diff --git a/src/commands/helper.ts b/src/commands/helper.ts
index 4a0ea50..33fc2b2 100644
--- a/src/commands/helper.ts
+++ b/src/commands/helper.ts
@@ -6,6 +6,7 @@ import {
 	type CommandInteraction,
 	type GuildThreadChannel,
 	InteractionContextType,
+	Permission,
 	TextDisplay
 } from "@buape/carbon"
 import BaseCommand from "./base.js"
@@ -113,6 +114,20 @@ const closeHelperThread = async (
 		return
 	}
 
+	const helperParentId = process.env.HELPER_THREAD_WELCOME_PARENT_ID?.trim()
+	if (helperParentId && channel.parentId !== helperParentId) {
+		await interaction.reply({
+			components: [
+				new Container([
+					new TextDisplay(
+						"This command can only be used in a helper thread."
+					)
+				])
+			]
+		})
+		return
+	}
+
 	await interaction.reply({
 		components: [new Container([new TextDisplay(closeThreadMessage)])]
 	})
@@ -126,6 +141,7 @@ export default class HelperRootCommand extends CommandWithSubcommands {
 	description = "Helper-channel moderation utilities"
 	integrationTypes = [ApplicationIntegrationType.GuildInstall]
 	contexts = [InteractionContextType.Guild]
+	permission = [Permission.ManageMessages, Permission.ManageThreads]
 	subcommands = [
 		new HelperWarnNewThreadCommand(),
 		new HelperCloseCommand(),
diff --git a/test/commands/helper.test.ts b/test/commands/helper.test.ts
new file mode 100644
index 0000000..bd7b8df
--- /dev/null
+++ b/test/commands/helper.test.ts
@@ -0,0 +1,105 @@
+import { afterEach, describe, expect, mock, test } from "bun:test"
+import { Permission, type Command, type CommandInteraction } from "@buape/carbon"
+import HelperRootCommand from "../../src/commands/helper.js"
+import SolvedModCommand from "../../src/commands/solvedMod.js"
+
+const helperParentId = "helper-forum-parent"
+
+type ThreadChannelMock = {
+	parentId: string | null
+	archive: ReturnType<typeof mock>
+	lock: ReturnType<typeof mock>
+}
+
+const extractReplyText = (reply: ReturnType<typeof mock>) => {
+	const payload = reply.mock.calls[0]?.[0] as {
+		components?: { components?: { content?: string }[] }[]
+	}
+	return payload?.components?.[0]?.components?.[0]?.content ?? ""
+}
+
+const makeThreadChannel = (parentId: string | null): ThreadChannelMock => ({
+	parentId,
+	archive: mock(() => Promise.resolve()),
+	lock: mock(() => Promise.resolve())
+})
+
+const makeInteraction = (channel: ThreadChannelMock | null) => {
+	const reply = mock(() => Promise.resolve())
+	const interaction = {
+		rawData: {
+			channel_id: "thread-1",
+			guild_id: "guild-1",
+			channel: { id: "thread-1" }
+		},
+		channel: { id: "thread-1" },
+		user: { id: "user-1", username: "helper", globalName: "Helper" },
+		client: {
+			fetchChannel: mock(() => Promise.resolve(channel))
+		},
+		reply
+	}
+	return { interaction, reply }
+}
+
+const getHelperSubcommand = (name: string): Command => {
+	const command = new HelperRootCommand().subcommands.find(
+		(subcommand) => subcommand.name === name
+	)
+	if (!command) {
+		throw new Error(`Missing /helper ${name} subcommand`)
+	}
+	return command
+}
+
+const runHelperClose = async (channel: ThreadChannelMock | null) => {
+	const { interaction, reply } = makeInteraction(channel)
+	await getHelperSubcommand("close").run(
+		interaction as unknown as CommandInteraction
+	)
+	return { reply, channel }
+}
+
+describe("HelperRootCommand close permissions", () => {
+	const originalHelperParent = process.env.HELPER_THREAD_WELCOME_PARENT_ID
+
+	afterEach(() => {
+		if (originalHelperParent === undefined) {
+			delete process.env.HELPER_THREAD_WELCOME_PARENT_ID
+		} else {
+			process.env.HELPER_THREAD_WELCOME_PARENT_ID = originalHelperParent
+		}
+	})
+
+	test("exposes the same permission bits as /solved", () => {
+		const helper = new HelperRootCommand()
+		const solved = new SolvedModCommand()
+		expect(helper.permission).toEqual(solved.permission)
+		expect(helper.permission).toEqual([
+			Permission.ManageMessages,
+			Permission.ManageThreads
+		])
+	})
+
+	test("close refuses a thread whose parent is not the helper parent", async () => {
+		process.env.HELPER_THREAD_WELCOME_PARENT_ID = helperParentId
+		const channel = makeThreadChannel("some-other-forum")
+		const { reply } = await runHelperClose(channel)
+		const text = extractReplyText(reply)
+
+		expect(text.toLowerCase()).toContain("helper")
+		expect(text.toLowerCase()).not.toContain("now closed")
+		expect(channel.archive).not.toHaveBeenCalled()
+		expect(channel.lock).not.toHaveBeenCalled()
+	})
+
+	test("close archives and locks when the parent matches", async () => {
+		process.env.HELPER_THREAD_WELCOME_PARENT_ID = helperParentId
+		const channel = makeThreadChannel(helperParentId)
+		const { reply } = await runHelperClose(channel)
+
+		expect(channel.archive).toHaveBeenCalledTimes(1)
+		expect(channel.lock).toHaveBeenCalledTimes(1)
+		expect(extractReplyText(reply)).toContain("This thread is now closed")
+	})
+})