SentinelCore — Anti-Knockback (Velocity) Detection

Added

New Knockback check: detects a client reducing or fully canceling the recoil applied after a melee hit ("NoKnockback"/"Anti-KB"), while filtering out lag, ping drops, and legitimate block/liquid/climbing interference. Uses a packet-confirmed synchronization window (via ProtocolLib, if installed) so only movement the client sent after actually receiving the knockback packet is measured - eliminates false positives from in-flight packet timing. Automatically exempts: wall/ceiling collision in the knockback's path, water/lava/bubble columns, ladders/vines/scaffolding, vehicles, stacked/conflicting damage sources, high ping, and ping jitter. Only evaluates velocity changes correlated with a recent melee hit - explosions, ender pearls, elytra boosts, and other plugin-driven velocity are ignored. Scores onto the existing decaying violation buffer, with its own configurable thresholds - no false-flag on a single deflection; sustained/full negation is required before any action. Optional automatic correction: re-applies the missing recoil directly (no teleport/rubberband) instead of only reporting.

Changed

None to existing checks' behavior - this is purely additive.

Requirements

Full precision requires ProtocolLib (already an optional soft-dependency for other features). Without it, the check still runs using a fixed-delay fallback, with reduced precision under network jitter.

Added (config.yml - checks.knockback)

enabled, sync-window-ticks, sync-timeout-ms, min-expected-horizontal, tolerance, full-negation-evidence, combat-correlation-window-ms, max-safe-ping-ms, max-ping-jitter-ms, correct-velocity, cancel-confidence, cancel-violations, alert-confidence, alert-violations, min-consecutive-flags, consecutive-window-ms

All defaults are tuned conservatively (20% recoil tolerance, requires 2 consecutive flags within 1.5s) to minimize false positives out of the box.

Known limitation for release notes: the ProtocolLib packet-handling code in KnockbackSyncService has not been compiled/tested against a live ProtocolLib build in this environment - verify it against your pinned ProtocolLib version before shipping a release build.