diff --git a/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/IPathSmoother.cs b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/IPathSmoother.cs
new file mode 100644
index 0000000..1a9c251
--- /dev/null
+++ b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/IPathSmoother.cs
@@ -0,0 +1,14 @@
+using System.Threading;
+
+namespace MultiWheelC.TrajectoryPlanning.PathSmoothing.Algorithms;
+
+/// <summary>单一平滑方法生成原始几何候选的内部契约。</summary>
+internal interface IPathSmoother
+{
+    SmoothingMethod Method { get; }
+
+    SmoothingCandidate Smooth(
+        SmoothingAlgorithmInput input,
+        double effectiveStrength,
+        CancellationToken cancellationToken);
+}
diff --git a/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingAlgorithmInput.cs b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingAlgorithmInput.cs
new file mode 100644
index 0000000..87c52cf
--- /dev/null
+++ b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingAlgorithmInput.cs
@@ -0,0 +1,34 @@
+using System;
+using MultiWheelC.TrajectoryPlanning.CoarsePath;
+using MultiWheelC.TrajectoryPlanning.Mapping;
+using MultiWheelC.TrajectoryPlanning.PathSmoothing.Processing;
+
+namespace MultiWheelC.TrajectoryPlanning.PathSmoothing.Algorithms;
+
+/// <summary>单次算法运行共享的已预处理路径和独立复核上下文。</summary>
+internal sealed class SmoothingAlgorithmInput
+{
+    internal SmoothingAlgorithmInput(
+        PreparedPath originalPath,
+        PlanningGridMap map,
+        VehicleParameters vehicle,
+        double maximumCollisionCheckStepMeters)
+    {
+        OriginalPath = originalPath ?? throw new ArgumentNullException(nameof(originalPath));
+        Map = map ?? throw new ArgumentNullException(nameof(map));
+        Vehicle = vehicle ?? throw new ArgumentNullException(nameof(vehicle));
+        MaximumCollisionCheckStepMeters = maximumCollisionCheckStepMeters;
+    }
+
+    /// <summary>已校验并按方向分段的原始路径。</summary>
+    internal PreparedPath OriginalPath { get; }
+
+    /// <summary>用于完整车体复核的不可变规划地图。</summary>
+    internal PlanningGridMap Map { get; }
+
+    /// <summary>用于曲率和足迹复核的车辆参数快照。</summary>
+    internal VehicleParameters Vehicle { get; }
+
+    /// <summary>连续车体碰撞检查的最大步长，单位 m。</summary>
+    internal double MaximumCollisionCheckStepMeters { get; }
+}
diff --git a/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingAlgorithmRunner.cs b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingAlgorithmRunner.cs
new file mode 100644
index 0000000..9f24798
--- /dev/null
+++ b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingAlgorithmRunner.cs
@@ -0,0 +1,446 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Threading;
+using MultiWheelC.TrajectoryPlanning.CoarsePath;
+using MultiWheelC.TrajectoryPlanning.Mapping;
+using MultiWheelC.TrajectoryPlanning.PathSmoothing.Processing;
+using MultiWheelC.TrajectoryPlanning.PathSmoothing.Validation;
+
+namespace MultiWheelC.TrajectoryPlanning.PathSmoothing.Algorithms;
+
+/// <summary>在有限强度计划内运行单一算法，并以共享分析和安全复核决定是否接受候选。</summary>
+internal sealed class SmoothingAlgorithmRunner
+{
+    private readonly PathGeometryAnalyzer _analyzer;
+    private readonly SmoothedPathValidator _validator;
+
+    internal SmoothingAlgorithmRunner()
+        : this(new PathGeometryAnalyzer(), new SmoothedPathValidator())
+    {
+    }
+
+    internal SmoothingAlgorithmRunner(PathGeometryAnalyzer analyzer, SmoothedPathValidator validator)
+    {
+        _analyzer = analyzer ?? throw new ArgumentNullException(nameof(analyzer));
+        _validator = validator ?? throw new ArgumentNullException(nameof(validator));
+    }
+
+    /// <summary>
+    /// 依次尝试配置的有限强度比例。取消直接向上传播，由门面转换为最终状态；
+    /// 数值失败和几何分析失败均不重试，以避免以较低强度掩盖算法退化。
+    /// </summary>
+    internal AlgorithmRunResult Run(
+        IPathSmoother smoother,
+        SmoothingAlgorithmInput input,
+        PathSmoothingConfiguration configuration,
+        CancellationToken cancellationToken)
+    {
+        var attemptedStrengths = new List<double>();
+        var failureReasons = new List<string>();
+        if (smoother == null || input == null || configuration == null)
+            return AlgorithmRunResult.Failed("平滑算法、输入或配置无效。", attemptedStrengths, failureReasons);
+        if (configuration.RetryStrengthScales == null || configuration.RetryStrengthScales.Count == 0)
+            return AlgorithmRunResult.Failed("平滑强度重试计划为空。", attemptedStrengths, failureReasons);
+
+        SmoothingCandidate rejectedCandidate = null;
+        foreach (double scale in configuration.RetryStrengthScales)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+            double effectiveStrength = configuration.SmoothingStrength * scale;
+            if (!IsPositiveFinite(effectiveStrength))
+                return AlgorithmRunResult.Failed("平滑强度或重试比例无效。", attemptedStrengths, failureReasons);
+
+            attemptedStrengths.Add(effectiveStrength);
+            SmoothingCandidate candidate = smoother.Smooth(input, effectiveStrength, cancellationToken);
+            if (candidate == null)
+                return AlgorithmRunResult.Failed("平滑算法未返回候选。", attemptedStrengths, failureReasons);
+            if (!candidate.Succeeded)
+            {
+                failureReasons.Add(candidate.Reason);
+                return AlgorithmRunResult.Failed(candidate.Reason, attemptedStrengths, failureReasons);
+            }
+
+            if (!_analyzer.TryAnalyze(candidate.Segments, configuration.OutputSpacingMeters,
+                out PathGeometryAnalysis analysis, out string reason))
+            {
+                failureReasons.Add(reason);
+                return AlgorithmRunResult.Failed(reason, attemptedStrengths, failureReasons);
+            }
+
+            if (_validator.TryValidate(analysis.Path, analysis.Segments, input.OriginalPath, input.Map, input.Vehicle,
+                input.MaximumCollisionCheckStepMeters, out IReadOnlyList<SmoothedPathPoint> safePath,
+                out double minimumClearanceMeters, out reason))
+            {
+                return AlgorithmRunResult.Success(safePath, analysis.Segments,
+                    CreateMetrics(analysis, minimumClearanceMeters), effectiveStrength,
+                    attemptedStrengths, failureReasons);
+            }
+
+            rejectedCandidate = candidate;
+            failureReasons.Add(reason);
+        }
+
+        return AlgorithmRunResult.Infeasible(rejectedCandidate, attemptedStrengths, failureReasons);
+    }
+
+    private static PathQualityMetrics CreateMetrics(PathGeometryAnalysis analysis, double minimumClearanceMeters)
+    {
+        return new PathQualityMetrics(
+            true,
+            analysis.PathLengthMeters,
+            analysis.MaximumAbsoluteVehicleCurvaturePerMeter,
+            analysis.RootMeanSquareVehicleCurvaturePerMeter,
+            analysis.TotalAbsoluteCurvatureVariationPerMeter,
+            analysis.CurvatureVariationEnergy,
+            minimumClearanceMeters,
+            0d,
+            0d,
+            0d,
+            0d);
+    }
+
+    private static bool IsPositiveFinite(double value)
+    {
+        return !double.IsNaN(value) && !double.IsInfinity(value) && value > 0d;
+    }
+
+    /// <summary>
+    /// Reflection-only deterministic coverage seam. It is nested in an internal runner and intentionally
+    /// does not construct or register a production smoothing method.
+    /// </summary>
+    public static class TestHooks
+    {
+        /// <summary>执行一个固定的内部假平滑器场景并返回可反射读取的快照。</summary>
+        public static RunnerTestSnapshot Execute(string scenario)
+        {
+            if (string.IsNullOrWhiteSpace(scenario)) throw new ArgumentException("A scenario is required.", nameof(scenario));
+
+            var cancellationSource = new CancellationTokenSource();
+            var smoother = new DeterministicTestSmoother(ParseScenario(scenario), cancellationSource);
+            var runner = new SmoothingAlgorithmRunner();
+            SmoothingAlgorithmInput input = CreateTestInput();
+            var configuration = new PathSmoothingConfiguration();
+            try
+            {
+                AlgorithmRunResult result = runner.Run(smoother, input, configuration, cancellationSource.Token);
+                return RunnerTestSnapshot.FromResult(result, false);
+            }
+            catch (OperationCanceledException)
+            {
+                return new RunnerTestSnapshot(
+                    "OperationCanceledException",
+                    smoother.AttemptedStrengths,
+                    0,
+                    0,
+                    0,
+                    true);
+            }
+            finally
+            {
+                cancellationSource.Dispose();
+            }
+        }
+
+        /// <summary>供 PowerShell 断言使用的不可变执行摘要。</summary>
+        public sealed class RunnerTestSnapshot
+        {
+            internal RunnerTestSnapshot(
+                string status,
+                IReadOnlyList<double> attemptedStrengths,
+                int acceptedPathPointCount,
+                int rejectedComparisonCandidatePointCount,
+                int failureCount,
+                bool cancellationPropagated)
+            {
+                Status = status ?? string.Empty;
+                AttemptedStrengths = CopyReadOnly(attemptedStrengths);
+                AcceptedPathPointCount = acceptedPathPointCount;
+                RejectedComparisonCandidatePointCount = rejectedComparisonCandidatePointCount;
+                FailureCount = failureCount;
+                CancellationPropagated = cancellationPropagated;
+            }
+
+            public string Status { get; }
+            public IReadOnlyList<double> AttemptedStrengths { get; }
+            public int AcceptedPathPointCount { get; }
+            public int RejectedComparisonCandidatePointCount { get; }
+            public int FailureCount { get; }
+            public bool CancellationPropagated { get; }
+
+            internal static RunnerTestSnapshot FromResult(AlgorithmRunResult result, bool cancellationPropagated)
+            {
+                int rejectedPointCount = result.RejectedComparisonCandidate == null
+                    ? 0
+                    : CountPoints(result.RejectedComparisonCandidate.Segments);
+                return new RunnerTestSnapshot(
+                    result.Status.ToString(),
+                    result.AttemptedStrengths,
+                    result.Path.Count,
+                    rejectedPointCount,
+                    result.FailureReasons.Count,
+                    cancellationPropagated);
+            }
+
+            private static IReadOnlyList<T> CopyReadOnly<T>(IReadOnlyList<T> source)
+            {
+                var copy = new List<T>(source == null ? 0 : source.Count);
+                if (source != null)
+                {
+                    for (int index = 0; index < source.Count; index++) copy.Add(source[index]);
+                }
+                return new ReadOnlyCollection<T>(copy);
+            }
+        }
+
+        private enum TestScenario
+        {
+            RejectAll,
+            AcceptFirst,
+            NumericalFailure,
+            CancelBeforeNextAttempt,
+        }
+
+        private sealed class DeterministicTestSmoother : IPathSmoother
+        {
+            private readonly TestScenario _scenario;
+            private readonly CancellationTokenSource _cancellationSource;
+
+            internal DeterministicTestSmoother(TestScenario scenario, CancellationTokenSource cancellationSource)
+            {
+                _scenario = scenario;
+                _cancellationSource = cancellationSource;
+                AttemptedStrengths = new List<double>();
+            }
+
+            public SmoothingMethod Method => SmoothingMethod.CubicBSpline;
+
+            internal List<double> AttemptedStrengths { get; }
+
+            public SmoothingCandidate Smooth(
+                SmoothingAlgorithmInput input,
+                double effectiveStrength,
+                CancellationToken cancellationToken)
+            {
+                AttemptedStrengths.Add(effectiveStrength);
+                if (_scenario == TestScenario.NumericalFailure)
+                    return SmoothingCandidate.Failed("确定性数值退化。");
+                if (_scenario == TestScenario.AcceptFirst)
+                    return CreateAcceptedCandidate();
+
+                SmoothingCandidate rejected = CreateRejectedCandidate();
+                if (_scenario == TestScenario.CancelBeforeNextAttempt)
+                    _cancellationSource.Cancel();
+                return rejected;
+            }
+        }
+
+        private static TestScenario ParseScenario(string scenario)
+        {
+            if (string.Equals(scenario, nameof(TestScenario.RejectAll), StringComparison.Ordinal)) return TestScenario.RejectAll;
+            if (string.Equals(scenario, nameof(TestScenario.AcceptFirst), StringComparison.Ordinal)) return TestScenario.AcceptFirst;
+            if (string.Equals(scenario, nameof(TestScenario.NumericalFailure), StringComparison.Ordinal)) return TestScenario.NumericalFailure;
+            if (string.Equals(scenario, nameof(TestScenario.CancelBeforeNextAttempt), StringComparison.Ordinal)) return TestScenario.CancelBeforeNextAttempt;
+            throw new ArgumentOutOfRangeException(nameof(scenario));
+        }
+
+        private static SmoothingAlgorithmInput CreateTestInput()
+        {
+            var mapRequest = new PlanningMapRequest
+            {
+                Bounds = new MapBoundsMm(0f, 5000f, 0f, 5000f),
+                ResolutionMm = 50f,
+                AllowExplicitEmptyMap = true,
+            };
+            PlanningMapBuildResult mapResult = new PlanningMapFactory().Create(mapRequest);
+            if (!mapResult.Succeeded || mapResult.Map == null)
+                throw new InvalidOperationException("The runner test hook could not create its empty map.");
+
+            var originalSegments = new List<PreparedDirectionSegment>
+            {
+                new PreparedDirectionSegment(
+                    0,
+                    TravelDirection.Forward,
+                    new List<SmoothingPoint2D>
+                    {
+                        CreatePoint(0.5d, 0.5d, 0d),
+                        CreatePoint(1.5d, 0.5d, 1d),
+                    },
+                    false,
+                    false),
+            };
+            var vehicle = new VehicleParameters
+            {
+                LengthMeters = 0.20d,
+                WidthMeters = 0.20d,
+                SafetyMarginMeters = 0d,
+                MaximumCurvaturePerMeter = 100d,
+                MinimumTurningRadiusMeters = 0.01d,
+            };
+            return new SmoothingAlgorithmInput(new PreparedPath(originalSegments), mapResult.Map, vehicle, 0.05d);
+        }
+
+        private static SmoothingCandidate CreateAcceptedCandidate()
+        {
+            return SmoothingCandidate.Success(new List<PreparedDirectionSegment>
+            {
+                new PreparedDirectionSegment(
+                    0,
+                    TravelDirection.Forward,
+                    new List<SmoothingPoint2D>
+                    {
+                        CreatePoint(0.5d, 0.5d, 0d),
+                        CreatePoint(1.5d, 0.5d, 1d),
+                    },
+                    false,
+                    false),
+            });
+        }
+
+        private static SmoothingCandidate CreateRejectedCandidate()
+        {
+            return SmoothingCandidate.Success(new List<PreparedDirectionSegment>
+            {
+                new PreparedDirectionSegment(
+                    0,
+                    TravelDirection.Forward,
+                    new List<SmoothingPoint2D>
+                    {
+                        CreatePoint(0.5d, 0.5d, 0d),
+                        CreatePoint(0.05d, 0.5d, 0.45d),
+                        CreatePoint(1.5d, 0.5d, 1.90d),
+                    },
+                    false,
+                    false),
+            });
+        }
+
+        private static SmoothingPoint2D CreatePoint(double x, double y, double arcLength)
+        {
+            return new SmoothingPoint2D(
+                x,
+                y,
+                arcLength,
+                0d,
+                0d,
+                1d,
+                false,
+                SmoothedPathPointSource.Anchor);
+        }
+
+        private static int CountPoints(IReadOnlyList<PreparedDirectionSegment> segments)
+        {
+            int count = 0;
+            for (int index = 0; index < segments.Count; index++) count += segments[index].Points.Count;
+            return count;
+        }
+    }
+
+    /// <summary>内部运行结果；只有成功路径可被正式门面发布，拒绝候选仅供比较诊断读取。</summary>
+    internal sealed class AlgorithmRunResult
+    {
+        private static readonly IReadOnlyList<SmoothedPathPoint> EmptyPath =
+            new ReadOnlyCollection<SmoothedPathPoint>(new List<SmoothedPathPoint>());
+        private static readonly IReadOnlyList<SmoothedPathSegment> EmptySegments =
+            new ReadOnlyCollection<SmoothedPathSegment>(new List<SmoothedPathSegment>());
+
+        private AlgorithmRunResult(
+            PathSmoothingStatus status,
+            IReadOnlyList<SmoothedPathPoint> path,
+            IReadOnlyList<SmoothedPathSegment> segments,
+            PathQualityMetrics metrics,
+            double acceptedStrength,
+            SmoothingCandidate rejectedComparisonCandidate,
+            IReadOnlyList<double> attemptedStrengths,
+            IReadOnlyList<string> failureReasons,
+            string reason)
+        {
+            Status = status;
+            Path = path ?? EmptyPath;
+            Segments = segments ?? EmptySegments;
+            Metrics = metrics ?? new PathQualityMetrics();
+            AcceptedStrength = acceptedStrength;
+            RejectedComparisonCandidate = rejectedComparisonCandidate;
+            AttemptedStrengths = CopyReadOnly(attemptedStrengths);
+            FailureReasons = CopyReadOnly(failureReasons);
+            Reason = reason ?? string.Empty;
+        }
+
+        internal PathSmoothingStatus Status { get; }
+        internal IReadOnlyList<SmoothedPathPoint> Path { get; }
+        internal IReadOnlyList<SmoothedPathSegment> Segments { get; }
+        internal PathQualityMetrics Metrics { get; }
+        internal double AcceptedStrength { get; }
+        internal SmoothingCandidate RejectedComparisonCandidate { get; }
+        internal IReadOnlyList<double> AttemptedStrengths { get; }
+        internal IReadOnlyList<string> FailureReasons { get; }
+        internal string Reason { get; }
+
+        internal static AlgorithmRunResult Success(
+            IReadOnlyList<SmoothedPathPoint> path,
+            IReadOnlyList<SmoothedPathSegment> segments,
+            PathQualityMetrics metrics,
+            double acceptedStrength,
+            IReadOnlyList<double> attemptedStrengths,
+            IReadOnlyList<string> failureReasons)
+        {
+            return new AlgorithmRunResult(
+                PathSmoothingStatus.Success,
+                CopyReadOnly(path),
+                CopyReadOnly(segments),
+                metrics,
+                acceptedStrength,
+                null,
+                attemptedStrengths,
+                failureReasons,
+                string.Empty);
+        }
+
+        internal static AlgorithmRunResult Infeasible(
+            SmoothingCandidate rejectedComparisonCandidate,
+            IReadOnlyList<double> attemptedStrengths,
+            IReadOnlyList<string> failureReasons)
+        {
+            string reason = failureReasons == null || failureReasons.Count == 0
+                ? "所有有限平滑尝试均未通过复核。"
+                : failureReasons[failureReasons.Count - 1];
+            return new AlgorithmRunResult(
+                PathSmoothingStatus.Infeasible,
+                null,
+                null,
+                null,
+                0d,
+                rejectedComparisonCandidate,
+                attemptedStrengths,
+                failureReasons,
+                reason);
+        }
+
+        internal static AlgorithmRunResult Failed(
+            string reason,
+            IReadOnlyList<double> attemptedStrengths,
+            IReadOnlyList<string> failureReasons)
+        {
+            return new AlgorithmRunResult(
+                PathSmoothingStatus.Failed,
+                null,
+                null,
+                null,
+                0d,
+                null,
+                attemptedStrengths,
+                failureReasons,
+                reason);
+        }
+
+        private static IReadOnlyList<T> CopyReadOnly<T>(IReadOnlyList<T> source)
+        {
+            var copy = new List<T>(source == null ? 0 : source.Count);
+            if (source != null)
+            {
+                for (int index = 0; index < source.Count; index++) copy.Add(source[index]);
+            }
+            return new ReadOnlyCollection<T>(copy);
+        }
+    }
+}
diff --git a/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingCandidate.cs b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingCandidate.cs
new file mode 100644
index 0000000..1016501
--- /dev/null
+++ b/ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/SmoothingCandidate.cs
@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using MultiWheelC.TrajectoryPlanning.PathSmoothing.Processing;
+
+namespace MultiWheelC.TrajectoryPlanning.PathSmoothing.Algorithms;
+
+/// <summary>平滑方法产生的原始方向段候选，尚未经过统一几何或安全复核。</summary>
+internal sealed class SmoothingCandidate
+{
+    private SmoothingCandidate(bool succeeded, IReadOnlyList<PreparedDirectionSegment> segments, string reason)
+    {
+        Succeeded = succeeded;
+        Segments = CopyReadOnly(segments);
+        Reason = reason ?? string.Empty;
+    }
+
+    /// <summary>候选是否成功产生有限的原始几何。</summary>
+    internal bool Succeeded { get; }
+
+    /// <summary>候选方向段；失败候选始终为空。</summary>
+    internal IReadOnlyList<PreparedDirectionSegment> Segments { get; }
+
+    /// <summary>失败或退化时的稳定说明；成功时为空。</summary>
+    internal string Reason { get; }
+
+    /// <summary>创建待统一分析和验证的成功候选。</summary>
+    internal static SmoothingCandidate Success(IReadOnlyList<PreparedDirectionSegment> segments)
+    {
+        if (segments == null || segments.Count == 0)
+            throw new ArgumentException("A successful smoothing candidate requires direction segments.", nameof(segments));
+        return new SmoothingCandidate(true, segments, string.Empty);
+    }
+
+    /// <summary>创建不应重试的数值或构造失败候选。</summary>
+    internal static SmoothingCandidate Failed(string reason)
+    {
+        if (string.IsNullOrWhiteSpace(reason))
+            throw new ArgumentException("A failed smoothing candidate requires a reason.", nameof(reason));
+        return new SmoothingCandidate(false, null, reason);
+    }
+
+    private static IReadOnlyList<T> CopyReadOnly<T>(IReadOnlyList<T> source)
+    {
+        var copy = new List<T>(source == null ? 0 : source.Count);
+        if (source != null)
+        {
+            for (int index = 0; index < source.Count; index++) copy.Add(source[index]);
+        }
+        return new ReadOnlyCollection<T>(copy);
+    }
+}
diff --git a/ClumsyPilot/tests/verify_path_smoothing_runner.ps1 b/ClumsyPilot/tests/verify_path_smoothing_runner.ps1
new file mode 100644
index 0000000..cad1830
--- /dev/null
+++ b/ClumsyPilot/tests/verify_path_smoothing_runner.ps1
@@ -0,0 +1,73 @@
+param([string]$AssemblyPath = (Join-Path $PSScriptRoot '..\bin\Debug\netstandard2.0\ClumsyPilot.dll'))
+
+$ErrorActionPreference = 'Stop'
+$assembly = [Reflection.Assembly]::LoadFrom((Resolve-Path $AssemblyPath))
+
+function Assert-True($Actual, [string]$Message) {
+    if (-not $Actual) { throw $Message }
+}
+
+function Assert-False($Actual, [string]$Message) {
+    if ($Actual) { throw $Message }
+}
+
+function Assert-Equal($Expected, $Actual, [string]$Message) {
+    if ($Expected -ne $Actual) { throw "$Message Expected=$Expected Actual=$Actual" }
+}
+
+function Assert-Near([double]$Expected, [double]$Actual, [string]$Message) {
+    if ([Math]::Abs($Expected - $Actual) -gt 0.000000001) {
+        throw "$Message Expected=$Expected Actual=$Actual"
+    }
+}
+
+function Get-RequiredType([string]$Name) {
+    return $assembly.GetType($Name, $true)
+}
+
+function Assert-AttemptedStrengths($Snapshot, [double[]]$Expected, [string]$Message) {
+    Assert-Equal $Expected.Length $Snapshot.AttemptedStrengths.Count ($Message + ' count')
+    for ($index = 0; $index -lt $Expected.Length; $index++) {
+        Assert-Near $Expected[$index] $Snapshot.AttemptedStrengths[$index] ($Message + " index=$index")
+    }
+}
+
+$root = 'MultiWheelC.TrajectoryPlanning.PathSmoothing.'
+$algorithms = $root + 'Algorithms.'
+$runnerType = Get-RequiredType ($algorithms + 'SmoothingAlgorithmRunner')
+$smootherType = Get-RequiredType ($algorithms + 'IPathSmoother')
+Assert-False $smootherType.IsPublic 'IPathSmoother must remain internal to the algorithm assembly.'
+
+$hooksType = $runnerType.GetNestedType('TestHooks', [Reflection.BindingFlags]'Public,NonPublic')
+Assert-True ($null -ne $hooksType) 'SmoothingAlgorithmRunner must expose its narrowly scoped nested TestHooks helper.'
+$executeMethod = $hooksType.GetMethod('Execute', [Reflection.BindingFlags]'Public,Static')
+Assert-True ($null -ne $executeMethod) 'TestHooks must expose deterministic scenario execution for reflection tests.'
+
+function Invoke-Scenario([string]$Scenario) {
+    return $executeMethod.Invoke($null, @($Scenario))
+}
+
+$allRejected = Invoke-Scenario 'RejectAll'
+Assert-Equal 'Infeasible' $allRejected.Status 'All rejected finite candidates must produce an Infeasible runner result.'
+Assert-AttemptedStrengths $allRejected @(1.00, 0.75, 0.50, 0.25) 'Rejected candidates must use the finite retry schedule exactly.'
+Assert-Equal 0 $allRejected.AcceptedPathPointCount 'An infeasible runner result must not retain a rejected candidate as an accepted path.'
+Assert-True ($allRejected.RejectedComparisonCandidatePointCount -gt 0) 'Only comparison diagnostics may retain the last rejected candidate geometry.'
+Assert-Equal 4 $allRejected.FailureCount 'Every rejected validation attempt must retain its failure reason.'
+
+$accepted = Invoke-Scenario 'AcceptFirst'
+Assert-Equal 'Success' $accepted.Status 'The first safe candidate must be accepted.'
+Assert-AttemptedStrengths $accepted @(1.00) 'The runner must stop immediately after the first accepted candidate.'
+Assert-True ($accepted.AcceptedPathPointCount -gt 0) 'A successful runner result must publish the validated path internally.'
+Assert-Equal 0 $accepted.RejectedComparisonCandidatePointCount 'An accepted candidate must not create rejected comparison geometry.'
+
+$numericalFailure = Invoke-Scenario 'NumericalFailure'
+Assert-Equal 'Failed' $numericalFailure.Status 'A numerical candidate failure must stop the runner as Failed.'
+Assert-AttemptedStrengths $numericalFailure @(1.00) 'Numerical candidate failure must not retry at lower strength.'
+Assert-Equal 0 $numericalFailure.RejectedComparisonCandidatePointCount 'A non-candidate numerical failure must not retain comparison geometry.'
+
+$cancelled = Invoke-Scenario 'CancelBeforeNextAttempt'
+Assert-True $cancelled.CancellationPropagated 'Cancellation between attempts must propagate out of the runner.'
+Assert-AttemptedStrengths $cancelled @(1.00) 'Cancellation before the next attempt must prevent another smoother call.'
+Assert-Equal 0 $cancelled.AcceptedPathPointCount 'A cancelled run must not publish a partial path.'
+
+Write-Output 'Path smoothing retry runner checks passed.'