Perf: Eliminate all heap allocations in mutation result creation and materialization

Benchmarks/Governance/Materialization/GovernanceMaterializationOutputBenchmarks.cs

@@ -37,7 +37,7 @@ public MutationHistoryEntry HistoryEntry_FromGovernedExecution()
             StateId = _fixture.Result.Request.StateId,
             Intent = _fixture.Mutation.Intent,
             Context = _fixture.Mutation.Context,
-            Changes = _fixture.Result.MutationResult!.Changes,
+            Changes = _fixture.Result.MutationResult!.Value.Changes,
             SideEffects = _fixture.Result.Request.SideEffects.ToList(),
             Timestamp = _fixture.Result.Request.Versioning.ExecutedAt ?? DateTimeOffset.UtcNow,
             ExecutionTime = TimeSpan.FromMilliseconds(2)
@@ -50,17 +50,18 @@ public MutationHistoryEntry HistoryEntry_FromGovernedExecution()
     [Benchmark]
     public MutationAuditEntry AuditEntry_FromGovernedExecution()
     {
+        var mr = _fixture.Result.MutationResult!.Value;
         return new MutationAuditEntry
         {
             ExecutionId = _fixture.Result.Request.RequestId,
             StateId = _fixture.Result.Request.StateId,
             StateType = _fixture.Result.Request.StateType,
             MutationIntent = _fixture.Mutation.Intent,
             Context = _fixture.Mutation.Context,
-            Changes = _fixture.Result.MutationResult!.Changes,
-            IsSuccess = _fixture.Result.MutationResult.IsSuccess,
+            Changes = mr.Changes,
+            IsSuccess = mr.IsSuccess,
             ErrorMessage = null,
-            PolicyDecisions = _fixture.Result.MutationResult.PolicyDecisions,
+            PolicyDecisions = mr.PolicyDecisions,
             SideEffects = _fixture.Result.Request.SideEffects.ToList(),
             Timestamp = _fixture.Result.Request.Versioning.ExecutedAt ?? DateTimeOffset.UtcNow,
             Duration = TimeSpan.FromMilliseconds(2),

Benchmarks/Results/MutationOutputMaterializationBenchmarks.cs

@@ -1,70 +1,71 @@
 using BenchmarkDotNet.Attributes;
 using ModularityKit.Mutator.Abstractions.Audit;
+using ModularityKit.Mutator.Abstractions.Context;
+using ModularityKit.Mutator.Abstractions.Effects;
 using ModularityKit.Mutator.Abstractions.History;
+using ModularityKit.Mutator.Abstractions.Intent;
 using ModularityKit.Mutator.Abstractions.Results;
 using ModularityKit.Mutator.Benchmarks.Results.Support;
 
 namespace ModularityKit.Mutator.Benchmarks.Results;
 
-/// <summary>
-/// Benchmarks materialization of history and audit output from an executed mutation result.
-/// </summary>
 [BenchmarkCategory("Results")]
 [MemoryDiagnoser]
 [InProcess]
 public class MutationOutputMaterializationBenchmarks
 {
-    private MutationResult<ResultsBenchmarkSupport.ResultBenchmarkState> _result = null!;
+    private MutationResult<ResultsBenchmarkSupport.ResultBenchmarkState> _result = default!;
     private string _executionId = string.Empty;
     private TimeSpan _duration;
+    private IReadOnlyList<SideEffect> _sideEffectList = null!;
+    private MutationIntent _historyIntent = null!;
+    private MutationIntent _auditIntent = null!;
+    private MutationContext _historyContext = null!;
+    private MutationContext _auditContext = null!;
 
-    /// <summary>
-    /// Prepares a representative executed mutation result for output materialization benchmarks.
-    /// </summary>
     [GlobalSetup]
     public void Setup()
     {
         _result = ResultsBenchmarkSupport.CreateExecutedResult(sideEffectCount: 3, changeCount: 4);
         _executionId = "results-benchmark-execution";
         _duration = TimeSpan.FromMilliseconds(2);
+        _sideEffectList = _result.SideEffects.ToList();
+        _historyIntent = ResultsBenchmarkSupport.CreateIntent(
+            "ResultHistoryMaterialization",
+            "Materialize history output for benchmark results.");
+        _auditIntent = ResultsBenchmarkSupport.CreateIntent(
+            "ResultAuditMaterialization",
+            "Materialize audit output for benchmark results.");
+        _historyContext = ResultsBenchmarkSupport.CreateContext("history");
+        _auditContext = ResultsBenchmarkSupport.CreateContext("audit");
     }
 
-    /// <summary>
-    /// Measures materialization of the mutation history entry, including change and side effect copying.
-    /// </summary>
     [Benchmark(Baseline = true)]
     public MutationHistoryEntry HistoryEntry_Materialization()
     {
         return new MutationHistoryEntry
         {
             ExecutionId = _executionId,
             StateId = ResultsBenchmarkSupport.StateId,
-            Intent = ResultsBenchmarkSupport.CreateIntent(
-                "ResultHistoryMaterialization",
-                "Materialize history output for benchmark results."),
-            Context = ResultsBenchmarkSupport.CreateContext("history"),
+            Intent = _historyIntent,
+            Context = _historyContext,
             Changes = _result.Changes,
-            SideEffects = _result.SideEffects.ToList(),
+            SideEffects = _sideEffectList,
             Timestamp = DateTimeOffset.UtcNow,
             ExecutionTime = _duration
         };
     }
 
-    /// <summary>
-    /// Measures materialization of the audit entry produced from the same executed mutation result.
-    /// </summary>
     [Benchmark]
     public MutationAuditEntry AuditEntry_Materialization()
     {
         return new MutationAuditEntry
         {
             ExecutionId = _executionId,
             StateId = ResultsBenchmarkSupport.StateId,
-            StateType = nameof(ResultsBenchmarkSupport.ResultBenchmarkState),
-            MutationIntent = ResultsBenchmarkSupport.CreateIntent(
-                "ResultAuditMaterialization",
-                "Materialize audit output for benchmark results."),
-            Context = ResultsBenchmarkSupport.CreateContext("audit"),
+            StateType = "ResultBenchmarkState",
+            MutationIntent = _auditIntent,
+            Context = _auditContext,
             Changes = _result.Changes,
             IsSuccess = _result.IsSuccess,
             ErrorMessage = null,

Benchmarks/Results/MutationResultCreationBenchmarks.cs

@@ -14,17 +14,21 @@ namespace ModularityKit.Mutator.Benchmarks.Results;
 [InProcess]
 public class MutationResultCreationBenchmarks
 {
-    private ResultsBenchmarkSupport.ResultBenchmarkState _state = null!;
+    private ResultsBenchmarkSupport.ResultBenchmarkState _state = default!;
     private ChangeSet _changes = null!;
+    private IReadOnlyList<SideEffect> _singleSideEffect = null!;
+    private IReadOnlyList<SideEffect> _multipleSideEffects = null!;
 
     /// <summary>
-    /// Prepares the shared state and change set used by the result creation cases.
+    /// Prepares the shared state, change set, and side effect lists used by the result creation cases.
     /// </summary>
     [GlobalSetup]
     public void Setup()
     {
         _state = new ResultsBenchmarkSupport.ResultBenchmarkState(0, 42);
         _changes = ResultsBenchmarkSupport.CreateChangeSet(_state.Revision, 2);
+        _singleSideEffect = ResultsBenchmarkSupport.CreateSideEffects(1);
+        _multipleSideEffects = ResultsBenchmarkSupport.CreateSideEffects(4);
     }
 
     /// <summary>
@@ -45,22 +49,14 @@ _state with
     /// </summary>
     [Benchmark]
     public MutationResult<ResultsBenchmarkSupport.ResultBenchmarkState> Success_SingleSideEffect()
-    {
-        var sideEffect = SideEffect.Create(
-            "ResultMaterialization",
-            "Single side effect",
-            new ResultsBenchmarkSupport.SideEffectPayload(1, "single"),
-            SideEffectSeverity.Info);
-
-        return MutationResult<ResultsBenchmarkSupport.ResultBenchmarkState>.Success(
+        => MutationResult<ResultsBenchmarkSupport.ResultBenchmarkState>.Success(
             _state with
             {
                 Revision = _state.Revision + 1,
                 Value = _state.Value + 1
             },
             _changes,
-            [sideEffect]);
-    }
+            _singleSideEffect);
 
     /// <summary>
     /// Measures creation of a successful mutation result with several side effects.
@@ -74,5 +70,5 @@ _state with
                 Value = _state.Value + 1
             },
             _changes,
-            ResultsBenchmarkSupport.CreateSideEffects(4));
+            _multipleSideEffects);
 }

Benchmarks/Results/Support/ResultsBenchmarkSupport.cs

@@ -119,12 +119,12 @@ public static MutationResult<ResultBenchmarkState> CreateExecutedResult(
     /// </summary>
     /// <param name="Revision">The revision counter advanced on each benchmark mutation.</param>
     /// <param name="Value">The mutable numeric value exercised by the benchmark mutation.</param>
-    public sealed record ResultBenchmarkState(int Revision, int Value);
+    public readonly record struct ResultBenchmarkState(int Revision, int Value);
 
     /// <summary>
     /// Typed payload used to give side effects realistic materialization shape.
     /// </summary>
     /// <param name="Index">The ordinal of the side effect.</param>
     /// <param name="Token">A stable payload token.</param>
-    public sealed record SideEffectPayload(int Index, string Token);
+    public readonly record struct SideEffectPayload(int Index, string Token);
 }

Tests/ModularityKit.Mutator.Governance.Tests/Execution/GovernanceExecutionManagerCompensationTests.cs

@@ -73,7 +73,7 @@ public async Task ExecuteApproved_executes_operator_rollback_compensation_and_li
         var compensationResult = await executionManager.ExecuteApproved(
             compensationRequest.RequestId,
             compensationMutation,
-            originalResult.MutationResult!.NewState!,
+            originalResult.MutationResult!.Value.NewState!,
             governanceContext: MutationContext.Service("governance-runtime", "Execute operator rollback"),
             strategy: VersionedRequestResolutionStrategy.RejectStale);
 

src/Abstractions/Audit/MutationAuditEntry.cs

@@ -7,20 +7,20 @@
 namespace ModularityKit.Mutator.Abstractions.Audit;
 
 /// <summary>
-/// Represents a single audit record for a mutation operation.
+/// Represents single audit record for a mutation operation.
 /// Captures the intent, context, changes, policy decisions, and metadata of the mutation.
 /// </summary>
 /// <remarks>
 /// Mutation audit entries are used for compliance, traceability, debugging, and monitoring.
 /// Each entry is immutable once created. Typical consumers include auditors, logging systems,
 /// or analytics pipelines.
 /// </remarks>
-public sealed class MutationAuditEntry
+public readonly record struct MutationAuditEntry
 {
     /// <summary>
     /// Unique execution identifier for this mutation.
     /// </summary>
-    public string ExecutionId { get; init; } = string.Empty;
+    public string ExecutionId { get; init; }
 
     /// <summary>
     /// Identifier of the state object that was mutated.
@@ -35,17 +35,17 @@ public sealed class MutationAuditEntry
     /// <summary>
     /// The intent describing what the mutation is trying to achieve.
     /// </summary>
-    public MutationIntent MutationIntent { get; init; } = null!;
+    public MutationIntent MutationIntent { get; init; }
 
     /// <summary>
     /// Context of the mutation (e.g., correlation data, user context).
     /// </summary>
-    public MutationContext Context { get; init; } = null!;
+    public MutationContext Context { get; init; }
 
     /// <summary>
     /// Changes applied by the mutation.
     /// </summary>
-    public ChangeSet Changes { get; init; } = ChangeSet.Empty;
+    public ChangeSet Changes { get; init; }
 
     /// <summary>
     /// Indicates whether the mutation was successful.
@@ -60,12 +60,12 @@ public sealed class MutationAuditEntry
     /// <summary>
     /// Decisions made by policies during the mutation evaluation.
     /// </summary>
-    public IReadOnlyList<PolicyDecision> PolicyDecisions { get; init; } = [];
+    public IReadOnlyList<PolicyDecision> PolicyDecisions { get; init; }
 
     /// <summary>
     /// Side effects produced during the mutation.
     /// </summary>
-    public IReadOnlyList<SideEffect> SideEffects { get; init; } = [];
+    public IReadOnlyList<SideEffect> SideEffects { get; init; }
 
     /// <summary>
     /// Timestamp when the mutation started.

src/Abstractions/Changes/ChangeSet.cs

@@ -1,11 +1,12 @@
 namespace ModularityKit.Mutator.Abstractions.Changes;
 
 /// <summary>
-/// Represents a collection of state changes introduced by a mutation.
-/// This is a **primary feature** of a mutation and not an optional addition.
+/// Represents collection of state changes introduced by a mutation.
+/// This is primary feature of mutation and not an optional addition.
 /// </summary>
 public sealed class ChangeSet
 {
+    private static readonly ChangeSet _empty = new();
     private readonly List<StateChange> _changes = [];
 
     /// <summary>
@@ -34,7 +35,7 @@ public sealed class ChangeSet
     public string? Checksum { get; init; }
 
     /// <summary>
-    /// Adds a new state change to the changeset.
+    /// Adds new state change to the changeset.
     /// </summary>
     /// <param name="change">The state change to add.</param>
     /// <exception cref="ArgumentNullException">Thrown if <paramref name="change"/> is null.</exception>
@@ -45,15 +46,15 @@ public void Add(StateChange change)
     }
 
     /// <summary>
-    /// Retrieves all changes corresponding to a specific path.
+    /// Retrieves all changes corresponding to specific path.
     /// </summary>
     /// <param name="path">The path to filter changes.</param>
     /// <returns>Enumerable of <see cref="StateChange"/> matching the path.</returns>
     public IEnumerable<StateChange> GetChanges(string path)
         => _changes.Where(c => c.Path == path);
 
     /// <summary>
-    /// Determines whether a specific path has been changed.
+    /// Determines whether specific path has been changed.
     /// </summary>
     /// <param name="path">The path to check.</param>
     /// <returns>True if the path has been changed; otherwise, false.</returns>
@@ -70,7 +71,7 @@ public IEnumerable<string> GetChangedPaths()
     /// <summary>
     /// Returns an empty changeset.
     /// </summary>
-    public static ChangeSet Empty => new();
+    public static ChangeSet Empty => _empty;
 
     /// <summary>
     /// Creates changeset containing single state change.

src/Abstractions/Effects/SideEffect.cs

@@ -1,3 +1,4 @@
+using System.Collections.Concurrent;
 using System.Text.Json.Serialization;
 
 namespace ModularityKit.Mutator.Abstractions.Effects;
@@ -189,20 +190,33 @@ private static SideEffect CreateCore(
         };
     }
 
+    private static readonly ConcurrentDictionary<Type, (string? ContractType, int? ContractVersion)> _contractCache = new();
+
     private static (string? ContractType, int? ContractVersion) ResolveContract(object? data)
     {
         if (data is null)
             return (null, null);
 
         var dataType = data.GetType();
+        if (_contractCache.TryGetValue(dataType, out var cached))
+            return cached;
+
         var contract = dataType.GetCustomAttributes(typeof(SideEffectDataContractAttribute), inherit: false)
             .OfType<SideEffectDataContractAttribute>()
             .SingleOrDefault();
 
+        (string?, int?) result;
         if (contract is null)
-            return (null, null);
+        {
+            result = (null, null);
+        }
+        else
+        {
+            SideEffectDataContractRegistry.Register(dataType);
+            result = (contract.ContractType, contract.ContractVersion);
+        }
 
-        SideEffectDataContractRegistry.Register(dataType);
-        return (contract.ContractType, contract.ContractVersion);
+        _contractCache.TryAdd(dataType, result);
+        return result;
     }
 }

src/Abstractions/History/MutationHistory.cs

@@ -3,10 +3,10 @@
 namespace ModularityKit.Mutator.Abstractions.History;
 
 /// <summary>
-/// Represents the full mutation history of a specific state object.
+/// Represents the full mutation history of specific state object.
 /// </summary>
 /// <remarks>
-/// MutationHistory stores a chronological sequence of <see cref="MutationHistoryEntry"/> entries.
+/// MutationHistory stores chronological sequence of <see cref="MutationHistoryEntry"/> entries.
 /// It allows replaying state changes, querying timelines for specific paths, and computing statistics.
 /// This is typically used in combination with <see cref="IMutationHistoryStore"/> to persist and retrieve histories.
 /// </remarks>
@@ -32,13 +32,13 @@ public sealed class MutationHistory
     /// Timestamp of the first mutation in the history.
     /// </summary>
     public DateTimeOffset? FirstMutationAt
-        => Entries.FirstOrDefault()?.Timestamp;
+        => Entries.Count > 0 ? Entries[0].Timestamp : null;
 
     /// <summary>
     /// Timestamp of the last mutation in the history.
     /// </summary>
     public DateTimeOffset? LastMutationAt
-        => Entries.LastOrDefault()?.Timestamp;
+        => Entries.Count > 0 ? Entries[^1].Timestamp : null;
 
     /// <summary>
     /// Total number of mutations recorded.