Check the run token on every prefetched chunk

Chunks of an earlier controller run's copy still in flight could land in a newer run's copy of the same generation. Every chunk now carries the token, and the scenario ignores a chunk whose token differs from its record's.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

plugins/player_sync/instance.ts

@@ -289,7 +289,8 @@ export default async function(context: InstancePluginContext) {
 		logger.verbose(`Prefetching ${name}`);
 		// This side doesn't know the save's cleared recipe list, so the whole stored list goes as a full delta
 		await sendPlayerData(playerData, undefined, (chunk, number, total, extra) => {
-			const tokenArg = number === 1 ? `,'${token}'` : "";
+			// Later chunks have no components argument, so nil holds its place
+			const tokenArg = number === 1 ? `,'${token}'` : `,nil,'${token}'`;
 			const args = `'${name}',${generation},'${chunk}',${number},${total}${extra}${tokenArg}`;
 			return `/sc player_sync.prefetch_inventory(${args})`;
 		}, true);

plugins/player_sync/module/player_sync.lua

@@ -701,11 +701,11 @@ end
 
 -- Called by instance.ts as /sc player_sync.prefetch_inventory('name', generation, 'chunk', number, total, components,
 -- token) with a copy of a player's stored data that the controller sent ahead (PrefetchEvent) while they switch to this
--- server. It holds
--- the copy for a player who is offline here or doesn't exist yet. It prints only when it refuses or ignores a chunk,
--- which stops the host sending the rest.
+-- server. It holds the copy for a player who is offline here or doesn't exist yet. Every chunk carries the token, so
+-- chunks of an earlier controller run's copy never land in a newer one. It prints only when it refuses or ignores a
+-- chunk, which stops the host sending the rest.
 --- @param components string? JSON of the components the instance stripped the copy by, given with the first chunk
---- @param token string? The controller run that sent the copy, given with the first chunk
+--- @param token string? The controller run that sent the copy
 function player_sync.prefetch_inventory(player_name, generation, data, number, total, components, token)
 	local script_data = get_script_data()
 	if number == 1 then
@@ -744,7 +744,7 @@ function player_sync.prefetch_inventory(player_name, generation, data, number, t
 	end
 
 	local record = script_data.active_downloads[player_name]
-	if not (record and record.prefetch and record.generation == generation) then
+	if not (record and record.prefetch and record.generation == generation and record.token == token) then
 		-- Refused at chunk 1, dropped by the acquire reply or the inactivity check, or replaced by a newer copy
 		rcon.print("Ignored prefetch chunk " .. number .. " for " .. player_name)
 		return

plugins/player_sync/test/instance.js

@@ -277,7 +277,7 @@ describe("player_sync", function() {
 			const sent = lib.escapeString(JSON.stringify(Object.fromEntries(enabled.map(c => [c, true]))));
 			return chunks.map((chunk, i) => "/sc player_sync.prefetch_inventory(" +
 				`'test',${playerData.generation},'${lib.escapeString(chunk)}',${i + 1},${chunks.length}` +
-				`${i === 0 ? `,'${sent}','tok'` : ""})`);
+				`${i === 0 ? `,'${sent}','tok'` : ",nil,'tok'"})`);
 		}
 
 		it("should send prefetch_inventory chunks with the generation and the full recipe list", async function() {
@@ -296,11 +296,11 @@ describe("player_sync", function() {
 			assert.ok(commands.length > 1, "more than one chunk");
 			assert.deepEqual(instance.server.rconCommands, commands);
 		});
-		it("should send the token with the first chunk only", async function() {
+		it("should send the token with every chunk", async function() {
 			await prefetch({ generation: 3, name: "test" });
 			const commands = instance.server.rconCommands;
 			assert.ok(commands[0].endsWith(",'tok')"));
-			assert.ok(commands.slice(1).every(command => !command.includes("tok")));
+			assert.ok(commands.length > 1 && commands.slice(1).every(command => command.endsWith(",nil,'tok')")));
 		});
 		it("should stop when the save refuses the first chunk", async function() {
 			const playerData = { generation: 3, name: "test" };