Captain's Modlist — Auto-Update Setup

Set this up once and the pack updates itself. After that you just hit Launch — it pulls the latest mods and configs automatically. No reinstalling when a new version drops.

Minecraft: 1.21.1  ·  Mod loader: NeoForge 21.1.230  ·  Recommended RAM: 10–12 GB

Already have a Captain's Modlist instance? (An older version, or one you set up by hand.) You don't need a fresh instance — skip to Converting an existing instance.

1. Install Prism Launcher

Download from prismlauncher.org/download and install:

  1. Windows: grab the Windows installer (.exe). If it complains about missing files, install the MSVC redistributable linked on that page.
  2. macOS: download the .dmg, drag Prism to Applications.
  3. Linux: Flatpak (flatpak install flathub org.prismlauncher.PrismLauncher) or your distro's package.

On first run, accept the defaults and let it auto-detect Java (it bundles one).

2. Add your Minecraft account

Accounts (top-right) → Manage Accounts → Add Microsoft → sign in with the account that owns Minecraft: Java Edition.

3. Create the instance

  1. Add Instance (top-left) → Custom tab.
  2. Name it Captain's Modlist.
  3. Minecraft version: 1.21.1 — not 1.21.10. These are two different versions and Prism lists both; pick exactly 1.21.1 or the pack won't load.
  4. Click Mod Loader → NeoForge, version 21.1.230.
  5. Click OK.

Then give it memory: right-click the instance → Edit → Settings → Java → tick Maximum memory allocation → set 10240–12288 MB.

Short on RAM? The biggest memory user is Distant Horizons' render distance. In-game, lower it under Options → Video Settings → Distant Horizons → Render Distance (e.g. from 128 down to 64–96 chunks) — lower = noticeably less RAM and VRAM. Note: the pack ships DH's config, so an update resets this — re-apply it after updating, or ask Captain to lower the pack default.

4. Connect the auto-updating pack (packwiz)

  1. Download packwiz-installer-bootstrap.jar from the packwiz releases page (the single .jar asset).
  2. Right-click the instance → Folder. Open the minecraft subfolder and drop packwiz-installer-bootstrap.jar inside it.
  3. Back in Edit → Settings → Custom commands, tick Custom commands and set the Pre-launch command. Almost everyone wants the Prod command: 
    "$INST_JAVA" -jar packwiz-installer-bootstrap.jar -g -s client https://files.boreal-mulley.ts.net/captains-modlist/pack.toml
    QA / testing only (LAN): to try a staged update before it's promoted to live, use this command instead. It points at the staging server (192.168.0.101:8089) and only works on the local network — off the LAN it can't reach the staged pack: 
    "$INST_JAVA" -jar packwiz-installer-bootstrap.jar -g -s client "http://192.168.0.101:8089/pack.toml"

5. First launch

Hit Launch. The first run downloads everything (~2 GB of mods + resourcepacks, straight from CurseForge/Modrinth) — this can take several minutes. When it finishes it boots straight into the game.

On first launch you may be prompted to download Analogue Audio FFmpeg. Please go ahead and accept it — it's expected and needed for in-game audio.

6. Updating later

Just launch the instance. The pre-launch step checks the pack every time and downloads only what changed. You never reinstall.

Converting an existing instance

If you already have a Captain's Modlist instance in Prism, do this instead of steps 1–5 to switch it over to auto-updating. (Use this only for a Captain's Modlist instance — pointing the updater at a different pack would mix the two together.)

  1. Check the version. Right-click the instance → Edit → Version. It must be Minecraft 1.21.1 with NeoForge 21.1.230. If it's anything else, set NeoForge to 21.1.230 there — or just make a fresh instance using steps 1–3 above (cleaner).
  2. Back up first. Right-click the instance → Copy instance (or copy its minecraft/mods, config, and kubejs folders somewhere safe). The updater overwrites config/ and kubejs/ and reconciles mods/, so keep a safety copy.
  3. Clear out the old mods. Edit → Open Folder → open minecraft/mods/ and delete everything inside it. The updater redownloads the exact current set; leftover old-version jars are the #1 cause of crashes after converting.
  4. Add the updater jar. Drop packwiz-installer-bootstrap.jar into the minecraft/ folder (download it from the packwiz releases page if you don't have it).
  5. Set the Pre-launch command. Edit → Settings → Custom commands, tick Custom commands, and paste the same command from step 4 above: 
    "$INST_JAVA" -jar packwiz-installer-bootstrap.jar -g -s client https://files.boreal-mulley.ts.net/captains-modlist/pack.toml
  6. Launch. It downloads the current pack and reconciles your instance — you're now auto-updating. From here on, just launch (see Updating later above).

Personal mods (unmanaged)

Want your own mods alongside the pack? Drop them directly into minecraft/mods/ (top level). The auto-updater only manages the mods it installed — it does not delete or touch your own jars, so they survive every update. The same goes for their config files in config/ (only the pack's own configs get overwritten).

Tips: give your mod a distinct filename so it can't collide with a pack mod; keep it at the top level of mods/ (NeoForge doesn't load jars from subfolders); and prefer client-only mods — a mod the server doesn't have can stop you joining multiplayer.

Known issues & fixes

Pre-launch fails: "Tag mismatch" — big mods won't download

If the pre-launch step stops with Pre-Launch command failed with code 1 and the log shows a few of the largest mods (AmbientSounds 6, Biomes O' Plenty, Ars Nouveau, Bosses'Rise) failing with Tag mismatch / AEADBadTagException — and retrying or switching networks doesn't help — this is a bug in the Java that Prism bundles (it miscomputes a security checksum on big downloads). It is not your internet.

Fix: edit your Pre-launch command (Edit → Settings → Custom commands) to add -XX:+UnlockDiagnosticVMOptions -XX:-UseGHASHIntrinsics just before -jar:

"$INST_JAVA" -XX:+UnlockDiagnosticVMOptions -XX:-UseGHASHIntrinsics -jar packwiz-installer-bootstrap.jar -g -s client https://files.boreal-mulley.ts.net/captains-modlist/pack.toml
The -XX:+UnlockDiagnosticVMOptions part must come first, or Java says "Unrecognized VM option". Still failing? Also add -XX:-UseAESIntrinsics -XX:-UseAESCTRIntrinsics in the same spot. The cleaner permanent fix is to install a newer Java 21 (e.g. Temurin 21) and point the instance at it under Settings → Java.

Troubleshooting

  1. "Failed to download" / hangs at pre-launch: open the pack URL from your pre-launch command in a browser to confirm it loads. If the public files.boreal-mulley.ts.net URL fails, use the LAN URL or ask Captain.
  2. "Tag mismatch" on the biggest mods: see Known issues above — add the -XX:-UseGHASHIntrinsics flag to your pre-launch command.
  3. Crash on first load after an update: a mod may have just updated — launch again (the updater sometimes needs a second pass), or report it.
  4. Want to run a personal mod? See Personal mods above — drop it straight into mods/; the updater leaves your own jars alone.
Heads up: config/ and kubejs/ are overwritten on every update (the host controls pack config). Your keybinds and video settings are safe — the pack uses the Default Options mod and does not sync your options.txt.