diff --git a/.luacheckrc b/.luacheckrc
index 681a68b..b4cb29d 100644
--- a/.luacheckrc
+++ b/.luacheckrc
@@ -648,6 +648,7 @@ stds.minetest = {
 stds.book_runner = {
 	globals = {
 		"book_runner",
+		minetest = {fields = {chat_send_player}},
 	},
 	read_globals = {
 		"default",
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 3d311a8..94c1c38 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -10,6 +10,20 @@ repos:
 
   - repo: local
     hooks:
+      - id: detect_debug
+        name: detect debug
+        language: pygrep
+        entry: DEBUG
+        pass_filenames: true
+        exclude: .pre-commit-config.yaml
+        fail_fast: true
+      - id: stylua
+        name: stylua
+        language: system
+        entry: stylua
+        pass_filenames: true
+        types: [ file, lua ]
+        fail_fast: true
       - id: luacheck
         name: luacheck
         language: system
@@ -17,9 +31,4 @@ repos:
         pass_filenames: true
         types: [ file, lua ]
         args: [ -q ]
-      - id: stylua
-        name: stylua
-        language: system
-        entry: stylua
-        pass_filenames: true
-        types: [ file, lua ]
+        fail_fast: true
diff --git a/command.lua b/command.lua
index f102ab3..1c08062 100644
--- a/command.lua
+++ b/command.lua
@@ -1,9 +1,13 @@
+local f = string.format
+
 local strip_colors = minetest.strip_colors
 
 local strip_translation = futil.strip_translation
 
 local S = default.get_translator
 
+local max_book_length = book_runner.settings.max_book_length
+
 minetest.register_chatcommand("run_in_book", {
 	params = "<command> [<args>]",
 	description = "run the command; put the output in the book's body",
@@ -38,11 +42,21 @@ minetest.register_chatcommand("run_in_book", {
 		end
 
 		local orig_chat_send_player = minetest.chat_send_player
+		local length = 0
+		local skipped_lines = 0
+		local too_long = false
 		local received_messages = {}
-		-- luacheck: push globals minetest.chat_send_player
 		function minetest.chat_send_player(name2, message)
 			if name == name2 then
-				table.insert(received_messages, strip_colors(strip_translation(message)))
+				if too_long then
+					skipped_lines = skipped_lines + 1
+				elseif length + #message + 1 > max_book_length then
+					too_long = true
+					skipped_lines = skipped_lines + 1
+				else
+					table.insert(received_messages, strip_colors(strip_translation(message)))
+					length = length + #message + 1
+				end
 			else
 				orig_chat_send_player(name2, message)
 			end
@@ -54,7 +68,10 @@ minetest.register_chatcommand("run_in_book", {
 		end
 
 		minetest.chat_send_player = orig_chat_send_player
-		-- luacheck: pop
+
+		if too_long then
+			table.insert(received_messages, f("WARNING: too much output, %i lines omitted", skipped_lines))
+		end
 
 		local text = table.concat(received_messages, "\n")
 		local written_book = ItemStack("default:book_written")
diff --git a/mod.conf b/mod.conf
index df86ea7..8a8bb2b 100644
--- a/mod.conf
+++ b/mod.conf
@@ -5,6 +5,6 @@ website = https://content.minetest.net/packages/rheo/book_runner/
 author = fluxionary
 license = AGPL-3.0-or-later
 media_license = CC-BY-SA-4.0
-version = 2022-11-27
+version = 2023-05-12
 min_minetest_version = 5.6.1
 depends = default, fmod, futil
diff --git a/settingtypes.txt b/settingtypes.txt
new file mode 100644
index 0000000..7f0d961
--- /dev/null
+++ b/settingtypes.txt
@@ -0,0 +1,2 @@
+# output will be truncated after this point, with a short message.
+book_runner:max_book_length (maximum length of the book) int 100000 0 640000