diff --git a/Endpoints/AdminWorkflowService.cs b/Endpoints/AdminWorkflowService.cs
index b869bed..973bb09 100644
--- a/Endpoints/AdminWorkflowService.cs
+++ b/Endpoints/AdminWorkflowService.cs
@@ -9,7 +9,7 @@ internal sealed class AdminWorkflowService(AppDbContext db)
 {
     public async Task<IResult> SetResultsOpenAsync(bool resultsOpen)
     {
-        var state = await db.AppState.FirstAsync();
+        var state = await db.AppState.SingleAsync();
         state.ResultsOpen = resultsOpen;
         state.UpdatedAt = DateTimeOffset.UtcNow;
 
@@ -26,7 +26,7 @@ internal sealed class AdminWorkflowService(AppDbContext db)
 
         await db.SaveChangesAsync();
         await tx.CommitAsync();
-        var currentState = await db.AppState.AsNoTracking().FirstAsync();
+        var currentState = await db.AppState.AsNoTracking().SingleAsync();
         return Results.Ok(new AdminResultsStateResponse(currentState.ResultsOpen, currentState.UpdatedAt));
     }
 
@@ -186,7 +186,7 @@ internal sealed class AdminWorkflowService(AppDbContext db)
         await db.Suggestions.ExecuteDeleteAsync();
 
         await db.Players.ExecuteUpdateAsync(p => p.SetProperty(x => x.CurrentPhase, Phase.Suggest).SetProperty(x => x.VotesFinal, false).SetProperty(x => x.HasJoker, false));
-        var state = await db.AppState.FirstAsync();
+        var state = await db.AppState.SingleAsync();
         state.ResultsOpen = false;
         state.UpdatedAt = DateTimeOffset.UtcNow;
         await db.SaveChangesAsync();
diff --git a/Endpoints/EndpointHelpers.cs b/Endpoints/EndpointHelpers.cs
index b55cbeb..e8c0b7d 100644
--- a/Endpoints/EndpointHelpers.cs
+++ b/Endpoints/EndpointHelpers.cs
@@ -44,7 +44,7 @@ internal static class EndpointHelpers
         if (playerPhase is null)
             return Phase.Suggest;
 
-        var resultsOpen = await db.AppState.AsNoTracking().Select(s => s.ResultsOpen).FirstAsync();
+        var resultsOpen = await db.AppState.AsNoTracking().Select(s => s.ResultsOpen).SingleAsync();
         return GetCurrentPhase(playerPhase.Value, resultsOpen);
     }
 
diff --git a/Endpoints/ResultsWorkflowService.cs b/Endpoints/ResultsWorkflowService.cs
index 2854bcb..aed8267 100644
--- a/Endpoints/ResultsWorkflowService.cs
+++ b/Endpoints/ResultsWorkflowService.cs
@@ -9,7 +9,7 @@ internal sealed class ResultsWorkflowService(AppDbContext db)
 {
     public async Task<IResult> GetResultsAsync(Guid playerId)
     {
-        var appState = await db.AppState.AsNoTracking().FirstAsync();
+        var appState = await db.AppState.AsNoTracking().SingleAsync();
         if (!appState.ResultsOpen)
             return EndpointHelpers.BadRequestError("Results are locked until the admin enables them.");
 
diff --git a/Endpoints/StateWorkflowService.cs b/Endpoints/StateWorkflowService.cs
index dc5ccea..8e11142 100644
--- a/Endpoints/StateWorkflowService.cs
+++ b/Endpoints/StateWorkflowService.cs
@@ -9,7 +9,7 @@ internal sealed class StateWorkflowService(AppDbContext db)
 {
     public async Task<IResult> GetStateAsync(Player player)
     {
-        var state = await db.AppState.AsNoTracking().FirstAsync();
+        var state = await db.AppState.AsNoTracking().SingleAsync();
         var phase = EndpointHelpers.GetCurrentPhase(player.CurrentPhase, state.ResultsOpen);
         var summary = new StateSummaryResponse(
             phase,
@@ -26,7 +26,7 @@ internal sealed class StateWorkflowService(AppDbContext db)
 
     public async Task<IResult> GetMeAsync(Player player)
     {
-        var state = await db.AppState.AsNoTracking().FirstAsync();
+        var state = await db.AppState.AsNoTracking().SingleAsync();
         var phase = EndpointHelpers.GetCurrentPhase(player.CurrentPhase, state.ResultsOpen);
         return Results.Ok(new MeResponse(
             player.Id,
@@ -41,7 +41,7 @@ internal sealed class StateWorkflowService(AppDbContext db)
 
     public async Task<IResult> NextPhaseAsync(Player player)
     {
-        var appState = await db.AppState.FirstAsync();
+        var appState = await db.AppState.SingleAsync();
         var shouldSave = EndpointHelpers.ReconcilePlayerPhase(player, appState.ResultsOpen);
 
         try
@@ -75,7 +75,7 @@ internal sealed class StateWorkflowService(AppDbContext db)
         if (!player.IsAdmin)
             return EndpointHelpers.BadRequestError("Only admins can move backward.");
 
-        var appState = await db.AppState.FirstAsync();
+        var appState = await db.AppState.SingleAsync();
         _ = EndpointHelpers.ReconcilePlayerPhase(player, appState.ResultsOpen);
 
         player.CurrentPhase = PrevPhase(player.CurrentPhase);
diff --git a/GameList.Tests/AdminTests.cs b/GameList.Tests/AdminTests.cs
index 22f88bf..a407b58 100644
--- a/GameList.Tests/AdminTests.cs
+++ b/GameList.Tests/AdminTests.cs
@@ -244,7 +244,7 @@ public class AdminTests
         {
             var p = await db.Players.FirstAsync(x => !x.IsAdmin);
             p.VotesFinal = true;
-            var state = await db.AppState.FirstAsync();
+            var state = await db.AppState.SingleAsync();
             state.UpdatedAt = DateTimeOffset.UnixEpoch;
             await db.SaveChangesAsync();
         });
@@ -257,7 +257,7 @@ public class AdminTests
             var p = await db.Players.FirstAsync(x => !x.IsAdmin);
             Assert.Equal(Phase.Vote, p.CurrentPhase);
             Assert.False(p.VotesFinal);
-            var state = await db.AppState.AsNoTracking().FirstAsync();
+            var state = await db.AppState.AsNoTracking().SingleAsync();
             Assert.False(state.ResultsOpen);
             Assert.True(state.UpdatedAt > DateTimeOffset.UnixEpoch);
         });
@@ -433,7 +433,7 @@ public class AdminTests
             var player = await db.Players.SingleAsync(x => x.Username == "flags");
             Assert.False(player.HasJoker);
             Assert.False(player.VotesFinal);
-            var state = await db.AppState.AsNoTracking().FirstAsync();
+            var state = await db.AppState.AsNoTracking().SingleAsync();
             Assert.False(state.ResultsOpen);
         });
 
@@ -441,7 +441,7 @@ public class AdminTests
         factoryReset.EnsureSuccessStatusCode();
         await factory.WithDbContextAsync(async db =>
         {
-            var state = await db.AppState.AsNoTracking().FirstAsync();
+            var state = await db.AppState.AsNoTracking().SingleAsync();
             Assert.False(state.ResultsOpen);
         });
     }
diff --git a/GameList.Tests/AuthTests.cs b/GameList.Tests/AuthTests.cs
index cae84bf..c0fd0a0 100644
--- a/GameList.Tests/AuthTests.cs
+++ b/GameList.Tests/AuthTests.cs
@@ -71,7 +71,7 @@ public class AuthTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var player = await db.Players.FirstAsync();
+            var player = await db.Players.SingleAsync();
             player.DisplayName = null;
             player.LastLoginAt = DateTimeOffset.UnixEpoch;
             await db.SaveChangesAsync();
diff --git a/GameList.Tests/FiltersTests.cs b/GameList.Tests/FiltersTests.cs
index 72b9b9d..7e15a90 100644
--- a/GameList.Tests/FiltersTests.cs
+++ b/GameList.Tests/FiltersTests.cs
@@ -91,7 +91,7 @@ public class FiltersTests
             DisplayName = "User"
         };
         db.Players.Add(player);
-        var state = await db.AppState.FirstAsync();
+        var state = await db.AppState.SingleAsync();
         state.ResultsOpen = resultsOpen;
         await db.SaveChangesAsync();
 
diff --git a/GameList.Tests/StateTests.cs b/GameList.Tests/StateTests.cs
index 8206b78..b873894 100644
--- a/GameList.Tests/StateTests.cs
+++ b/GameList.Tests/StateTests.cs
@@ -19,7 +19,7 @@ public class StateTests
         await client.RegisterAsync("payload");
         await factory.WithDbContextAsync(async db =>
         {
-            var player = await db.Players.FirstAsync();
+            var player = await db.Players.SingleAsync();
             player.HasJoker = true;
             await db.SaveChangesAsync();
         });
@@ -55,7 +55,7 @@ public class StateTests
             };
             playerId = player.Id;
             db.Players.Add(player);
-            var state = await db.AppState.FirstAsync();
+            var state = await db.AppState.SingleAsync();
             state.ResultsOpen = true;
             await db.SaveChangesAsync();
         });
@@ -69,7 +69,7 @@ public class StateTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var state = await db.AppState.FirstAsync();
+            var state = await db.AppState.SingleAsync();
             state.ResultsOpen = false;
             await db.SaveChangesAsync();
         });
@@ -95,7 +95,7 @@ public class StateTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var player = await db.Players.FirstAsync();
+            var player = await db.Players.SingleAsync();
             player.VotesFinal = true;
             await db.SaveChangesAsync();
         });
@@ -127,7 +127,7 @@ public class StateTests
         await admin.PostAsJsonAsync("/api/me/phase/next", new { }); // Vote
         await factory.WithDbContextAsync(async db =>
         {
-            var player = await db.Players.FirstAsync();
+            var player = await db.Players.SingleAsync();
             player.VotesFinal = true;
             await db.SaveChangesAsync();
         });
@@ -255,7 +255,7 @@ public class StateTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var player = await db.Players.FirstAsync();
+            var player = await db.Players.SingleAsync();
             db.Players.Remove(player);
             await db.SaveChangesAsync();
         });
@@ -284,10 +284,10 @@ public class StateTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var player = await db.Players.FirstAsync();
+            var player = await db.Players.SingleAsync();
             player.CurrentPhase = Phase.Results;
             player.VotesFinal = true;
-            var state = await db.AppState.FirstAsync();
+            var state = await db.AppState.SingleAsync();
             state.ResultsOpen = false;
             await db.SaveChangesAsync();
         });
@@ -300,7 +300,7 @@ public class StateTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var player = await db.Players.AsNoTracking().FirstAsync();
+            var player = await db.Players.AsNoTracking().SingleAsync();
             Assert.Equal(Phase.Results, player.CurrentPhase);
             Assert.True(player.VotesFinal);
         });
@@ -323,17 +323,18 @@ public class StateTests
                 CurrentPhase = Phase.Vote
             };
             db.Players.Add(player);
-            var state = await db.AppState.FirstAsync();
+            var state = await db.AppState.SingleAsync();
             state.ResultsOpen = true;
             await db.SaveChangesAsync();
         });
 
         using var scope = factory.Services.CreateScope();
         var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
-        var playerId = await db.Players.Select(p => p.Id).FirstAsync();
+        var playerId = await db.Players.Select(p => p.Id).SingleAsync();
         var phase = await Endpoints.EndpointHelpers.GetCurrentPhaseAsync(db, playerId);
 
         Assert.Equal(Phase.Results, phase);
     }
 }
 
+
diff --git a/GameList.Tests/SuggestionTests.cs b/GameList.Tests/SuggestionTests.cs
index 3a95a2c..46b6001 100644
--- a/GameList.Tests/SuggestionTests.cs
+++ b/GameList.Tests/SuggestionTests.cs
@@ -91,7 +91,7 @@ public class SuggestionTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync(x => x.Username == "joker");
             p.HasJoker = true;
             p.CurrentPhase = Domain.Phase.Vote;
             var o = await db.Players.SingleAsync(x => x.Username == "other");
@@ -114,7 +114,7 @@ public class SuggestionTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync(x => x.Username == "joker");
             Assert.False(p.HasJoker);
             Assert.False(p.VotesFinal);
             var o = await db.Players.SingleAsync(x => x.Username == "other");
@@ -187,9 +187,9 @@ public class SuggestionTests
         // Move everyone to Results
         await factory.WithDbContextAsync(async db =>
         {
-            var state = await db.AppState.FirstAsync();
+            var state = await db.AppState.SingleAsync();
             state.ResultsOpen = true;
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync();
             p.CurrentPhase = Domain.Phase.Results;
             await db.SaveChangesAsync();
         });
@@ -267,7 +267,7 @@ public class SuggestionTests
         await client.PostAsJsonAsync("/api/me/phase/next", new { });
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync();
             p.HasJoker = true;
             await db.SaveChangesAsync();
         });
@@ -288,7 +288,7 @@ public class SuggestionTests
         // Grant another joker and add a seventh suggestion
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync();
             p.HasJoker = true;
             await db.SaveChangesAsync();
         });
@@ -389,7 +389,7 @@ public class SuggestionTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync();
             p.CurrentPhase = Domain.Phase.Vote;
             p.DisplayName = null;
             await db.SaveChangesAsync();
@@ -410,7 +410,7 @@ public class SuggestionTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync();
             p.CurrentPhase = Domain.Phase.Suggest;
             await db.SaveChangesAsync();
         });
@@ -526,7 +526,7 @@ public class SuggestionTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var s = await db.Suggestions.AsNoTracking().FirstAsync();
+            var s = await db.Suggestions.AsNoTracking().SingleAsync();
             Assert.Equal(50, s.Genre!.Length);
             Assert.Equal(500, s.Description!.Length);
             Assert.Equal("http://example.com/img.png", s.ScreenshotUrl);
diff --git a/GameList.Tests/VoteTests.cs b/GameList.Tests/VoteTests.cs
index c5ed476..5ccb67d 100644
--- a/GameList.Tests/VoteTests.cs
+++ b/GameList.Tests/VoteTests.cs
@@ -98,7 +98,7 @@ public class VoteTests
 
         await factory.WithDbContextAsync(async db =>
         {
-            var p = await db.Players.FirstAsync();
+            var p = await db.Players.SingleAsync();
             p.DisplayName = null;
             await db.SaveChangesAsync();
         });