Lazy TNT Utils
- By
Accurate TNT and entity state in lazy chunks: fuse timers, motion vectors and precise explosion particles.
A Minecraft Fabric mod that shows the true state of TNT and item entities in lazy chunks, aimed at developing lazy-chunk TNT contraptions. Supports 26.1.2, 26.2 and 26.3.
How it works
In lazy chunks the server does not tick entities, so TNT neither counts down its fuse nor moves on its own — but the client keeps simulating locally, runs the fuse out, and detonates the TNT early.
What this mod does
- Client: in single player, corrects supported entities to the integrated server's real state every tick; in multiplayer, cancels the client-side local simulation, so TNT neither detonates early nor drifts.
- Server: every tick, collects the real state (position / velocity / fuse) of entities within 160 blocks of a player and sends it to that player over a custom packet; the client caches it and corrects its local entities. Off by default.
Features
Client-side, with an optional server-side component, configured through YACL:
- ✅ TNT in lazy chunks no longer detonates early or drifts
- ✅ Entity render positions in lazy chunks stay in sync
- ✅ F3+B draws motion arrows for TNT
- ✅ Hide entity facing arrows
- ✅ Toggle everything from the config screen (ModMenu + YACL)
- ✅ Precise explosion particles (can be disabled to fall back to the vanilla random blob)
- ✅ Disable the TNT flashing and scaling effect
- ✅ Show a label with the ticks left before detonation
- ✅ Adjust render distance and simulation distance
- ✅ Lift the ±10 clamp on Motion
Supported entity categories
| Category | Entities covered |
|---|---|
| TNT | PrimedTnt |
| Items | ItemEntity |
| Projectiles | Projectile subclasses (arrows / ender pearls / wind charges, …) |
| Falling blocks | FallingBlockEntity |
| Experience | ExperienceOrb |
Performance and known limits
The server sends the full state of nearby entities every tick (about 65 bytes per entity).
Order of magnitude per player at 20 tps:
- A single TNT: roughly 1.3 KB/s, scaling linearly with more players.
- For comparison, vanilla sync is delta-based and throttled — around 1/10 of this mod down to zero in the same scenario.
- Sync pauses during a tick sprint.
Bandwidth only matters on a dedicated server; single player goes over loopback and costs nothing.
Lazy TNT Utils Team
