diff --git a/src/Agent/AutopilotMonitor.Agent/buildcounter.txt b/src/Agent/AutopilotMonitor.Agent/buildcounter.txt
index 82d45208..cb3e25bb 100644
--- a/src/Agent/AutopilotMonitor.Agent/buildcounter.txt
+++ b/src/Agent/AutopilotMonitor.Agent/buildcounter.txt
@@ -1 +1 @@
-589
+609
diff --git a/src/Backend/AutopilotMonitor.Functions/Functions/Ingest/IngestEventsFunction.Processing.cs b/src/Backend/AutopilotMonitor.Functions/Functions/Ingest/IngestEventsFunction.Processing.cs
index fdab016a..95f5c6ae 100644
--- a/src/Backend/AutopilotMonitor.Functions/Functions/Ingest/IngestEventsFunction.Processing.cs
+++ b/src/Backend/AutopilotMonitor.Functions/Functions/Ingest/IngestEventsFunction.Processing.cs
@@ -471,7 +471,7 @@ namespace AutopilotMonitor.Functions.Functions.Ingest
                         break;
                 }
 
-                AggregateAppInstallEvent(evt, storedEvents[0].TenantId, storedEvents[0].SessionId, classification.AppInstallUpdates);
+                AggregateAppInstallEvent(evt, storedEvents[0].TenantId!, storedEvents[0].SessionId!, classification.AppInstallUpdates);
             }
 
             return classification;
diff --git a/src/Shared/AutopilotMonitor.Shared/AutopilotMonitor.Shared.csproj b/src/Shared/AutopilotMonitor.Shared/AutopilotMonitor.Shared.csproj
index 594d0e6d..2e218256 100644
--- a/src/Shared/AutopilotMonitor.Shared/AutopilotMonitor.Shared.csproj
+++ b/src/Shared/AutopilotMonitor.Shared/AutopilotMonitor.Shared.csproj
@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <LangVersion>9.0</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/Shared/AutopilotMonitor.Shared/Models/Config/TenantConfiguration.cs b/src/Shared/AutopilotMonitor.Shared/Models/Config/TenantConfiguration.cs
index 8e0eb1b0..f75d7bf6 100644
--- a/src/Shared/AutopilotMonitor.Shared/Models/Config/TenantConfiguration.cs
+++ b/src/Shared/AutopilotMonitor.Shared/Models/Config/TenantConfiguration.cs
@@ -53,7 +53,7 @@ namespace AutopilotMonitor.Shared.Models
         /// Optional reason why the tenant was disabled
         /// Displayed to users attempting to log in
         /// </summary>
-        public string DisabledReason { get; set; }
+        public string? DisabledReason { get; set; }
 
         /// <summary>
         /// Optional date/time until which the tenant is disabled
diff --git a/src/Shared/AutopilotMonitor.Shared/Models/Enrollment/EnrollmentEvent.cs b/src/Shared/AutopilotMonitor.Shared/Models/Enrollment/EnrollmentEvent.cs
index c881541e..cc1d82ec 100644
--- a/src/Shared/AutopilotMonitor.Shared/Models/Enrollment/EnrollmentEvent.cs
+++ b/src/Shared/AutopilotMonitor.Shared/Models/Enrollment/EnrollmentEvent.cs
@@ -17,12 +17,12 @@ namespace AutopilotMonitor.Shared.Models
         /// <summary>
         /// Session identifier this event belongs to
         /// </summary>
-        public string SessionId { get; set; }
+        public string? SessionId { get; set; }
 
         /// <summary>
         /// Tenant identifier
         /// </summary>
-        public string TenantId { get; set; }
+        public string? TenantId { get; set; }
 
         /// <summary>
         /// Timestamp when the agent detected/created this event on the device (UTC).
diff --git a/src/Shared/AutopilotMonitor.Shared/Models/GeographicApiModels.cs b/src/Shared/AutopilotMonitor.Shared/Models/GeographicApiModels.cs
index 5a7555ed..8ebf3d28 100644
--- a/src/Shared/AutopilotMonitor.Shared/Models/GeographicApiModels.cs
+++ b/src/Shared/AutopilotMonitor.Shared/Models/GeographicApiModels.cs
@@ -56,7 +56,7 @@ namespace AutopilotMonitor.Shared.Models
 
         public bool IsOutlier { get; set; }
         /// <summary>"fast", "slow", or null</summary>
-        public string OutlierDirection { get; set; }
+        public string? OutlierDirection { get; set; }
     }
 
     /// <summary>
diff --git a/src/Shared/AutopilotMonitor.Shared/Models/SessionApiModels.cs b/src/Shared/AutopilotMonitor.Shared/Models/SessionApiModels.cs
index d40983f2..a0ae236b 100644
--- a/src/Shared/AutopilotMonitor.Shared/Models/SessionApiModels.cs
+++ b/src/Shared/AutopilotMonitor.Shared/Models/SessionApiModels.cs
@@ -25,7 +25,7 @@ namespace AutopilotMonitor.Shared.Models
         /// Non-null when the session was already marked as terminal by an admin before agent restart.
         /// Values: "Succeeded", "Failed". Agent should run cleanup instead of starting monitoring.
         /// </summary>
-        public string AdminAction { get; set; }
+        public string? AdminAction { get; set; }
     }
 
     /// <summary>
@@ -63,7 +63,7 @@ namespace AutopilotMonitor.Shared.Models
         /// <summary>
         /// Rate limit details (only populated if RateLimitExceeded is true)
         /// </summary>
-        public RateLimitInfo RateLimitInfo { get; set; }
+        public RateLimitInfo? RateLimitInfo { get; set; }
 
         /// <summary>
         /// Whether the device has been temporarily blocked by an admin
@@ -85,7 +85,7 @@ namespace AutopilotMonitor.Shared.Models
         /// Non-null when an admin has externally changed the session status.
         /// Values: "Succeeded", "Failed". Agent should treat as terminal signal and run cleanup.
         /// </summary>
-        public string AdminAction { get; set; }
+        public string? AdminAction { get; set; }
     }
 
     /// <summary>
@@ -131,9 +131,9 @@ namespace AutopilotMonitor.Shared.Models
     public class GetDiagnosticsUploadUrlResponse
     {
         public bool Success { get; set; }
-        public string UploadUrl { get; set; }
+        public string? UploadUrl { get; set; }
         public DateTime ExpiresAt { get; set; }
-        public string Message { get; set; }
+        public string? Message { get; set; }
     }
 
     /// <summary>
@@ -222,7 +222,7 @@ namespace AutopilotMonitor.Shared.Models
     {
         public List<SessionSummary> Sessions { get; set; } = new();
         public bool HasMore { get; set; }
-        public string Cursor { get; set; }
+        public string? Cursor { get; set; }
     }
 
     /// <summary>
diff --git a/src/Shared/AutopilotMonitor.Shared/Models/SessionSearchFilter.cs b/src/Shared/AutopilotMonitor.Shared/Models/SessionSearchFilter.cs
index 06f88203..64e9281f 100644
--- a/src/Shared/AutopilotMonitor.Shared/Models/SessionSearchFilter.cs
+++ b/src/Shared/AutopilotMonitor.Shared/Models/SessionSearchFilter.cs
@@ -6,25 +6,25 @@ namespace AutopilotMonitor.Shared.Models
     public class SessionSearchFilter
     {
         // Basic (SessionSummary fields)
-        public string Status { get; set; }
-        public string SerialNumber { get; set; }
-        public string AgentVersion { get; set; }
-        public string ImeAgentVersion { get; set; }
-        public string DeviceName { get; set; }
-        public string Manufacturer { get; set; }
-        public string Model { get; set; }
-        public string OsBuild { get; set; }
-        public string EnrollmentType { get; set; }
+        public string? Status { get; set; }
+        public string? SerialNumber { get; set; }
+        public string? AgentVersion { get; set; }
+        public string? ImeAgentVersion { get; set; }
+        public string? DeviceName { get; set; }
+        public string? Manufacturer { get; set; }
+        public string? Model { get; set; }
+        public string? OsBuild { get; set; }
+        public string? EnrollmentType { get; set; }
         public bool? IsPreProvisioned { get; set; }
         public bool? IsHybridJoin { get; set; }
-        public string GeoCountry { get; set; }
+        public string? GeoCountry { get; set; }
         public DateTime? StartedAfter { get; set; }
         public DateTime? StartedBefore { get; set; }
         public int Limit { get; set; } = 50;
 
         // Dynamic device property filters (key = "eventType.propertyName", value = filter expression)
         // Examples: "tpm_status.specVersion" = "2.0", "hardware_spec.ramTotalGB" = ">=8"
-        public Dictionary<string, string> DeviceProperties { get; set; }
+        public Dictionary<string, string>? DeviceProperties { get; set; }
 
         public bool HasDeviceSnapshotFilters =>
             DeviceProperties != null && DeviceProperties.Count > 0;