diff --git a/README.md b/README.md
index 5955e302..52ac01bc 100644
--- a/README.md
+++ b/README.md
@@ -73,7 +73,7 @@ Plugins add functionality to Factorio servers, Clusterio itself or both.
 These are the plugins supported and maintained by the Clusterio developers:
 
 - [Global Chat](/plugins/global_chat/README.md): share the in-game chat between servers.
-- [Research Sync](/plugins/research_sync/README.md): synchronize research progress and technologies unlocked between servers.
+- [Research Sync](/plugins/research_sync/README.md): synchronize research progress and technologies unlocked and the research queue between servers.
 - [Statistics Exporter](/plugins/statistics_exporter/README.md): collect in-game statistics from all the servers and makes it available to the Prometheus endpoint on the controller.
 - [Subspace Storage](https://github.com/clusterio/subspace_storage): Provide shared storage that can transport items between servers via teleport chests.
 - [Player Auth](/plugins/player_auth/README.md): Provides authentication to the cluster via logging into a Factorio server.
diff --git a/plugins/research_sync/README.md b/plugins/research_sync/README.md
index 46315762..0c0889a9 100644
--- a/plugins/research_sync/README.md
+++ b/plugins/research_sync/README.md
@@ -2,6 +2,27 @@
 
 Plugin synchronizing research progress between instances and the cluster.
 
+## Research queue
+
+Each server can follow one cluster research queue.
+It is set from the normal research screen: queueing, moving or cancelling a technology there changes it for every following server.
+So does a lab whose circuit "set research" picks a technology, and so can another mod.
+
+The "Follow the cluster research queue" checkbox on the lab window turns this on or off per server.
+Turning it on replaces the server's queue with the cluster's, turning it off clears it.
+It is on by default.
+On the first start after installing or upgrading, the first server to start shares its queue as the cluster queue, and later servers take it.
+Every change prints a chat line on every server.
+
+It needs Factorio 2.0.56 or later, older servers ignore the queue.
+To turn it off without the GUI, run `/sc research_sync.set_follow(false)` on that server.
+
+Known gaps:
+
+- A script that assigns the queue directly to `{}` isn't seen.
+- Two following servers whose labs want different research keep flipping the cluster queue, as two labs do on one server.
+- A technology a server can't queue yet is dropped there, and an edit on that server then drops it for everyone.
+
 
 ## Installation
 
diff --git a/plugins/research_sync/instance.ts b/plugins/research_sync/instance.ts
index c79617c9..38457c03 100644
--- a/plugins/research_sync/instance.ts
+++ b/plugins/research_sync/instance.ts
@@ -21,6 +21,7 @@ type IpcFinished = {
 	name: string,
 	level: number,
 };
+type IpcQueue = { queue: unknown, player?: string };
 
 export default async function(context: InstancePluginContext) {
 	const { instance, logger, plugin } = context;
@@ -68,14 +69,14 @@ export default async function(context: InstancePluginContext) {
 		researchFinished(tech).catch(err => unexpectedError(err));
 	});
 
-	instance.server.on("ipc-research_sync:queue", (data: { queue?: unknown, player?: string }) => {
+	instance.server.on("ipc-research_sync:queue", (data: IpcQueue) => {
 		try {
 			instance.sendTo("controller", new QueueUpdateEvent(asArray(data.queue), data.player ?? null));
 		} catch (err: any) {
 			unexpectedError(err);
 		}
 	});
-	instance.server.on("ipc-research_sync:follow", (data: { queue?: unknown, player?: string }) => {
+	instance.server.on("ipc-research_sync:follow", (data: IpcQueue) => {
 		followQueue(asArray(data.queue), data.player ?? null).catch(err => unexpectedError(err));
 	});
 
diff --git a/plugins/research_sync/module/sync.lua b/plugins/research_sync/module/sync.lua
index b3da483f..81ab132d 100644
--- a/plugins/research_sync/module/sync.lua
+++ b/plugins/research_sync/module/sync.lua
@@ -40,7 +40,7 @@ end
 --- @class ResearchSyncData
 --- @field technologies table<string, ResearchSyncTechnology>
 --- @field ignore_research_finished boolean
---- @field follow boolean? nil until first set; nil counts as following
+--- @field follow boolean? nil until the first queue_state sets it; the checkbox shows ticked but nil does not send or apply
 --- @field ignore_queue_events boolean
 --- @field queue_dirty boolean
 --- @field queue_player string?
@@ -159,7 +159,7 @@ end
 --- @return string[]
 local function queue_names(force)
 	local names = {}
-	for _, tech in pairs(force.research_queue) do
+	for _, tech in ipairs(force.research_queue) do
 		table.insert(names, tech.name)
 	end
 	return names
@@ -217,11 +217,13 @@ local function ensure_gui(player)
 end
 
 if queue_sync then
+	--- @param event EventData.on_player_created
 	sync.events[defines.events.on_player_created] = function(event)
 		ensure_gui(game.get_player(event.player_index) --[[@as LuaPlayer]])
 	end
 	sync.events[defines.events.on_player_joined_game] = sync.events[defines.events.on_player_created]
 
+	--- @param event EventData.on_gui_checked_state_changed
 	sync.events[defines.events.on_gui_checked_state_changed] = function(event)
 		if event.element.name == "research_sync_follow" then
 			local player = game.get_player(event.player_index) --[[@as LuaPlayer]]
@@ -229,6 +231,7 @@ if queue_sync then
 		end
 	end
 
+	--- @param event EventData.on_research_queued|EventData.on_research_moved|EventData.on_research_cancelled
 	local function on_queue_event(event)
 		if event.force.name ~= "player" then
 			return
@@ -247,7 +250,8 @@ if queue_sync then
 	sync.events[defines.events.on_research_cancelled] = on_queue_event
 
 	-- One send per tick however many events fired (a lab raises several at once).
-	sync.events[defines.events.on_tick] = function()
+	--- @param event EventData.on_tick
+	sync.events[defines.events.on_tick] = function(event)
 		local script_data = get_script_data()
 		if not script_data.queue_dirty then
 			return
diff --git a/plugins/research_sync/test/controller.js b/plugins/research_sync/test/controller.js
index dcbd2dfb..b3cf0a9d 100644
--- a/plugins/research_sync/test/controller.js
+++ b/plugins/research_sync/test/controller.js
@@ -63,6 +63,15 @@ describe("research_sync controller", function() {
 		await update(["a", "b"]);
 		assert.equal(queueEvents().length, 1);
 	});
+	it("should broadcast a clear to an empty queue", async function() {
+		await update(["a"], "Bob");
+		sent.length = 0;
+		await update([], null);
+		assert.equal(queueEvents().length, 1);
+		assert.deepEqual(queueEvents()[0][1].queue, []);
+		assert.equal(queueEvents()[0][1].player, null);
+		assert.deepEqual(await sync(null, null), []);
+	});
 	it("should cap the queue at 7", async function() {
 		await update(["1", "2", "3", "4", "5", "6", "7", "8", "9"]);
 		assert.deepEqual(queueEvents()[0][1].queue, ["1", "2", "3", "4", "5", "6", "7"]);
diff --git a/plugins/research_sync/test/missing.js b/plugins/research_sync/test/missing.js
index 4d585e2b..579cf2ed 100644
--- a/plugins/research_sync/test/missing.js
+++ b/plugins/research_sync/test/missing.js
@@ -2,4 +2,3 @@
 // required here in order to track coverage for them.
 
 import "../dist/node/instance.js";
-import "../dist/node/controller.js";