diff --git a/Data/JobTrackerContext.cs b/Data/JobTrackerContext.cs
index d797617..49994c8 100644
--- a/Data/JobTrackerContext.cs
+++ b/Data/JobTrackerContext.cs
@@ -32,16 +32,16 @@ namespace JobTrackerApi.Data
         base.OnModelCreating(modelBuilder);
 
         modelBuilder.Entity<Company>()
-            .HasQueryFilter(c => CurrentUserId == null || c.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(c => CurrentUserId != null && c.OwnerUserId == CurrentUserId);
 
         modelBuilder.Entity<JobApplication>()
-            .HasQueryFilter(j => CurrentUserId == null || j.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(j => CurrentUserId != null && j.OwnerUserId == CurrentUserId);
 
         modelBuilder.Entity<UserRuleSettings>()
             .HasKey(x => x.OwnerUserId);
 
         modelBuilder.Entity<UserRuleSettings>()
-            .HasQueryFilter(x => CurrentUserId == null || x.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(x => CurrentUserId != null && x.OwnerUserId == CurrentUserId);
 
         modelBuilder.Entity<RuleSettings>()
             .HasData(new RuleSettings { Id = 1 });
@@ -65,10 +65,10 @@ namespace JobTrackerApi.Data
             .OnDelete(DeleteBehavior.Cascade);
 
         modelBuilder.Entity<GmailConnection>()
-            .HasQueryFilter(x => CurrentUserId == null || x.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(x => CurrentUserId != null && x.OwnerUserId == CurrentUserId);
 
         modelBuilder.Entity<GmailReviewDecision>()
-            .HasQueryFilter(x => CurrentUserId == null || x.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(x => CurrentUserId != null && x.OwnerUserId == CurrentUserId);
 
         modelBuilder.Ignore<CorrespondenceAttachmentMetadata>();
 
@@ -92,13 +92,13 @@ namespace JobTrackerApi.Data
             .OnDelete(DeleteBehavior.Cascade);
 
         modelBuilder.Entity<CvUploadArtifact>()
-            .HasQueryFilter(x => CurrentUserId == null || x.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(x => CurrentUserId != null && x.OwnerUserId == CurrentUserId);
 
         modelBuilder.Entity<CvUploadArtifact>()
             .HasIndex(x => new { x.OwnerUserId, x.UploadedAtUtc });
 
         modelBuilder.Entity<CvExtractionRun>()
-            .HasQueryFilter(x => CurrentUserId == null || x.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(x => CurrentUserId != null && x.OwnerUserId == CurrentUserId);
 
         modelBuilder.Entity<CvExtractionRun>()
             .HasIndex(x => new { x.OwnerUserId, x.StartedAtUtc });
@@ -110,7 +110,7 @@ namespace JobTrackerApi.Data
             .OnDelete(DeleteBehavior.SetNull);
 
         modelBuilder.Entity<TailoredCvDraft>()
-            .HasQueryFilter(x => CurrentUserId == null || x.OwnerUserId == CurrentUserId);
+            .HasQueryFilter(x => CurrentUserId != null && x.OwnerUserId == CurrentUserId);
 
         modelBuilder.Entity<TailoredCvDraft>()
             .HasIndex(x => new { x.OwnerUserId, x.JobApplicationId })
diff --git a/JobTrackerApi.Tests/LocalAuthIdentityTests.cs b/JobTrackerApi.Tests/LocalAuthIdentityTests.cs
new file mode 100644
index 0000000..ee4aebd
--- /dev/null
+++ b/JobTrackerApi.Tests/LocalAuthIdentityTests.cs
@@ -0,0 +1,52 @@
+using System.Security.Claims;
+using JobTrackerApi.Data;
+using JobTrackerApi.Models;
+using JobTrackerApi.Services;
+using JobTrackerApi.Tests.TestSupport;
+using Microsoft.EntityFrameworkCore;
+using Xunit;
+
+namespace JobTrackerApi.Tests;
+
+public sealed class LocalAuthIdentityTests
+{
+    [Fact]
+    public void GetRequiredUserId_returns_null_when_subject_claim_is_missing()
+    {
+        var principal = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim(ClaimTypes.Email, "ghost@example.com")
+        }, "local"));
+
+        var userId = LocalAuthIdentity.GetRequiredUserId(principal);
+
+        Assert.Null(userId);
+    }
+
+    [Fact]
+    public void GetRequiredUserId_returns_nameidentifier_when_present()
+    {
+        var principal = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim(ClaimTypes.NameIdentifier, "user-123")
+        }, "local"));
+
+        var userId = LocalAuthIdentity.GetRequiredUserId(principal);
+
+        Assert.Equal("user-123", userId);
+    }
+
+    [Fact]
+    public async Task Owner_scoped_query_filters_fail_closed_when_current_user_is_missing()
+    {
+        await using var db = TestHostFactory.CreateInMemoryDb(null);
+        db.Companies.Add(new Company { Name = "Secret Co", OwnerUserId = "user-1" });
+        db.JobApplications.Add(new JobApplication { JobTitle = "Secret Job", Status = "Applied", OwnerUserId = "user-1" });
+        db.UserRuleSettings.Add(new UserRuleSettings { OwnerUserId = "user-1", AppliedFollowUpDays = 5 });
+        await db.SaveChangesAsync();
+
+        Assert.Empty(await db.Companies.ToListAsync());
+        Assert.Empty(await db.JobApplications.ToListAsync());
+        Assert.Empty(await db.UserRuleSettings.ToListAsync());
+    }
+}
diff --git a/JobTrackerApi.Tests/TestSupport/TestHostFactory.cs b/JobTrackerApi.Tests/TestSupport/TestHostFactory.cs
index 26f9acd..8e663ef 100644
--- a/JobTrackerApi.Tests/TestSupport/TestHostFactory.cs
+++ b/JobTrackerApi.Tests/TestSupport/TestHostFactory.cs
@@ -13,7 +13,7 @@ public static class TestHostFactory
 {
     // Keep the EF-backed controller tests on the same minimal setup so they fail for product
     // reasons, not because each file drifted into a slightly different fake host configuration.
-    public static JobTrackerContext CreateInMemoryDb(string userId = "user-1")
+    public static JobTrackerContext CreateInMemoryDb(string? userId = "user-1")
     {
         var options = new DbContextOptionsBuilder<JobTrackerContext>()
             .UseInMemoryDatabase(Guid.NewGuid().ToString())
diff --git a/JobTrackerApi/Program.cs b/JobTrackerApi/Program.cs
index 48afbd6..852e9bb 100644
--- a/JobTrackerApi/Program.cs
+++ b/JobTrackerApi/Program.cs
@@ -253,6 +253,17 @@ builder.Services.AddAuthentication(options =>
                     context.Token = cookieToken;
                 }
 
+                return Task.CompletedTask;
+            },
+            OnTokenValidated = context =>
+            {
+                var userId = LocalAuthIdentity.GetRequiredUserId(context.Principal);
+                if (userId is not null)
+                {
+                    return Task.CompletedTask;
+                }
+
+                context.Fail("Local tokens must include a subject/nameidentifier claim.");
                 return Task.CompletedTask;
             }
         };
diff --git a/JobTrackerApi/Services/CurrentUserService.cs b/JobTrackerApi/Services/CurrentUserService.cs
index 03e2432..bc5e165 100644
--- a/JobTrackerApi/Services/CurrentUserService.cs
+++ b/JobTrackerApi/Services/CurrentUserService.cs
@@ -16,14 +16,5 @@ public sealed class CurrentUserService : ICurrentUserService
         _http = http;
     }
 
-    public string? UserId
-    {
-        get
-        {
-            var u = _http.HttpContext?.User;
-            if (u is null) return null;
-            if (u.Identity?.IsAuthenticated != true) return null;
-            return u.FindFirstValue(ClaimTypes.NameIdentifier) ?? u.FindFirstValue("sub");
-        }
-    }
+    public string? UserId => LocalAuthIdentity.GetRequiredUserId(_http.HttpContext?.User);
 }
diff --git a/JobTrackerApi/Services/LocalAuthIdentity.cs b/JobTrackerApi/Services/LocalAuthIdentity.cs
new file mode 100644
index 0000000..7376a1a
--- /dev/null
+++ b/JobTrackerApi/Services/LocalAuthIdentity.cs
@@ -0,0 +1,17 @@
+using System.Security.Claims;
+
+namespace JobTrackerApi.Services;
+
+public static class LocalAuthIdentity
+{
+    public static string? GetRequiredUserId(ClaimsPrincipal? user)
+    {
+        if (user?.Identity?.IsAuthenticated != true)
+        {
+            return null;
+        }
+
+        var userId = user.FindFirstValue(ClaimTypes.NameIdentifier) ?? user.FindFirstValue("sub");
+        return string.IsNullOrWhiteSpace(userId) ? null : userId;
+    }
+}