player connect-disconnect

GAME_STATE_ARCHITECTURE.md

@@ -147,10 +147,12 @@ Snapshots have a monotonically increasing revision. `InternalGameServer` caches
 - Trigger-zone state.
 - Quest-definition reloads.
 
-The remote implementation currently serializes only
-`SetCharacterDestinationCommand` as player intent. The server derives the
+The remote implementation serializes destination intent from clients, while
+the server emits connection-lifecycle presence commands. The server derives the
 character and location from the assigned connection slot; arbitrary state
 mutation commands are not accepted from the network.
+`SetCharacterEnabledCommand` is consumed by the server and replicated to every
+client in the ordered tick bundle when a slot connects or disconnects.
 
 ### Presentation events
 
@@ -407,6 +409,9 @@ server interface. They can remain empty or disabled in multiplayer mode as plann
 Protocol v2 uses server-sequenced deterministic lockstep:
 
 - The server assigns a connection to a preconfigured campaign player slot.
+- Player slots are disabled in the authoritative initial state. A successful
+  connection schedules `SetCharacterEnabledCommand(enabled=true)` for the next
+  lockstep tick; disconnect schedules the corresponding `enabled=false` command.
 - Connection receives one authoritative state at a completed tick plus its
   assigned player ID, tick duration, input delay, and compatibility fingerprint.
 - Destination input is normalized and scheduled two ticks in the future.
@@ -424,7 +429,8 @@ there is no prediction or rollback.
 
 Current boundaries remain:
 
-- only `SetCharacterDestinationCommand` crosses the network;
+- client intent is limited to `SetCharacterDestinationCommand`; server presence
+  changes use `SetCharacterEnabledCommand` in tick bundles;
 - player characters must already exist in the initial state and campaign slot
   list; dynamic spawning and reconnect history are not implemented;
 - authentication and automatic checkpoint resynchronization are absent;

WEBSOCKET_NETWORKING.md

@@ -5,11 +5,12 @@
 The Windows WebSocket transport uses Boost.Asio and Boost.Beast to run a
 server-sequenced deterministic lockstep simulation. A client receives one
 authoritative state at a completed tick boundary. After that, the server sends
-only numbered tick messages containing ordered player commands (or an empty
-command list).
+	only numbered tick messages containing ordered destination and presence
+	commands (or an empty command list).
 
-The current command surface is intentionally limited to
-`SetCharacterDestinationCommand`.
+Client intent is intentionally limited to `SetCharacterDestinationCommand`.
+The server also sends `SetCharacterEnabledCommand` in tick bundles when a
+configured player slot connects or disconnects.
 
 ## Runtime Architecture
 
@@ -21,6 +22,9 @@ The current command surface is intentionally limited to
 - Each accepted connection is assigned the first free character ID from the
   campaign's `networkPlayerSlots`; the connection is rejected when all slots
   are occupied.
+- Player slots start disabled. The server consumes and broadcasts an enabled
+  command on the next tick for each connection and disconnection, including to
+  the newly connected client.
 - The initial message contains the state, completed snapshot tick, assigned
   player ID, tick duration, two-tick input delay, and compatibility fingerprint.
 - Destination inputs cross from the Asio thread through a queue. The simulation
@@ -102,8 +106,8 @@ Message types are:
 - `initial_state` (server to client): one state snapshot and lockstep metadata;
 - `destination_input` (client to server): monotonic client sequence and a
   centimetre-normalized finite target;
-- `tick` (server to client): tick ID, globally sequenced commands, and
-  post-tick diagnostic state hash;
+- `tick` (server to client): tick ID, globally sequenced destination and
+  character-presence commands, and post-tick diagnostic state hash;
 - `error` (server to client): invalid input, incompatibility, or full server.
 
 Protocol v1 is not compatible. Malformed payloads, non-finite or out-of-range
@@ -161,7 +165,8 @@ Launch the Windows game and select `battle_zone_multiplayer`. The client connect
 
 CTest covers protocol-v2 round trips and validation, input-delay ordering,
 fixed-tick replica behavior, campaign slot metadata, initial connection and
-slot assignment, destination submission, and contiguous tick consumption.
+slot assignment, connection/disconnection presence propagation, destination
+submission, and contiguous tick consumption.
 
 ## Current Limitations
 

resources/config/start_state_battle_zone.json

@@ -162,7 +162,7 @@
         "battle_state": 0,
         "currentState": 0,
         "currentWaypointIndex": 0,
-        "enabled": true,
+        "enabled": false,
         "faceTargetId": "",
         "facingAngle": 0.0,
         "homeDriftCheckTimer": 5.0,
@@ -199,7 +199,7 @@
         "battle_state": 0,
         "currentState": 0,
         "currentWaypointIndex": 0,
-        "enabled": true,
+        "enabled": false,
         "faceTargetId": "",
         "facingAngle": 0.0,
         "homeDriftCheckTimer": 5.0,

server/tests/LocationGameStateTests.cpp

@@ -135,6 +135,18 @@ int main()
 
 	FRG::PlayerStateMap noPlayers;
 	state.update(50, noPlayers, false);
+	auto disabledPlayer = std::make_shared<FRG::CharacterState>();
+	disabledPlayer->configureAsPlayer();
+	disabledPlayer->enabled = false;
+	state.location->targetInteractiveObjectId = "object";
+	state.location->targetInteractNpcId = "npc";
+	FRG::PlayerStateMap disabledPlayers{{"player", disabledPlayer}};
+	const FRG::LocationSimulationEvents disabledEvents =
+		state.update(50, disabledPlayers, false);
+	if (!disabledEvents.interactiveObjects.empty() ||
+		!disabledEvents.npcInteractionId.empty()) {
+		return fail("Disabled player interacted with location entities");
+	}
 
 	FRG::CampaignConfig battleZone;
 	battleZone.id = "battle_zone";
@@ -165,6 +177,8 @@ int main()
 		return fail("Network campaign shared player was not created");
 	if (networkSnapshot->players.count("player2") != 0)
 		return fail("Network campaign unexpectedly created the test bot");
+	if (networkSnapshot->players.at("player").state.enabled)
+		return fail("Network campaign player slot was enabled before connection");
 
 	nlohmann::json loadedNetworkState;
 	networkServer.save(loadedNetworkState);
@@ -186,6 +200,35 @@ int main()
 			Eigen::Vector3f(4.f, 0.f, 5.f))) {
 		return fail("Loaded multiplayer slot position was overwritten");
 	}
+	if (loadedNetworkBot->second.state.enabled)
+		return fail("Loaded multiplayer slot was enabled before connection");
+
+	const std::string locationId = loadedNetworkSnapshot->currentLocationId;
+	networkServer.submit(FRG::SetCharacterPositionCommand{
+		locationId, "player2", Eigen::Vector3f(7.f, 0.f, 8.f), true});
+	networkServer.submit(FRG::SetCharacterFacingAngleCommand{
+		locationId, "player2", 1.5f, true});
+	networkServer.submit(FRG::SetCharacterFaceTargetCommand{
+		locationId, "player2", "player"});
+	networkServer.submit(FRG::SetCharacterEnabledCommand{
+		locationId, "player2", false});
+	const auto commandSnapshot = networkServer.snapshot();
+	const auto commandCharacter = commandSnapshot->players.at("player2").state;
+	if (!commandCharacter.position.isApprox(Eigen::Vector3f(7.f, 0.f, 8.f)) ||
+		!commandCharacter.homePosition.isApprox(Eigen::Vector3f(7.f, 0.f, 8.f)) ||
+		commandCharacter.facingAngle != 1.5f ||
+		commandCharacter.targetFacingAngle != 1.5f ||
+		!commandCharacter.faceTargetId.empty() ||
+		commandCharacter.enabled) {
+		return fail("Semantic character commands were not applied");
+	}
+	networkServer.submit(FRG::SetCharacterEnabledCommand{
+		locationId, "player2", true});
+	const auto enabledPlayer =
+		networkServer.snapshot()->players.at("player2").state;
+	if (!enabledPlayer.enabled || !enabledPlayer.attackTargetId.empty()) {
+		return fail("Enabled player acquired an autonomous attack target");
+	}
 
 	return EXIT_SUCCESS;
 }

server/tests/NetworkProtocolTests.cpp

@@ -62,7 +62,10 @@ int main()
 
 	FRG::TickMessage tick;
 	tick.tickId = 43;
-	tick.commands.push_back({1, "player", parsedInput.target});
+	tick.commands.push_back(FRG::ScheduledDestinationCommand{
+		1, "player", parsedInput.target});
+	tick.commands.push_back(FRG::ScheduledCharacterEnabledCommand{
+		2, "uni_exterior", "player2", true});
 	tick.stateHash = "0123456789abcdef";
 	FRG::TickMessage parsedTick;
 	require(
@@ -70,7 +73,11 @@ int main()
 			FRG::makeTickMessage(tick), parsedTick, error),
 		"tick message did not round trip");
 	require(
-		parsedTick.tickId == 43 && parsedTick.commands.size() == 1,
+		parsedTick.tickId == 43 && parsedTick.commands.size() == 2 &&
+		std::holds_alternative<FRG::ScheduledCharacterEnabledCommand>(
+			parsedTick.commands[1]) &&
+		std::get<FRG::ScheduledCharacterEnabledCommand>(
+			parsedTick.commands[1]).enabled,
 		"tick contents did not round trip");
 
 	require(
@@ -120,9 +127,19 @@ int main()
 	const FRG::TickMessage commandTick = timeline.advance();
 	require(
 		commandTick.tickId == 2 && commandTick.commands.size() == 2 &&
-		commandTick.commands[0].commandSequence == firstSequence &&
-		commandTick.commands[1].commandSequence == secondSequence,
+		std::get<FRG::ScheduledDestinationCommand>(
+			commandTick.commands[0]).commandSequence == firstSequence &&
+		std::get<FRG::ScheduledDestinationCommand>(
+			commandTick.commands[1]).commandSequence == secondSequence,
 		"scheduled commands were not finalized in stable order");
 
+	timeline.scheduleCharacterEnabled("uni_exterior", "player2", true);
+	const FRG::TickMessage presenceTick = timeline.advance();
+	require(
+		presenceTick.commands.size() == 1 &&
+		std::holds_alternative<FRG::ScheduledCharacterEnabledCommand>(
+			presenceTick.commands[0]),
+		"character enabled command was not scheduled for the next tick");
+
 	return EXIT_SUCCESS;
 }

server/tests/WebsocketLockstepTests.cpp

@@ -34,11 +34,16 @@ int main()
 {
 	FRG::CampaignConfig campaign;
 	campaign.id = "test_lockstep";
+	campaign.networkPlayerSlots = {"player", "player2"};
 
 	FRG::InternalGameServer authoritative;
 	authoritative.startCampaign(campaign, {}, true, false);
+	nlohmann::json initialState;
+	authoritative.save(initialState);
+	initialState["players"]["player2"] = initialState["players"]["player"];
+	authoritative.load(initialState);
 	FRG::WebsocketGameServer server(
-		authoritative, {"player"}, "lockstep-v2:test_lockstep",
+		authoritative, {"player", "player2"}, "lockstep-v2:test_lockstep",
 		"127.0.0.1", 0);
 	auto client = std::make_unique<FRG::WebsocketGameClient>(
 		"127.0.0.1", std::to_string(server.port()), "/");
@@ -54,6 +59,18 @@ int main()
 		"client did not receive initial state");
 	require(client->localPlayerId() == "player", "wrong player slot assigned");
 
+	auto secondClient = std::make_unique<FRG::WebsocketGameClient>(
+		"127.0.0.1", std::to_string(server.port()), "/");
+	require(
+		waitFor([&]() {
+			secondClient->update(0);
+			return secondClient->initialized();
+		}),
+		"second client did not receive initial state");
+	require(
+		secondClient->localPlayerId() == "player2",
+		"second client received the wrong player slot");
+
 	FRG::WebsocketGameClient overflow(
 		"127.0.0.1", std::to_string(server.port()), "/");
 	require(
@@ -63,6 +80,18 @@ int main()
 		}),
 		"connection beyond configured slots was not rejected");
 
+	server.update();
+	require(
+		waitFor([&]() {
+			client->update(0);
+			secondClient->update(0);
+			return client->snapshot()->players.at("player2").state.enabled &&
+				secondClient->snapshot()->players.at("player").state.enabled;
+		}) &&
+		authoritative.snapshot()->players.at("player").state.enabled &&
+		authoritative.snapshot()->players.at("player2").state.enabled,
+		"connection presence was not broadcast to all replicas");
+
 	client->submit(FRG::SetCharacterDestinationCommand{
 		{}, "spoofed", Eigen::Vector3f(1.234f, 0.f, 2.345f), "ignored"});
 	std::this_thread::sleep_for(std::chrono::milliseconds(20));
@@ -75,8 +104,17 @@ int main()
 		}),
 		"client did not consume finalized lockstep ticks");
 
-	client.reset();
+	secondClient.reset();
 	std::this_thread::sleep_for(std::chrono::milliseconds(50));
+	server.update();
+	require(
+		waitFor([&]() {
+			client->update(0);
+			return !client->snapshot()->players.at("player2").state.enabled;
+		}) &&
+		!authoritative.snapshot()->players.at("player2").state.enabled,
+		"disconnect presence was not propagated");
+
 	FRG::WebsocketGameClient replacement(
 		"127.0.0.1", std::to_string(server.port()), "/");
 	require(
@@ -85,6 +123,15 @@ int main()
 			return replacement.initialized();
 		}),
 		"disconnected player slot was not reusable");
+	server.update();
+	require(
+		waitFor([&]() {
+			client->update(0);
+			replacement.update(0);
+			return client->snapshot()->players.at("player2").state.enabled;
+		}) &&
+		authoritative.snapshot()->players.at("player2").state.enabled,
+		"reconnected player was not enabled");
 
 	return EXIT_SUCCESS;
 }

src/Campaign.cpp

@@ -3,6 +3,7 @@
 #include "external/nlohmann/json.hpp"
 #include <iostream>
 
+
 namespace FRG {
 
 	using json = nlohmann::json;

src/Character.cpp

@@ -268,10 +268,6 @@ void Character::update(int64_t deltaMs, const CharacterUpdateEvents* events) {
 }
 
 void Character::draw(Renderer& renderer) {
-    if (hitSparkEmitter.isConfigured() && hitSparkEmitter.getActiveParticleCount() > 0) {
-        hitSparkEmitter.draw(renderer, 1.0f, Environment::width, Environment::height, false);
-    }
-
     renderer.RenderUniform1f("uAlpha", 1.0f);
     glDisable(GL_BLEND);
 
@@ -279,6 +275,9 @@ void Character::draw(Renderer& renderer) {
     if (!stateSnapshot) return;
     CharacterState state = interpolatedState(*stateSnapshot);
     if (!state.enabled) return;
+    if (hitSparkEmitter.isConfigured() && hitSparkEmitter.getActiveParticleCount() > 0) {
+        hitSparkEmitter.draw(renderer, 1.0f, Environment::width, Environment::height, false);
+    }
     updateAnimationForRender(state);
 
     if (state.useGpuSkinning) {

src/CharacterState.h

@@ -63,7 +63,7 @@ public:
     // --- Identity ---
     std::string npcName;
     bool isPlayer  = false;
-    bool enabled   = true;
+    bool enabled   = false;
     bool canAttack = false;
 
     // --- Position / orientation ---

src/Location.cpp

@@ -1902,7 +1902,8 @@ namespace FRG
 		if (player) {
 			player->update(delta, eventFor(gameServer_.localPlayerId()));
 			auto playerState = player->stateSnapshot();
-			if (playerState) updateTriggerZones(playerState->position);
+			if (playerState && playerState->enabled)
+				updateTriggerZones(playerState->position);
 		}
 		for (auto& [id, remote] : remotePlayers_)
 			if (remote) remote->update(delta, eventFor(id));
@@ -1937,7 +1938,8 @@ namespace FRG
 		}
 
 		auto playerState = player ? player->stateSnapshot() : nullptr;
-		if (auto* tz = getTargetTeleportZone(*locationState); tz && playerState) {
+		if (auto* tz = getTargetTeleportZone(*locationState);
+			tz && playerState && playerState->enabled) {
 			float dist = (playerState->position - tz->position).norm();
 			if (dist <= tz->radius) {
 				logger() << "[TELEPORT] Player reached teleport zone '" << tz->id << "'" << std::endl;
@@ -1951,7 +1953,7 @@ namespace FRG
 			}
 		}
 
-		if (playerState) {
+		if (playerState && playerState->enabled) {
 			for (auto& tz : teleportZones) {
 				if (!tz.active || !tz.automatic) continue;
 				const float autoR = tz.automaticRadius > 0.0f ? tz.automaticRadius : tz.radius;
@@ -1990,7 +1992,7 @@ namespace FRG
 		}
 
 		auto playerState = player ? player->stateSnapshot() : nullptr;
-		if (!playerState) return;
+		if (!playerState || !playerState->enabled) return;
 		auto locationState = stateSnapshot();
 		if (!locationState) return;
 		const std::string lastPlayerAttackTarget = playerState->attackTargetId;

src/LocationGameState.cpp

@@ -255,11 +255,11 @@ LocationSimulationEvents LocationGameState::update(
 	// after every state has advanced, so vector order cannot suppress an attack.
 	std::unordered_map<std::string, CharacterObservation> observations;
 	for (const auto& [id, player] : players)
-		if (player)
+		if (player && player->enabled)
 			observations.emplace(
 				id, CharacterObservation{player->position, player->hp});
 	for (const auto& [id, npc] : npcs)
-		if (npc)
+		if (npc && npc->enabled)
 			observations.emplace(
 				id, CharacterObservation{npc->position, npc->hp});
 
@@ -282,6 +282,7 @@ LocationSimulationEvents LocationGameState::update(
 		if (player) playerIds.push_back(id);
 	std::sort(playerIds.begin(), playerIds.end());
 	for (const std::string& id : playerIds)
+		if (players.at(id)->enabled)
 			advance(id, *players.at(id));
 	std::vector<std::string> npcIds;
 	npcIds.reserve(npcs.size());
@@ -289,12 +290,13 @@ LocationSimulationEvents LocationGameState::update(
 		if (npc) npcIds.push_back(id);
 	std::sort(npcIds.begin(), npcIds.end());
 	for (const std::string& id : npcIds)
+		if (npcs.at(id)->enabled)
 			advance(id, *npcs.at(id));
 
 	for (const CharacterSimulationEvent& source : result.characters) {
 		if (!source.events.attackImpact) continue;
 		CharacterState* target = findCharacter(source.events.attackTargetId, players);
-		if (!target) continue;
+		if (!target || !target->enabled) continue;
 		constexpr float damage = 10.f;
 		target->setHp(target->hp - damage);
 		result.damage.push_back({
@@ -309,7 +311,7 @@ LocationSimulationEvents LocationGameState::update(
 	auto player = players.find("player");
 	if (!interactiveObjectsLocked &&
 		!location->targetInteractiveObjectId.empty() &&
-		player != players.end() && player->second) {
+		player != players.end() && player->second && player->second->enabled) {
 		auto target = interactiveObjects.find(location->targetInteractiveObjectId);
 		const auto object =
 			target == interactiveObjects.end() ? nullptr : target->second;
@@ -326,7 +328,7 @@ LocationSimulationEvents LocationGameState::update(
 	}
 
 	if (!location->targetInteractNpcId.empty() &&
-		player != players.end() && player->second &&
+		player != players.end() && player->second && player->second->enabled &&
 		npcs.count(location->targetInteractNpcId) != 0 &&
 		npcs.at(location->targetInteractNpcId)) {
 		const auto& npc = npcs.at(location->targetInteractNpcId);

src/game_server/InternalGameServer.cpp

@@ -51,6 +51,7 @@ void InternalGameServer::ensureBattleZoneTestBot()
 	auto& bot = state_.players[kBattleZonePlayer2Id];
 	if (!bot) bot = std::make_shared<CharacterState>();
 	bot->configureAsPlayer();
+	bot->enabled = true;
 	configurePlayerAnimations(*bot, resourceZipFile_);
 	bot->npcName = "Test Bot";
 }
@@ -104,6 +105,7 @@ void InternalGameServer::startCampaign(
 	if (createLocalPlayer) {
 		auto player = std::make_shared<CharacterState>();
 		player->configureAsPlayer();
+		player->enabled = campaign.networkPlayerSlots.empty();
 		configurePlayerAnimations(*player, zipFile);
 		state_.players.emplace(localPlayerId_, std::move(player));
 	}
@@ -415,7 +417,10 @@ void InternalGameServer::submit(const GameCommand& command)
 				character->attack = 0;
 				character->attack_cooldown = 0;
 				character->currentState = AnimationState::STAND;
-				if (character->canAttack)
+				character->stopInPlace();
+				character->faceTargetId.clear();
+				character->attackTargetId.clear();
+				if (value.enabled && !character->isPlayer && character->canAttack)
 					character->attackTargetId = "player";
 				character->battle_state = 0;
 			}
@@ -544,6 +549,7 @@ void InternalGameServer::load(const nlohmann::json& in)
 		if (player == state_.players.end() || !player->second) continue;
 		player->second->configureAsPlayer();
 		configurePlayerAnimations(*player->second, resourceZipFile_);
+		//player->second->enabled = false;
 	}
 	battleZoneTestBotElapsedMs_ = 0;
 	ensureBattleZoneTestBot();

src/game_server/NetworkProtocol.cpp

@@ -4,6 +4,7 @@
 #include <iomanip>
 #include <limits>
 #include <sstream>
+#include <type_traits>
 
 
 namespace FRG {
@@ -143,7 +144,18 @@ std::uint64_t LockstepTimeline::schedule(
 {
 	const std::uint64_t sequence = nextCommandSequence_++;
 	pending_[currentTick_ + inputDelayTicks_].push_back(
-		{sequence, playerId, target});
+		ScheduledDestinationCommand{sequence, playerId, target});
+	return sequence;
+}
+
+std::uint64_t LockstepTimeline::scheduleCharacterEnabled(
+	const std::string& locationId, const std::string& characterId,
+	bool enabled)
+{
+	const std::uint64_t sequence = nextCommandSequence_++;
+	pending_[currentTick_ + 1].push_back(
+		ScheduledCharacterEnabledCommand{
+			sequence, locationId, characterId, enabled});
 	return sequence;
 }
 
@@ -182,12 +194,26 @@ bool parseDestinationInputMessage(
 std::string makeTickMessage(const TickMessage& message)
 {
 	nlohmann::json commands = nlohmann::json::array();
-	for (const ScheduledDestinationCommand& command : message.commands) {
+	for (const ScheduledCommand& scheduled : message.commands) {
+		std::visit([&commands](const auto& command) {
+			using T = std::decay_t<decltype(command)>;
+			if constexpr (std::is_same_v<T, ScheduledDestinationCommand>) {
 				commands.push_back({
+					{"type", "destination"},
 					{"commandSequence", command.commandSequence},
 					{"playerId", command.playerId},
 					{"target", targetJson(command.target)}
 				});
+			} else {
+				commands.push_back({
+					{"type", "character_enabled"},
+					{"commandSequence", command.commandSequence},
+					{"locationId", command.locationId},
+					{"characterId", command.characterId},
+					{"enabled", command.enabled}
+				});
+			}
+		}, scheduled);
 	}
 	return envelope("tick", {
 		{"tickId", message.tickId},
@@ -209,22 +235,57 @@ bool parseTickMessage(
 	message.commands.clear();
 	std::uint64_t previousSequence = 0;
 	for (const nlohmann::json& value : payload["commands"]) {
-		ScheduledDestinationCommand command;
 		if (!value.is_object() ||
-			!readTick(value, "commandSequence", command.commandSequence, error) ||
-			!value.contains("playerId") || !value["playerId"].is_string() ||
-			!value.contains("target") ||
-			!readTarget(value["target"], command.target, error)) {
+			!readTick(value, "commandSequence", previousSequence, error)) {
 			if (error.empty()) error = "invalid scheduled command";
 			return false;
 		}
-		command.playerId = value["playerId"].get<std::string>();
-		if (command.playerId.empty() || command.commandSequence == 0 ||
-			command.commandSequence <= previousSequence) {
+		const std::string type = value.value("type", "destination");
+		ScheduledCommand command;
+		if (type == "destination") {
+			ScheduledDestinationCommand destination;
+			destination.commandSequence = previousSequence;
+			if (!value.contains("playerId") || !value["playerId"].is_string() ||
+				!value.contains("target") ||
+				!readTarget(value["target"], destination.target, error)) {
+				if (error.empty()) error = "invalid destination command";
+				return false;
+			}
+			destination.playerId = value["playerId"].get<std::string>();
+			if (destination.playerId.empty()) {
+				error = "destination command playerId must not be empty";
+				return false;
+			}
+			command = std::move(destination);
+		} else if (type == "character_enabled") {
+			ScheduledCharacterEnabledCommand enabled;
+			enabled.commandSequence = previousSequence;
+			if (!value.contains("locationId") || !value["locationId"].is_string() ||
+				!value.contains("characterId") || !value["characterId"].is_string() ||
+				!value.contains("enabled") || !value["enabled"].is_boolean()) {
+				error = "invalid character enabled command";
+				return false;
+			}
+			enabled.locationId = value["locationId"].get<std::string>();
+			enabled.characterId = value["characterId"].get<std::string>();
+			enabled.enabled = value["enabled"].get<bool>();
+			if (enabled.locationId.empty() || enabled.characterId.empty()) {
+				error = "character enabled command IDs must not be empty";
+				return false;
+			}
+			command = std::move(enabled);
+		} else {
+			error = "unsupported scheduled command type";
+			return false;
+		}
+		if (previousSequence == 0 ||
+			(!message.commands.empty() &&
+				previousSequence <= std::visit(
+					[](const auto& item) { return item.commandSequence; },
+					message.commands.back()))) {
 			error = "commands must have unique increasing sequences";
 			return false;
 		}
-		previousSequence = command.commandSequence;
 		message.commands.push_back(std::move(command));
 	}
 	message.stateHash = payload.value("stateHash", std::string());

src/game_server/NetworkProtocol.h

@@ -5,6 +5,7 @@
 #include <cstdint>
 #include <map>
 #include <string>
+#include <variant>
 #include <vector>
 
 namespace FRG {
@@ -33,9 +34,20 @@ struct ScheduledDestinationCommand {
 	Eigen::Vector3f target = Eigen::Vector3f::Zero();
 };
 
+struct ScheduledCharacterEnabledCommand {
+	std::uint64_t commandSequence = 0;
+	std::string locationId;
+	std::string characterId;
+	bool enabled = false;
+};
+
+using ScheduledCommand = std::variant<
+	ScheduledDestinationCommand,
+	ScheduledCharacterEnabledCommand>;
+
 struct TickMessage {
 	std::uint64_t tickId = 0;
-	std::vector<ScheduledDestinationCommand> commands;
+	std::vector<ScheduledCommand> commands;
 	std::string stateHash;
 };
 
@@ -48,13 +60,16 @@ public:
 	std::uint64_t currentTick() const { return currentTick_; }
 	std::uint64_t schedule(
 		const std::string& playerId, const Eigen::Vector3f& target);
+	std::uint64_t scheduleCharacterEnabled(
+		const std::string& locationId, const std::string& characterId,
+		bool enabled);
 	TickMessage advance();
 
 private:
 	std::uint32_t inputDelayTicks_;
 	std::uint64_t currentTick_ = 0;
 	std::uint64_t nextCommandSequence_ = 1;
-	std::map<std::uint64_t, std::vector<ScheduledDestinationCommand>> pending_;
+	std::map<std::uint64_t, std::vector<ScheduledCommand>> pending_;
 };
 
 std::string makeInitialStateMessage(const InitialStateMessage& message);

src/game_server/WebsocketGameClient.cpp

@@ -7,6 +7,7 @@
 #include <iostream>
 #include <mutex>
 #include <thread>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -252,9 +253,17 @@ void WebsocketGameClient::update(std::int64_t)
 		pendingTicks_.erase(next);
 		const std::string locationId =
 			replica_.snapshot()->currentLocationId;
-		for (const ScheduledDestinationCommand& command : tick.commands) {
+		for (const ScheduledCommand& scheduled : tick.commands) {
+			std::visit([&](const auto& command) {
+				using T = std::decay_t<decltype(command)>;
+				if constexpr (std::is_same_v<T, ScheduledDestinationCommand>) {
 					replica_.submit(SetCharacterDestinationCommand{
 						locationId, command.playerId, command.target, {}});
+				} else {
+					replica_.submit(SetCharacterEnabledCommand{
+						command.locationId, command.characterId, command.enabled});
+				}
+			}, scheduled);
 		}
 		replica_.update(kSimulationTickMs);
 		completedSimulationTicks_.push_back({

src/game_server/WebsocketGameServer.cpp

@@ -10,6 +10,7 @@
 #include <memory>
 #include <mutex>
 #include <thread>
+#include <type_traits>
 #include <unordered_map>
 #include <vector>
 
@@ -179,6 +180,14 @@ public:
 		return result;
 	}
 
+	std::vector<std::string> takeConnectedPlayers()
+	{
+		std::lock_guard<std::mutex> lock(inputsMutex_);
+		std::vector<std::string> result;
+		result.swap(connectedPlayers_);
+		return result;
+	}
+
 	void publishTick(
 		std::string tick, nlohmann::json latestState, std::uint64_t tickId)
 	{
@@ -237,6 +246,7 @@ private:
 										<< "' disconnected" << std::endl;
 								assignedSlots_.erase(source->playerId());
 								std::lock_guard<std::mutex> lock(inputsMutex_);
+								if (!source->playerId().empty())
 									releasedPlayers_.push_back(source->playerId());
 							});
 					if (playerId.empty()) {
@@ -251,6 +261,10 @@ private:
 							<< playerId << "' at snapshot tick "
 							<< latestTick_ << std::endl;
 						sessions_.push_back(session);
+						{
+							std::lock_guard<std::mutex> lock(inputsMutex_);
+							connectedPlayers_.push_back(playerId);
+						}
 						InitialStateMessage initial;
 						initial.state = latestState_;
 						initial.assignedPlayerId = playerId;
@@ -280,6 +294,7 @@ private:
 	std::uint64_t latestTick_ = 0;
 	std::mutex inputsMutex_;
 	std::vector<PendingInput> pendingInputs_;
+	std::vector<std::string> connectedPlayers_;
 	std::vector<std::string> releasedPlayers_;
 	std::uint16_t port_ = 0;
 };
@@ -303,7 +318,14 @@ WebsocketGameServer::~WebsocketGameServer() = default;
 
 void WebsocketGameServer::update()
 {
-	for (const std::string& playerId : impl_->takeReleasedPlayers())
+	const std::string locationId = gameServer_.snapshot()->currentLocationId;
+	for (const std::string& playerId : impl_->takeConnectedPlayers())
+		timeline_.scheduleCharacterEnabled(locationId, playerId, true);
+	const std::vector<std::string> releasedPlayers =
+		impl_->takeReleasedPlayers();
+	for (const std::string& playerId : releasedPlayers)
+		timeline_.scheduleCharacterEnabled(locationId, playerId, false);
+	for (const std::string& playerId : releasedPlayers)
 		lastClientSequences_.erase(playerId);
 	for (const Impl::PendingInput& pending : impl_->takeInputs()) {
 		std::uint64_t& previous = lastClientSequences_[pending.playerId];
@@ -313,10 +335,18 @@ void WebsocketGameServer::update()
 	}
 
 	TickMessage tick = timeline_.advance();
-	for (const ScheduledDestinationCommand& command : tick.commands) {
+	for (const ScheduledCommand& scheduled : tick.commands) {
+		std::visit([this](const auto& command) {
+			using T = std::decay_t<decltype(command)>;
+			if constexpr (std::is_same_v<T, ScheduledDestinationCommand>) {
 				gameServer_.submit(SetCharacterDestinationCommand{
 					gameServer_.snapshot()->currentLocationId,
 					command.playerId, command.target, {}});
+			} else {
+				gameServer_.submit(SetCharacterEnabledCommand{
+					command.locationId, command.characterId, command.enabled});
+			}
+		}, scheduled);
 	}
 	gameServer_.update(kSimulationTickMs);
 	nlohmann::json state;