Perf: Eliminate audit and history entry allocations when auditor/store is disabled

src/Abstractions/Audit/IMutationAuditor.cs

@@ -11,6 +11,11 @@ namespace ModularityKit.Mutator.Abstractions.Audit;
 /// </remarks>
 public interface IMutationAuditor
 {
+    /// <summary>
+    /// When <see langword="false" />, the runtime may skip creating audit entries for this auditor.
+    /// </summary>
+    bool IsEnabled => true;
+
     /// <summary>
     /// Records an audit entry for a mutation.
     /// </summary>

src/Abstractions/History/IMutationHistoryStore.cs

@@ -27,6 +27,11 @@ namespace ModularityKit.Mutator.Abstractions.History;
 /// </example>
 public interface IMutationHistoryStore
 {
+    /// <summary>
+    /// When <see langword="false" />, the runtime may skip creating history entries for this store.
+    /// </summary>
+    bool IsEnabled => true;
+
     /// <summary>
     /// Persists a mutation history entry.
     /// </summary>

src/Runtime/Diagnostics/MutationAuditEntryFactory.cs

@@ -116,7 +116,7 @@ public static MutationHistoryEntry CreateHistoryEntry<TState>(
             Intent = mutation.Intent,
             Context = mutation.Context,
             Changes = result.Changes,
-            SideEffects = result.SideEffects.ToList(),
+            SideEffects = result.SideEffects,
             Timestamp = mutation.Context.Timestamp,
             ExecutionTime = duration
         };

src/Runtime/Internal/Execution/MutationExecutionOutcomeProcessor.cs

@@ -12,8 +12,17 @@
 namespace ModularityKit.Mutator.Runtime.Internal.Execution;
 
 /// <summary>
-/// Handles blocked, failed, and completed mutation outcomes after policy evaluation and execution.
+/// Processes mutation outcomes after policy evaluation and mutation execution.
 /// </summary>
+/// <remarks>
+/// Handles policy blocked, validation failed, successfully completed, and finalized
+/// mutation outcomes. Coordinates interceptor notifications, audit recording,
+/// mutation history persistence, and metrics collection.
+/// </remarks>
+/// <param name="interceptorPipeline">Pipeline responsible for notifying registered mutation interceptors about execution outcomes.</param>
+/// <param name="auditor">Auditor responsible for recording mutation success and failure audit entries. </param>
+/// <param name="historyStore">Store responsible for persisting mutation history for committed mutations.</param>
+/// <param name="metricsCollector">Collector responsible for recording mutation execution metrics.</param>
 internal sealed class MutationExecutionOutcomeProcessor(
     IInterceptorPipeline interceptorPipeline,
     IMutationAuditor auditor,
@@ -28,8 +37,15 @@ internal sealed class MutationExecutionOutcomeProcessor(
     private readonly IMetricsCollector _metricsCollector = metricsCollector ?? throw new ArgumentNullException(nameof(metricsCollector));
 
     /// <summary>
-    /// Handles a policy-blocked mutation result.
+    /// Handles mutation that was blocked by a policy decision.
     /// </summary>
+    /// <typeparam name="TState">The type of state associated with the mutation.</typeparam>
+    /// <param name="executionContext">
+    /// The context containing the mutation, current state, execution metadata,
+    /// cancellation token, and metrics information.
+    /// </param>
+    /// <param name="policyDecision">The policy decision that blocked the mutation.</param>
+    /// <returns>Policy blocked mutation result with audit and execution metrics finalized.</returns>
     public async Task<MutationResult<TState>> HandleBlockedPolicyAsync<TState>(
         MutationExecutionContext<TState> executionContext,
         PolicyDecision policyDecision)
@@ -53,9 +69,17 @@ await AuditFailureAsync(
         return await FinalizeResultAsync(executionContext, blockedResult).ConfigureAwait(false);
     }
 
+
     /// <summary>
-    /// Handles a validation-failed mutation result.
+    /// Handles mutation that failed validation.
     /// </summary>
+    /// <typeparam name="TState">The type of state associated with the mutation.</typeparam>
+    /// <param name="executionContext">
+    /// The context containing the mutation, current state, execution metadata,
+    /// cancellation token, and metrics information.
+    /// </param>
+    /// <param name="validationFailureResult">The mutation result containing validation errors.</param>
+    /// <returns>The validation failure result with audit and execution metrics finalized.</returns>
     public async Task<MutationResult<TState>> HandleValidationFailureAsync<TState>(
         MutationExecutionContext<TState> executionContext,
         MutationResult<TState> validationFailureResult)
@@ -70,8 +94,20 @@ await AuditFailureAsync(
     }
 
     /// <summary>
-    /// Completes a mutation result after execution and policy modifications.
+    /// Completes mutation execution after applying policy modifications and
+    /// processing successful mutation outcomes.
     /// </summary>
+    /// <typeparam name="TState">The type of state associated with the mutation.</typeparam>
+    /// <param name="executionContext">
+    /// The context containing the mutation, current state, execution metadata,
+    /// cancellation token, and metrics information.
+    /// </param>
+    /// <param name="mutationResult">The result produced by the mutation execution.</param>
+    /// <param name="policyDecision">The policy decision containing any modifications to apply to the mutation result.</param>
+    /// <returns>
+    /// The finalized mutation result after interceptor notification, auditing,
+    /// optional history persistence, and metrics processing.
+    /// </returns>
     public async Task<MutationResult<TState>> CompleteMutationAsync<TState>(
         MutationExecutionContext<TState> executionContext,
         MutationResult<TState> mutationResult,
@@ -110,8 +146,13 @@ await StoreInHistoryAsync(
     }
 
     /// <summary>
-    /// Finalizes a runtime result by recording metrics and attaching total execution time.
+    /// Finalizes mutation result by recording execution metrics and attaching
+    /// the total execution duration to the result.
     /// </summary>
+    /// <typeparam name="TState">The type of state associated with the mutation.</typeparam>
+    /// <param name="executionContext">The context containing execution timing and metrics information.</param>
+    /// <param name="result">The mutation result to finalize.</param>
+    /// <returns>The mutation result with finalized execution metrics.</returns>
     public async Task<MutationResult<TState>> FinalizeResultAsync<TState>(
         MutationExecutionContext<TState> executionContext,
         MutationResult<TState> result)
@@ -133,13 +174,25 @@ await _metricsCollector.RecordAsync(
         };
     }
 
+    /// <summary>
+    /// Records successful mutation execution in the audit system when auditing is enabled.
+    /// </summary>
+    /// <typeparam name="TState">The type of state associated with the mutation.</typeparam>
+    /// <param name="mutation">The mutation that was executed.</param>
+    /// <param name="result">The resulting mutation result.</param>
+    /// <param name="policyDecision">The policy decision applied to the mutation.</param>
+    /// <param name="executionId">The unique identifier of the mutation execution.</param>
+    /// <param name="duration">The total execution duration.</param>
     private async Task AuditSuccessAsync<TState>(
         IMutation<TState> mutation,
         MutationResult<TState> result,
         PolicyDecision policyDecision,
         string executionId,
         TimeSpan duration)
     {
+        if (!_auditor.IsEnabled)
+            return;
+
         var entry = MutationAuditEntryFactory.CreateSuccess(
             mutation,
             result,
@@ -150,12 +203,23 @@ private async Task AuditSuccessAsync<TState>(
         await _auditor.AuditAsync(entry).ConfigureAwait(false);
     }
 
+    /// <summary>
+    /// Records failed mutation execution in the audit system when auditing is enabled.
+    /// </summary>
+    /// <typeparam name="TState">The type of state associated with the mutation.</typeparam>
+    /// <param name="mutation">The mutation that failed.</param>
+    /// <param name="result">The resulting mutation failure.</param>
+    /// <param name="executionId">The unique identifier of the mutation execution.</param>
+    /// <param name="duration">The total execution duration.</param>
     private async Task AuditFailureAsync<TState>(
         IMutation<TState> mutation,
         MutationResult<TState> result,
         string executionId,
         TimeSpan duration)
     {
+        if (!_auditor.IsEnabled)
+            return;
+
         var entry = MutationAuditEntryFactory.CreateFailure(
             mutation,
             result,
@@ -165,13 +229,26 @@ private async Task AuditFailureAsync<TState>(
         await _auditor.AuditAsync(entry).ConfigureAwait(false);
     }
 
-    private async Task StoreInHistoryAsync<TState>(
+    /// <summary>
+    /// Stores successful committed mutation in the mutation history store when history
+    /// persistence is enabled and state identifier can be resolved.
+    /// </summary>
+    /// <typeparam name="TState">The type of state associated with the mutation.</typeparam>
+    /// <param name="mutation">The mutation that was executed.</param>
+    /// <param name="result">The resulting mutation result.</param>
+    /// <param name="executionId">The unique identifier of the mutation execution.</param>
+    /// <param name="duration">The total execution duration.</param>
+    /// <param name="cancellationToken">Token that can be used to cancel the history persistence operation. </param>
+   private async Task StoreInHistoryAsync<TState>(
         IMutation<TState> mutation,
         MutationResult<TState> result,
         string executionId,
         TimeSpan duration,
         CancellationToken cancellationToken)
     {
+        if (!_historyStore.IsEnabled)
+            return;
+
         var stateId = MutationAuditEntryFactory.ResolveStateId(mutation.Context);
         if (string.IsNullOrEmpty(stateId))
             return;