feat: enforce per-layer retention intervals in maintenance worker

.env.production.example

@@ -114,6 +114,16 @@ API_PORT=5000
 DASHBOARD_API_PORT=5001
 WEB_ADMIN_PORT=5002
 
+# -----------------------------------------------------------------------------
+# Memory Retention Intervals (days per layer before archival eligibility)
+# -----------------------------------------------------------------------------
+# Memories below confidence threshold with low access are archived after
+# exceeding their layer's retention period. L4_HEURISTIC is never archived.
+RETENTION_L0_RAW_DAYS=30
+RETENTION_L1_CONTEXT_DAYS=90
+RETENTION_L2_SUMMARY_DAYS=180
+RETENTION_L3_KNOWLEDGE_DAYS=365
+
 # -----------------------------------------------------------------------------
 # Feature Flags (Production Defaults)
 # -----------------------------------------------------------------------------

SerialMemory.EventSourcing/Maintenance/MaintenanceWorkers.cs

@@ -132,20 +132,38 @@ private async Task<int> ArchiveColdMemoriesAsync(NpgsqlConnection conn, Cancella
         // ArchiveMemoryCommand per memory. This bypasses event sourcing for performance --
         // archiving cold memories is a bulk housekeeping operation. The aggregate cycle log
         // records how many rows were archived.
+        //
+        // Layer-specific retention intervals:
+        //   L0_RAW       = 30 days   (raw input, ephemeral)
+        //   L1_CONTEXT   = 90 days   (processed notes)
+        //   L2_SUMMARY   = 180 days  (synthesized concepts)
+        //   L3_KNOWLEDGE = 365 days  (validated learnings)
+        //   L4_HEURISTIC = indefinite (never archived)
         var archivedCount = await conn.ExecuteAsync(new CommandDefinition(@"
             UPDATE memory_projections
             SET is_archived = TRUE
             WHERE is_active = TRUE
                 AND is_archived = FALSE
                 AND confidence_score < @ArchiveThreshold
                 AND access_count < @MinAccessCount
-                AND last_accessed_at < NOW() - @ColdPeriod::INTERVAL
-                AND layer NOT IN ('L3_KNOWLEDGE', 'L4_HEURISTIC')",
+                AND layer != 'L4_HEURISTIC'
+                AND last_accessed_at < NOW() - make_interval(days =>
+                    CASE layer
+                        WHEN 'L0_RAW'       THEN @L0RetentionDays
+                        WHEN 'L1_CONTEXT'   THEN @L1RetentionDays
+                        WHEN 'L2_SUMMARY'   THEN @L2RetentionDays
+                        WHEN 'L3_KNOWLEDGE' THEN @L3RetentionDays
+                        ELSE @L0RetentionDays
+                    END
+                )",
             new
             {
                 ArchiveThreshold = _config.ArchiveConfidenceThreshold,
                 MinAccessCount = _config.MinAccessCountForRetention,
-                ColdPeriod = $"{_config.ColdPeriodDays} days"
+                L0RetentionDays = _config.L0RawRetentionDays,
+                L1RetentionDays = _config.L1ContextRetentionDays,
+                L2RetentionDays = _config.L2SummaryRetentionDays,
+                L3RetentionDays = _config.L3KnowledgeRetentionDays
             },
             cancellationToken: cancellationToken));
 
@@ -327,6 +345,16 @@ public sealed class MaintenanceConfig
     public int ReinforceIntervalDays { get; set; } = 7;
     public float DuplicateSimilarityThreshold { get; set; } = 0.95f;
 
+    /// <summary>
+    /// Per-layer retention intervals in days. Memories are eligible for archival
+    /// only after they exceed their layer's retention period.
+    /// L4_HEURISTIC is always excluded (indefinite retention).
+    /// </summary>
+    public int L0RawRetentionDays { get; set; } = 30;
+    public int L1ContextRetentionDays { get; set; } = 90;
+    public int L2SummaryRetentionDays { get; set; } = 180;
+    public int L3KnowledgeRetentionDays { get; set; } = 365;
+
     public static MaintenanceConfig Default => new();
 }
 

SerialMemory.Worker/Program.cs

@@ -185,11 +185,29 @@
 
 // 1. Memory Maintenance Worker - handles decay, archiving, reinforcement
 //    Uses batch SQL operations directly (bypasses per-item event sourcing for performance).
+var maintenanceConfig = new MaintenanceConfig
+{
+    L0RawRetentionDays = int.TryParse(
+        builder.Configuration["RETENTION_L0_RAW_DAYS"] ?? Environment.GetEnvironmentVariable("RETENTION_L0_RAW_DAYS"),
+        out var l0) ? l0 : 30,
+    L1ContextRetentionDays = int.TryParse(
+        builder.Configuration["RETENTION_L1_CONTEXT_DAYS"] ?? Environment.GetEnvironmentVariable("RETENTION_L1_CONTEXT_DAYS"),
+        out var l1) ? l1 : 90,
+    L2SummaryRetentionDays = int.TryParse(
+        builder.Configuration["RETENTION_L2_SUMMARY_DAYS"] ?? Environment.GetEnvironmentVariable("RETENTION_L2_SUMMARY_DAYS"),
+        out var l2) ? l2 : 180,
+    L3KnowledgeRetentionDays = int.TryParse(
+        builder.Configuration["RETENTION_L3_KNOWLEDGE_DAYS"] ?? Environment.GetEnvironmentVariable("RETENTION_L3_KNOWLEDGE_DAYS"),
+        out var l3) ? l3 : 365,
+};
+
+builder.Services.AddSingleton(maintenanceConfig);
 builder.Services.AddHostedService<MemoryMaintenanceWorker>(sp =>
     new MemoryMaintenanceWorker(
         pgConnectionString,
         sp.GetRequiredService<IRetrievalEngine>(),
-        sp.GetRequiredService<ILoggerFactory>().CreateLogger<MemoryMaintenanceWorker>()));
+        sp.GetRequiredService<ILoggerFactory>().CreateLogger<MemoryMaintenanceWorker>(),
+        sp.GetRequiredService<MaintenanceConfig>()));
 
 // 2. Projection Host - processes events and updates read models
 // Wrapped in a BackgroundService since ProjectionHost doesn't implement IHostedService