The H1 Editing Kit is the set of official modding tools used to create custom maps for Halo: Combat Evolved. They have been released in 2004 by Gearbox as the Halo Editing Kit (HEK) for Custom Edition, and again by 343i as the updated Halo: CE Mod Tools (HCEEK or H1A-EK) targeting MCC on PC and distributed via Steam.

Both the legacy HEK and newer H1A-EK are derived from Bungie's original content tools and work nearly the same way as each other. However, the newer tools benefit from countless bug fixes, quality of life improvements, extended limits, new features and tools, and the inclusion of source tags and scripts for the stock maps (see summary of changes).

Getting started

See the general Steam installation steps for the H1A-EK, or the HEK installation steps. Both have important actions you need to perform after installing.

The resources and tools installed may differ between the HEK and H1A-EK:

  • Tool: Imports source assets like textures and models into tag format, and builds maps.
  • Guerilla: A general-purpose tag editor.
  • Sapien: Used to populate levels with objects and encounters.
  • Standalone: A build of Halo that loads tags instead of maps (H1A-EK only).
  • Tags: A set of base tags for the HEK, or all stock map tags for the H1A-EK.
  • Data: For the H1A-EK this includes all singleplayer scripts.

Head over to the general information section or H1 guides to learn more.

Using the H1A-EK with Custom Edition

Maps built using the H1A-EK are not backwards compatible with Custom Edition, but you can use the H1A-EK to create content for H1CE as long as you avoid relying on backwards-incompatible tag features, limits, or script functions, and you build the map with invader-build. Using the new tools this way is not officially supported but can improve your experience over the HEK.

  • Use a tagset intended for Custom Edition. Although the H1A-EK is backwards compatible with legacy tags, the opposite is not true. Legacy tools and Custom Edition itself cannot handle some MCC tags correctly because they can take advantage of engine features only available in MCC, like the extended script node limit and working shader_transparent_generic. If you need stock tags, be sure to extract them from Halo PC or Custom Edition maps using invader-extract.
  • Avoid using backwards-incompatible features. You need to be aware of which additions were made to MCC (see changelog and HEK comparison). This includes tag fields and flags, script functions, and limit extensions.
  • The map must be with invader-build targeting Custom Edition. MCC's Tool will produce maps with the wrong version for Custom Edition, and the HEK's Tool cannot handle scenario tags that have been edited with MCC Sapien because it expands the script node count.

You can point the MCC tools at different data and tags folders, or create a separate copy of the MCC tools with your Custom Edition tagset.


This changelog lists notable modding-related changes and is not guaranteed to be complete.

February 2024

  • Fixed multiplayer level scripts only running for the host.

July 2023 hotfix

  • Using a non-default FOV setting no longer causes campaign cutscenes to have the incorrect FOV.
  • Fixed vehicle secondary weapons being unusable in Standalone on mouse and keyboard.

July 2023

  • Inclusion of digsite content.
  • Biped seats are now functional, meaning rideable bipeds are possible.
  • BSPs without lightmaps now properly render fullbright rather than being invisible.
  • Added a weapon flag to use third person camera while holding it.
  • Added 4 new outer center anchors for HUD elements (usable in hud_globals, grenade_hud_interface, unit_hud_interface, and weapon_hud_interface).
  • Added a new bitmap compression format, BC7 high-quality compression.
  • Alpha channel is no longer discarded when importing fully transparent bitmaps to an uncompressed format.
  • Added the alternate bump attenuation flag to shader_environment to prevent shading artifacts.
  • Raised model_animations units limit to 512, matching OpenSauce.
  • Resetting a player's inventory through the HS function player_add_equipment no longer causes an exception.
  • Trigger volume placement is no longer buggy after the first. This required hiding their parameter fields under expert mode.
  • Classic mode HUD text elements scale properly.
  • Console messages warning of generic shaders missing maps/stages now specify which shader.
  • Fog planes can now be reassigned back to "none" using Sapien.
  • AI enable and disable now use correct command in debug menu.
  • Fixed rename.txt sometimes crashing Tool during imports.
  • Fixed a shading artifact on shader_environment when lightmaps contain invalid incident radiosity vectors.
  • Standalone no longer crashes when rapidly reloading and meleeing at the same time.
  • Added secondary reload animation support for weapons with dual triggers and magazines.
  • Sapien no longer crashes on close if you have selected the trigger volume node and there exist trigger volumes.
  • Filthy part indices in gbxmodel now only default to -1 if both prev and next indices are 0.
  • Standalone no longer raises asserts when loading certain old profile save data.
  • rasterizer_stats 2 no longer causes buggy rendering and crashes.
  • Addition of new script functions and globals:

December 2022

  • A flag was added to the bitmap tag that allows users to opt into Halo 2's mipmap fade behaviour rather than it being the default.
  • Vertex explosion when going above 30 FPS fixed.

September 2022


  • New script functions sleep_forever, debug_script_thread, debug_scripting, breakpoint, kill_active_scripts, get_executing_running_thread, kill_thread, script_started and script_finished
  • New script globals hs_verbose and breakpoints_enabled
  • Support for script parameters similar to the ones seen in H3+.
  • First person permutations will match the third person permutations when object render models match.
  • The Movement Penalized field in weapon tags is now functional.
  • HUD prompts for actions such as entering vehicles will now display correctly.
  • Remove hard-coded behaviour in Tool that prevented tool structure levels\b20 b20 from being able to find any shader tags.


  • Various changes to tags and data files. Updating your tag set is highly recommended.


  • Mouseover text for the inconsequential flag is no longer cut off.
  • Added support for 3rd and 4th grenade slots.
  • Added flag to toggle runtime tag patches to the scenario tag.


  • The command core_load_name now loads instead of saving.
  • The debug menu now has the option for debug_menu_rebuild
  • The command player_spawn_count will no longer cause an assertion when used without multiple controllers.
  • Decals will no longer appear in front of geometry when viewed from a certain distance.


  • Zoom in hud messages will no longer be treated as crouch when importing strings.

March 2022


  • Add script function game_time_authoritative


  • Fixed mirrors on AOTCR showing clipping near the player boots. This is a tag change so make sure to update your files for this to take effect.
  • Various changes to tags and data zips. Updating your tag set is highly recommended.


  • Fix flags displaying weirdly unless the window was refreshed.


  • Now has a debug menu similar to the one seen in H2+. Commands can be defined in the debug_menu_init.txt found in the root folder.
  • Fixed mouse sensitivity in vehicle and zoom.


  • Now supports loading MP scenarios for testing.
  • Now has a debug menu similar to the one seen in H2+. Commands can be defined in the debug_menu_init.txt found in the root folder.
  • Fixed mouse sensitivity in vehicle and zoom.

November 2021


  • Autocomplete in console should display columns a little more evenly.
  • Game view window now uses an aspect ratio that fits the size the user sets.
  • Fix toggling "Draw transparent geometry" causing a crash.
  • UI tooltips should flicker less.


  • UI tooltips should flicker less.

October 2021


  • Many changes to the base game will also apply to the tools. Reading the official update is recommended.
  • Some functions for handling tag names and unicode_string_list were changed to more gracefully handle missing data.


  • Tags were updated to season 8 content. Updating your tag set is highly recommended.
  • Shader source code is now included.


  • FBX converter performance was improved.
  • Fixed FBX marker radius not being handled correctly.

Guerilla: Some tag field names were changed to better reflect their usage, used fields were hidden and some tooltips were updated.


  • Some of these also apply to standalone or MCC itself.
  • A rare vertex explosion issue that occurred when the framerate was not capped was fixed.
  • Real time mirror rendering was fixed.
  • A crash that could occur when rotating objects was fixed.
  • Framebuffer blend function double multiply was changed to better match Custom Edition, enabled for H1CE maps and tags that set "custom edition blending".
  • Windows can now be automatically re-arranged using the Window menu (works similarly to Guerilla)

Comparison to the HEK

Pictured: kornman00 eliminating editing kit bugs, circa June 2021

Users of the Custom Edition HEK will notice two big additions:

  • Scripts and source tags for the stock multiplayer and campaign maps, removing the need to extract them to create variants of those maps.
  • A new standalone build of Halo which loads tags instead of maps (like Sapien) and supports all console commands, intended for fast iteration and troubleshooting.

The new CE mod tools were released with season 7 of MCC (patch notes). It was a significant milestone for the Halo 1 engine, representing the recombination of code and tags from Anniversary, Custom Edition, OG Xbox. Aspects of Halo 2's tools or limits from later games have even been backported.



  • All the tags used in retail MCC plus the ones used for the old HEK tutorial are included alongside the tools, meaning tag extraction with Refinery or invader-extract or prebuilt tag sets are no longer required if someone wants to mod the stock maps. Note that these tags are partially incompatible with H1CE due to their use new flags, shader_transparent_generic, etc. The tags are intended for targeting H1A.
  • The original source HSC scripts are included for all campaign missions.


  • Stability improvements:
    • Negative fog opaque distance and depth no longer causes a crash.
    • Negative power values for skies no longer causes a radiosity crash.
    • Fixed bitmap group sequence blocks crashing when crosshair overlay sequence index was out of bounds.
    • Fixed exception when AI try to fire weapons without projectile references.
    • Fixed a crash resulting from ejection from flipped vehicles not resetting unit animation state.
    • Removed an incorrect assertion related to drawing HUD numbers and bitmap sequences.
    • AI debug code now safely checks for an actor's secondary look direction prop index being NONE.
    • Various buffer overflow, index out of range, and stale pointer fixes.
    • Increase MAXIMUM_NUMBER_OF_BUILD_SPRITE_BITMAPS from 8 to 16 (renderer stability).
  • The engine will now check and log when an invalid particle_system using rotational complex render mode has a particle state where the sprites bitmap does not include another "sideways" sequence after the given "forward" sequence index.
  • The tools are in general faster and more responsive (in part due to manual optimizations, in part due to play builds built with a modern optimizing compiler being used instead of test builds).
  • Asserts can be disabled using the -noassert command line flag.
  • The tags, data, and maps directories can now be set when running all tools. See custom content paths for more info. This makes it easier to work with different tag sets.
  • All tools are still 32-bit but they are now large address aware (LAA). This allows them to use up to 4 GiB of virtual memory instead of 2, which prevents Sapien from running out of memory when editing scenarios with many large assets.
  • Various cases of unnecessary/confusing logging in the tools have been removed, such as "Couldn't read map file" and "Sound card doesn't meet minimum hardware requirements".


  • The tools now use the modern DX11 graphics API instead of the obsolete D3D9 API. this should result in better performance and support on modern systems.
  • First person models now use the highest LOD available instead of the lowest.
  • Increased MAXIMUM_RENDERED_ENVIRONMENT_SURFACES from 16k to 32k. This means BSPs can now have more visible triangles without culling happening. It is still important to use portals to manage visible clusters.
  • Many Gearbox visual bugs were fixed. Some examples are:
    • Restoration of shader_transparent_generic and shader_transparent_plasma
    • fog screen layers
    • Fog planes draw over sky
    • Environment bump mapping
    • Interpolation on screen shake, antennas, flags, and some UI fading
    • Water mipmap order
    • Camo tint
    • Glass with bumped reflections
    • Flashlight distance
    • Widget alignment in mirror reflections


  • Lots of new verbs have been added. See the Tool page for details.
  • A -verbose flag can be added to see additional logging.
  • Lightmapping code has been optimized and is even faster with the -noassert command line flag. Lightmapping now takes roughly a quarter of the time of legacy Tool and is even faster than LM tool. Additionally this code now only uses 32-bit integers instead of an unsafe mix with 16-bit ones, and 16 MiB stack reserve. This increases the crash stability of radiosity.
  • Most logs (like debug.txt) are now saved to a reports subfolder (similarly to Halo 2+).
  • Bitmaps compilation
    • Bitmap DXT1-3 (BC1-3) encoding now uses DirectXTex instead of some S3TC code. This should result in higher quality similar to the original XDK.
    • The bitmaps verb now accepts both .tiff and .tif extensions like bitmap does.
  • Map compilation (build-cache-file):
    • Script data is properly recompiled from source files when available now. A bug previously caused Tool to always fall back to sources stored in the scenario tag.
    • Resource maps can optionally be updated to include all the resource data for the scenario being packaged.
    • Maps can target "classic" or "remastered" mode.
    • resource maps are no longer generated or used as they are not used by H1A (aside from H1CE backwards compatibility).
    • Tool will now log errors when the user attempts to use swarm actors in firing-position based combat; always charge at enemies must be set to prevent runtime crashes.
  • Model and structure compilation:
    • A flag to fix collision artifacts is now exposed for compiling BSPs (structure verb) and model_collision_geometry (collision-geometry verb).
    • WRL files are saved alongside the JMS file being compiled rather than the HEK root. The user is now told that this file was generated.
    • When compiling a structure BSP and shaders do not yet exist, the chosen types of shaders will now be generated in the level's shaders directory instead of the tags root.
    • Model compilation can now optionally use Halo 2's logic for LOD selection, which is more intuitive.
    • Model and collision importing have more verbose output. Use -verbose for the most troubleshooting information.
  • Usage and feedback clarity:
    • Argument parsing is now less primitive. Verbs can include optional arguments and flags and any unrecognized options are presented to the user.
    • The usage printout when Tool is run without arguments is now sorted. The names and argument descriptions of some existing verbs have been updated for clarity and consistency.
    • zoners_model_upgrade and strings verbs have been removed since they weren't useful.
    • Tool will now tell you if it couldn't find a directory rather than simply logging nothing like some verbs previously did (looking at you model).
    • Verbs which accept a tag path as an argument will now automatically strip data\ and tags\ prefixes, allowing you to use tab completion on the command line (Halo 3 backport).
    • Tool will no longer exception (but will log errors) when compiling a gbxmodel where the JMS has invalid node weights (two nodes where one has weight 1.0).
  • Tool supports a -pause flag which keeps the process running after completion until the user presses Enter. This was meant for community-made launchers like Osoyoos.
  • Stability improvements:
    • ogg/vorbis upgraded to to 1.3.5/1.3.7 which should improve sound compilation stability.
    • Fixes for various unsafe code: uninitialized variables, bad printf args, etc.


  • When Sapien crashes it will attempt to autosave the scenario to a new file.
  • The lightmap painting feature was fixed. The user can perform touchups to fix light leaks or add missing lights and save changes to the lightmap.
  • Garbage collection now takes into account Sapien's 5x higher objects per map and object memory pool limits so Sapien no longer spams "garbage collection critical" errors after loading the c10 scenario.
  • Multiple Sapien instances can now be launched at once using the -multipleinstance command line flag.
  • Game window improvements:
    • Weather and particle effects like smoke and fire will now render.
    • When the camera is outside the BSP, you will now see structure debug lines by default (debug_structure_automatic) (like H2 Sapien). This helps you find the BSP if you get lost or the camera begins outside it, as with b40.
    • Interpolation code from H1A is included and framerate_throttle is disabled by default, allowing for smooth animation and movement.
    • The camera speed can be temporarily boosted by holding Control.
    • The Game window resolution has been increased from 800x600 to 1280x720 (widescreen).
    • A gamepad can be used to control the camera, though this feature is experimental.
  • User interface improvements:
    • Sapien now features a modern Windows file open dialog which includes locations like quick access. This is also true for the Edit Types menu when finding new tags to add to a palette.
    • Invalid block indices are now shown as BAD: # rather than being set to -1.
    • UI has been cleaned up a bit with unsupported elements removed (e.g. File > New) and others renamed.
    • Added "Clear" button to tag reference dialog.
    • The View menu now includes ways to reopen the Output window and Tool window if they are closed.
    • Widened layouts for strings, references, block indices, etc.
    • When placing netgame flags, the Properties palette now includes explanations for how to set up each game mode.
    • When placing netgame equipment the team index field also has a helpful reminder that 0=red and 1=blue.
  • Stability improvement:
    • Transparent shaders with no maps no longer cause Sapien to crash. The shader is simply not rendered.
    • Objects with transparent self occlusion enabled while also referencing a transparent shader with extra layers will no longer cause a crash.
    • Sapien no longer crashes if a BSP fog plane has a fog region set to NONE.
    • The snap to normal hotkey, N, no longer puts the editor into a bad state.
    • Detail object painting is possibly more stable now. More testing is needed to confirm.
    • Sapien now supports -nosound and -nojoystick arguments as a mitigation for any device-related problems which need to be worked around.
    • The New instance and Delete buttons in the hierarchy view are now properly disabled when not applicable.
    • Recording and model view modes no longer cause a crash on closing Sapien.
    • Closing the Output window now properly sets its handle to NULL.
    • Fixed a crash related to selecting custom device_control names.
    • Fixed issues with invalid platoon indices.


  • Guerilla now features a modern Windows file open dialog which includes locations like quick access.
  • H2 Guerilla backported features:
    • Tag blocks can now be collapsed.
    • UI elements have been upgraded to look more modern, with wider inputs.
    • Expert mode, Show tag block sizes, and Copy tag name options.
    • A zoom level feature has been added to the bitmap viewer. The alpha channel drop-down label has also been corrected.
  • Fields which reference a block element by index, shown as a drop-down, now update their appearance in real time as the referenced block is edited. For example, when a referenced element is deleted the field will immediately show "BAD INDEX: #". When the name of a referenced block element is changed, the label in the drop-down is updated in real time too.
  • Some unused UI options have been removed.
  • Guerilla now enforces sound tag gain modifiers are within a valid 0.0 to 1.0 range.
  • When tags are loaded for editing, tag references with an unknown group ID are now clamped to NONE. This fixes cases like the leftover weapon_collection reference in the Bloodgulch scenario from causing downstream problems.
  • Save as now makes copies of read-only tags editable without having to reopen the tag.
  • Hover-over tooltips for flags after unused sections are no longer off-by-one, e.g. multiplayer spawn flags for vehicles.
  • Fixed a crash from changing a "go to" command list atom modifier field in the scenario tag.

HaloScript and console

  • The developer console now supports the Home and End keys to move the cursor to the start and end of the input line.
  • Console history size has been increased from 8 to 16 entries.
  • Many defunct globals and functions have been removed because they are not functioning or applicable to H1A (e.g. for troubleshooting Gearbox netcode).
  • Built-in script docs:
    • The script_doc HSC function now includes external globals in the output file in addition to functions.
    • Script docs and help output now show return value types for functions.
    • Many instances of profanity in function descriptions have been cleaned up.
    • The player is now referred to in a gender-neutral way.
  • Custom Edition-specific functions like sv_say and multiplayer_draw_teammates_names were stubbed out for compatibility with CE maps (avoids crashes).
  • Unrecognized script functions and globals will now cause script data to be dropped rather than crashing the game.
  • Numerous new functions were added:
    • Numeric functions: pin, abs_integer, abs_real.
    • Logical functions: bitwise_and, bitwise_or, bitwise_xor, bitwise_left_shift, bitwise_right_shift, bitwise_flags_toggle, bit_toggle, bit_test.
    • Listing players: players_on_multiplayer_team, local_players.
    • Printing: print_if, log_print.
    • Distances: objects_distance_to_object, objects_distance_to_flag.
    • Physics: physics_set_gravity, physics_get_gravity, physics_constants_reset.
    • Debug camera: debug_camera_save_name, debug_camera_load_name, debug_camera_save_simple_name, debug_camera_load_simple_name, debug_camera_load_text.
    • Other: objects_delete_by_definition, list_count_not_dead, game_is_authoritative, debug_structure_automatic.
  • Changes to existing functions:
    • The print function no longer unsafely interprets its argument as a format string.
    • unit_kill and unit_kill_silent no longer crash the game if the given unit does not exist.
    • debug_camera_save and debug_camera_load now save and load camera_<mapname>.txt instead of camera.txt. A console message is now logged when the camera file isn't found.
    • player_effect_set_max_rumble is no longer a hard-coded alias for player_effect_set_max_vibrate. Map scripts (like a10 and d40) were updated.
  • H1A's versions of map scripts no longer use a repurposed core_save_name to signal mission segments. The function again behaves like legacy and a new mcc_mission_segment function was added instead.
  • Globals and functions are no longer locked to specific contexts like server or multiplayer. For example, you can use cheat_spawn_warthog in SP maps now when using H1A Standalone.

Debug globals

  • debug_structure shows invisible collision surfaces in semi-transparent red and includes a BSP bounding box now (Halo 2 Sapien backport).
  • debug_objects behavior has been changed. It no longer shows bounding spheres and collision geometry by default but these can still be toggled on their own.
  • cheat_jetpack now works like it was intended to. Hold crouch to float and jump to fly.

Tag classes

  • unit and actor_variant now each include the metagame type and metagame class fields for MCC's scoring system.
  • shader_model received a new flag to use "OG Xbox" channel order for the multipurpose map. Guerilla's explanation of channel usage is now updated to explain both H1X and Gearbox+ channel orders.
  • Some runtime tag fields have been made invisible, such as object, weapon, and scenario_structure_bsp predicted resources, some other BSP fields.
  • gbxmodel:
    • Node limit was increased from 48 to 63 to match Custom Edition 1.10.
    • The node count fields are now marked deprecated and are invisible in Guerilla. They are written to during postprocessing but never actually used by the game.
    • The markers block is hidden in Guerilla since it is processed from permutation markers and not intended for editing.
  • model_collision_geometry pathfinding sphere limit increased from 32 to 256.
  • scenery received a new flags field which is unused in current versions of MCC.
  • effect parts and particles each previously had two fields called create in. The second in each case has been corrected to violence mode.
  • weapon:
    • Trigger distribution angle is now typed as an "angle" instead of a plain float so it can be edited in degrees (radians internally).
    • Trigger flags has a new option to force legacy (buggy) aiming behaviour seen in the Spirit dropship's turret.
  • scenario:
    • Unused fields have been marked deprecated and no longer appear in Guerilla and Sapien:
    • The previously hidden cutscene title fields text style and text flags are now exposed.
    • There is a new scenario flag disable color correction although it is unused at this time.
    • Script source text is now visible in Guerilla and Sapien.
    • Netgame flags team index was renamed to usage id and explanations were added in the tag for how to set this ID depending on the flag type.
    • BSP switch trigger volumes source and destination BSPs are now typed as proper block indices rather than integers, which causes Guerilla to display them as drop-downs.
    • The following blocks are now hidden by default unless Expert mode is enabled in the menu: BSP switch trigger volumes, scripts, globals, and references.
    • Increased limits:
      • MAXIMUM_OBJECT_NAMES_PER_SCENARIO from 512 to 640.
      • MAXIMUM_HS_SCRIPTS_PER_SCENARIO from 512 to 1024.
      • MAXIMUM_HS_GLOBALS_PER_SCENARIO from 128 to 512.
      • MAXIMUM_HS_STRING_DATA_PER_SCENARIO from 256kb to 800kb.
      • MAXIMUM_HS_SOURCE_DATA_PER_FILE from 256kb to 1MB.
  • The unused spheroid tag has been removed.

Maps and map loading

  • Custom maps compiled with H1A Tool are identified by having cache version 13 in their header (H1CE is 609).
  • The map file size limit was increased to 2 GiB.
  • Tag space is increased from 23 MiB to 64 MiB.
  • A new flags field was added to the cache header for controlling H1A features.
  • Tags, BSP verts (16 MiB), and game state are now stored in separate dedicated allocations rather than one giant one.
  • Protected maps will be detected and force a crash because they are unsupported.
  • H1CE's resource maps are now included in MCC and are used when playing a H1CE map.
  • Some changes were made to map loading.

Game state

Due to changes in the game state structure, savegames from before season 7 are invalidated.

  • Some AI-related game state was space-optimized (roughly 90 KiB savings) to make room for growing other datum arrays.
  • Increased antennas limit from 12 to 24.
  • MAXIMUM_RENDERED_OBJECTS increased from 256 to 512.


Thanks to the following individuals for their research or contributions to this topic:

  • Vaporeon (Tips on using the H1A-EK with Custom Edition)