feat(api): expose opt-in classic combat and off-hand eligibility

paper-api/src/main/java/org/bukkit/entity/AbstractArrow.java

@@ -12,6 +12,29 @@
  */
 public interface AbstractArrow extends Projectile {
 
+    /**
+     * Enables Minecraft 1.7-style flight for this arrow only. Disabled by default.
+     * This selects the nearest ray intersection against a constant 0.3-block
+     * entity margin, permits owner collision from the fifth airborne tick, and
+     * applies water drag after movement. Native collision, damage, visibility,
+     * protection and knockback events remain authoritative.
+     * <p>
+     * Launch position, initial velocity and combat balance remain the caller's
+     * responsibility. The setting survives chunk unloads; airborne owner-immunity
+     * age resets on load, as in the legacy implementation.
+     * Apply before insertion into the world for a complete flight.
+     *
+     * @param legacyFlight whether to use legacy flight
+     */
+    void setLegacyFlight(boolean legacyFlight);
+
+    /**
+     * Returns whether this arrow uses legacy flight.
+     *
+     * @return legacy flight enabled
+     */
+    boolean hasLegacyFlight();
+
     /**
      * Gets the knockback strength for an arrow, which is the
      * {@link org.bukkit.enchantments.Enchantment#KNOCKBACK KnockBack} level

paper-api/src/main/java/org/bukkit/entity/FishHook.java

@@ -383,4 +383,15 @@ public enum HookState {
      *                               {@link org.bukkit.inventory.ItemType#FISHING_ROD} in the specified equipment slot.
      */
     int retrieve(@NotNull EquipmentSlot slot);
+    /**
+     * Enables opt-in legacy PvP flight, impact acceptance and reel equations.
+     * Native fishing loot, bite timers, water buoyancy and protection events remain active.
+     *
+     * @param legacyFlight whether the profile is enabled (disabled by default)
+     */
+    void setLegacyFlight(boolean legacyFlight);
+
+    /** @return whether opt-in legacy PvP flight is enabled */
+    boolean hasLegacyFlight();
+
 }

paper-api/src/main/java/org/bukkit/entity/Player.java

@@ -74,6 +74,46 @@
 @NullMarked
 public interface Player extends HumanEntity, Conversable, OfflinePlayer, PluginMessageRecipient, net.kyori.adventure.identity.Identified, net.kyori.adventure.bossbar.BossBarViewer, com.destroystokyo.paper.network.NetworkClient, ObjectContentsLike { // Paper
 
+    /**
+     * Selects 1.7.10-style combat physics for this player. Disabled by default.
+     * Classic explosion damage uses the legacy integer curve. Small velocity
+     * components use the legacy cutoff and jumps replace vertical velocity. Base knockback
+     * halves all velocity axes even in the air, attack bonuses
+     * add an impulse, and melee velocity is delivered by the native tracker.
+     * Spear, mace-smash and shield-block impulses retain native physics.
+     * Native damage acceptance, resistance attributes and knockback/velocity
+     * events remain authoritative. This runtime setting is not persisted.
+     *
+     * @param legacyCombat whether to use legacy combat physics
+     */
+    void setLegacyCombat(boolean legacyCombat);
+
+    /**
+     * Gets whether this player uses legacy combat physics.
+     *
+     * @return legacy combat physics enabled
+     */
+    boolean hasLegacyCombat();
+
+    /**
+     * Controls off-hand equipment eligibility, player-inventory menu placement
+     * and automatic merging into stored off-hand items. Enabled by default.
+     * Disabling this runtime setting does not
+     * remove stored items or prevent their pickup. Other inventory mutations,
+     * hand-swap and creative actions remain governed by their native events.
+     * The setting is copied when this player respawns and is not persisted.
+     *
+     * @param enabled whether off-hand equipment is enabled
+     */
+    void setOffHandEnabled(boolean enabled);
+
+    /**
+     * Gets whether off-hand equipment is enabled for this player.
+     *
+     * @return whether off-hand placement is enabled
+     */
+    boolean isOffHandEnabled();
+
     // Paper start
     @Override
     default net.kyori.adventure.identity.Identity identity() {

paper-api/src/main/java/org/bukkit/entity/Projectile.java

@@ -8,6 +8,17 @@
  */
 public interface Projectile extends Entity {
 
+    /**
+     * Changes the initial position of an projectile before its native spawn attempt.
+     * Does not insert, teleport, replace or respawn the entity, and leaves the
+     * cancellable native launch/spawn transaction in control.
+     *
+     * @param position finite coordinates in this projectile's world
+     * @throws IllegalArgumentException if the position is invalid or in another world
+     * @throws IllegalStateException if the projectile has already been inserted or ticked
+     */
+    void setPositionBeforeSpawn(@org.jetbrains.annotations.NotNull org.bukkit.Location position);
+
     /**
      * Retrieve the shooter of this projectile.
      *

paper-api/src/main/java/org/bukkit/entity/ThrowableProjectile.java

@@ -19,4 +19,15 @@ public interface ThrowableProjectile extends Projectile {
      * @param item ItemStack set to be displayed
      */
     void setItem(ItemStack item);
+    /**
+     * Enables opt-in legacy flight order, gravity, owner grace and entity intersections.
+     * Native impact callbacks and protection events remain active.
+     *
+     * @param legacyFlight whether the profile is enabled (disabled by default)
+     */
+    void setLegacyFlight(boolean legacyFlight);
+
+    /** @return whether opt-in legacy flight is enabled */
+    boolean hasLegacyFlight();
+
 }

paper-server/patches/features/0001-Moonrise-optimisation-patches.patch

@@ -27387,7 +27387,7 @@ index 229035e15113419080187263c7fa5e004a12c3f3..550b915d4ed457231605247c3e21844f
      }
  }
 diff --git a/net/minecraft/server/level/ServerEntity.java b/net/minecraft/server/level/ServerEntity.java
-index f11c5ea1ee9381e7bf65305b959bd7da67423ece..26822e1211194b411dd8ea75ce523133e5389e47 100644
+index eb4b85405e2a0d86a26a617133720c3949ed1acd..ae76db3d2fdc806f6c64a01d364ea261420850c1 100644
 --- a/net/minecraft/server/level/ServerEntity.java
 +++ b/net/minecraft/server/level/ServerEntity.java
 @@ -90,6 +90,11 @@ public class ServerEntity {
@@ -28191,7 +28191,7 @@ index 473feb1aa6ccf0f03ce0bc895de367b3e554e1bc..4fce291cb7cd6eb2f4e47237fe247a5d
              "Server weather",
              () -> String.format(
 diff --git a/net/minecraft/server/level/ServerPlayer.java b/net/minecraft/server/level/ServerPlayer.java
-index b569df775fcc9885b7cfee1b8280b68f33f4cd71..220409fd6335e17445e1acdbfac8d83ae36a99b4 100644
+index f32b702bad5f5b26c484cb468218a0aa0ab1ba2c..a03d2e889b516ee6f9ace96ae1d29f18f6aebe69 100644
 --- a/net/minecraft/server/level/ServerPlayer.java
 +++ b/net/minecraft/server/level/ServerPlayer.java
 @@ -206,7 +206,7 @@ import net.minecraft.world.scores.criteria.ObjectiveCriteria;
@@ -29298,7 +29298,7 @@ index 09b6da207530987b483444cebeadc2f1c9a15247..3666c3efd188508153b6482db425648e
 +    // Paper end - block counting
  }
 diff --git a/net/minecraft/world/entity/Entity.java b/net/minecraft/world/entity/Entity.java
-index ec8b47eebc30a73adb3195aa91fd5b82518cac2d..4b74c91b47318d048abc53952ebeae7615f50524 100644
+index 80d57f833a4b5d26e5302708f8b7f41e40d71085..97f28bbdaab46357db6de27d17abb285d6745c9f 100644
 --- a/net/minecraft/world/entity/Entity.java
 +++ b/net/minecraft/world/entity/Entity.java
 @@ -164,7 +164,7 @@ public abstract class Entity
@@ -31374,7 +31374,7 @@ index 254a967292938a9ed6a0291bbc9cf6e971eeaf01..416646f15ceea04fbbb5a5b0044c2a49
 
      @Nullable ChunkAccess getChunkIfLoadedImmediately(int x, int z); // Paper - ifLoaded api (we need this since current impl blocks if the chunk is loading)
 diff --git a/net/minecraft/world/level/ServerExplosion.java b/net/minecraft/world/level/ServerExplosion.java
-index def5a92046a663e53b29f9863c541ddc30ee9d3a..91bb2ac15b9e9350552f4eeb9573c2f564854ce4 100644
+index d664956c4b74a84a8858939706a5b52b0765bd11..da0d74e6d5efff433b517c82bcb13c098ce54c0f 100644
 --- a/net/minecraft/world/level/ServerExplosion.java
 +++ b/net/minecraft/world/level/ServerExplosion.java
 @@ -54,6 +54,249 @@ public class ServerExplosion implements Explosion {
@@ -31777,7 +31777,7 @@ index def5a92046a663e53b29f9863c541ddc30ee9d3a..91bb2ac15b9e9350552f4eeb9573c2f5
      }
 
      private void hurtEntities() {
-@@ -341,6 +623,14 @@ public class ServerExplosion implements Explosion {
+@@ -343,6 +625,14 @@ public class ServerExplosion implements Explosion {
      }
 
      public int explode() {
@@ -31792,7 +31792,7 @@ index def5a92046a663e53b29f9863c541ddc30ee9d3a..91bb2ac15b9e9350552f4eeb9573c2f5
          this.level.gameEvent(this.source, GameEvent.EXPLODE, this.center);
          List<BlockPos> toBlow = this.calculateExplodedPositions();
          this.hurtEntities();
-@@ -355,6 +645,13 @@ public class ServerExplosion implements Explosion {
+@@ -357,6 +647,13 @@ public class ServerExplosion implements Explosion {
              this.createFire(toBlow);
          }
 
@@ -31806,7 +31806,7 @@ index def5a92046a663e53b29f9863c541ddc30ee9d3a..91bb2ac15b9e9350552f4eeb9573c2f5
          return toBlow.size();
      }
 
-@@ -437,12 +734,12 @@ public class ServerExplosion implements Explosion {
+@@ -439,12 +736,12 @@ public class ServerExplosion implements Explosion {
      // Paper start - Optimize explosions
      private float getBlockDensity(Vec3 vec3d, Entity entity) {
          if (!this.level.paperConfig().environment.optimizeExplosions) {

paper-server/patches/features/0003-Entity-Activation-Range-2.0.patch

@@ -355,7 +355,7 @@ index 0000000000000000000000000000000000000000..829f7685904fd741e00403647ae76d32
 +    }
 +}
 diff --git a/net/minecraft/server/level/ServerLevel.java b/net/minecraft/server/level/ServerLevel.java
-index e5328f08d6a323aa1307ed791a88916b4588939c..1afbe7a877f8055702809bc33b110bdf2933f999 100644
+index 4fce291cb7cd6eb2f4e47237fe247a5d666da0ad..6cf92a7ae011fe4fa55cd744dce8d5f8fb49b1ec 100644
 --- a/net/minecraft/server/level/ServerLevel.java
 +++ b/net/minecraft/server/level/ServerLevel.java
 @@ -880,6 +880,7 @@ public class ServerLevel extends Level implements WorldGenLevel, ServerEntityGet
@@ -463,7 +463,7 @@ index 271ed1128959287f6c1b6ca59ded377b88f5afff..f03fa06c0ba56f7f5e1e45bc1568a490
      public void tick() {
          super.tick();
 diff --git a/net/minecraft/world/entity/Entity.java b/net/minecraft/world/entity/Entity.java
-index a5792bc27fdc85ecf388ab44c0b1b3055fc41d21..4a18f74c7513f0ac6a3415163165d9239ee5b567 100644
+index 97f28bbdaab46357db6de27d17abb285d6745c9f..4929cc856531c07b3c7e37dc22e7de0ea44bc156 100644
 --- a/net/minecraft/world/entity/Entity.java
 +++ b/net/minecraft/world/entity/Entity.java
 @@ -383,6 +383,15 @@ public abstract class Entity
@@ -522,10 +522,10 @@ index a5792bc27fdc85ecf388ab44c0b1b3055fc41d21..4a18f74c7513f0ac6a3415163165d923
              delta = this.maybeBackOffFromEdge(delta, moverType);
              Vec3 movement = this.collide(delta);
 diff --git a/net/minecraft/world/entity/LivingEntity.java b/net/minecraft/world/entity/LivingEntity.java
-index 2837e630ae414bd37c4afc72c83a78e4d38a945a..3a4da514c163e7565fc241835db52c464a5c4734 100644
+index 416f920e3e7e46cb5ef423373112e1ffe9fb49a1..380663766e48a9d04db732f994600f50fa304226 100644
 --- a/net/minecraft/world/entity/LivingEntity.java
 +++ b/net/minecraft/world/entity/LivingEntity.java
-@@ -3385,6 +3385,14 @@ public abstract class LivingEntity extends Entity implements Attackable, Waypoin
+@@ -3449,6 +3449,14 @@ public abstract class LivingEntity extends Entity implements Attackable, Waypoin
      protected void playAttackSound() {
      }
 
@@ -541,7 +541,7 @@ index 2837e630ae414bd37c4afc72c83a78e4d38a945a..3a4da514c163e7565fc241835db52c46
      public void tick() {
          super.tick();
 diff --git a/net/minecraft/world/entity/Mob.java b/net/minecraft/world/entity/Mob.java
-index fd17e62b99fd59130739b4c8c6c0c49122aec094..c2dd2da4bfb7d65ad2730ba1ce771e2b488beda4 100644
+index a87c1343e28114f513c9f52dcc4fe7ddd04bc5bb..1b89e5909d810d9da528c3e6cc312ef93d1c9d84 100644
 --- a/net/minecraft/world/entity/Mob.java
 +++ b/net/minecraft/world/entity/Mob.java
 @@ -215,6 +215,20 @@ public abstract class Mob extends LivingEntity implements Targeting, EquipmentUs

paper-server/patches/features/0023-Fix-entity-tracker-desync-when-new-players-are-added.patch

@@ -60,7 +60,7 @@ index 3a6410f4b061c7431ad09b23be9691160c36ef6c..29e02b01ba7eeb7767e8dad6b3be909f
                  } else {
                      this.removePlayer(player);
 diff --git a/net/minecraft/server/level/ServerEntity.java b/net/minecraft/server/level/ServerEntity.java
-index 26822e1211194b411dd8ea75ce523133e5389e47..60af82925d2f7e605bf7340cf01f1a5668f4d725 100644
+index ae76db3d2fdc806f6c64a01d364ea261420850c1..8c7ee0e3122baddfde140357adf89201fa6c1a4e 100644
 --- a/net/minecraft/server/level/ServerEntity.java
 +++ b/net/minecraft/server/level/ServerEntity.java
 @@ -89,6 +89,13 @@ public class ServerEntity {
@@ -95,7 +95,7 @@ index 26822e1211194b411dd8ea75ce523133e5389e47..60af82925d2f7e605bf7340cf01f1a56
                      || deltaTooBig
                      || this.teleportDelay > 400
                      || this.wasRiding
-@@ -238,6 +245,7 @@ public class ServerEntity {
+@@ -239,6 +246,7 @@ public class ServerEntity {
              }
 
              this.entity.needsSync = false;

paper-server/patches/sources/net/minecraft/server/level/ServerEntity.java.patch

@@ -61,7 +61,17 @@
                  Packet<ClientGamePacketListener> packet = null;
                  boolean pos = positionChanged || this.tickCount % 60 == 0;
                  boolean sentPosition = false;
-@@ -223,6 +_,25 @@
+@@ -174,7 +_,8 @@
+                     sentRotation = true;
+                 }
+
+-                if (this.entity.needsSync || this.trackDelta || this.entity instanceof LivingEntity livingEntity && livingEntity.isFallFlying()) {
++                if (!(this.entity.hurtMarked && this.entity instanceof ServerPlayer player && player.legacyCombat)
++                    && (this.entity.needsSync || this.trackDelta || this.entity instanceof LivingEntity livingEntity && livingEntity.isFallFlying())) {
+                     Vec3 movement = this.entity.getDeltaMovement();
+                     double diff = movement.distanceToSqr(this.lastSentMovement);
+                     if (diff > 1.0E-7 || diff > 0.0 && movement.lengthSqr() == 0.0) {
+@@ -223,6 +_,26 @@
 
          this.tickCount++;
          if (this.entity.hurtMarked) {
@@ -81,6 +91,7 @@
 +            }
 +
 +            if (cancelled) {
++                if (this.entity instanceof ServerPlayer player && player.legacyCombat) this.entity.hurtMarked = false;
 +                return;
 +            }
 +            // CraftBukkit end

paper-server/patches/sources/net/minecraft/server/level/ServerPlayer.java.patch

@@ -1187,7 +1187,14 @@
      }
 
      @Override
-@@ -1602,18 +_,18 @@
+@@ -1596,24 +_,25 @@
+     }
+
+     public void restoreFrom(final ServerPlayer oldPlayer, final boolean restoreAll) {
++        this.offHandEnabled = oldPlayer.offHandEnabled; // Preserve runtime inventory capability across respawn.
+         this.wardenSpawnTracker = oldPlayer.wardenSpawnTracker;
+         this.chatSession = oldPlayer.chatSession;
+         this.gameMode.setGameModeForPlayer(oldPlayer.gameMode.getGameModeForPlayer(), oldPlayer.gameMode.getPreviousGameModeForPlayer());
          this.onUpdateAbilities();
          this.getAttributes().assignBaseValues(oldPlayer.getAttributes());
          if (restoreAll) {

paper-server/patches/sources/net/minecraft/world/entity/Entity.java.patch

@@ -1261,6 +1261,15 @@
      }
 
      protected boolean canAddPassenger(final Entity passenger) {
+@@ -2585,7 +_,7 @@
+         if (!(this instanceof Player player)) {
+             return Vec3.ZERO;
+         } else {
+-            boolean itemOnlyInOffhand = player.getOffhandItem().is(item) && !player.getMainHandItem().is(item);
++            boolean itemOnlyInOffhand = player.canUseSlot(EquipmentSlot.OFFHAND) && player.getOffhandItem().is(item) && !player.getMainHandItem().is(item); // Paper - configurable off-hand eligibility
+             HumanoidArm itemArm = itemOnlyInOffhand ? player.getMainArm().getOpposite() : player.getMainArm();
+             return this.calculateViewVector(0.0F, this.getYRot() + (itemArm == HumanoidArm.RIGHT ? 80 : -80)).scale(0.5);
+         }
 @@ -2704,7 +_,7 @@
      }