horizon-airdef/docs/launcher-commands.md

Launcher commands

Every command of horizon-launcher, and the tool horizon-launcher mcp offers for it. A tool's arguments are the command's, in snake_case. A tool runs the command with --json and returns what it printed. The tools that change the player's things for good need confirm: true. The tools that send something or reach other people say "only when the player asks". The game's own tools, game_*, are in horizon-ctl-commands.md. With No AI on, mcp and agent-config are hidden and refuse; every other command stays. See agent-control.md.

horizon-launcher versions

List Horizon releases, or the installed versions.

horizon-launcher versions

• --installed: Only the versions installed here (no network)

MCP: versions.

horizon-launcher install

Download and install a release (a tag such as v2026.10.13, or "latest").

horizon-launcher install <TAG>

• TAG

MCP: install.

horizon-launcher remove

Remove an installed version.

horizon-launcher remove <TAG>

• TAG

MCP: remove, needs confirm: true.

horizon-launcher prepare

Prepare a version's resources from your own Minecraft install.

horizon-launcher prepare

• --minecraft: The game folder of the official launcher, Prism Launcher, MultiMC, the Modrinth App, ATLauncher or GDLauncher (default: the launcher's, then every launcher's default)

MCP: prepare.

horizon-launcher play

Start the client.

horizon-launcher play

• --world: Open or create this world (a folder under saves) at once
• --creative: Creative mode for a new world
• --join: Join a friend's world with its invite code
• --arg: An extra argument for the game, passed through as-is (repeatable), for example --server-thread

MCP: play, then the game_* tools.

horizon-launcher server

Run a dedicated server here; type commands into its console.

horizon-launcher server

• --dir: The server's folder (default: the one the launcher uses)
• --accept-eula: Agree to the Minecraft EULA (https://aka.ms/MinecraftEULA)

MCP: server, server_command, server_log, server_stop.

horizon-launcher notes

Show a release's patch notes (default: the newest).

horizon-launcher notes [TAG]

• TAG

MCP: notes.

horizon-launcher links

Show the Discord, sponsor and website links.

horizon-launcher links

MCP: links.

horizon-launcher account list

The signed-in accounts and which one plays.

horizon-launcher account list

MCP: account_list.

horizon-launcher account sign-in

Sign in with a Microsoft account in your browser (device code).

horizon-launcher account sign-in

MCP: account_sign_in.

horizon-launcher account sign-out

Sign out: the account's tokens leave the keychain.

horizon-launcher account sign-out <WHO>

• WHO: Its name or UUID

MCP: account_sign_out, needs confirm: true.

horizon-launcher account select

Play as this account.

horizon-launcher account select <WHO>

• WHO

MCP: account_select.

horizon-launcher account offline

Play offline, without an account.

horizon-launcher account offline

MCP: account_offline.

horizon-launcher settings

Show the launcher's settings, or set one (the Settings page): selected-version TAG, minecraft-dir PATH, server-dir PATH ("default" resets a folder), install-new-versions on|off, opening-animation on|off.

horizon-launcher settings [KEY] [VALUE]

• KEY (selected-version, minecraft-dir, server-dir, install-new-versions, opening-animation)
• VALUE: The new value (with KEY)

MCP: settings.

horizon-launcher game-args

Show or set the extra arguments the game starts with (for example --server-thread); quotes group a word with spaces in it.

horizon-launcher game-args [ARGS]

• ARGS: Omit to show the current arguments

MCP: game_args.

horizon-launcher logs

Print the end of the game's log (logs/latest.log in the game folder), or its newest crash report.

horizon-launcher logs

• --lines: How many lines of latest.log
• --crash: The newest crash report instead

MCP: logs.

horizon-launcher update

Look for a newer Horizon release and launcher, and install them.

horizon-launcher update

• --check: Only report what is available

MCP: update.

horizon-launcher desktop-entry

Linux: put Horizon in the applications menu (an entry and the icon, under $XDG_DATA_HOME), or take it out with --remove.

horizon-launcher desktop-entry

• --remove: Remove the entry and the icon, and stop adding them back

MCP: desktop_entry.

horizon-launcher data status

What is allowed, the install ID and how many items wait (the default).

horizon-launcher data status

MCP: data_status.

horizon-launcher data allow

Turn kinds on: performance, crashes, bugs, benchmarks, or all.

horizon-launcher data allow <KINDS>...

• KINDS

MCP: data_allow, only when the player asks.

horizon-launcher data deny

Turn kinds off: performance, crashes, bugs, benchmarks, or all.

horizon-launcher data deny <KINDS>...

• KINDS

MCP: data_deny.

horizon-launcher data show

Print exactly what would be sent.

horizon-launcher data show

MCP: data_show.

horizon-launcher data delete

Delete everything sent from here, and what waits, and take a new install ID.

horizon-launcher data delete

MCP: data_delete, needs confirm: true.

horizon-launcher data send

Send what is waiting now.

horizon-launcher data send

MCP: data_send, only when the player asks.

horizon-launcher data bug

Send a bug report you write; it is printed first, as it would leave.

horizon-launcher data bug <TEXT>

• TEXT
• --log: Add the end of the game's log (scrubbed, without chat)
• --yes: Send without asking

MCP: data_bug, only when the player asks.

horizon-launcher data benchmark

Upload a benchmark report (docs/benchmark-report.md); it is printed first.

horizon-launcher data benchmark <FILE>

• FILE
• --yes

MCP: data_benchmark, only when the player asks.

horizon-launcher modpack list

The imported packs and their coverage (the default).

horizon-launcher modpack list

MCP: modpack_list.

horizon-launcher modpack import

Import a .mrpack, a CurseForge zip or an instance folder, and write its coverage report.

horizon-launcher modpack import <PATH>

• PATH

MCP: modpack_import.

horizon-launcher modpack port

Get the jars of what this computer can port and carry them over.

horizon-launcher modpack port <PACK>

• PACK: The pack's folder name, as list shows it
• --from: A folder with your own jars (an installed instance, a downloads folder)

MCP: modpack_port.

horizon-launcher modpack play

Play a ported pack as its own profile.

horizon-launcher modpack play <PACK>

• PACK

MCP: modpack_play.

horizon-launcher modpack remove

Remove an imported pack: its jars, ports and the profile's saves.

horizon-launcher modpack remove <PACK>

• PACK

MCP: modpack_remove, needs confirm: true.

horizon-launcher mods list

What the browser installed (the default).

horizon-launcher mods list

MCP: mods_list.

horizon-launcher mods search

Search for packs Horizon loads.

horizon-launcher mods search [TEXT]...

• TEXT
• --kind (mod, resource, modpack)
• --everything: Also what was made for other versions or runs only partly, each marked
• --source (modrinth, curseforge, horizon)

MCP: mods_search.

horizon-launcher mods check

Say how well a Java mod runs in Horizon: its jar is downloaded (checksum checked), carried over and read; the answer is kept.

horizon-launcher mods check <PROJECT>

• PROJECT
• --everything: Allow a version made for another Minecraft version (1.21 and later)
• --source (modrinth, curseforge, horizon)

MCP: mods_check.

horizon-launcher mods install

Install a pack and what it needs, by its id or slug (checksums checked); a Java mod is ported into horizon-mods and turned on; a modpack is imported.

horizon-launcher mods install <PROJECT>

• PROJECT
• --everything: Allow a version made for another Minecraft version
• --source (modrinth, curseforge, horizon)

MCP: mods_install.

horizon-launcher mods update

Update what the browser installed (or one pack).

horizon-launcher mods update [PROJECT]

• PROJECT
• --check: Only say what is newer

MCP: mods_update.

horizon-launcher mods remove

Remove a pack the browser installed.

horizon-launcher mods remove <PROJECT>

• PROJECT

MCP: mods_remove, needs confirm: true.

horizon-launcher mods enable

Turn on a mod the browser installed (horizon-mods.txt, as the game's Options > Mods does).

horizon-launcher mods enable <PROJECT>

• PROJECT

MCP: mods_enable.

horizon-launcher mods disable

Turn off a mod the browser installed; it stays installed.

horizon-launcher mods disable <PROJECT>

• PROJECT

MCP: mods_disable.

horizon-launcher servers list

The servers, their folder and whether they run.

horizon-launcher servers list

MCP: servers_list.

horizon-launcher servers create

Create a server; with no options it is a new world, survival, normal, 10 players, friends only.

horizon-launcher servers create

• --name
• --seed: The new world's seed (default: random)
• --copy-world: Start from a copy of this world folder (one of your saves)
• --mode (survival, creative, adventure, spectator)
• --difficulty (peaceful, easy, normal, hard)
• --max-players
• --open: Let anyone in (no whitelist)
• --check-accounts: Check players' Minecraft accounts (they must sign in with Microsoft)
• --player: Who may join (repeatable); the first becomes an operator
• --accept-eula: Agree to the Minecraft EULA (https://aka.ms/MinecraftEULA)

MCP: servers_create, only when the player asks.

horizon-launcher servers set-up

Copy an installed, prepared version's programs and game files for the servers (again).

horizon-launcher servers set-up

MCP: servers_set_up.

horizon-launcher servers run

Run a horizon-server command on a server, for example: servers run "My server" -- status.

horizon-launcher servers run <SERVER> -- <ARGS>...

• SERVER: The server's name or folder
• ARGS

MCP: servers_run.

horizon-launcher servers forget

Take a server off the list (its folder stays).

horizon-launcher servers forget <SERVER>

• SERVER

MCP: servers_forget, needs confirm: true.

horizon-launcher mcp

Serve the Model Context Protocol on stdin and stdout, for AI agents (refused while No AI is on).

horizon-launcher mcp

MCP: none: this command is the MCP server.

horizon-launcher agent-config

How to connect an AI agent (Claude Code, Codex, Cursor, any MCP client) to mcp: the config to paste and the command that adds it (refused while No AI is on).

horizon-launcher agent-config

• --client (claude-code, codex, cursor, generic): Only this client
• --test: Start the MCP server as a client would and say whether it answered

MCP: none: it prints how to connect a client to mcp.

horizon-launcher no-ai

Show or set No AI: on hides and turns off every AI feature (the companion, agent control, horizon-ctl and both MCP servers); off, the default, makes them available.

horizon-launcher no-ai [STATE]

• STATE (on, off): Omit to show the current state

MCP: none: the player's switch.

horizon-launcher benchmark

Measure the launcher: starts (the first is the cold one), page switching, idle CPU and memory, the release list fetch; writes a benchmark report to benchmarks/ in its data folder.

horizon-launcher benchmark

• --repeats: How many times to start it

MCP: benchmark.