Research notes

Build Lock

Current build: 2026.08.11.1121610.2-Rel-i343-Meteorite-2607-CU4 (Steam), Unreal Engine 5.5.4Locked: 2026-08-18Lock file: config/hce-build.lock.json

Every finding in docs/ is only true of the build it was measured on, and the game updates without

Game Update Pipeline

Since: CU4 (2026.08.11.1121610.2-Rel-i343-Meteorite-2607-CU4), 2026-08-18

Steam updates the game in place. The moment a patch lands, the previous build is gone, and with

Blam Tag Data in Halo Campaign Evolved

Status: Active researchLast verified: 2026-09-06Game build: 2026.06.26.1097863.1-Rel-i343-Meteorite-2606-CU2

Does Halo Campaign Evolved run on real Blam tag data like the classic games, or are bipeds,

Blam Tag Body Format (`blay` Layout Section)

Build: 2026.06.26.1097863.1-Rel-i343-Meteorite-2606-CU2 (Steam)Artifacts: Meteorite/Content/Paks/.utoc + .ucas, 28 containersTool: crates/blam-cli (mjolnir)

Verified: the Blam tag body that follows the 0x4C-byte container header is

Getting an Edited Tag Into the Game

Status: Solved. An edited tag runs in the game. A single-chunk override container named

with the P patch suffix mounts, wins the chunk lookup, and its Blam payload is what the

Cooked Texture2D / Virtual Texture Format in Halo Campaign Evolved

Status: Verified on the CU2 build below; not yet re-measured on CU4Last verified: 2026-08-03Game build: 2026.06.26.1097863.1-Rel-i343-Meteorite-2606-CU2

A shipped Texture2D in this build cooks one of two ways, and both are common:

Where the Audio Lives in Halo Campaign Evolved

Status: Verified on the CU2 build below; not yet re-measured on CU4Last verified: 2026-08-03Game build: 2026.06.26.1097863.1-Rel-i343-Meteorite-2606-CU2

Almost none of the game's audio is reachable through the IoStore reader. The

HaloSimulation_tag_release.dll Analysis

Status: Active researchLast verified: 2026-07-26Game build: 2026.06.26.1097863.1-Rel-i343-Meteorite-2606-CU2

| Property | Value |

The Blam console

Build: 2026.08.11.1121610.2-Rel-i343-Meteorite-2607-CU4 (Steam)Mod: mods/MJOLNIRBlamConsole (Lua) + native/blamconsole (C)Definitions: defs/hce/console.json, from mjolnir console

Halo Campaign Evolved's simulation DLL still carries the classic Blam

MJOLNIR Multiplayer Investigation — Session Notes

Date: 2026-07-25 ~11:50 PM PSTConversation ID: f74b07be-cdb9-4b3f-ac8b-b193380aa670Status: Research history, 2026-07-25 to 2026-08-20, superseded turns included. Multiplayer later shipped another way: converted CE maps, each a scenario of its own, run under the simulation's Megalo engine and are hosted from MJOLNIRLobby's MULTIPLAYER menu (mods-v0.7.0, PR #106; the .mglo game types ship in the release from mods-v0.9.0, PR #119; re/megaloengine.md).

The working log of the first multiplayer and custom-world investigation, in the order it was found.

The `.mjolnir` Release Archive

Status: v1, enforced by the hub's upload scanner (hub/src/lib/api/scan.ts).

A .mjolnir file is a plain zip with a manifest at the root and IoStore

MJOLNIR Hub — Mod Distribution Architecture

Status: Partly built. Phase 0 is met, and Phases 1, 2, 2.5 and 3 have shipped — with the

deviations each phase note records. Phase 4 has not started. Section headings note what is live.

Mod Authoring: Design

Status: implemented through publishing (tag editor ≥ 0.3); texture swaps in the recipe

since 0.8.0 (not BC7/BC6H). Recipe distribution and the pre-upload conflict check are future

The MJOLNIR level format (`.level.json`)

The interchange format of the level authoring pipeline: what the Blender exporter writes, what

Converting a Classic CE Map

Status: 2026-10-21. The 19 stock maps and the Custom Edition maps

Yoyorast Island and Coldsnap convert with the one command below. A converted

Distributing converted maps

Status: 2026-10-21. Format v1 is proven with Blood Gulch: a pack built by

mjolnir map pack, installed as the launcher will install it and registered

Mod Signing and Attribution: Design

Status: shipped. Tag editor 0.3.0 signs; launcher 0.5.3 verifies; hub migration

0005 carries the key registry and per-release attribution. Rollout step 2 is done:

Contributing a Code Mod

Scope: UE4SS Lua mods (and, case by case, native DLLs). For content

mods — tags, textures, maps, sounds — you don't need any of this: upload a

Security advisory: the `arrayref` 0.3.10 supply-chain attack

On 2026-08-20 a malicious version of the widely used Rust crate arrayref