feat: derive the Running bit from the step pace and fix step-pacing bursts (#2599)

Stacked on #2594. Fixes jerky creature movement (lich / Fast-bucket melee chases) by choosing the client animation flag from the actual step pace instead of a caller-supplied `run` argument, and fixes three step-pacing defects in the move budget found while verifying it with paired server/client traces.

### Why

The `Direction.Running` bit does nothing for creatures server-side (`Mobile.OnMove` reads it only for the player throttle and stealth reveal). Its whole effect is on the client, which animates each step over a fixed time selected by that bit: walk 400 ms / run 200 ms on foot, 200 / 100 ms mounted. ClassicUO queues up to 5 steps and *drops* the sixth, so a creature stepping every 300 ms while flagged as walking backs the queue up until it snaps forward — the observed jerk.

The `run` argument never carried the one fact that matters (the step interval). RunUO passed `true` in combat / `false` for pets and gated it on `dist > 5`; #2271 flipped every combat site to `false`; pets passed `currentDistance > 2`. None of that is a coherent signal.

### What

**Pace-derived run flag**
- `BaseAI.ShouldRun()`: run iff the effective step delay (move clock + badly-hurt inflation) is shorter than `Movement.WalkFootDelay` / `WalkMountDelay` (mounted or flying) — with a continuity rule: an *isolated* step (taken after standing at least a walk interval) goes out as a walk, because the client renders each step alone and a lone run-flagged step is a 200 ms dart. Only a continuing cadence flags run; a true sprinter (pace under the run interpolation) always runs, since a walk-rendered first step would flood the client's 5-step queue. This reproduces RunUO's close-in feel (its `dist > 5` gate) from first principles.
- `DoMoveImpl` stamps the bit; it is the single place the flag is set.
- `run` removed from `MoveTo`, `WalkMobileRange`, `ApproachTarget`, `MoveToPoint`, `MoveToWithGroup`, `MoveToWithCollisionAvoidance`, the move intent, and `PathFollower.Follow`. All 35 call sites updated. **API change** for custom scripts — documented in the RunUO migration docs (`09-items-mobiles-creatures.md`, `11-api-reference.md`) and `content-patterns.md` § Creature Speeds.

**Move-budget pacing fixes** (each confirmed by UTC-aligned server/client step traces)
- A stall no longer banks catch-up steps: the budget's snap-to-now released up to three steps in ~300 ms when a creature resumed chasing after standing beside its target — rendered as a teleport.
- Debt accrual removed entirely: a step landing sub-period late (think-grid vs budget misalignment during reactive mirroring) kept the remainder and fired a follow-up ~100 ms later — a dart pair. `ConsumeMoveBudget` now paces every step from when it was actually taken; in continuous pursuit the move-wake lands within wheel resolution of the deadline, so the cost is single-digit-ms drift.
- Net effect: a creature can never step faster than its pace, verified across a full chase session (zero sub-pace steps; metronomic 350 ms cadence for a 0.3 s lich).

- Test fixture now runs `Movement.Configure()` (the walk delays were 0 in tests).

### Accepted trade-off

Animal (LOW group) bodies without a run animation slide on their stand frames when flagged as running. Most are slow enough to stay flagged as walking; the client-side fallback is in ClassicUO/ClassicUO#1930.

### Tests

`RunFlagTests`: foot thresholds (0.3 / 0.125 run; 0.4 / 0.45 / 1.05 walk), flying uses the mount threshold, badly-hurt inflation flips a 0.35 s creature back to walk, a real `DoMove` stamps the bit, isolated steps drop to walk (sprinters keep running), a stall restarts the cadence with no banked steps, and a late step earns no quicker follow-up. Full suite: 837 Server + 747 UOContent green.

Projects/UOContent.Tests/Fixtures/TestServerInitializer.cs

@@ -103,6 +103,7 @@ internal static class TestServerInitializer
             // Registers the Accounts entity persistence; without it no test can construct an Account.
             Server.Accounting.Accounts.Configure();
             RaceDefinitions.Configure();
+            Server.Movement.Movement.Configure();
             MovementImpl.Configure();
             PathFollower.Configure();
             World.Load();

Projects/UOContent.Tests/Tests/Mobiles/AI/ApproachTargetTests.cs

@@ -40,7 +40,7 @@ public class ApproachTargetTests
         for (var i = 0; i < maxTicks; i++)
         {
             ai.NextMove = 0;
-            ai.WalkMobileRange(target, 1, false, 1, 2);
+            ai.WalkMobileRange(target, 1, 1, 2);
             if (bc.InRange(target, arriveDist))
             {
                 return true;
@@ -123,7 +123,7 @@ public class ApproachTargetTests
         for (var i = 0; i < 200; i++)
         {
             ai.NextMove = 0;
-            ai.MoveTo(target, false, 1);
+            ai.MoveTo(target, 1);
             if (bc.InRange(target, 1))
             {
                 arrived = true;
@@ -154,7 +154,7 @@ public class ApproachTargetTests
         for (var i = 0; i < 60; i++)
         {
             ai.NextMove = 0;
-            ai.MoveTo(target, true, 1);
+            ai.MoveTo(target, 1);
 
             // Target walks west every other tick for its first several steps, then stops,
             // so a same-speed chaser eventually closes the gap.
@@ -214,7 +214,7 @@ public class ApproachTargetTests
         for (var i = 0; i < 120; i++)
         {
             ai.NextMove = 0;
-            ai.MoveTo(target, false, 1);
+            ai.MoveTo(target, 1);
         }
 
         // After giving up, the creature must idle (not oscillate) while the goal is still.
@@ -223,7 +223,7 @@ public class ApproachTargetTests
         for (var i = 0; i < 20; i++)
         {
             ai.NextMove = 0;
-            ai.MoveTo(target, false, 1);
+            ai.MoveTo(target, 1);
             if (bc.Location != idleStart)
             {
                 stayedIdle = false;

Projects/UOContent.Tests/Tests/Mobiles/AI/RunFlagTests.cs

@@ -0,0 +1,162 @@
+using System.Collections.Generic;
+using Server;
+using Server.Mobiles;
+using Xunit;
+
+namespace UOContent.Tests.Mobiles.AI;
+
+// The Running bit is derived from the step pace: a step shorter than the client's walk
+// interpolation (400ms on foot, 200ms mounted/flying) is flagged as a run.
+[Collection("Sequential Pathfinding Tests")]
+public class RunFlagTests : System.IDisposable
+{
+    private readonly List<Mobile> _created = new();
+
+    private PetTestStub Spawn(double activeMove)
+    {
+        var pet = new PetTestStub();
+        pet.MoveToWorld(new Point3D(1000, 1000, 0), Map.Felucca);
+        pet.AIObject.AITimer?.Stop();
+        pet.SetMoveSpeed(activeMove, activeMove * 3);
+        pet.SetCurrentSpeedToActive();
+        pet.LastMoveTime = Core.TickCount; // mid-cadence unless a test says otherwise
+        _created.Add(pet);
+        return pet;
+    }
+
+    public void Dispose()
+    {
+        foreach (var m in _created)
+        {
+            m?.Delete();
+        }
+
+        _created.Clear();
+    }
+
+    [Theory]
+    [InlineData(0.3, true)]
+    [InlineData(0.125, true)]
+    [InlineData(0.4, false)]
+    [InlineData(0.45, false)]
+    [InlineData(1.05, false)]
+    public void FootCreature_RunsOnlyWhenFasterThanWalk(double activeMove, bool expected)
+    {
+        var pet = Spawn(activeMove);
+
+        Assert.Equal(activeMove, pet.CurrentMoveSpeed);
+        Assert.Equal(expected, pet.AIObject.ShouldRun());
+    }
+
+    [Theory]
+    [InlineData(0.3, false)]
+    [InlineData(0.15, true)]
+    public void FlyingCreature_UsesMountThresholds(double activeMove, bool expected)
+    {
+        var pet = Spawn(activeMove);
+        pet.Flying = true;
+
+        Assert.Equal(expected, pet.AIObject.ShouldRun());
+    }
+
+    [Fact]
+    public void BadlyHurt_SlowsBelowWalk_DropsToWalk()
+    {
+        var pet = Spawn(0.35);
+        Assert.True(pet.AIObject.ShouldRun());
+
+        // The hurt inflation is on the observed step pace, so the flag follows it.
+        pet.SetHits(100);
+        pet.Hits = 5;
+        pet.SetStam(100);
+        pet.Stam = 5;
+
+        Assert.False(pet.AIObject.ShouldRun());
+    }
+
+    [Theory]
+    [InlineData(0.3, true)]
+    [InlineData(0.45, false)]
+    public void DoMove_StampsRunningBit(double activeMove, bool expected)
+    {
+        var map = Map.Maps[1];
+        Assert.NotNull(map);
+        map.GetAverageZ(1500, 1600, out _, out var z, out _);
+
+        var pet = Spawn(activeMove);
+        pet.MoveToWorld(new Point3D(1500, 1600, (sbyte)z), map);
+
+        var ai = pet.AIObject;
+        ai.NextMove = 0;
+        var start = pet.Location;
+
+        Assert.True(ai.DoMove(Direction.West));
+        Assert.NotEqual(start, pet.Location);
+        Assert.Equal(expected, (pet.Direction & Direction.Running) != 0);
+    }
+
+    // An isolated step (after standing at least a walk interval) renders alone and darts
+    // if run-flagged, so it walks; continuing cadences and true sprinters keep the flag.
+    [Fact]
+    public void IsolatedStep_DropsToWalk()
+    {
+        var pet = Spawn(0.3);
+        pet.LastMoveTime = Core.TickCount - 1000;
+
+        Assert.False(pet.AIObject.ShouldRun());
+    }
+
+    [Fact]
+    public void IsolatedStep_SprinterStillRuns()
+    {
+        var pet = Spawn(0.125);
+        pet.LastMoveTime = Core.TickCount - 1000;
+
+        Assert.True(pet.AIObject.ShouldRun());
+    }
+
+    [Fact]
+    public void StallDoesNotBankCatchUpSteps()
+    {
+        var map = Map.Maps[1];
+        Assert.NotNull(map);
+        map.GetAverageZ(1500, 1600, out _, out var z, out _);
+
+        var pet = Spawn(0.3);
+        pet.MoveToWorld(new Point3D(1500, 1600, (sbyte)z), map);
+
+        var ai = pet.AIObject;
+        ai.NextMove = Core.TickCount - 1000;
+
+        Assert.True(ai.DoMove(Direction.West));
+
+        // A stall must restart the cadence at full pace: banked catch-up steps
+        // release as a burst the client renders as a sprint/teleport.
+        Assert.False(ai.CanMoveNow(out _));
+        Assert.True(ai.NextMove - Core.TickCount > 250);
+    }
+
+    [Fact]
+    public void LateStepDoesNotEarnAQuickerFollowUp()
+    {
+        var map = Map.Maps[1];
+        Assert.NotNull(map);
+        map.GetAverageZ(1500, 1600, out _, out var z, out _);
+
+        var pet = Spawn(0.3);
+        pet.MoveToWorld(new Point3D(1500, 1600, (sbyte)z), map);
+
+        pet.Warmode = true; // keep the active move clock through the step
+
+        var ai = pet.AIObject;
+        // The step lands 200ms past the budget — under one period, the reactive
+        // mirroring case (think grid vs budget deadline misalignment).
+        ai.NextMove = Core.TickCount - 200;
+
+        Assert.True(ai.DoMove(Direction.West));
+
+        // The debt must not be repaid: a sub-period catch-up step follows ~100ms
+        // behind and renders as a dart pair beside the player.
+        Assert.True(ai.NextMove - Core.TickCount > 250);
+    }
+}

Projects/UOContent/Engines/Factions/Mobiles/Guards/GuardAI.cs

@@ -359,14 +359,14 @@ namespace Server.Factions
             {
               if (m_Mobile.InRange( m, 1 ))
                 RunFrom( m );
-              else if (!m_Mobile.InRange( m, m_Mobile.RangeFight > 2 ? m_Mobile.RangeFight : 2 ) && !MoveTo( m, true, 1 ))
+              else if (!m_Mobile.InRange( m, m_Mobile.RangeFight > 2 ? m_Mobile.RangeFight : 2 ) && !MoveTo(m, 1))
                 OnFailedMove();
             }
             else
             {*/
             if (!Mobile.InRange(m, Mobile.RangeFight))
             {
-                if (!MoveTo(m, true, 1))
+                if (!MoveTo(m, 1))
                 {
                     OnFailedMove();
                 }

Projects/UOContent/Engines/Pathing/PathFollower.cs

@@ -83,7 +83,7 @@ public class PathFollower
     public static bool Check(Point3D loc, Point3D goal, int range) =>
         Utility.InRange(loc, goal, range) && (range > 1 || (loc.Z - goal.Z).Abs() < 16);
 
-    public bool Follow(bool run, int range)
+    public bool Follow(int range)
     {
         var goal = GetGoalLocation();
         Direction d;
@@ -97,13 +97,13 @@ public class PathFollower
 
         if (!(Enabled && m_Path.Success))
         {
-            d = m_From.GetDirectionTo(goal, run);
+            d = m_From.GetDirectionTo(goal);
             m_From.SetDirection(d);
 
             return Move(d) is MoveResult.Success or MoveResult.SuccessAutoTurn && Check(m_From.Location, goal, range);
         }
 
-        d = m_From.GetDirectionTo(m_Next, run);
+        d = m_From.GetDirectionTo(m_Next);
         m_From.SetDirection(d);
         var res = Move(d);
 

Projects/UOContent/Mobiles/AI/AnimalAI.cs

@@ -38,7 +38,7 @@ public class AnimalAI : BaseAI
             return true;
         }
 
-        if (!WalkMobileRange(combatant, 1, false, Mobile.RangeFight, Mobile.RangeFight))
+        if (!WalkMobileRange(combatant, 1, Mobile.RangeFight, Mobile.RangeFight))
         {
             if (Mobile.GetDistanceToSqrt(combatant) > Mobile.RangePerception + 1)
             {

Projects/UOContent/Mobiles/AI/ArcherAI.cs

@@ -43,7 +43,7 @@ public class ArcherAI : BaseAI
             return true;
         }
 
-        if (!WalkMobileRange(combatant, 1, false, Mobile.RangeFight, Mobile.Weapon.MaxRange))
+        if (!WalkMobileRange(combatant, 1, Mobile.RangeFight, Mobile.Weapon.MaxRange))
         {
             this.DebugSayFormatted($"I am still not in range of {combatant.Name}");
 

Projects/UOContent/Mobiles/AI/BaseAI/AIGroupMovement.cs

@@ -63,7 +63,7 @@ public abstract partial class BaseAI
         return crowding;
     }
 
-    public static bool MoveToWithGroup(BaseAI ai, Mobile target, bool run, int range)
+    public static bool MoveToWithGroup(BaseAI ai, Mobile target, int range)
     {
         if (Core.TickCount - _lastGroupUpdateTime > 1000)
         {
@@ -79,7 +79,7 @@ public abstract partial class BaseAI
             if (optimalPosition == Point3D.Zero)
             {
 
-                return ai.MoveToWithCollisionAvoidance(target, run, range);
+                return ai.MoveToWithCollisionAvoidance(target, range);
             }
 
             _reservedPositions[mobile] = optimalPosition;
@@ -99,7 +99,7 @@ public abstract partial class BaseAI
             }
 
             // A blocked or wall-slid step is not progress — route around the obstacle.
-            return ai.ApproachTarget(target, run, range);
+            return ai.ApproachTarget(target, range);
         }
         finally
         {

Projects/UOContent/Mobiles/AI/BaseAI/AIMovement.cs

@@ -18,6 +18,7 @@ using System.Runtime.CompilerServices;
 using Server.Collections;
 using Server.Items;
 using MoveImpl = Server.Movement.MovementImpl;
+using Moves = Server.Movement.Movement;
 
 namespace Server.Mobiles;
 
@@ -43,7 +44,6 @@ public abstract partial class BaseAI
     // live, the AITimer wakes at NextMove between think ticks to advance the step.
     private Mobile _moveIntentTarget;
     private IPoint3D _moveIntentPoint;
-    private bool _moveIntentRun;
     private int _moveIntentRange;
     private long _moveIntentExpire;
 
@@ -74,23 +74,42 @@ public abstract partial class BaseAI
         return Core.TickCount - NextMove >= 0;
     }
 
-    // Accumulative full-step budget: long-run pacing averages CurrentMoveSpeed exactly
-    // regardless of timer-grid jitter; snap-to-now caps stall catch-up at one step.
-    private void ConsumeMoveBudget()
+    // Seconds per step as the client observes it: the move clock plus the hurt inflation.
+    private double EffectiveStepDelay()
     {
         var stepDelay = Mobile.CurrentMoveSpeed;
 
-        if (!(Core.AOS && IsFollowingMaster()))
+        return Core.AOS && IsFollowingMaster() ? stepDelay : BadlyHurtMoveDelay(Mobile, stepDelay);
+    }
+
+    // The Running bit only selects the client's per-step interpolation (walk 400ms / run
+    // 200ms on foot, 200/100 mounted). A step shorter than the walk time must run or the
+    // client falls behind and snaps — but an isolated step (after standing at least a walk
+    // interval) renders alone and darts if run-flagged, so it goes out as a walk. A true
+    // sprinter always runs: a walk-rendered first step would flood the client's queue.
+    public bool ShouldRun()
+    {
+        var mounted = Mobile.Mounted || Mobile.Flying;
+        var walkDelay = mounted ? Moves.WalkMountDelay : Moves.WalkFootDelay;
+        var pace = EffectiveStepDelay() * 1000;
+
+        if (pace >= walkDelay)
         {
-            stepDelay = BadlyHurtMoveDelay(Mobile, stepDelay);
+            return false;
         }
 
-        NextMove += Math.Max(50, (long)(stepDelay * 1000));
+        var runDelay = mounted ? Moves.RunMountDelay : Moves.RunFootDelay;
 
-        if (Core.TickCount - NextMove > 0)
-        {
-            NextMove = Core.TickCount;
-        }
+        return pace < runDelay || Core.TickCount - Mobile.LastMoveTime < walkDelay;
+    }
+
+    // One step per period, paced from the step just taken — no debt accrual: repaying a
+    // late step with a quicker follow-up puts two steps ~100ms apart, which renders as a
+    // dart. In continuous pursuit the move-wake lands within wheel resolution of this
+    // deadline, so the only cost is single-digit-ms drift per step.
+    private void ConsumeMoveBudget()
+    {
+        NextMove = Core.TickCount + Math.Max(50, (long)(EffectiveStepDelay() * 1000));
     }
 
     public virtual bool CheckMove() => !(Mobile.Deleted || Mobile.DisallowAllMoves);
@@ -108,6 +127,8 @@ public abstract partial class BaseAI
             return MoveResult.BadState;
         }
 
+        d = (d & Direction.Mask) | (ShouldRun() ? Direction.Running : 0);
+
         if ((Mobile.Direction & Direction.Mask) != (d & Direction.Mask))
         {
             Mobile.Direction = d;
@@ -334,7 +355,7 @@ public abstract partial class BaseAI
     /// best-distance stall counter idles the creature if an in-range goal is genuinely
     /// unreachable, without ever abandoning a real chase or detour.
     /// </summary>
-    protected bool ApproachTarget(Mobile target, bool run, int range)
+    protected bool ApproachTarget(Mobile target, int range)
     {
         if (Mobile.Deleted || Mobile.DisallowAllMoves || target?.Deleted != false)
         {
@@ -361,7 +382,7 @@ public abstract partial class BaseAI
             ResetApproach(); // target moved — try again fresh
         }
 
-        RenewMoveIntent(target, null, run, range);
+        RenewMoveIntent(target, null, range);
 
         // FAST PATH: greedy step toward the target, counted as success ONLY when the move
         // fully succeeded (not an auto-turn sidestep) and actually got us closer. An
@@ -373,7 +394,7 @@ public abstract partial class BaseAI
         if (Path == null && Mobile.InLOS(target))
         {
             var distBefore = Mobile.GetDistanceToSqrt(target);
-            var res = DoMoveImpl(Mobile.GetDirectionTo(target, run), true);
+            var res = DoMoveImpl(Mobile.GetDirectionTo(target), true);
 
             if (res == MoveResult.BadState)
             {
@@ -402,7 +423,7 @@ public abstract partial class BaseAI
         var couldMove = CanMoveNow(out _) && !IsInBadState();
         var locBefore = Mobile.Location;
 
-        if (Path.Follow(run, range))
+        if (Path.Follow(range))
         {
             ResetApproach();
             return true;
@@ -421,7 +442,7 @@ public abstract partial class BaseAI
     /// Walks toward a fixed point (e.g. a target's last-known position), pathfinding around
     /// obstacles. Returns false on arrival or when genuinely unable to make progress.
     /// </summary>
-    public bool MoveToPoint(IPoint3D goal, bool run)
+    public bool MoveToPoint(IPoint3D goal)
     {
         if (Mobile.Deleted || Mobile.DisallowAllMoves || goal == null)
         {
@@ -434,12 +455,12 @@ public abstract partial class BaseAI
             Path = new PathFollower(Mobile, goal) { Mover = DoMoveImpl };
         }
 
-        RenewMoveIntent(null, goal, run, 1);
+        RenewMoveIntent(null, goal, 1);
 
         var couldMove = CanMoveNow(out _) && !IsInBadState();
         var locBefore = Mobile.Location;
 
-        if (Path.Follow(run, 1))
+        if (Path.Follow(1))
         {
             Path = null;
             ClearMoveIntent();
@@ -515,11 +536,10 @@ public abstract partial class BaseAI
         _approachGaveUp = false;
     }
 
-    private void RenewMoveIntent(Mobile target, IPoint3D point, bool run, int range)
+    private void RenewMoveIntent(Mobile target, IPoint3D point, int range)
     {
         _moveIntentTarget = target;
         _moveIntentPoint = point;
-        _moveIntentRun = run;
         _moveIntentRange = range;
 
         // A live pursuit renews every think tick; unrenewed intent dies on its own.
@@ -556,26 +576,21 @@ public abstract partial class BaseAI
 
         if (_moveIntentTarget != null)
         {
-            ApproachTarget(_moveIntentTarget, _moveIntentRun, _moveIntentRange);
+            ApproachTarget(_moveIntentTarget, _moveIntentRange);
         }
         else
         {
-            MoveToPoint(_moveIntentPoint, _moveIntentRun);
+            MoveToPoint(_moveIntentPoint);
         }
     }
 
-    public virtual bool MoveTo(Mobile m, bool run, int range)
+    public virtual bool MoveTo(Mobile m, int range)
     {
         if (Mobile.Deleted || Mobile.DisallowAllMoves || m?.Deleted != false)
         {
             return false;
         }
 
-        var distance = (int)Mobile.GetDistanceToSqrt(m);
-        //TODO Derive the Running bit from CurrentMoveSpeed in DoMoveImpl and drop the run parameter
-        var distanceThreshold = Core.AOS && IsFollowingMaster() ? 1 : 3;
-        var shouldRun = distance > distanceThreshold;
-
         if (Mobile.InRange(m, range))
         {
             ResetApproach();
@@ -584,10 +599,10 @@ public abstract partial class BaseAI
 
         if (UseGroupMovement(m, range))
         {
-            return MoveToWithGroup(this, m, shouldRun, range);
+            return MoveToWithGroup(this, m, range);
         }
 
-        return ApproachTarget(m, shouldRun, range);
+        return ApproachTarget(m, range);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -604,12 +619,8 @@ public abstract partial class BaseAI
         Mobile.Combatant == null &&
         Mobile.ControlOrder is OrderType.Come or OrderType.Follow or OrderType.Guard;
 
-    private bool MoveToWithCollisionAvoidance(Mobile target, bool run, int range)
+    private bool MoveToWithCollisionAvoidance(Mobile target, int range)
     {
-        var distance = (int)Mobile.GetDistanceToSqrt(target);
-
-        var shouldRun = run && distance > 5;
-
         var direction = Mobile.GetDirectionTo(target);
 
         // Wall-slide auto-turns must not count as progress, or a creature pinned on
@@ -640,10 +651,10 @@ public abstract partial class BaseAI
 
         // Tactical sidesteps exhausted — route around the obstacle via the centralized
         // approach primitive (persistent PathFollower, no oscillation).
-        return ApproachTarget(target, shouldRun, range);
+        return ApproachTarget(target, range);
     }
 
-    public virtual bool WalkMobileRange(Mobile m, int iSteps, bool run, int iWantDistMin, int iWantDistMax)
+    public virtual bool WalkMobileRange(Mobile m, int iSteps, int iWantDistMin, int iWantDistMax)
     {
         if (Mobile.Deleted || Mobile.DisallowAllMoves || m == null)
         {
@@ -659,7 +670,7 @@ public abstract partial class BaseAI
                 return true;
             }
 
-            if (!MoveTowardsOrAwayFrom(m, run, iCurrDist, iWantDistMax))
+            if (!MoveTowardsOrAwayFrom(m, iCurrDist, iWantDistMax))
             {
                 return false;
             }
@@ -670,17 +681,16 @@ public abstract partial class BaseAI
         return dist >= iWantDistMin && dist <= iWantDistMax;
     }
 
-    // run only sets the client animation; callers gate it on their own distance thresholds.
-    private bool MoveTowardsOrAwayFrom(Mobile m, bool run, int iCurrDist, int iWantDistMax)
+    private bool MoveTowardsOrAwayFrom(Mobile m, int iCurrDist, int iWantDistMax)
     {
         if (iCurrDist > iWantDistMax)
         {
             // Too far: approach via the centralized progress-based primitive.
-            return ApproachTarget(m, run, iWantDistMax);
+            return ApproachTarget(m, iWantDistMax);
         }
 
         // Too close: back away. Retreat keeps the simple greedy behavior (out of scope).
-        if (DoMove(m.GetDirectionTo(Mobile, run), true))
+        if (DoMove(m.GetDirectionTo(Mobile), true))
         {
             Path = null;
             return true;

Projects/UOContent/Mobiles/AI/BaseAI/BaseAI.cs

@@ -442,7 +442,7 @@ public abstract partial class BaseAI
         var master = Mobile.SummonMaster;
         if (master != null && master.Map == Mobile.Map && master.InRange(Mobile, Mobile.RangePerception))
         {
-            MoveTo(master, false, 1);
+            MoveTo(master, 1);
         }
     }
 
@@ -592,7 +592,7 @@ public abstract partial class BaseAI
         }
 
         _lkpGoal ??= _lkpLocation;
-        return MoveToPoint(_lkpGoal, false);
+        return MoveToPoint(_lkpGoal);
     }
 
     private void ClearLastKnown()
@@ -644,7 +644,7 @@ public abstract partial class BaseAI
                 _herdGoal = new Point3D(target.X, target.Y, Mobile.Map?.GetAverageZ(target.X, target.Y) ?? Mobile.Z);
             }
 
-            MoveToPoint(_herdGoal, false);
+            MoveToPoint(_herdGoal);
             return true;
         }
 
@@ -798,7 +798,7 @@ public abstract partial class BaseAI
     {
         if (AcquireFocusMob(Mobile.RangePerception * 2, FightMode.Closest, true, false, true))
         {
-            if (WalkMobileRange(Mobile.FocusMob, 1, false, Mobile.RangePerception, Mobile.RangePerception * 2))
+            if (WalkMobileRange(Mobile.FocusMob, 1, Mobile.RangePerception, Mobile.RangePerception * 2))
             {
                 DebugSay("I backed off to safety. Wandering...");
 

Projects/UOContent/Mobiles/AI/BaseAI/PetOrders.cs

@@ -84,7 +84,7 @@ public abstract partial class BaseAI
             return true;
         }
 
-        WalkMobileRange(Mobile.ControlMaster, 1, false, 1, 2);
+        WalkMobileRange(Mobile.ControlMaster, 1, 1, 2);
 
         if (Mobile.GetDistanceToSqrt(Mobile.ControlMaster) <= 2)
         {
@@ -136,7 +136,7 @@ public abstract partial class BaseAI
 
         if (currentDistance > 1)
         {
-            WalkMobileRange(Mobile.ControlTarget, 1, currentDistance > 2, 1, 2);
+            WalkMobileRange(Mobile.ControlTarget, 1, 1, 2);
         }
     }
 
@@ -333,7 +333,7 @@ public abstract partial class BaseAI
                     Mobile.SetCurrentSpeedToActive();
                 }
 
-                WalkMobileRange(controlMaster, 1, true, 1, 3);
+                WalkMobileRange(controlMaster, 1, 1, 3);
             }
             else
             {

Projects/UOContent/Mobiles/AI/BerserkAI.cs

@@ -38,7 +38,7 @@ public class BerserkAI : BaseAI
             return true;
         }
 
-        if (!WalkMobileRange(combatant, 1, false, Mobile.RangeFight, Mobile.RangeFight))
+        if (!WalkMobileRange(combatant, 1, Mobile.RangeFight, Mobile.RangeFight))
         {
             this.DebugSayFormatted($"I am still not in range of {combatant.Name}");
 

Projects/UOContent/Mobiles/AI/HealerAI.cs

@@ -81,7 +81,7 @@ public class HealerAI : BaseAI
             return true;
         }
 
-        WalkMobileRange(Mobile.FocusMob, 1, false, 4, 7);
+        WalkMobileRange(Mobile.FocusMob, 1, 4, 7);
 
         // TODO: Should it be able to do this?
         if (Mobile.TriggerAbility(MonsterAbilityTrigger.CombatAction, Mobile.Combatant))

Projects/UOContent/Mobiles/AI/MageAI.cs

@@ -171,7 +171,7 @@ public class MageAI : BaseAI
     {
         if (!SmartAI)
         {
-            if (!MoveTo(m, false, Mobile.RangeFight))
+            if (!MoveTo(m, Mobile.RangeFight))
             {
                 OnFailedMove();
             }
@@ -185,14 +185,14 @@ public class MageAI : BaseAI
             {
                 RunFrom(m);
             }
-            else if (!Mobile.InRange(m, Math.Max(Mobile.RangeFight, 2)) && !MoveTo(m, false, 1))
+            else if (!Mobile.InRange(m, Math.Max(Mobile.RangeFight, 2)) && !MoveTo(m, 1))
             {
                 OnFailedMove();
             }
         }
         else if (!Mobile.InRange(m, Mobile.RangeFight))
         {
-            if (!MoveTo(m, false, 1))
+            if (!MoveTo(m, 1))
             {
                 OnFailedMove();
             }
@@ -701,7 +701,7 @@ public class MageAI : BaseAI
         {
             DebugSay("I cannot see my target, moving to regain line of sight");
 
-            if (!MoveTo(c, false, 1))
+            if (!MoveTo(c, 1))
             {
                 OnFailedMove();
             }
@@ -1039,7 +1039,7 @@ public class MageAI : BaseAI
                 // target can be invoked.
                 if (!Mobile.InLOS(toTarget))
                 {
-                    MoveTo(toTarget, true, 1);
+                    MoveTo(toTarget, 1);
                 }
                 else
                 {

Projects/UOContent/Mobiles/AI/MeleeAI.cs

@@ -99,7 +99,7 @@ public class MeleeAI : BaseAI
 
     private bool AttemptMoveToCombatant(Mobile combatant)
     {
-        if (MoveTo(combatant, false, Mobile.RangeFight))
+        if (MoveTo(combatant, Mobile.RangeFight))
         {
             return true;
         }

Projects/UOContent/Mobiles/AI/PredatorAI.cs

@@ -41,7 +41,7 @@ public class PredatorAI : BaseAI
             return true;
         }
 
-        if (!WalkMobileRange(combatant, 1, false, Mobile.RangeFight, Mobile.RangeFight))
+        if (!WalkMobileRange(combatant, 1, Mobile.RangeFight, Mobile.RangeFight))
         {
             if (Mobile.GetDistanceToSqrt(combatant) > Mobile.RangePerception + 1)
             {
@@ -70,7 +70,7 @@ public class PredatorAI : BaseAI
         }
         else if (AcquireFocusMob(Mobile.RangePerception * 2, FightMode.Closest, true, false, true))
         {
-            if (WalkMobileRange(Mobile.FocusMob, 1, false, Mobile.RangePerception, Mobile.RangePerception * 2))
+            if (WalkMobileRange(Mobile.FocusMob, 1, Mobile.RangePerception, Mobile.RangePerception * 2))
             {
                 DebugSay("Well, here I am safe");
 

Projects/UOContent/Mobiles/AI/ThiefAI.cs

@@ -43,7 +43,7 @@ public class ThiefAI : BaseAI
             return true;
         }
 
-        if (!WalkMobileRange(combatant, 1, false, Mobile.RangeFight, Mobile.RangeFight))
+        if (!WalkMobileRange(combatant, 1, Mobile.RangeFight, Mobile.RangeFight))
         {
             this.DebugSayFormatted($"I should be closer to {combatant.Name}");
         }

Projects/UOContent/Mobiles/BaseCreature.cs

@@ -2861,7 +2861,7 @@ namespace Server.Mobiles
                     CanBeHarmful(m) && IsEnemy(m))
                 {
                     Combatant = FocusMob = m;
-                    AIObject?.MoveTo(m, true, 1);
+                    AIObject?.MoveTo(m, 1);
                     DoHarmful(m);
                 }
             }

Projects/UOContent/Mobiles/Familiars/BaseFamiliar.cs

@@ -92,7 +92,7 @@ public abstract partial class BaseFamiliar : BaseCreature
             Hidden = m_LastHidden = master.Hidden;
         }
 
-        if (AIObject?.WalkMobileRange(master, 5, false, 1, 1) == true)
+        if (AIObject?.WalkMobileRange(master, 5, 1, 1) == true)
         {
             Warmode = master.Warmode;
             Combatant = master.Combatant;

Projects/UOContent/Mobiles/Monsters/LBR/Meers/EnragedCreatures.cs

@@ -108,7 +108,7 @@ namespace Server.Mobiles
             */
             else if (!Combat(this))
             {
-                AIObject?.MoveTo(SummonMaster, false, 5);
+                AIObject?.MoveTo(SummonMaster, 5);
             }
             /*
               On OSI, if the summon attacks a mobile, the summoner meer also

Projects/UOContent/Spells/Ninjitsu/MirrorImage.cs

@@ -238,10 +238,7 @@ namespace Server.Mobiles
 
             if (master?.Map == Mobile.Map && master?.InRange(Mobile, Mobile.RangePerception) == true)
             {
-                var iCurrDist = (int)Mobile.GetDistanceToSqrt(master);
-                var bRun = iCurrDist > 5;
-
-                WalkMobileRange(master, 2, bRun, 0, 1);
+                WalkMobileRange(master, 2, 0, 1);
             }
             else
             {

dev-docs/claude-skills/migrate-from-runuo/migrate-items-mobiles.md

@@ -29,6 +29,7 @@ description: >
 - `BaseCreature(AI, Fight, 10, 1, 0.2, 0.4)` -> `BaseCreature(AI, Fight)` (extra params default)
 - `Name = "text"` -> `public override string DefaultName => "text";`
 - Expression-bodied overrides: `public override int Meat { get { return 1; } }` -> `public override int Meat => 1;`
+- AI movement calls lose the `run` flag: `MoveTo(m, true, range)` -> `MoveTo(m, range)` (also `WalkMobileRange`, `ApproachTarget`, `MoveToPoint`, `PathFollower.Follow`); the Running bit is derived from step pace -> `dev-docs/runuo-migration-docs/09-items-mobiles-creatures.md` § AI Movement
 
 ## Anti-Patterns
 - Using `_field--` instead of `Property--` (bypasses MarkDirty tracking)

dev-docs/claude-skills/modernuo-content-patterns.md

@@ -27,8 +27,9 @@ description: >
    (`ActiveSpeed`/`PassiveSpeed`, seconds per AI decision) and move
    (`ActiveMoveSpeed`/`PassiveMoveSpeed`, seconds per step; inherits think until
    overridden). Prefer `npc-speeds.json` buckets (`SpeedClass`); `SetSpeed()` sets think
-   AND clears move overrides, `SetMoveSpeed()` sets move only -- see
-   `dev-docs/content-patterns.md` § Creature Speeds
+   AND clears move overrides, `SetMoveSpeed()` sets move only. The client `Running` bit is
+   derived from the step pace (`BaseAI.ShouldRun`); movement APIs take no run argument --
+   see `dev-docs/content-patterns.md` § Creature Speeds
 8. **`OnThink` overrides must be excess-call tolerant** -- it fires more often than the
    think cadence (player commands prod it; speed-ups reschedule it). Gate consequential
    work on a tick-count deadline (subtraction form) or make it idempotent; bare per-call

dev-docs/content-patterns.md

@@ -283,6 +283,18 @@ ClearMoveSpeed();            // back to inheriting the think clock
 All four are `[props`-tunable per instance (move values: set `0` to re-inherit); per-instance
 move overrides serialize. Being badly hurt slows steps, never decisions (RunUO parity).
 
+The client's `Running` bit is derived from the step pace, never passed by callers
+(`BaseAI.ShouldRun`, stamped in `DoMoveImpl`): a step shorter than the client's walk
+interpolation — 400 ms on foot, 200 ms mounted/flying (`Movement.WalkFootDelay` /
+`WalkMountDelay`) — is flagged as a run, or the client falls behind and snaps. An isolated
+step (resuming after at least a walk interval standing) goes out as a walk regardless of
+pace — the client renders each step alone, so a run-flagged single step darts — unless the
+pace beats the run interpolation (a true sprinter), where a walk-rendered first step would
+flood the client's step queue. Movement APIs (`MoveTo`, `WalkMobileRange`,
+`ApproachTarget`, `MoveToPoint`) take no run argument; to make a creature run, make it
+fast. Creatures step at most once per `CurrentMoveSpeed` period, paced from the step just
+taken — a stall never banks catch-up steps, so a resumed chase restarts at full pace.
+
 ### OnThink: the excess-call contract
 
 `OnThink()` is a scheduler pass, not an action. The AI timer calls it *at least* at the

dev-docs/runuo-migration-docs/09-items-mobiles-creatures.md

@@ -474,6 +474,29 @@ The extra parameters (RangePerception, RangeFight, ActiveSpeed, PassiveSpeed) ha
 | `Name = "a creature"` in constructor | `public override string DefaultName => "a creature";` |
 | `get { return value; }` | `=> value;` expression-bodied |
 
+## AI Movement: No `run` Argument
+
+RunUO's movement calls took a `run` flag that callers set inconsistently (`true` in
+combat, `false` for pets, gated by `dist > 5` inside `MoveTo`). The flag only selects the
+client's per-step animation time, so ModernUO derives it from the creature's step pace
+(`BaseAI.ShouldRun`) and the parameter is gone:
+
+```csharp
+// RunUO
+MoveTo(combatant, true, m_Mobile.RangeFight);
+WalkMobileRange(m_Mobile.ControlMaster, 1, false, 0, 1);
+
+// ModernUO
+MoveTo(combatant, Mobile.RangeFight);
+WalkMobileRange(Mobile.ControlMaster, 1, 0, 1);
+```
+
+`ApproachTarget`, `MoveToPoint` and `PathFollower.Follow` lose the argument the same way.
+To make a creature run, make it fast (`SetMoveSpeed` / `npc-speeds.json`), not flagged.
+An isolated step (after the creature stood for at least a walk interval) goes out as a
+walk regardless of pace — only a continuing cadence, or a pace faster than the run
+interpolation, flags run.
+
 ## Item Name Changes
 
 ```csharp

dev-docs/runuo-migration-docs/11-api-reference.md

@@ -130,6 +130,9 @@ Alphabetical by RunUO API name. Use Ctrl+F / Cmd+F to search.
 | `writer.WriteEncodedInt(value)` | `writer.WriteEncodedInt(value)` | Same |
 | `InvalidateProperties()` | `InvalidateProperties()` | Same, or use `[InvalidateProperties]` |
 | `this.MarkDirty()` | `this.MarkDirty()` | NEW — required in custom setters |
+| `MoveTo(m, run, range)` | `MoveTo(m, range)` | `run` removed; the Running bit is derived from the step pace (`BaseAI.ShouldRun`) |
+| `WalkMobileRange(m, steps, run, min, max)` | `WalkMobileRange(m, steps, min, max)` | Same |
+| `PathFollower.Follow(run, range)` | `Follow(range)` | Same |
 
 ## Networking