Minecraft Matrix Bridge (Forge/NeoForge, Server-Only)

Bridges chat between a Minecraft server and one Matrix room (unencrypted only).

Features

• MC → Matrix: forwards player chat into a Matrix room.
• Matrix → MC: forwards Matrix m.text room messages into Minecraft server chat.
• Server-only: vanilla clients can join without installing anything (no client mod).
• Sync state stored in the world save (prevents replay spam on restart).
• The "Matrix room connected: …" notice is localized server-side based on each player's reported client language (currently includes en_us and zh_cn).
• If the bot is invited to the configured room but not joined yet, it will auto-accept the invite and join on startup.
• Event Taps: dynamically subscribe to Forge/NeoForge events and forward them to Matrix for debugging/monitoring.

Requirements

• Java 17 (Forge 1.18–1.20), Java 21 (Forge/NeoForge 1.21.x), or Java 25 (Forge/NeoForge 26.1)
• Minecraft Forge/NeoForge server matching the versions. I only manually test it in popular minor versions, and hopefully it works in other minor versions.
  • 1.18.2
  • 1.19.2
  • 1.20.1
  • 1.21.1
  • 26.1
• Matrix room must be unencrypted (no E2EE)

Installation

1. Download the jar or build it locally with ./scripts/build_dist.sh (all supported versions) or ./scripts/build_dist_26.sh (26.x only). The generated jars are written to dist/.
2. Drop the jar into your Forge/NeoForge server's mods/ folder (pick the jar matching your loader + Minecraft major).
3. Start the server once to generate config.

Build all versions (creates dist/)

To build jars for all supported Minecraft versions and collect them into dist/:

• ./scripts/build_dist.sh

dist/ includes Forge jars for 1.18.x–1.21.x and 26.x, plus NeoForge jars for 1.21.x and 26.x.

Build only the 26.x line

The 26.x projects use the dedicated Gradle 9 wrapper and are conditionally included by settings.gradle.

• Build and collect both 26.x jars into dist/: ./scripts/build_dist_26.sh
• Build Forge 26 only: ./gradlew-26 -Pomx_modern_26=true :forge-26:build
• Build NeoForge 26 only: ./gradlew-26 -Pomx_modern_26=true :neoforge-26:build
• On Windows, use gradlew-26.bat instead of ./gradlew-26

./scripts/build_dist_26.sh produces:

• dist/minecraftmatrixbridge-forge-26.x-<version>.jar
• dist/minecraftmatrixbridge-neoforge-26.x-<version>.jar
• dist/SHA256SUMS.txt

Configuration

Edit config/minecraftmatrixbridge.toml:

• matrix.homeserver (required) e.g. https://matrix.example.com
• matrix.roomId (required) room ID !abcdef:example.com or room alias #myroom:example.com (the room should not be encrypted)
• matrix.accessToken (required, or use env variable MATRIX_ACCESS_TOKEN)

Bridge Options

• bridge.enableMcToMatrix (default true) - Forward MC chat to Matrix
• bridge.enableMatrixToMc (default true) - Forward Matrix messages to MC
• bridge.announceConnected (default true) - Announce Matrix room connected: {roomIdOrAlias} when bridge starts
• bridge.enableJoinLeaveToMatrix (default false) - Send {player} joined/left the game to Matrix
• bridge.enableServerLifecycleToMatrix (default false) - Send Server started/stopping to Matrix
• bridge.mcToMatrixPrefix (default [MC] ) - Prefix for MC messages in Matrix
• bridge.matrixToMcPrefix (default [Matrix] ) - Prefix for Matrix messages in MC
• bridge.matrixBotPrefix (default !mc) - Matrix bot command prefix; messages starting with this prefix are treated as bot commands and are not forwarded to Minecraft chat
• bridge.syncTimeoutMs (default 30000) - Matrix sync timeout in milliseconds
• bridge.timelineLimit (default 20) - Maximum timeline events per sync
• bridge.maxQueueSize (default 1000) - Maximum outgoing message queue size
• bridge.dedupSize (default 512) - Event deduplication cache size

Event Tap Options

• bridge.enableEventTaps (default true) - Enable or disable event taps feature entirely. When disabled, no event indexing occurs at startup.
• bridge.maxActiveEventTaps (default 10) - Maximum concurrent event subscriptions
• bridge.defaultEventThrottleMs (default 1000) - Minimum interval between forwarded events (prevents spam)
• bridge.eventCommandMinPowerLevel (default 50) - Minimum Matrix power level required to use event commands from Matrix (0=default user, 50=moderator, 100=admin)

World-save state

Sync state is stored at:

• <world>/data/minecraftmatrixbridge/state.json

Commands

Minecraft Commands (OP-only)

• /matrix status - Show bridge status
• /matrix reload - Reload bridge config
• /matrix test - Send a test message to Matrix

Matrix Bot Commands

Matrix room bot commands (requires bridge.enableMatrixToMc=true):

• !mc help (or replace !mc with bridge.matrixBotPrefix)
• !mc list - Replies with online player names; command messages are not forwarded into Minecraft chat

Event Taps (Advanced)

Event taps allow server operators to subscribe to Forge/NeoForge events at runtime and forward them to the Matrix room. This is useful for debugging and monitoring.

Minecraft Commands (OP-only)

• /matrix event on <eventName> [filter] [duration] - Enable event tap
  • eventName: Simple class name (e.g., ServerChatEvent) or fully-qualified class name
  • filter: Optional substring filter (case-insensitive)
  • duration: once (default), permanent, or time-based (30s, 10m, 2h, 1d)
• /matrix event off <eventName> - Disable event tap
• /matrix event list - List active event taps
• /matrix event search <query> - Search available events
• /matrix event help - Show help

Matrix Bot Commands

Same commands available via Matrix (requires bridge.enableMatrixToMc=true and bridge.enableEventTaps=true):

• !mc event on <eventName> [filter] [duration]
• !mc event off <eventName>
• !mc event list
• !mc event search <query>
• !mc event help

Matrix event commands require the sender to have a power level >= bridge.eventCommandMinPowerLevel (default 50).

Safety Features

• Master switch (enableEventTaps) - Disable entirely to skip event indexing at startup
• Maximum 10 concurrent event taps (configurable)
• Default 1-second throttle between forwarded events
• Tick events automatically enforce minimum 1-second throttle
• Event output truncated to 2048 characters
• Client-only events are rejected on dedicated servers

Examples

AI use declaration

Codex and cursor are used to develop this project.

Acknowledgments

I appreciate the great mod projects (e.g. Matrix Bridge) that have inspired me to create this project.

License

The mod is licensed under the AGPL-3.0 license.