        generate_token(gateway, token);
+        maze32_session_t* session = NULL;
+        maze32_lobby_result_t result =
+            message->role == MAZE32_ROLE_PLAYER
+                ? maze32_lobby_join_player(&gateway->lobby, socket_fd, message->name, token,
+                                           &session)
+                : maze32_lobby_join_observer(&gateway->lobby, socket_fd, token, &session);
+        if (result != MAZE32_LOBBY_OK) {
+            send_lobby_error(gateway, socket_fd, message->request_id, result);
+            return;
+        }
+        send_session(gateway, socket_fd, session, message->request_id);
+        broadcast_snapshot(gateway);
+        return;
+    }
+    if (message->type == MAZE32_MESSAGE_RESTORE) {
+        if (maze32_lobby_session_for_connection(&gateway->lobby, socket_fd) != NULL) {
+            send_error(gateway, socket_fd, message->request_id, "already_joined",
+                       "Сессия уже восстановлена");
+            return;
+        }
+        maze32_session_t* session = NULL;
+        maze32_lobby_result_t result =
+            maze32_lobby_restore(&gateway->lobby, socket_fd, message->token, &session);
+        if (result != MAZE32_LOBBY_OK) {
+            send_lobby_error(gateway, socket_fd, message->request_id, result);
+            return;
+        }
+        send_session(gateway, socket_fd, session, message->request_id);
+        broadcast_snapshot(gateway);
+        return;
+    }
+
+    const maze32_session_t* session =
+        maze32_lobby_session_for_connection(&gateway->lobby, socket_fd);
+    if (session == NULL) {
+        send_error(gateway, socket_fd, message->request_id, "unauthorized",
+                   "Сначала выберите роль или восстановите сессию");
+        return;
+    }
+    if (message->type == MAZE32_MESSAGE_START) {
+        maze32_lobby_result_t result = maze32_lobby_start(&gateway->lobby, socket_fd, now_ms());
+        if (result != MAZE32_LOBBY_OK) {
+            send_lobby_error(gateway, socket_fd, message->request_id, result);
+            return;
+        }
+        broadcast_snapshot(gateway);
+        broadcast_countdown(gateway);
+        esp_err_t timer_result =
+            esp_timer_start_once(gateway->countdown_timer, MAZE32_COUNTDOWN_DURATION_MS * 1000U);
+        if (timer_result != ESP_OK) {
+            ESP_LOGE(TAG, "Countdown timer could not start: %s", esp_err_to_name(timer_result));
+        }
+        return;
+    }
+    if (message->type == MAZE32_MESSAGE_HEARTBEAT) {
+        char response[MAZE32_GATEWAY_OUTGOING_LIMIT] = "";
+        size_t length = 0U;
+        char prefix[128];
+        int written = snprintf(prefix, sizeof(prefix), "{\"v\":1,\"type\":\"ack\",\"seq\":%" PRIu32,
+                               next_server_sequence(gateway));
+        if (written >= 0 && (size_t)written < sizeof(prefix) &&
+            append_text(response, sizeof(response), &length, prefix) &&
+            append_text(response, sizeof(response), &length, ",\"requestId\":") &&
+            append_json_string(response, sizeof(response), &length, message->request_id) &&
+            append_text(response, sizeof(response), &length,
+                        ",\"payload\":{\"command\":\"heartbeat\"}}")) {
+            enqueue(gateway, socket_fd, response);
+        }
+    }
+}
+
+static esp_err_t websocket_handler(httpd_req_t* request) {
+    maze32_gateway_t* gateway = request->user_ctx;
+    int socket_fd = httpd_req_to_sockfd(request);
+    maze32_gateway_connection_t* connection = find_connection(gateway, socket_fd);
+    if (connection == NULL) {
+        connection = open_connection(gateway, socket_fd);
+        if (connection == NULL) {
+            ESP_LOGW(TAG, "WebSocket connection limit reached; rejecting fd=%d", socket_fd);
+            shutdown(socket_fd, SHUT_RDWR);
+            return ESP_OK;
+        }
+    }
+    httpd_ws_frame_t frame = {0};
+    esp_err_t result = httpd_ws_recv_frame(request, &frame, 0U);
+    if (result != ESP_OK) {
+        return result;
+    }
+    if (frame.len > MAZE32_PROTOCOL_MESSAGE_LIMIT) {
+        ESP_LOGW(TAG, "Oversized WebSocket frame rejected: fd=%d, length=%u", socket_fd,
+                 (unsigned int)frame.len);
+        shutdown(socket_fd, SHUT_RDWR);
+        return ESP_OK;
+    }
+    uint8_t payload[MAZE32_PROTOCOL_MESSAGE_LIMIT + 1U];
+    frame.payload = payload;
+    result = httpd_ws_recv_frame(request, &frame, MAZE32_PROTOCOL_MESSAGE_LIMIT);
+    if (result != ESP_OK) {
+        return result;
+    }
+    if (frame.type == HTTPD_WS_TYPE_CLOSE) {
+        return ESP_OK;
+    }
+    if (frame.type != HTTPD_WS_TYPE_TEXT) {
+        send_error(gateway, socket_fd, "", "text_required", "Нужен текстовый JSON-пакет");
+        drain_queue(gateway);
+        return ESP_OK;
+    }
+    payload[frame.len] = '\0';
+    if (!rate_limit_allows(connection, now_ms())) {
+        send_error(gateway, socket_fd, "", "rate_limited", "Слишком много команд");
+        drain_queue(gateway);
+        return ESP_OK;
+    }
+
+    maze32_client_message_t message;
+    maze32_protocol_result_t parse_result =
+        maze32_protocol_parse((const char*)payload, frame.len, &message);
+    if (parse_result != MAZE32_PROTOCOL_OK) {
+        send_error(gateway, socket_fd, "", maze32_protocol_result_name(parse_result),
+                   "Пакет не прошёл проверку протокола");
+        drain_queue(gateway);
+        return ESP_OK;
+    }
+    if (message.sequence <= connection->last_client_sequence) {
+        send_error(gateway, socket_fd, message.request_id, "stale_sequence",
+                   "Команда устарела или уже обработана");
+        drain_queue(gateway);
+        return ESP_OK;
+    }
+    connection->last_client_sequence = message.sequence;
+    handle_message(gateway, connection, &message);
+    drain_queue(gateway);
+    return ESP_OK;
+}
+
+static esp_err_t websocket_pre_handshake(httpd_req_t* request) {
+    maze32_gateway_t* gateway = request->user_ctx;
+    int socket_fd = httpd_req_to_sockfd(request);
+    if (open_connection(gateway, socket_fd) == NULL) {
+        ESP_LOGW(TAG, "WebSocket connection limit reached; rejecting fd=%d", socket_fd);
+        return ESP_ERR_NO_MEM;
+    }
+    return ESP_OK;
+}
+
+esp_err_t maze32_gateway_init(maze32_gateway_t* gateway) {
+    if (gateway == NULL) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    memset(gateway, 0, sizeof(*gateway));
+    maze32_lobby_init(&gateway->lobby);
+    const esp_timer_create_args_t timer_arguments = {
+        .callback = countdown_timer_callback,
+        .arg = gateway,
+        .dispatch_method = ESP_TIMER_TASK,
+        .name = "lobby_countdown",
+        .skip_unhandled_events = true,
+    };
+    return esp_timer_create(&timer_arguments, &gateway->countdown_timer);
+}
+
+void maze32_gateway_set_server(maze32_gateway_t* gateway, httpd_handle_t server) {
+    if (gateway != NULL) {
+        gateway->server = server;
+    }
+}
+
+esp_err_t maze32_gateway_register(httpd_handle_t server, maze32_gateway_t* gateway) {
+    if (server == NULL || gateway == NULL) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    maze32_gateway_set_server(gateway, server);
+    const httpd_uri_t websocket = {
+        .uri = "/ws",
+        .method = HTTP_GET,
+        .handler = websocket_handler,
+        .user_ctx = gateway,
+        .is_websocket = true,
+        .ws_pre_handshake_cb = websocket_pre_handshake,
+    };
+    esp_err_t result = httpd_register_uri_handler(server, &websocket);
+    if (result == ESP_OK) {
+        ESP_LOGI(TAG, "WebSocket gateway ready: connections=%u, message=%u, queue=%u",
+                 (unsigned int)MAZE32_GATEWAY_CONNECTION_LIMIT,
+                 (unsigned int)MAZE32_PROTOCOL_MESSAGE_LIMIT,
+                 (unsigned int)MAZE32_GATEWAY_QUEUE_LIMIT);
+    }
+    return result;
+}
+
+void maze32_gateway_close_socket(httpd_handle_t server, int socket_fd) {
+    maze32_gateway_t* gateway = httpd_get_global_user_ctx(server);
+    if (gateway != NULL) {
+        maze32_gateway_connection_t* connection = find_connection(gateway, socket_fd);
+        if (connection != NULL) {
+            maze32_lobby_disconnect(&gateway->lobby, socket_fd);
+            memset(connection, 0, sizeof(*connection));
+            broadcast_snapshot(gateway);
+            drain_queue(gateway);
+            ESP_LOGI(TAG, "WebSocket disconnected: fd=%d", socket_fd);
+        }
+    }
+    close(socket_fd);
+}
+
+int maze32_gateway_can_reconfigure(const maze32_gateway_t* gateway) {
+    return gateway != NULL && maze32_lobby_can_reconfigure(&gateway->lobby);
+}
diff --git a/components/maze32_web/maze32_web.c b/components/maze32_web/maze32_web.c
index f84ea1d..29b281f 100644
--- a/components/maze32_web/maze32_web.c
+++ b/components/maze32_web/maze32_web.c
@@ -6,16 +6,19 @@
 
 #define MAZE32_STATIC_CHUNK_SIZE 1024
 
-static const char *TAG = "maze32_web";
-static const char *INDEX_PATH = "/littlefs/index.html.gz";
+static const char* TAG = "maze32_web";
+static const char* INDEX_PATH = "/littlefs/index.html.gz";
 
-static esp_err_t send_index(httpd_req_t *request)
-{
-    FILE *file = fopen(INDEX_PATH, "rb");
+static void preserve_static_context(void* context) {
+    (void)context;
+}
+
+static esp_err_t send_index(httpd_req_t* request) {
+    FILE* file = fopen(INDEX_PATH, "rb");
     if (file == NULL) {
         ESP_LOGE(TAG, "Static asset is unavailable: %s", INDEX_PATH);
         httpd_resp_send_err(request, HTTPD_500_INTERNAL_SERVER_ERROR,
-                            "Static application is unavailable");
+                            "Приложение временно недоступно");
         return ESP_FAIL;
     }
 
@@ -45,18 +48,17 @@ static esp_err_t send_index(httpd_req_t *request)
     return result;
 }
 
-static esp_err_t send_health(httpd_req_t *request)
-{
-    const maze32_health_t *health = request->user_ctx;
+static esp_err_t send_health(httpd_req_t* request) {
+    const maze32_health_t* health = request->user_ctx;
     char response[192];
     int length = snprintf(response, sizeof(response),
                           "{\"status\":\"%s\",\"healthy\":%s,\"version\":\"%s\",\"errorCode\":%d}",
                           maze32_health_state_name(health->state),
-                          maze32_health_is_healthy(health) ? "true" : "false",
-                          health->version, health->error_code);
+                          maze32_health_is_healthy(health) ? "true" : "false", health->version,
+                          health->error_code);
     if (length < 0 || (size_t)length >= sizeof(response)) {
         httpd_resp_send_err(request, HTTPD_500_INTERNAL_SERVER_ERROR,
-                            "Health response exceeded its fixed buffer");
+                            "Диагностический ответ слишком большой");
         return ESP_FAIL;
     }
 
@@ -65,16 +67,21 @@ static esp_err_t send_health(httpd_req_t *request)
     return httpd_resp_send(request, response, length);
 }
 
-esp_err_t maze32_web_start(httpd_handle_t *server, maze32_health_t *health)
-{
-    if (server == NULL || health == NULL) {
+esp_err_t maze32_web_start(httpd_handle_t* server, maze32_health_t* health,
+                           maze32_gateway_t* gateway) {
+    if (server == NULL || health == NULL || gateway == NULL) {
         return ESP_ERR_INVALID_ARG;
     }
 
     httpd_config_t configuration = HTTPD_DEFAULT_CONFIG();
-    configuration.max_uri_handlers = 8;
-    configuration.max_open_sockets = 7;
-    configuration.lru_purge_enable = true;
+    configuration.max_uri_handlers = 9;
+    configuration.max_open_sockets = 9;
+    configuration.lru_purge_enable = false;
+    configuration.recv_wait_timeout = 5;
+    configuration.send_wait_timeout = 1;
+    configuration.global_user_ctx = gateway;
+    configuration.global_user_ctx_free_fn = preserve_static_context;
+    configuration.close_fn = maze32_gateway_close_socket;
 
     esp_err_t result = httpd_start(server, &configuration);
     if (result != ESP_OK) {
diff --git a/data/index.html.gz b/data/index.html.gz
index 3a0e6dd..49ff6e6 100644
Binary files a/data/index.html.gz and b/data/index.html.gz differ
diff --git a/docs/PROTOCOL.md b/docs/PROTOCOL.md
new file mode 100644
index 0000000..1e13684
--- /dev/null
+++ b/docs/PROTOCOL.md
@@ -0,0 +1,56 @@
+# maze32 WebSocket protocol v1
+
+## Limits and ordering
+
+- Endpoint: `/ws`.
+- At most six WebSocket connections are accepted: two players and four
+  observers.
+- A text frame is at most 512 bytes. Binary frames are rejected.
+- Each connection may submit at most 20 messages in a one-second monotonic
+  window.
+- The gateway uses a fixed 12-entry outgoing queue with 768 bytes per entry.
+- Client sequence numbers start above zero and strictly increase for the life
+  of one WebSocket connection. Replayed or decreasing values are rejected.
+- Server sequence numbers strictly increase until reboot. Clients discard
+  stale server messages.
+
+All messages use this envelope:
+
+```json
+{"v":1,"type":"message_type","seq":1,"requestId":"optional","payload":{}}
+```
+
+Envelope keys may appear in any order except that `type` must precede
+`payload`. Unknown and duplicate keys are rejected. `requestId` is optional and
+is only echoed for correlation; it grants no authority.
+
+## Client messages
+
+- `join`: `{"role":"player","name":"..."}` or `{"role":"observer"}`.
+  Player names contain 1–32 UTF-8 bytes, have no control bytes or outer spaces,
+  and are unique within the current lobby.
+- `restore`: `{"token":"32 lowercase hexadecimal characters"}`.
+- `suggest_name`: `{}`.
+- `start`: `{}`. Only connected Player 1 may use it, and both player slots must
+  be connected.
+- `heartbeat`: `{}` after a session has been joined or restored.
+
+No Milestone 005 maze or movement messages are implemented by this milestone.
+
+## Server messages
+
+- `session`: the private role result containing `role`, `slot`, and temporary
+  `token`. The token is never included in a shared snapshot.
+- `name_suggestion`: an available humorous Russian player name.
+- `lobby`: the authoritative phase, revision, readiness, public player slots,
+  connected observer count, and limits.
+- `countdown`: the single authoritative `[3,2,1]` event with common monotonic
+  `startedAtMs` and `activationAtMs` values. It is sent to both players.
+- `active`: the exact authoritative activation instant.
+- `ack`: successful heartbeat correlation.
+- `error`: a stable English `code` and Russian player-facing `message`.
+
+An observer session can receive snapshots but cannot issue `start`. Player
+tokens reserve their original slot after disconnection so a refresh can restore
+it. A disconnected observer token may be restored until its bounded slot is
+reused by a new observer.
diff --git a/scripts/run_host_tests.sh b/scripts/run_host_tests.sh
index d98d4f7..5eed0fd 100755
--- a/scripts/run_host_tests.sh
+++ b/scripts/run_host_tests.sh
@@ -41,4 +41,13 @@ cc -std=c11 -Wall -Wextra -Werror -pedantic \
     -o "$test_directory/test_provisioning_protocol"
 
 "$test_directory/test_provisioning_protocol"
+
+cc -std=c11 -Wall -Wextra -Werror -pedantic \
+    -I"$project_directory/components/maze32_lobby/include" \
+    "$project_directory/components/maze32_lobby/maze32_lobby.c" \
+    "$project_directory/components/maze32_lobby/maze32_protocol.c" \
+    "$project_directory/test/host/test_lobby_protocol.c" \
+    -o "$test_directory/test_lobby_protocol"
+
+"$test_directory/test_lobby_protocol"
 python3 "$project_directory/scripts/verify_web_assets.py"
diff --git a/scripts/ws_protocol_client.py b/scripts/ws_protocol_client.py
new file mode 100644
index 0000000..94ef0ec
--- /dev/null
+++ b/scripts/ws_protocol_client.py
@@ -0,0 +1,237 @@
+#!/usr/bin/env python3
+"""Dependency-free maze32 WebSocket protocol and six-client verifier."""
+
+from __future__ import annotations
+
+import argparse
+import base64
+import hashlib
+import json
+import os
+import socket
+import struct
+import time
+from typing import Any
+
+
+class WebSocket:
+    def __init__(self, host: str, port: int = 80, timeout: float = 8.0):
+        self.host = host
+        self.sequence = 0
+        self.socket = socket.create_connection((host, port), timeout=timeout)
+        self.socket.settimeout(timeout)
+        key = base64.b64encode(os.urandom(16)).decode("ascii")
+        request = (
+            f"GET /ws HTTP/1.1\r\nHost: {host}:{port}\r\nUpgrade: websocket\r\n"
+            f"Connection: Upgrade\r\nSec-WebSocket-Key: {key}\r\n"
+            "Sec-WebSocket-Version: 13\r\n\r\n"
+        )
+        self.socket.sendall(request.encode("ascii"))
+        response = self._receive_until(b"\r\n\r\n")
+        if not response.startswith(b"HTTP/1.1 101"):
+            self.socket.close()
+            raise RuntimeError(response.decode("utf-8", "replace").strip())
+        expected = base64.b64encode(
+            hashlib.sha1((key + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11").encode()).digest()
+        )
+        if expected not in response:
+            self.socket.close()
+            raise RuntimeError("WebSocket accept key did not match")
+
+    def _receive_until(self, marker: bytes) -> bytes:
+        data = bytearray()
+        while marker not in data:
+            chunk = self.socket.recv(1024)
+            if not chunk:
+                raise ConnectionError("connection closed")
+            data.extend(chunk)
+        return bytes(data)
+
+    def send(self, message_type: str, payload: dict[str, Any], request_id: str) -> None:
+        self.sequence += 1
+        message = json.dumps(
+            {"v": 1, "type": message_type, "seq": self.sequence,
+             "requestId": request_id, "payload": payload},
+            ensure_ascii=False,
+            separators=(",", ":"),
+        ).encode("utf-8")
+        self.send_raw(message)
+
+    def send_raw(self, message: bytes) -> None:
+        mask = os.urandom(4)
+        length = len(message)
+        if length < 126:
+            header = bytes((0x81, 0x80 | length))
+        else:
+            header = bytes((0x81, 0x80 | 126)) + struct.pack("!H", length)
+        masked = bytes(value ^ mask[index % 4] for index, value in enumerate(message))
+        self.socket.sendall(header + mask + masked)
+
+    def receive(self) -> dict[str, Any]:
+        first, second = self._read_exact(2)
+        opcode = first & 0x0F
+        length = second & 0x7F
+        if length == 126:
+            length = struct.unpack("!H", self._read_exact(2))[0]
+        elif length == 127:
+            length = struct.unpack("!Q", self._read_exact(8))[0]
+        if second & 0x80:
+            mask = self._read_exact(4)
+        else:
+            mask = None
+        payload = self._read_exact(length)
+        if mask:
+            payload = bytes(value ^ mask[index % 4] for index, value in enumerate(payload))
+        if opcode == 0x8:
+            raise ConnectionError("WebSocket closed")
+        if opcode != 0x1:
+            return self.receive()
+        return json.loads(payload.decode("utf-8"))
+
+    def receive_type(self, message_type: str, attempts: int = 20) -> dict[str, Any]:
+        for _ in range(attempts):
+            message = self.receive()
+            if message.get("type") == message_type:
+                return message
+        raise RuntimeError(f"did not receive {message_type}")
+
+    def _read_exact(self, length: int) -> bytes:
+        data = bytearray()
+        while len(data) < length:
+            chunk = self.socket.recv(length - len(data))
+            if not chunk:
+                raise ConnectionError("connection closed")
+            data.extend(chunk)
+        return bytes(data)
+
+    def close(self) -> None:
+        try:
+            self.socket.sendall(b"\x88\x80" + b"\0\0\0\0")
+        except OSError:
+            pass
+        self.socket.close()
+
+
+def join(client: WebSocket, role: str, name: str | None = None) -> dict[str, Any]:
+    payload = {"role": role}
+    if name is not None:
+        payload["name"] = name
+    client.send("join", payload, f"join-{role}")
+    return client.receive_type("session")["payload"]
+
+
+def verify(host: str) -> None:
+    clients: list[WebSocket] = []
+    try:
+        player_1 = WebSocket(host)
+        clients.append(player_1)
+        player_1.send_raw(b"{")
+        error = player_1.receive_type("error")
+        assert error["payload"]["code"] == "malformed"
+        session_1 = join(player_1, "player", "Тестовый Пилот")
+        player_1.send_raw(
+            b'{"v":1,"type":"start","seq":1,"requestId":"stale","payload":{}}'
+        )
+        error = player_1.receive_type("error")
+        assert error["payload"]["code"] == "stale_sequence"
+        print("malformed and stale message rejection: PASS")
+        duplicate = WebSocket(host)
+        clients.append(duplicate)
+        duplicate.send("join", {"role": "player", "name": "Тестовый Пилот"}, "duplicate")
+        error = duplicate.receive_type("error")
+        assert error["payload"]["code"] == "duplicate_name"
+        duplicate.send("join", {"role": "player", "name": "Запасной Пилот"}, "player-2")
+        session_2 = duplicate.receive_type("session")["payload"]
+        assert session_1["slot"] == 1 and session_2["slot"] == 2
+
+        observers = []
+        for _ in range(4):
+            observer = WebSocket(host)
+            clients.append(observer)
+            join(observer, "observer")
+            observers.append(observer)
+        lobby = observers[-1].receive_type("lobby")["payload"]
+        assert lobby["ready"] and lobby["observers"] == 4
+        print("six-client capacity: PASS (2 players + 4 observers)")
+        print("duplicate player name: PASS")
+
+        try:
+            excess = WebSocket(host, timeout=1.0)
+        except (OSError, RuntimeError, ConnectionError):
+            print("seventh connection rejection: PASS")
+        else:
+            try:
+                excess.send("join", {"role": "observer"}, "excess")
+                excess.receive()
+            except (OSError, ConnectionError):
+                print("seventh connection rejection: PASS")
+            else:
+                raise AssertionError("seventh WebSocket unexpectedly remained connected")
+            finally:
+                excess.close()
+        time.sleep(0.5)
+
+        duplicate.send("start", {}, "not-owner")
+        error = duplicate.receive_type("error")
+        assert error["payload"]["code"] == "not_owner"
+        print("Player 2 start authorization: PASS")
+
+        token_2 = session_2["token"]
+        duplicate.close()
+        clients.remove(duplicate)
+        time.sleep(0.15)
+        restored = WebSocket(host)
+        clients.append(restored)
+        restored.send("restore", {"token": token_2}, "restore")
+        restored_session = restored.receive_type("session")["payload"]
+        assert restored_session["slot"] == 2 and restored_session["token"] == token_2
+        print("session refresh restoration: PASS (Player 2 retained slot 2)")
+
+        player_1.send("start", {}, "owner-start")
+        countdown_1 = player_1.receive_type("countdown")["payload"]
+        countdown_2 = restored.receive_type("countdown")["payload"]
+        assert countdown_1 == countdown_2
+        assert countdown_1["steps"] == [3, 2, 1]
+        active_1 = player_1.receive_type("active")["payload"]
+        active_2 = restored.receive_type("active")["payload"]
+        assert active_1["activatedAtMs"] == countdown_1["activationAtMs"]
+        assert active_1 == active_2
+        print(
+            "authoritative countdown: PASS "
+            f"(activationAtMs={countdown_1['activationAtMs']})"
+        )
+
+        observer = observers.pop()
+        observer.close()
+        clients.remove(observer)
+        time.sleep(0.5)
+        oversized = WebSocket(host)
+        oversized.send_raw(b"x" * 513)
+        try:
+            error = oversized.receive_type("error")
+            assert error["payload"]["code"] == "too_large"
+        except (OSError, ConnectionError):
+            pass
+        print("oversized message rejection: PASS")
+        oversized.close()
+    finally:
+        for client in clients:
+            client.close()
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("host", help="maze32 IP address or hostname")
+    parser.add_argument("--verify", action="store_true", help="run the Milestone 004 scenario")
+    arguments = parser.parse_args()
+    if arguments.verify:
+        verify(arguments.host)
+    else:
+        client = WebSocket(arguments.host)
+        client.send("suggest_name", {}, "manual")
+        print(json.dumps(client.receive(), ensure_ascii=False, indent=2))
+        client.close()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/sdkconfig.defaults b/sdkconfig.defaults
index f93fe83..8863c43 100644
--- a/sdkconfig.defaults
+++ b/sdkconfig.defaults
@@ -1,4 +1,6 @@
 CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
 CONFIG_LWIP_MAX_SOCKETS=16
+CONFIG_HTTPD_WS_SUPPORT=y
+CONFIG_HTTPD_WS_PRE_HANDSHAKE_CB_SUPPORT=y
 CONFIG_ESP_CONSOLE_USB_SERIAL_JTAG=y
 CONFIG_ESP_CONSOLE_SECONDARY_NONE=y
diff --git a/sdkconfig.esp32-c6-devkitm-1 b/sdkconfig.esp32-c6-devkitm-1
index 174593e..587d1a6 100644
--- a/sdkconfig.esp32-c6-devkitm-1
+++ b/sdkconfig.esp32-c6-devkitm-1
@@ -1559,12 +1559,14 @@ CONFIG_HTTPD_ERR_RESP_NO_DELAY=y
 CONFIG_HTTPD_PURGE_BUF_LEN=32
 # default:
 # CONFIG_HTTPD_LOG_PURGE_DATA is not set
-# default:
-# CONFIG_HTTPD_WS_SUPPORT is not set
+CONFIG_HTTPD_WS_SUPPORT=y
 # default:
 # CONFIG_HTTPD_QUEUE_WORK_BLOCKING is not set
 # default:
 CONFIG_HTTPD_SERVER_EVENT_POST_TIMEOUT=2000
+CONFIG_HTTPD_WS_PRE_HANDSHAKE_CB_SUPPORT=y
+# default:
+# CONFIG_HTTPD_WS_POST_HANDSHAKE_CB_SUPPORT is not set
 # end of HTTP Server
 
 #
diff --git a/src/main.c b/src/main.c
index a6e6d6d..28c25d3 100644
--- a/src/main.c
+++ b/src/main.c
@@ -10,21 +10,21 @@
 #endif
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
-#include "maze32_health.h"
 #include "maze32_config_store.h"
+#include "maze32_health.h"
 #include "maze32_network.h"
 #include "maze32_web.h"
 
-static const char *TAG = "maze32";
+static const char* TAG = "maze32";
 static maze32_health_t health;
 static httpd_handle_t web_server;
 static maze32_network_t network;
+static maze32_gateway_t gateway;
 
 #ifdef MAZE32_MILESTONE_003_DEVICE_TEST
 static int device_test_has_persisted_credentials;
 
-static esp_err_t run_device_test_before_network(void)
-{
+static esp_err_t run_device_test_before_network(void) {
     const maze32_wifi_credentials_t expected = {
         .ssid = "maze32-unavailable-test",
         .password = "test-only-password",
@@ -49,8 +49,7 @@ static esp_err_t run_device_test_before_network(void)
     return ESP_OK;
 }
 
-static esp_err_t finish_device_test(void)
-{
+static esp_err_t finish_device_test(void) {
     if (!device_test_has_persisted_credentials) {
         return ESP_ERR_INVALID_STATE;
     }
@@ -62,15 +61,17 @@ static esp_err_t finish_device_test(void)
 }
 #endif
 
-static int prepare_for_network_reconfiguration(void *context)
-{
-    (void)context;
-    ESP_LOGW(TAG, "Runtime accepted network reconfiguration; no active match exists");
+static int prepare_for_network_reconfiguration(void* context) {
+    const maze32_gateway_t* current_gateway = context;
+    if (!maze32_gateway_can_reconfigure(current_gateway)) {
+        ESP_LOGW(TAG, "Network reconfiguration rejected while lobby is active");
+        return -1;
+    }
+    ESP_LOGW(TAG, "Runtime accepted network reconfiguration while lobby is waiting");
     return 0;
 }
 
-static esp_err_t mount_littlefs(void)
-{
+static esp_err_t mount_littlefs(void) {
     const esp_vfs_littlefs_conf_t configuration = {
         .base_path = "/littlefs",
         .partition_label = "littlefs",
@@ -91,14 +92,13 @@ static esp_err_t mount_littlefs(void)
         return result;
     }
 
-    ESP_LOGI(TAG, "LittleFS mounted: total=%u bytes, used=%u bytes",
-             (unsigned int)total_bytes, (unsigned int)used_bytes);
+    ESP_LOGI(TAG, "LittleFS mounted: total=%u bytes, used=%u bytes", (unsigned int)total_bytes,
+             (unsigned int)used_bytes);
     return ESP_OK;
 }
 
-void app_main(void)
-{
-    const esp_app_desc_t *application = esp_app_get_description();
+void app_main(void) {
+    const esp_app_desc_t* application = esp_app_get_description();
     maze32_health_init(&health, application->version);
 
     vTaskDelay(pdMS_TO_TICKS(1500));
@@ -143,7 +143,14 @@ void app_main(void)
         return;
     }
 
-    result = maze32_network_init(&network, prepare_for_network_reconfiguration, NULL);
+    result = maze32_gateway_init(&gateway);
+    if (result != ESP_OK) {
+        maze32_health_set(&health, MAZE32_HEALTH_ERROR, (int)result);
+        ESP_LOGE(TAG, "WebSocket gateway initialization failed: %s", esp_err_to_name(result));
+        return;
+    }
+
+    result = maze32_network_init(&network, prepare_for_network_reconfiguration, &gateway);
     if (result == ESP_OK) {
         result = maze32_network_start(&network);
     }
@@ -161,7 +168,10 @@ void app_main(void)
     }
 #endif
 
-    result = maze32_web_start(&web_server, &health);
+    result = maze32_web_start(&web_server, &health, &gateway);
+    if (result == ESP_OK) {
+        result = maze32_gateway_register(web_server, &gateway);
+    }
     if (result == ESP_OK) {
         result = maze32_provisioning_register(web_server, &network);
     }
diff --git a/test/host/test_lobby_protocol.c b/test/host/test_lobby_protocol.c
new file mode 100644
index 0000000..f2055d5
--- /dev/null
+++ b/test/host/test_lobby_protocol.c
@@ -0,0 +1,102 @@
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "maze32_lobby.h"
+#include "maze32_protocol.h"
+
+static const char* TOKEN_1 = "000102030405060708090a0b0c0d0e0f";
+static const char* TOKEN_2 = "101112131415161718191a1b1c1d1e1f";
+static const char* OBSERVER_TOKENS[] = {
+    "202122232425262728292a2b2c2d2e2f", "303132333435363738393a3b3c3d3e3f",
+    "404142434445464748494a4b4c4d4e4f", "505152535455565758595a5b5c5d5e5f",
+    "606162636465666768696a6b6c6d6e6f",
+};
+
+static void test_protocol_schema(void) {
+    maze32_client_message_t message;
+    const char* join = "{\"v\":1,\"type\":\"join\",\"seq\":1,\"requestId\":\"join-1\","
+                       "\"payload\":{\"role\":\"player\",\"name\":\"Лорд Лабиринт\"}}";
+    assert(maze32_protocol_parse(join, strlen(join), &message) == MAZE32_PROTOCOL_OK);
+    assert(message.type == MAZE32_MESSAGE_JOIN);
+    assert(message.sequence == 1U);
+    assert(message.role == MAZE32_ROLE_PLAYER);
+    assert(strcmp(message.name, "Лорд Лабиринт") == 0);
+
+    const char* restore = "{\"v\":1,\"type\":\"restore\",\"seq\":2,\"payload\":{\"token\":"
+                          "\"000102030405060708090a0b0c0d0e0f\"}}";
+    assert(maze32_protocol_parse(restore, strlen(restore), &message) == MAZE32_PROTOCOL_OK);
+    assert(message.type == MAZE32_MESSAGE_RESTORE);
+    assert(strcmp(message.token, TOKEN_1) == 0);
+
+    const char* bad_version = "{\"v\":2,\"type\":\"start\",\"seq\":1,\"payload\":{}}";
+    assert(maze32_protocol_parse(bad_version, strlen(bad_version), &message) ==
+           MAZE32_PROTOCOL_UNSUPPORTED_VERSION);
+    const char* unknown = "{\"v\":1,\"type\":\"teleport\",\"seq\":1,\"payload\":{}}";
+    assert(maze32_protocol_parse(unknown, strlen(unknown), &message) ==
+           MAZE32_PROTOCOL_UNKNOWN_TYPE);
+    const char* extra = "{\"v\":1,\"type\":\"start\",\"seq\":1,\"payload\":{\"power\":\"yes\"}}";
+    assert(maze32_protocol_parse(extra, strlen(extra), &message) ==
+           MAZE32_PROTOCOL_INVALID_PAYLOAD);
+    const char* duplicate = "{\"v\":1,\"v\":1,\"type\":\"start\",\"seq\":1,\"payload\":{}}";
+    assert(maze32_protocol_parse(duplicate, strlen(duplicate), &message) ==
+           MAZE32_PROTOCOL_MALFORMED);
+    char oversized[MAZE32_PROTOCOL_MESSAGE_LIMIT + 2U];
+    memset(oversized, 'x', sizeof(oversized));
+    assert(maze32_protocol_parse(oversized, sizeof(oversized), &message) ==
+           MAZE32_PROTOCOL_TOO_LARGE);
+}
+
+static void test_lobby_limits_restoration_and_authority(void) {
+    maze32_lobby_t lobby;
+    maze32_lobby_init(&lobby);
+    maze32_session_t* player_1 = NULL;
+    maze32_session_t* player_2 = NULL;
+    assert(maze32_lobby_join_player(&lobby, 10, "Капитан Клавиша", TOKEN_1, &player_1) ==
+           MAZE32_LOBBY_OK);
+    assert(player_1->player_slot == 1U);
+    uint32_t revision = lobby.revision;
+    assert(maze32_lobby_join_player(&lobby, 11, "Капитан Клавиша", TOKEN_2, &player_2) ==
+           MAZE32_LOBBY_DUPLICATE_NAME);
+    assert(lobby.revision == revision);
+    assert(maze32_lobby_join_player(&lobby, 11, "Мышь в доспехах", TOKEN_2, &player_2) ==
+           MAZE32_LOBBY_OK);
+    assert(player_2->player_slot == 2U);
+    assert(maze32_lobby_ready(&lobby));
+
+    for (unsigned int index = 0U; index < MAZE32_OBSERVER_LIMIT; ++index) {
+        maze32_session_t* observer = NULL;
+        assert(maze32_lobby_join_observer(&lobby, 20 + (int)index, OBSERVER_TOKENS[index],
+                                          &observer) == MAZE32_LOBBY_OK);
+        assert(observer->role == MAZE32_ROLE_OBSERVER);
+    }
+    assert(maze32_lobby_connected_observers(&lobby) == MAZE32_OBSERVER_LIMIT);
+    maze32_session_t* extra = NULL;
+    revision = lobby.revision;
+    assert(maze32_lobby_join_observer(&lobby, 30, OBSERVER_TOKENS[4], &extra) ==
+           MAZE32_LOBBY_ROLE_FULL);
+    assert(lobby.revision == revision);
+
+    assert(maze32_lobby_start(&lobby, 11, 1000U) == MAZE32_LOBBY_NOT_OWNER);
+    assert(lobby.phase == MAZE32_LOBBY_WAITING);
+    maze32_lobby_disconnect(&lobby, 11);
+    assert(!maze32_lobby_ready(&lobby));
+    assert(maze32_lobby_start(&lobby, 10, 1000U) == MAZE32_LOBBY_NOT_READY);
+    assert(maze32_lobby_restore(&lobby, 31, TOKEN_2, &player_2) == MAZE32_LOBBY_OK);
+    assert(player_2->player_slot == 2U && player_2->connection_id == 31);
+
+    assert(maze32_lobby_start(&lobby, 10, 2000U) == MAZE32_LOBBY_OK);
+    assert(lobby.phase == MAZE32_LOBBY_COUNTDOWN);
+    assert(lobby.activation_ms == 5000U);
+    assert(!maze32_lobby_can_reconfigure(&lobby));
+    assert(!maze32_lobby_activate_if_due(&lobby, 4999U));
+    assert(maze32_lobby_activate_if_due(&lobby, 5000U));
+    assert(lobby.phase == MAZE32_LOBBY_ACTIVE);
+}
+
+int main(void) {
+    test_protocol_schema();
+    test_lobby_limits_restoration_and_authority();
+    puts("lobby and protocol tests: PASS");
+    return 0;
+}
diff --git a/version.txt b/version.txt
index 0d91a54..1d0ba9e 100644
--- a/version.txt
+++ b/version.txt
@@ -1 +1 @@
-0.3.0
+0.4.0
diff --git a/web/index.html b/web/index.html
index 7a05ea1..abe6437 100644
--- a/web/index.html
+++ b/web/index.html
@@ -1,29 +1,130 @@
 <!doctype html>
-<html lang="en">
+<html lang="ru">
 <head>
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width,initial-scale=1">
-  <title>maze32</title>
+  <title>maze32 — лобби</title>
   <style>
-    :root { color-scheme: dark; font-family: system-ui, sans-serif; }
-    body { display: grid; min-height: 100vh; margin: 0; place-items: center; background: #10151d; color: #e7edf5; }
-    main { width: min(32rem, calc(100% - 3rem)); padding: 2rem; border: 1px solid #344255; border-radius: 1rem; background: #18212d; }
-    h1 { margin-top: 0; letter-spacing: .08em; }
-    output { color: #79dfa3; }
+    :root { color-scheme: dark; font-family: ui-monospace, "Cascadia Mono", monospace; --ink:#f5edff; --bg:#090711; --panel:#1d1230; --edge:#65488a; --aqua:#42ead2; --p1:#59a9ff; --p2:#ff73bf; --ok:#72e28b; --warn:#ffd75a; --bad:#ff657a; }
+    * { box-sizing: border-box; }
+    body { min-height:100vh; margin:0; padding:max(1rem,env(safe-area-inset-top)) max(1rem,env(safe-area-inset-right)) max(1rem,env(safe-area-inset-bottom)) max(1rem,env(safe-area-inset-left)); background:radial-gradient(circle at top,#24113a,var(--bg) 55%); color:var(--ink); }
+    main { width:min(70rem,100%); margin:auto; }
+    header { display:flex; flex-wrap:wrap; align-items:center; justify-content:space-between; gap:.75rem; margin-bottom:1rem; }
+    h1,h2 { margin:.2rem 0; text-transform:uppercase; letter-spacing:.09em; text-shadow:2px 2px #000; }
+    h1 { color:var(--aqua); }
+    .status { padding:.45rem .7rem; border:1px solid var(--edge); background:#10091d; }
+    .grid { display:grid; grid-template-columns:repeat(auto-fit,minmax(17rem,1fr)); gap:1rem; }
+    section { min-height:13rem; padding:1rem; border:2px solid var(--edge); box-shadow:5px 5px 0 #050307; background:var(--panel); }
+    .player { display:grid; grid-template-columns:2.2rem 1fr auto; gap:.7rem; align-items:center; margin:.75rem 0; padding:.75rem; border:1px solid #493563; background:#130c20; }
+    .p1 { border-left:5px solid var(--p1); } .p2 { border-left:5px solid var(--p2); }
+    .lamp { color:var(--bad); } .online .lamp { color:var(--ok); }
+    label { display:block; margin:.8rem 0 .3rem; }
+    input,button { min-height:2.8rem; border:2px solid var(--aqua); border-radius:0; background:#0c1520; color:var(--ink); font:inherit; }
+    input { width:100%; padding:.55rem; }
+    button { padding:.5rem .8rem; cursor:pointer; box-shadow:3px 3px 0 #020506; }
+    button:hover:not(:disabled) { background:#123a40; } button:active:not(:disabled) { transform:translate(2px,2px); box-shadow:1px 1px 0 #020506; }
+    button:disabled { opacity:.45; cursor:not-allowed; }
+    .actions { display:flex; flex-wrap:wrap; gap:.6rem; margin-top:.7rem; }
+    #notice { min-height:2.8rem; margin-top:1rem; padding:.7rem; border-left:4px solid var(--warn); background:#17101f; }
+    #notice.error { border-color:var(--bad); color:#ffc0c8; }
+    #notice.good { border-color:var(--ok); color:#b5ffc4; }
+    dialog { width:min(28rem,calc(100% - 2rem)); border:3px solid var(--aqua); background:#0b0712ef; color:var(--ink); text-align:center; }
+    dialog::backdrop { background:#030205d9; }
+    #count { margin:1rem; color:var(--warn); font-size:clamp(5rem,30vw,12rem); animation:pulse .65s steps(2,end) infinite; }
+    .observer-warning { display:none; color:var(--warn); }
+    body.observer-mode .observer-warning { display:block; }
+    @media (min-width:1024px) and (min-height:768px) { body.observer-mode .observer-warning { display:none; } }
+    @keyframes pulse { 50% { transform:scale(1.08); } }
   </style>
 </head>
 <body>
   <main>
-    <h1>maze32</h1>
-    <p>The firmware and static application are running.</p>
-    <p>Device health: <output id="health">checking</output></p>
+    <header><h1>maze32</h1><span class="status" id="connection">Подключаем провода к воздуху…</span></header>
+    <div class="grid">
+      <section>
+        <h2>Игроки</h2>
+        <div class="player p1" id="p1"><b>P1</b><span class="name">Свободно</span><span class="lamp">●</span></div>
+        <div class="player p2" id="p2"><b>P2</b><span class="name">Свободно</span><span class="lamp">●</span></div>
+      </section>
+      <section>
+        <h2>Наблюдатели</h2>
+        <p><strong id="observers">0</strong> / 4 смотрят очень внимательно.</p>
+        <p class="observer-warning">Для режима наблюдателя нужен экран не меньше 1024 × 768.</p>
+        <button id="observe">Смотреть лабиринт</button>
+      </section>
+      <section>
+        <h2>Пульт запуска</h2>
+        <div id="join">
+          <label for="name">Позывной игрока</label>
+          <input id="name" maxlength="32" autocomplete="nickname" placeholder="Например, Байт-Беглец">
+          <div class="actions"><button id="suggest">Подкинуть имя</button><button id="play">Занять слот</button></div>
+        </div>
+        <div class="actions"><button id="start" disabled>Начать 3-2-1</button><a href="/provision"><button>Wi‑Fi</button></a></div>
+      </section>
+    </div>
+    <div id="notice" role="status">Сервер решает всё. Браузер только красиво моргает.</div>
   </main>
+  <dialog id="overlay"><h2 id="overlay-title">Приготовились!</h2><div id="count">3</div><p id="overlay-text">Сервер синхронизирует старт.</p></dialog>
   <script>
-    const output = document.querySelector('#health');
-    fetch('/health', { cache: 'no-store' })
-      .then(response => response.ok ? response.json() : Promise.reject(new Error('Health request failed')))
-      .then(health => { output.textContent = `${health.status} · version ${health.version}`; })
-      .catch(() => { output.textContent = 'unavailable'; });
+    (() => {
+      const $ = id => document.getElementById(id);
+      const state = { socket:null, clientSeq:0, serverSeq:0, session:null, lobby:null, reconnect:null };
+      const tokenKey = 'maze32.session.v1';
+      const notice = (text, kind='') => { $('notice').textContent=text; $('notice').className=kind; };
+      const send = (type,payload={},requestId=type) => {
+        if (!state.socket || state.socket.readyState !== WebSocket.OPEN) return;
+        state.socket.send(JSON.stringify({v:1,type,seq:++state.clientSeq,requestId,payload}));
+      };
+      const render = () => {
+        if (!state.lobby) return;
+        state.lobby.players.forEach(player => {
+          const row = $('p'+player.slot);
+          row.querySelector('.name').textContent = player.occupied ? player.name : 'Свободно';
+          row.classList.toggle('online',player.connected);
+        });
+        $('observers').textContent=state.lobby.observers;
+        $('join').hidden=!!state.session;
+        $('observe').hidden=!!state.session;
+        const owner=state.session?.role==='player' && state.session.slot===1;
+        $('start').disabled=!(owner && state.lobby.ready && state.lobby.phase==='waiting');
+        document.body.classList.toggle('observer-mode',state.session?.role==='observer');
+      };
+      const countdown = () => {
+        const dialog=$('overlay'); $('overlay-title').textContent='Приготовились!'; $('overlay-text').textContent='Один сервер — один момент старта.';
+        if (!dialog.open) dialog.showModal();
+        let value=3; $('count').textContent=value;
+        const timer=setInterval(() => { value--; if (value>0) $('count').textContent=value; else clearInterval(timer); },1000);
+      };
+      const handle = event => {
+        let message; try { message=JSON.parse(event.data); } catch { notice('Сервер прислал нечитаемый пакет.','error'); return; }
+        if (message.v!==1 || !Number.isInteger(message.seq) || message.seq<=state.serverSeq) return;
+        state.serverSeq=message.seq;
+        if (message.type==='session') {
+          state.session=message.payload; localStorage.setItem(tokenKey,message.payload.token);
+          notice(message.payload.role==='player' ? `Слот P${message.payload.slot} закреплён. Токен спрятан в этом браузере.` : 'Вы в зрительном зале. Руками не трогаем!','good');
+        } else if (message.type==='lobby') { state.lobby=message.payload; render();
+        } else if (message.type==='name_suggestion') { $('name').value=message.payload.name;
+        } else if (message.type==='countdown') { countdown();
+        } else if (message.type==='active') { $('count').textContent='GO'; $('overlay-title').textContent='Старт!'; $('overlay-text').textContent='Лобби активировано. Лабиринт появится в следующем этапе.'; setTimeout(()=>$('overlay').close(),1200);
+        } else if (message.type==='error') {
+          if (message.payload.code==='invalid_token') { localStorage.removeItem(tokenKey); state.session=null; render(); }
+          notice(message.payload.message || 'Команда отклонена сервером.','error');
+        }
+      };
+      const connect = () => {
+        clearTimeout(state.reconnect); state.clientSeq=0; state.serverSeq=0;
+        const scheme=location.protocol==='https:'?'wss':'ws'; state.socket=new WebSocket(`${scheme}://${location.host}/ws`);
+        state.socket.onopen=() => { $('connection').textContent='Связь с ESP: есть'; const token=localStorage.getItem(tokenKey); if(token) send('restore',{token},'refresh'); };
+        state.socket.onmessage=handle;
+        state.socket.onclose=() => { $('connection').textContent='Связь потеряна, переподключаемся…'; state.reconnect=setTimeout(connect,1000); };
+        state.socket.onerror=() => notice('WebSocket споткнулся. Пробуем снова…','error');
+      };
+      $('suggest').onclick=()=>send('suggest_name',{},'suggest');
+      $('play').onclick=()=>send('join',{role:'player',name:$('name').value},'join-player');
+      $('observe').onclick=()=>send('join',{role:'observer'},'join-observer');
+      $('start').onclick=()=>send('start',{},'start');
+      connect();
+    })();
   </script>
 </body>
 </html>