MeshAC 1.0.0

MeshAC is a server-side anticheat for Fabric 26.2. It has movement simulation, packet analysis, and (hopefully) accurate heuristics to detect hacked clients like meteor.

This mod doesn't scan clients, collect files, inspect mods, or bundle other software.

---

Why MeshAC

Feature	Description
43 checks	Movement, combat, player, and exploit checks
Low false flagging	Every check accumulates evidence before flagging
Lag-compensated	Ping-derived tolerances, TPS floor guard, packet-stall detection
Statistical awareness	CPS distribution shape, reach histograms, rotation GCD, click movement correlation
SQLite database	Violation history, ban records, autoclean
454 unit tests	Every check validated against falsepositive and truepositive scenarios

---

Compatibility

Component	Version
Minecraft Fabric Server/World	26.2
Fabric Loader	0.19.3+
Fabric API	0.154.2+26.2
Java runtime	25

---

Detection Suite

Movement (12 checks)

Check	Detects	Method
Fly	Flight, hover, anti-kick	Gravity validation, Y-velocity history,
Speed	Speed hacks, BHop	Dynamic speed cap with potion/ice/slime/sprint-jump awareness
NoFall	Fall damage bypass	Server-side fall-distance accumulator + ground-spoof detection
Step	Step hacks	Jump-height validation with jump-boost/bounce exemption
Jesus	Water-walking	Dynamic water speed cap with depth-strider/dolphin's-grace awareness
ElytraFly	Elytra exploits	Firework-boost tracking, descent validation
Spider	Wall climbing	Vertical velocity analysis
Blink	Packet delay	Movement packet timing
Phase	Block clipping, VClip	AABB intersection + ray-cast interpolation between positions
BHop	Bunny hop	Sprint-jump momentum analysis
BoatFly	Boat flight	Vehicle vertical/horizontal speed limits
EntitySpeed	Entity speed hacks	Per-vehicle-type speed caps

Combat (13 checks)

Check	Detects	Method
KillAura	Aura hacks	Yaw-wraparound-safe multi-target detection, angular consistency, rotation-vs-target validation
Reach	Reach extenders	Eye-to-hitbox distance with statistical tracking (50-attack histogram)
AimAssist	Aim bots	Rotation snap detection, smooth-aim analysis
AutoClicker	Click macros	CPS + standard-deviation + distribution skewness + zero-movement correlation
Criticals	Forced crits	Pre-attack Y-velocity pattern, critical-hit rate tracking
Velocity	Anti-knockback	Extended 10-tick window, horizontal + vertical velocity validation
AntiKnockback	KB reduction	Damage-coupled knockback ratio check
HitBoxes	Hitbox expansion	Angular reach validation
AutoBlock	Auto-block	Attack-block coupling detection
MultiAura	Multi-target aura	Per-tick entity attack counting
Backtrack	Position backtrack	Server-position vs attack-position desync
TriggerBot	Reaction bots	Reaction-time statistical analysis
BowAimbot	Bow aimbot	Draw-time + aim-lock correlation
TPAura	Teleport aura	Distance-jump detection

Player & Exploit (18 checks)

Check	Detects	Method
Scaffold	Auto-bridge	Pitch analysis + placement cadence + rotation coupling
Timer	Timer cheats	Short-window PPS + long-window balance drift
NoSlow	NoSlow bypass	Vanilla 0.2x item-use multiplier enforcement
FastPlace	Fast placement	Per-tick placement counting
FastUse	Fast consume	Item-use duration validation
SpeedMine	Fast break	Break-duration validation per block type
GhostHand	Ghost reach	Block-interaction distance validation
Nuker	Multi-break	Per-tick block break counting
PacketAbuse	Malformed packets	NaN/infinity/out-of-bounds validation
Freecam	Camera desync	Server vs client position divergence
XRay	X-ray tracking	Per-dimension ore-ratio weighted scoring
AutoFish	Fishing automation	Cast interval variance analysis
BadPackets	Invalid packets	Ground-state + rotation validation
InvWalk	Inventory movement	Inventory-open + movement coupling
ServerCrasher	Crash exploits	Command-block/payload detection
CMDBlock	Command exploits	Command-block/sign abuse
Regen	Fast regeneration	Health-gain rate validation
EntitySpeed	Vehicle speed	Per-entity speed limits

---

Anti-Cheat Architecture

Buffer System

Every check uses a per player, per check buffer that gains evidence before producing a violation. This prevents singletick errors like lag spikes, chunk borders, and vehicle dismounts from ever punishing legit players.

Check detects anomaly → buffer += weight
                       → if buffer > threshold → produce VL
                       → else → no action
Check sees normal behaviour → buffer *= decay (0.8-0.9)

Lag Compensation

• TPS floor: All checks pause below a configurable TPS (default 18.0)
• Ping aware tolerances: Reach, timer, and velocity checks scale with the player's ping
• Packet stall detection: Timer check ignores deficits during 5s+ stalls
• Velocity window: Knockback tracking runs for 10 ticks to catch partial anti KB

Detection Layers

MeshAC combines multiple heuristics so that a cheater has to bypass all of them at the same time:

1. Hard limit — biologically impossible values
2. Soft limit — sustained values beyond human capability
3. Statistical analysis — distribution shape, standard deviation, skewness
4. Behavioural correlation — click-to-movement, rotation-to-target, placement cadence
5. Server simulation — tick-accurate prediction with AABB collision

Escalating Punishment

VL accumulates → notify staff → setback → kick → tempban → permanent ban

Each stage fires once and is configurable per check.

---

Install

1. Install Fabric Loader and Fabric API for Minecraft 26.2.
2. Copy meshac-1.0.0.jar to the server's mods/ directory.
3. Start the server once. MeshAC writes config/meshac.yml.
4. Keep defaults while observing, then tune individual checks.

---

Configuration

config/meshac.yml:

checks:
  enabled: true
  entries:
    fly:
      enabled: true
      threshold: 0.05
      actions: ["notify", "setback"]
      max_vl: 6
      decay_ticks: 600
      check_interval: 1
      max_vl_per_tick: 5.0

performance:
  min_tps: 18.0
  max_players_per_tick: 50
  mode: balanced  # aggressive | balanced | relaxed

alerts:
  enabled: true
  min_vl: 2

geyser:
  exempt: true

Per-check options

Option	Description
enabled	Master toggle for this check
threshold	More tolerance for checks that support numeric buffers
actions	notify, setback, kick, ban
max_vl	VL required to enter an action stage
decay_ticks	Interval before 0.5 VL is removed
check_interval	Run every _ server ticks
max_vl_per_tick	Caps a single check's contribution per tick

Performance modes

Mode	Check interval	Max VL/tick	Use case
aggressive	1	10.0	Small servers, maximum detection
balanced	1	5.0	Default — good accuracy, low overhead
relaxed	2	3.0	Large servers, minimal false-positive risk

---

Commands

All commands are under /meshac and require operator permissions:

Command	Description
info	Server status, check count, TPS
alerts [player]	Toggle or view alerts
freeze <player>	Freeze a player in place
kick <player> [reason]	Kick a player
ban <player> [reason]	Permanently ban a player
tempban <player> <seconds>	Temp ban a player
spectate <player>	Spectate a suspected cheater
violations <player>	Shows a player's violation levels
history <player>	Show persisted violation/ban history
reload	Reload configuration
debug <player>	Detailed per-check debug info

---